MX2008007369A

MX2008007369A - Bispecific ligands with binding specificity to cell surface targets and methods of use therefor

Info

Publication number: MX2008007369A
Application number: MXMX/A/2008/007369A
Authority: MX
Inventors: Holmes Steve; M Tomlinson Ian; De Angelis Elena; Yichun Huang Eric; E Everett Claire
Original assignee: De Angelis Elena; Domantis Limited; E Everett Claire; Holmes Steve; Holt Lucy J; HUANG Eric Yichun; Tomlison Ian M
Priority date: 2005-12-06
Filing date: 2008-06-06
Publication date: 2008-09-02

Abstract

Disclosed are ligands comprising a first polypeptide domain having a binding site with binding specificity for a first cell surface target and a second polypeptide domain having a binding site for a second cell surface target, wherein each target are different and on the same cell. In some embodiments, the ligands described further comprise a toxin. In other embodiments, the ligands further comprise half-life extending moieties. Also disclosed are methods of using these ligands. In particular, the use of these ligands for cancer therapy is described.

Description

LIGAN TWO BIESPECIFICOS WITH SPECIFICITY OF LACE FOR THE OBJECTIVES OF CELLULAR SURFACE. AND METHODS OF USE OF THE M ISMS RELATED APPLICATION This application claims the benefit of the Application of the United States of America Number 60/742, 992, filed on December 6, 2005, the total teachings of which are incorporated herein by reference. BACKGROUND OF THE INVENTION An approach to cancer therapy and diagnosis involves directing antibodies or antibody fragments into diseased tissues, wherein the antibody or antibody fragment can direct a diagnostic agent or a therapeutic agent to the site of treatment. the illness . It has been shown that pathogenic cells, such as cancer cells, overexpress certain targets, or express different targets when compared to normal cells. For example, in multiple myeloma, a malignancy of B-cells characterized by proliferation of plasma cells in the bone marrow, antigens CD38, CD1 38, and CD56 are highly expressed. Antibodies that bind to these targets are useful in the therapy and diagnosis of cancer. H ERCEPTI N ® (Trastuzumab) and RITUXAN ® (rituximab) (both from Genentech, S. San Francisco), have been used successfully to treat breast cancer and non-Hodgkin's lymphoma, respectively. RITUXAN® is a genetically engineered chimeric mouse / human monoclonal antibody directed against CD20. H ERCEPTI N® is a humanized monoclonal antibody derived from recombinant DNA that binds selectively with the extracellular domain of the proto-oncogene of the human epidermal growth factor receptor 2 (H ER2). The target of Herceptin, H ER-2 / neu, also known as c-erb B-2, is a transmembrane receptor of 1 85 kDa with protein tyrosine kinase activity, which is a member of the family of factor receptor receptors. epithelial growth (EGF), expressed in breast, ovarian, gastric, and prostate tumors of the subsets of patients with these disorders. This receptor is modestly expressed in normal adult tissues; however, it is strongly associated with solid epithelial malignancies, and is over-expressed in approximately 25 to 35 percent of gastric, lung, prostate, and human breast carcinomas. Current therapies, including monoclonal antibodies, typically target individually defined goals that are different across an entire population, or change, evolve, or mutate during the spread of the disease through an entire population or within a population. i ndividuo. Additionally, a single antibody or domain will probably not recognize all tumor cells in a patient, but combinations of antibodies or domains can be significantly more effective. Additionally, cross-reactivity can be a problem with antibodies. One of the main drawbacks of the use of anti-CEA antibodies for clinical purposes has been the cross-reactivity of these antibodies with some apparently normal adult tissues. Previous studies have shown that most conventional hyperimmune antisera reproduced against different immunogenic forms of CEA cross-react with CEA-related antigens found in the normal colonic mucosa, in the spleen, in the liver, in the lung, in the sweat glands, in the polymorphonuclear leukocytes, and in the monocytes of normal individuals, as well as many different types of carcinomas. Accordingly, there is a need for better agents for the treatment of pathogenic conditions (eg, cancer). BRIEF DESCRIPTION OF THE INVENTION The invention relates to ligands that bind to two cell surface targets that are present in a cell. For example, the ligand may comprise a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and a second polypeptide domain having a binding site with a binding specificity for a second target of cell surface. Preferably, the first polypeptide domain (eg, the single immunoglobulin variable domain) binds to the first cell surface target with low affinity, and the second polypeptide domain (the single immunoglobulin variable domain) is binds to the second cell surface target with low affinity. As described and exemplified herein, these ligands can be selectively linked to double positive cells that contain both the first cell surface target and the second cell surface target. In accordance with the above, polypeptides that bind to a desired cell surface antigen with a low affinity, and antigen binding antibodies and fragments of the antigens, can be formatted into ligands, as described herein, for provide agents that can be selectively linked to the double positive cells. The ligands of the invention provide several advantages. For example, as described herein, ligands that bind to two different cell surface targets can be internalized into cells after the binding of the two targets on the surface of a cell. Accordingly, the ligands can be used to deliver a therapeutic agent, such as a toxin, to a double positive cell expressing a first cell surface target and a second cell surface target, such as a cancer cell. Because the ligand can selectively bind to the positive double cells, possible undesirable effects that could result from the delivery of a therapeutic agent to a single positive cell (e.g., side effects such as immunosuppression) can be eliminated, using the ligands of the invention. Ligands of the invention can bind to cell surface targets that are both present in normal cells, but that are present at higher levels in a pathogenic cell. Under these circumstances, the ligand can be used to preferentially deliver a therapeutic agent (eg, a toxin) to the pathogenic cell. For example, due to the higher level of cell surface targets on the pathogenic cell, more ligand will bind and be internalized in the pathogenic cell, from which it will bind and be internalized in the normal cell. Therefore, an effective amount of toxin can be delivered preferentially to the pathogenic cell. In addition, as described herein, the ligand can be tailored to have a desired in vivo serum half life. Accordingly, the ligands can be used to control, reduce, or eliminate the general toxicity of the therapeutic agents, such as the cytotoxin used for the treatment of cancer. In general, both cell surface targets with which the ligand binds are present in a pathogenic cell, but are not both present in normal cells. As shown herein, in these situations, the ligand can be used in a concentration that results in a selective binding to the pathogenic cells containing both cell surface targets (at a concentration where the ligand is not substantially bound to individual positive normal cells). Certain normal cells can have both cell surface targets that are linked by a ligand of the invention present on their cell surfaces, but the targets are present at higher levels on the surface of a pathogenic cell (e.g., a cancer cell). Preferably, both cell surface targets are not substantially present on the surface of normal cells. Under these circumstances, the ligand can be used in a concentration that results in a selective binding to the pathogenic cells containing both cell surface targets (at a concentration where the ligand does not substantially bind to the normal cell containing low levels). of cell surface targets). In one aspect, the ligand comprises a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and a second polypeptide domain having a binding site with a binding specificity for a second cell surface target, wherein the first cell surface target and the second cell surface target are different, and the first cell surface target and the second cell surface target are present in a pathogenic cell, where this ligand is linkage is linked to the first cell surface target and to the second cell surface target on the pathogenic cell, and wherein this ligand is internalized by the pathogenic cell. Preferably, the ligand is preferentially internalized by a pathogenic cell. For example, the ligand is not substantially internalized by the individual or normal positive cells, or selectively binds to a pathogenic cell. In some embodiments, the ligand selectively binds to a pathogenic cell when this ligand is present at a concentration that is between about 1 pM and about 150 nM. In some embodiments, the first polypeptide domain binds to a first cell surface target with a low affinity, and the second polypeptide domain binds to a second cell surface target with a low affinity. For example, the first polypeptide domain and the second polypeptide domain can each bind to their respective cell surface targets with an affinity (KD) that is between about 1.0 μM and about 10 nM, as determined by surface plasmon resonance. In preferred embodiments, the first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and the second polypeptide domain having a binding site with a binding specificity for a second target of cell surface, they are a first single variable domain of immunoglobulin, and a second single variable domain of immunoglobulin, respectively. For example, the first single variable domain of immunoglobulin and / or the second single variable domain of immunoglobulin may be a VHH >; Either the first single variable domain of immunoglobulin and the second single variable domain of immunoglobulin can be independently selected from the group consisting of a human VH and a human V. In more particular embodiments, the first single variable domain of immunoglobulin has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD1 38, carcinoembryonic antigen (CEA), CD56, vascular endothelial growth factor (VEG F), epidermal growth factor receptor (EGFR), and HER2. In some embodiments, the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CDI 38, CEA, CD56, VEGF, EGFR, and HER2 , with the proviso that this first single variable domain of immunoglobulin and this second single variable domain of immunoglobulin do not bind to the same cell surface target. In certain embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD38, and competes for binding with CD38, with an anti-CD38 domain (dAb) antibody selected from the group consisting of at: DOM11-14 (SEQ ID NO: 242), DOM11-22 (SEQ ID NO: 246), DOM11-23 (SEQ ID NO: 247), DOM11-25 (SEQ ID NO: 249), DOM11-26 ( SEQ ID NO: 250), DOM11-27 (SEQ ID NO: 251), DOM 11-29 (SEQ ID NO: 253), DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254) ), DOM11-31 (SEQ ID NO: 255), DOM11-32 (SEQ ID NO: 256), DOM11-36 (SEQ ID NO: 260), DOM11-4 (SEQ ID NO: 235), DOM11-43 ( SEQ ID NO: 266), DOM11-44 (SEQ ID NO: 267), DOM11-45 (SEQ ID NO: 268), DOM11-5 (SEQ ID NO: 236), DOM11-7 (SEQ ID NO: 238), DOM11-1 (SEQ ID NO: 232), DOM11 -10 (SEQ ID NO: 241), DOM11-16 (SEQ ID NO: 243), DOM11-2 (SEQ ID NO: 233), DOM11-20 (SEQ ID NO: 244), DOM11-21 (SEQ ID NO. : 245), DOM11-24 (SEQ ID NO: 248), DOM11-28 (SEQ ID NO: 252), DOM11-33 (SEQ ID NO: 257), DOM11-34 (SEQ ID NO: 258), DOM11- 35 (SEQ ID NO: 259), DOM11-37 (SEQ ID NO: 261), DOM11-38 (SEQ ID NO: 262), DOMI1-39 (SEQ ID NO: 293), DOM11-41 (SEQ ID NO: 264), DOM11-42 (SEQ ID NO: 265), DOM11-6 (SEQ ID NO: 237), DOM11-8 (SEQ ID NO: 239), and DOM11-9 (SEQ ID NO: 240). In other embodiments, the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain binds to CD38, and competes for CD38 binding, with an anti-CD38 domain (dAb) antibody selected from the group consisting of in: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11-3-10 (SEQ ID NO: 275), DOM 11-3-11 (SEQ ID NO: 276 DOM 11-3-14 (SEQ ID NO: 277) DOM 11-3-15 (SEQ ID NO: 278 DOM 11-3-17 (SEQ ID NO: 279) DOM 11-3-19 (SEQ ID NO: 280 DOM 11-3-20 (SEQ ID NO: 281) DOM 11-3-21 (SEQ ID NO: 282 DOM 11-3-22 (SEQ ID NO: 283) DOM 11-3-23 (SEQ ID NO: 284 DOM 11-3-24 (SEQ ID NO: 285) DOM 11-3-25 (SEQ ID NO: 286 DOM 11-3-26 (SEQ ID NO: 287) DOM 11-3-27 (SEQ ID NO: 288 DOM 11-3-28 (SEQ ID NO: 289) DOM 11-30-1 (SEQ ID NO: 290 DOM 11-30-2 (SEQ ID NO: 291) DOM 11-30-3 (SEQ ID NO: 292 DOM 11-30-5 (SEQ ID NO: 293) DOM 11-30-6 (SEQ ID NO: 294 DOM 11-30-7 (SEQ ID NO: 295) DOM 11-30-8 (SEQ ID NO: 296 DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298 DOM 11-30-11 (SEQ ID NO: 299) DOM 11-30-12 (SEQ. ID NO: 300 DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302 DOM 11-30-15 (SEQ ID NO: 303), DOM 11-30-16 (SEQ ID NO: 304 and DOM 11-30-17 (SEQ ID NO: 305) In certain embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence that has an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM11-14 (SEQ ID NO: 242), DOM11-22 (SEQ ID NO. : 246), DOM11-23 (SEQ ID NO: 247), DOM11-25 (SEQ ID NO: 249), DOM11-26 (SEQ ID NO: 250), DOM11-27 (SEQ ID NO: 251), DOM 11 -29 (SEQ ID NO: 253), DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254), DOM11-31 (SEQ ID NO: 255), DOM11-32 (SEQ ID NO. : 256), DOM11-36 (SEQ ID NO: 260), DOM11-4 (SEQ ID NO: 235), DOM11-43 (SEQ ID NO: 266), DOM11-44 (SEQ ID NO: 267), DOM11-45 (SEQ ID NO: 268), DOM11-5 (SEQ ID NO: 236), DOM11-7 (SEQ ID NO: 238), DOM11-1 (SEQ ID NO: 232), DOM11-10 (SEQ ID NO: 241), DOM11-16 (SEQ ID NO: 243), DOM11-2 (SEQ ID NO: 233), DOM11-20 (SEQ ID NO: 244), DOM11- 21 (SEQ ID NO: 245), DOM11-24 (SEQ IDNO: 248), DOM11-28 (SEQ IDNO: 252), DOM11-33 (SEQ ID NO: 257), DOM11-34 (SEQ ID NO: 258), DOM11-35 (SEQ ID NO: 259), DOM11-37 (SEQ ID NO: 261), DOM11 -38 (SEQ ID NO: 262), DOM11-39 (SEQ ID NO: 293), DOM11-41 (SEQ ID NO: 264), DOM11-42 (SEQ ID NO: 265), DOM11-6 (SEQ ID NO. : 237), DOM11-8 (SEQ ID NO: 239), and DOM11-9 (SEQ ID NO: 240). In other embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11-3-10 (SEQ ID NO: 275 DOM 11-3-11 (SEQ ID NO: 276 DOM 11-3-14 (SEQ ID NO: 277 DOM 11-3-15 (SEQ ID NO: 278 DOM 11-3-17 (SEQ ID NO: 279 SUN 11-3-19 (SEQ ID NO: 280 SUN 11-3-20 (SEQ ID NO: 281 SUN 11-3-21 (SEQ ID NO: 282 SUN 11-3-22 (SEQ ID NO: 283 DOM 11-3-23 (SEQ ID NO: 284 DOM 11-3-24 (SEQ ID NO: 285 DOM 11-3-25 (SEQ ID NO: 286 DOM 11-3-26 (SEQ ID NO: 287 DOM 11-3-27 (SEQ ID NO: 288 DOM 11-3-28 (SEQ ID NO: 289 DOM 11-30-1 (SEQ ID NO: 290 DOM 11-30-2 (SEQ ID NO: 291 DOM 11-30-3 (SEQ ID NO : 292 DOM 11-30-5 (SEQ ID NO: 293 DOM 11-30-6 (SEQ ID NO: 294 DOM 11-30-7 (SEQ ID NO: 295 DOM 11-30-8 (SEQ ID NO: 296 SUN 11-30-9 (SEQ ID NO: 297 SUN 11-30-10 (SEQ ID NO: 298 SUN 11-30-11 (SEQ ID NO: 299 SUN 11-30-12 (SEQ ID NO: 300 SUN 11 -30-13 (SEQ ID NO: 301 DOM 11-30-14 (SEQ ID NO: 302 DOM 11-30-15 (SEQ ID NO: 303 DOM 11-30-16 (SEQ ID NO: 304), and DOM 11-30-17 (SEQ ID NO: 305) In other embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD138, and competes for binding to CD138, with an anti-CD138 domain (dAb) antibody selected from from the group consisting of: DOM12-1 (SEQ ID NO: 289), DOM12-15 (SEQ ID NO: 290), DOM12-17 (SEQ ID NO: 11), DOM12-19 (SEQ ID NO: 291), DOM12-2 (SEQ ID NO: 292), DOM12-20 (SEQ ID NO: 293), DOM12-21 (SEQ ID NO: 294), DOM12-22 (SEQ ID NO: 295), DOM12-3 (SEQ ID NO: 296), DOM12-33 (SEQ ID NO: 297), DOM12-39 (SEQ ID NO: 298), DOM12-4 (SEQ ID NO: 299), DOM12-40 (SEQ ID NO: 300), DOM12 -41 (SEQ ID NO: 301), DOM12-42 (SEQ ID NO: 302), DOM12-44 (SEQ ID NO: 303), DOM12-46 (SEQ ID NO: 304), DOM12-6 (SEQ ID NO. : 305), DOM12-7 (SEQ ID NO: 306), DOM12-10 (SEQ ID NO: 307), DOM12-11 (SEQ ID NO: 308), DOM12-18 (SEQ ID NO: 309), DOM12-23 (SEQ ID NO: 310), DOM12-24 (SEQ ID NO: 311), DOM12-25 (SEQ ID NO: 312), DOM12-26 (SEQ ID NO: 12), DOM12-27 (SEQ ID NO: 313), DOM12-28 (SEQ ID NO: 314), DOM12-29 (SEQ ID NO: 315), DOM12-30 (SEQ ID NO.316), DOM12-31 (SEQ ID NO: 317), DOM12 -32 (SEQ ID NO: 318), DOM12-34 (SEQ ID NO: 319), DOM12-35 (SEQ ID NO: 320), DOM12-36 (SEQ ID NO: 321), DOM12-37 (SEQ ID NO. : 322), DOM12-38 (SEQ ID NO: 323), DOM12-43 (SEQ ID NO: 324), DOM12-45 (SEQ ID NO: 310), DOM12-5 (SEQ ID NO: 325), DOM12- 8 (SEQ ID NO: 326), and DOM12-9 (SEQ ID NO: 327). In certain embodiments, the first single variable immunoglobulin domain or the second unique immunoglobulin variable domain binds to CD138, and competes for binding to CD138, with an anti-CD138 domain (dAb) antibody selected from the group consisting of in: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351), DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353), DOM 12-45-8 (SEQ. ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355), DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357), DOM 12 -45-12 (SEQ ID NO: 358), DOM 12-45-13 (SEQ ID NO: 359), DOM 12-45-14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ ID NO. : 361), DOM 12-45-16 (SEQ ID NO: 362), DOM 12-45-17 (SEQ ID NO: 363), DOM 12-45-18 (SEQ ID NO: 364), DOM 12-45-19 (SEQ ID NO: 365), DOM 12-45-20 (SEQ ID NO: 366), DOM 12-45-21 (SEQ ID NO: 367), DOM 12-45-22 (SEQ ID NO: 368), DOM 12-45-23 (SEQ ID NO: 369), DOM 12-45-24 (SEQ ID NO: 370), DOM 12-45-25 (SEQ ID NO: 371) DOM 12-45-26 (SEQ ID NO: 372) DOM 12-45-27 (SEQ ID NO: 373) DOM 12-45-28 (SEQ ID NO: 374) DOM 12-45-29 (SEQ ID NO: 375) DOM 12-45-30 (SEQ ID NO: 376) DOM 12-45-31 (SEQ ID NO: 377) DOM 12-45-32 (SEQ ID NO: 378) DDOOMM 1122--4455--3333 ((SSEEQQ IIDD NNOO :: 337799)), DOM 12-45-34 (SEQ ID NO: 380) DOM 12-45-35 (SEQ ID NO: 381) DOM 12-45-36 (SEQ ID NO: 382) DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384).

In other embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM12-1 (SEQ ID NO: 289), DOM12-15 (SEQ ID NO: 290), DOM12-17 (SEQ ID NO: 11), DOM12-19 (SEQ ID NO: 291), DOM12-2 (SEQ ID NO: 292) ), DOM12-20 (SEQ ID NO: 293), DOM12-21 (SEQ ID NO: 294), DOM12-22 (SEQ ID NO: 295), DOM12-3 (SEQ ID NO: 296), DOM12-33 (SEQ ID NO: 297), DOM12-39 (SEQ ID NO: 298), DOM12-4 (SEQ ID NO: 299), DOM12-40 (SEQ ID NO: 300), DOM12-41 (SEQ ID NO: 301), DOM12-42 (SEQ ID NO: 302), DOM12-44 (SEQ ID NO: 303), DOM12 - 46 (SEQ ID NO: 304), DOM12-6 (SEQ ID NO: 305), DOM12-7 (SEQ ID NO: 306), DOM12-10 (SEQ ID NO: 307), DOM12-11 (SEQ ID NO. : 308), DOM12-18 (SEQ ID NO: 309), DOM12-23 (SEQ ID NO: 310), DOM12-24 (SEQ ID NO: 311), DOM12-25 (SEQ ID NO: 312), DOM12- 26 (SEQ ID NO: 12), DOM12-27 (SEQ ID NO: 313), DOM12-28 (SEQ ID NO: 314), DOM12-29 (SEQ ID NO: 315), DOM12-30 (SEQ ID NO: 316), DOM12-31 (SEQ ID NO: 317), DOM12-32 (SEQ ID NO: 318), DOM12 -34 (SEQ ID NO: 319), DOM12-35 (SEQ ID NO: 320), DOM12-36 (SEQ ID NO: 321), DOM12-37 (SEQ ID NO: 322), DOM12-38 (SEQ ID NO. : 323), DOM12-43 (SEQ ID NO: 324), DOM12-45 (SEQ ID NO: 310), DOM12-5 (SEQ ID NO: 325), DOM12-8 (SEQ ID NO: 326), and DOM12-9 (SEQ ID NO: 327). In certain embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351), DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353), DOM 12-45-8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355), DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357), DOM 12- 45-12 (SEQ ID NO: 358), DOM 12-45-13 (SEQ ID NO: 359), DOM 12-45-14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ ID NO: 361), DOM 12-45-16 (SEQ ID NO: 362) DOM 12-45-17 (SEQ ID NO: 363), DOM 12-45-18 (SEQ ID NO: 364) DOM 12-45-19 (SEQ ID NO: 365), DOM 12-45-20 (SEQ ID NO: 366) DOM 12-45-21 (SEQ ID NO: 367), DOM 12 -45-22 (SEQ ID NO: 368) DOM 12-45-23 (SEQ ID NO: 369), DOM 12-45-24 (SEQ ID NO: 370) DOM 12-45-25 (SEQ ID NO: 371) ), DOM 12-45-26 (SEQ ID NO: 372) DOM 12-45-27 (SEQ ID NO: 373), DOM 12-45-28 (SEQ ID NO: 374) DOM 12-45-29 (SEQ. ID NO: 375), DOM 12-45-30 (SEQ ID NO: 376) DOM 12-45-31 (SEQ ID NO: 377), DOM 12-45-32 (SEQ ID NO: 378) DOM 12-45 -33 (SEQ ID NO: 379), DOM 12-45-34 ((SSEEQQ IIDD NNOO :: 338800)), DOM 12-45-35 (SEQ ID NO: 381), DOM 12-45-36 (SEQ ID NO: 382), DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384). In other embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CEA, and competes for binding to CEA, with an anti-CEA domain (dAb) antibody selected from the group consisting of: DOM13-1 (SEQ ID NO: 328), DOM13-12 (SEQ ID NO: 329), DOM13-13 (SEQ ID NO: 330), DOM13-14 (SEQ ID NO: 331), DOM13-15 (SEQ ID NO: 332), DOM13-16 (SEQ ID) NO: 333), DOM13-17 (SEQ ID NO: 334), DOM13-18 (SEQ ID NO: 335), DOM13-19 (SEQ ID NO: 336), DOM13-2 (SEQ ID NO: 337), DOM13-20 (SEQ ID NO: 338), DOM13-21 (SEQ ID NO: 339), DOM13-22 (SEQ ID NO: 340), DOM13-23 (SEQ ID NO: 341), DOM13-24 (SEQ.

ID NO: 342), DOM13-25 (SEQ ID NO: 13), DOM13-26 (SEQ ID NO: 343), DOM13-27 (SEQ ID NO.344), DOM13-28 (SEQ ID NO: 345), DOM13-29 (SEQ ID NO: 346), DOM13-3 (SEQ ID NO: 347), DOM13-30 (SEQ ID NO: 348), DOM13-31 (SEQ ID NO: 349), DOM13-32 (SEQ ID NO: 350), DOM13-33 (SEQ ID NO: 351), DOM-13-34 (SEQ ID NO: 352), DOM13-35 (SEQ ID NO: 353), DOM13-36 (SEQ ID NO: 354) , DOM13-37 (SEQ ID NO: 355), DOM13-4 (SEQ ID NO: 356), DOM13-42 (SEQ.

ID NO: 357), DOM13-43 (SEQ ID NO: 358), DOM13-44 (SEQ ID NO: 359), DOM13-45 (SEQ ID NO: 360), DOM13-46 (SEQ ID NO: 361), DOM13-47 (SEQ ID NO: 362), DOM13-48 (SEQ ID NO: 363), DOM13-49 (SEQ ID NO: 364), DOM13-5 (SEQ ID NO: 365), DOM13-50 (SEQ ID NO: 366), DOM13-51 (SEQ ID NO: 367), DOM13-52 (SEQ ID NO: 368), DOM13-53 (SEQ ID NO: 369), DOM13-54 (SEQ ID NO: 370), DOM13-55 (SEQ ID NO: 371), DOM13-56 (SEQ ID NO: 372), DOM13 -57 (SEQ ID NO: 14), DOM13-58 (SEQ ID NO: 15), DOM13-59 (SEQ ID NO: 16), DOM13-6 (SEQ ID NO: 373), DOM13-60 (SEQ ID NO. : 374), DOM13-61 (SEQ ID NO: 375), DOM13-62 (SEQ ID NO: 376), DOM13-63 (SEQ ID NO: 377), DOM13-64 (SEQ ID NO: 17), DOM13- 65 (SEQ ID NO: 18), DOM13-66 (SEQ ID NO: 378), DOM13-67 (SEQ ID NO: 379), DOM13-68 (SEQ ID NO: 380), DOM13-69 (SEQ ID NO: 381), DOM13-7 (SEQ ID NO: 382), DOM13-70 (SEQ ID NO: 383), DOM13-71 (SEQ ID NO: 384), DOM13-72 (SEQ ID NO: 385), DOM13-73 (SEQ ID NO: 386), DOM13-74 (SEQ ID NO: 19), DOM13-75 (SEQ ID NO: 387), DOM13-76 (SEQ ID NO: 388), DOM13-77 (SEQ ID NO: 389), DOM13 -78 (SEQ ID NO: 390), DOM13-79 (SEQ ID NO: 391), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO: 393), DOM13-81 (SEQ ID NO. : 394), DOM13-82 (SEQ ID NO: 395), DOM13-83 (SEQ ID NO: 396), DOM13-84 (SEQ ID NO: 397), DOM13-85 (SEQ ID NO: 398), DOM13- 86 (SEQ ID NO: 399), DOM13-87 (SEQ ID NO: 400), DOM13-88 (SEQ ID NO: 401), DOM13-89 (SEQ ID NO: 402), DOM13-90 (SEQ ID NO: 403), DOM13-91 (SEQ ID NO: 404), DOM13-92 (SEQ ID NO: 405), DOM13-93 (SEQ ID NO: 20), DOM13-94 (SEQ ID NO: 406), and DOM13-95 (SEQ ID NO: 21). In certain embodiments, the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain binds to CEA, and competes for CEA binding, with an anti-CEA domain (dAb) antibody selected from the group consisting of in: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25- 80 (SEQ ID NO: 476). In other embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM13-1 (SEQ ID NO: 328), DOM13-12 (SEQ ID NO: 329), DOM13-13 (SEQ ID) NO: 330), DOM13-14 (SEQ ID NO: 331), DOM13-15 (SEQ ID NO: 332), DOM13-16 (SEQ ID NO: 333), DOM13-17 (SEQ ID NO: 334), DOM13 -18 (SEQ ID NO: 335), DOM13-19 (SEQ ID NO: 336), DOM13-2 (SEQ ID NO: 337), DOM13-20 (SEQ ID NO: 338), DOM13-21 (SEQ ID NO. : 339), DOM13-22 (SEQ ID NO: 340), DOM13-23 (SEQ ID NO: 341), DOM13-24 (SEQ ID NO: 342), DOM13-25 (SEQ ID NO: 13), DOM13- 26 (SEQ ID NO: 343), DOM13-27 (SEQ ID NO: 344), DOM13-28 (SEQ ID NO: 345), DOM13-29 (SEQ ID NO: 346), DOM13-3 (SEQ ID NO: 347), DOM13-30 (SEQ ID NO: 348), DOM13-31 (SEQ ID NO: 349), DOM13-32 (SEQ ID NO: 350), DOM13-33 (SEQ ID NO: 351), DOM-13 -34 (SEQ ID NO: 352), DOM13-35 (SEQ ID NO: 353), DOM13-36 (SEQ ID NO: 354), DOM13-37 (SEQ ID NO: 355), DOM13-4 (SEQ ID NO: 356), DOM13-42 (SEQ ID NO: 357), DOM13-43 (SEQ ID NO: 358), DOM13-44 (SEQ ID NO: 359), DOM13-45 (SEQ ID NO: 360), DOM13-46 (SEQ ID NO: 361), DOM13-47 (SEQ ID NO: 362), DOM13-48 (SEQ ID NO: 363), DOM13-49 (SEQ ID NO: 364), DOM13-5 (SEQ ID NO: 365), DOM13-50 (SEQ ID NO: 366), DOM13-51 (SEQ ID NO: 367), DOM13 -52 (SEQ ID NO: 368), DOM13-53 (SEQ ID NO: 369), DOM13-54 (SEQ ID NO: 370), DOM13-55 (SEQ ID NO: 371), DOM13-56 (SEQ ID NO. : 372), DOM13-57 (SEQ ID NO: 14), DOM13-58 (SEQ ID NO: 15), DOM13-59 (SEQ ID NO: 16), DOM13-6 (SEQ ID NO: 373), DOM13-60 (SEQ ID NO: 374), DOM13-61 (SEQ ID NO: 375), DOM13-62 (SEQ ID NO: 376), DOM13-63 (SEQ ID NO: 377), DOM13-64 (SEQ ID NO: 17), DOM13-65 (SEQ ID NO: 18), DOM13-66 (SEQ ID NO: 378), DOM13 -67 (SEQ ID NO: 379), DOM13-68 (SEQ ID NO: 380), DOM13-69 (SEQ ID NO: 381), DOM13-7 (SEQ ID NO: 382), DOM13-70 (SEQ ID NO: 383), DOM13-71 (SEQ ID NO: 384), DOM13-72 (SEQ ID NO: 385), DOM13 -73 (SEQ ID NO: 386), DOM13-74 (SEQ ID NO: 19), DOM13-75 (SEQ ID NO: 387), DOM13-76 (SEQ ID NO: 388), DOM13-77 (SEQ ID NO. : 389), DOM13-78 (SEQ ID NO: 390), DOM13-79 (SEQ ID NO: 391), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO: 393), DOM13- 81 (SEQ ID NO: 394), DOM13-82 (SEQ ID NO: 395), DOM13-83 (SEQ ID NO: 396), DOM13-84 (SEQ ID NO: 397), DOM13-85 (SEQ ID NO: 398), DOM13-86 (SEQ ID NO: 399), DOM13-87 (SEQ ID NO: 400), DOM13-88 (SEQ ID NO: 401), DOM13-89 (SEQ ID NO: 402), DOM13-90 (I KNOW THAT ID NO: 403), DOM13-91 (SEQ ID NO: 404), DOM13-92 (SEQ ID NO: 405), DOM13-93 (SEQ ID NO: 20), DOM13-94 (SEQ ID NO: 406), and DOM13-95 (SEQ ID NO: 21). In certain embodiments, the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). In other embodiments, the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain binds to CD56, and competes for binding with CD56, with an anti-CD56 domain (dAb) antibody, selected from the group that consists of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487) ), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14-20 ( SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495) , DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ.

ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14 -44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO. : 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14 -60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO. : 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14- 68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). In other embodiments, the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a selected dAb. from the group consisting of: DOM 14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482) ), DOM14-12 (SEQ ID NO.483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 ( SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ.

ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO.479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14 -35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO. : 508), DOM14-4 (SEQ ID NO.480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO.513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14 -50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO. : 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO-.525), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14 -59 (SEQ ID NO: 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ.

ID NO: 532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). In more particular embodiments, the first single variable domain of immunoglobulin has a binding site with a binding specificity of CD38, and the second single variable domain of immunoglobulin has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD138, CEA, CD56, CEGF, EGFR, and HER2. In certain embodiments, the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD138. In another embodiment, the first single variable domain of immunoglobulin has a binding site with a binding specificity for CD138, and the second single variable domain of immunoglobulin has a binding site with a binding specificity for a selected cell surface target to from the group consisting of CD38, CEA, CD56, CEGF, EGFR, and HER2. In certain embodiments, the second unique immunoglobulin variable domain has a binding site with a binding specificity for CEA. In other embodiments, the first single variable domain of immunoglobulin has a binding site with a binding specificity for CEA, and the second unique variable domain of immunoglobulin has a binding site with a binding specificity for a selected cell surface target to from the group consisting of CD38, CEA, VEGF, EG FR, and H ER2. In certain modalities, the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD56. If desired, the ligand may additionally comprise a toxin, such as a surface activity toxin. The surface activity toxin may comprise a free radical generator or a radionuclide. In some embodiments, the ligand further comprises a fraction that prolongs the half-life, such as a polyalkylene glycol fraction, serum albumin or a fragment thereof, transferrin receptor or a transferrin binding portion thereof, or an antibody or antibody fragment comprising a binding site for a polypeptide that improves the half-life in vivo. In some embodiments, the fraction that prolongs the half-life is a polyethylene glycol fraction. In other embodiments, the half-life-prolonging fraction is an antibody or an antibody fragment, such as a single immunoglobulin variable domain, which comprises a binding site for serum albumin or the neonatal Fc receptor.

In particular embodiments, the fraction that prolongs the half-life is a single variable domain of immunoglobulin that competes for binding to human serum albumin with a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO.552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h -7 (SEQ ID NO: 477), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO.563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r -20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578) ), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 ( SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). In another embodiment, the fraction that prolongs the half-life is a single variable domain of immunoglobulin that binds to serum albumin, and that comprises an amino acid sequence that has an amino acid sequence identity of at least 90 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r -1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO. : 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h -6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO. : 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h -25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ. ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r -28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO. : 584), and DOM7r-33 (SEQ ID NO: 585). In another aspect, the ligand comprises a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, a second polypeptide domain having a binding site with a binding specificity for a second target cell surface, and at least a fraction of toxin; wherein the first cell surface target and the second cell surface target are different, and the first cell surface target and the second cell surface target are present in a pathogenic cell; wherein this ligand binds to the first cell surface target and to the second cell surface target on the pathogenic cell with an avidity of between about 1 0"6M and about 10" 2M; and where this ligand is internalized by this pathogenic cell. As described herein, the toxin may be a toxin of surface activity. The surface activity toxin may comprise a free radical generator or a radionuclide. In a preferable way, the ligand is internalized preferentially by a pathogenic cell. For example, the ligand is not substantially internalized by an individual or normal positive cell, or selectively binds with a pathogenic cell. In some embodiments, the ligand selectively binds to a pathogenic cell when this ligand is present at a concentration that is between about 1 pM and about 150 nM. The invention also relates to a ligand for use in therapy or diagnosis, and to the use of a ligand for the manufacture of a medicament for the treatment of a disease as described herein (eg, cancer, multiple myeloma, carcinoma). pulmonary). The invention also relates to the use of a ligand for the manufacture of a medicament for selectively killing cancer cells on normal cells. The invention also relates to the use of a ligand for the manufacture of a medicament for delivering a therapeutic agent intracellularly. The invention also relates to the use of a ligand for the manufacture of a medicament for delivering a therapeutic agent to a compartment of cathepsin B in a cell. The invention also relates to the use of a ligand for the manufacture of a medicament for locating the ligand in a compartment of cathepsin B in a cell. The invention also relates to a method for the treatment of a disease, which comprises administering to a subject in need, a therapeutically effective amount of a ligand of the invention. In some embodiments, the disease is cancer, e.g., multiple myeloma or lung cancer (e.g., microcellular lung carcinoma).

The invention also relates to a method for delivering a therapeutic agent (eg, a toxin) internally to a cell, which comprises contacting a cell with a ligand of the invention. The invention also relates to a composition (e.g., a pharmaceutical composition), which comprises a ligand of the invention and a physiologically acceptable carrier. In some embodiments, the composition comprises a vehicle for intravenous, intramuscular, intraperitoneal, intra-arterial, intrathecal, intra-articular, or subcutaneous administration. In other embodiments, the composition comprises a vehicle for pulmonary, intranasal, vaginal, or rectal administration. The invention also relates to a drug delivery device, which comprises the composition of the invention. In some embodiments, the drug delivery system is selected from the group consisting of a parenteral delivery device, an intravenous delivery device, an intramuscular delivery device, an intraperitoneal delivery device, a transdermal delivery device, a pulmonary delivery device, an intra-arterial delivery device, an intrathecal delivery device, an intra-articular delivery device, a subcutaneous delivery device, an intranasal delivery device, a vaginal delivery device, and a delivery device rectal. In other embodiments, the drug delivery system is selected from the group consisting of a syringe, a transdermal delivery device, a capsule, a tablet, a nebulizer, an inhaler, an atomizer, an aerosolizer, a fog nebulizer fine, a dry powder inhaler, a metered dose inhaler, a metered dose sprayer, a metered dose nebulizer, a metered dose sprayer, and a catheter. The invention also relates to an isolated or recombinant nucleic acid encoding a ligand of the invention, and to a vector comprising the recombinant nucleic acid of the invention, and to a host cell comprising the recombinant nucleic acid or the vector of the invention. The invention also relates to a method for producing a ligand, which comprises maintaining a host cell of the invention under conditions suitable for the expression of the nucleic acid or the vector of the invention, whereby a ligand is produced. In some embodiments, the method further comprises isolating the ligand. In some embodiments, the ligand of the invention is internalized by the cells that contain the cell surface targets. For example, at least about 40 percent, or at least about 50 percent, or at least about 60 percent, or at least about 70 percent, or at least about 80 percent, or at least about 90 percent, or substantially all of the ligand, is internalized by a cell (e.g., the ligand that binds to a double positive cell or a pathogenic cell). The invention also relates to the domain antibodies disclosed herein, and to ligands and formats comprising them. The invention also relates to isolated or recombinant nucleic acids encoding the domination antibodies disclosed herein, and to vectors comprising the recombinant nucleic acid, and to host cells comprising the recombinant nucleic acid or the vector. The invention also relates to a method for producing a dAb as disclosed herein, or a ligand or format comprising this dAb, which comprises maintaining a host cell of the invention under conditions suitable for the expression of the nucleic acid or of the vector of the invention, whereby a dAb disclosed herein is produced, or a ligand or format comprising this dAb. In some modalities, the method further comprises isolating the ligand. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A-1H are fluorescence histograms showing the binding specificity of the dAbs that bind to CD38, CD 1 38, CEA, or CD56. Figures 1A and 1B show that dAbs that bind to CD38 (DOM 1 1 -3 and DOM 1 1-30) bind to CD38 + cells (RPM l cells), but not to CD38- cells (cells K299). Figures 1 C and 1 D show a dAb that binds to CD1 38 (DOM 1 2-45), which binds to CD1 38 + cells (RPMl cells), but not to CD138- cells (K299 cells). Figures 1E and 1F show that a dAb that binds to CEA (DOM13-25) binds to CEA + cells (H69 cells), but not to CEA- cells (CHO cells). Figures 1G and 1H show that a dAb that binds to CD56 (DOM14-23) binds to CD56 + cells (H69 cells), but not to CD56- cells (CHO cells). Figure 2 is a sensorgram illustrating the binding and dissociation of dAbs that bind to CD38 (DOM11-3 and DOM11-30), as determined by surface plasmon resonance. The affinity (KD) of DOM11-3 was determined at 250 nM, and the affinity of DOM11-30 was determined at 150 nM. Figures 3A-3D are sensograms showing that the dAbs that bind to CD38 (DOM11-3, DOM11-30, and DOM11-23) bind to different epitopes on CD38. CD38 was immobilized on a surface plasmon resonance chip, and a first anti-CD38 dAb was flowed on the surface (first arrow), then a second dAb was flowed on the surface (second arrow). The figures show that DOM11-30 was linked to CD38 that had DOM11-3 already bound to it (Figure 3A), that DOM11-23 was linked to CD38 that had DOM11-30 already bound to it (Figure 3B), and that DOM11-3 was linked to CD38 that had DOM11-23 already bound to it (Figure 3C), demonstrating that these dAbs bind to different epitopes on the CD38 antigen. In contrast, the DOM11-30 flow on CD38 that had DOM11-30 already bound to it, did not result in a greater link.

Figures 4A-4D are graphs of fluorescence dots showing that a ligand that binds CD38 and CD138 (DOM11-3 / DOM12-45) (50 nM), selectively binds with double positive RPMI82265 cells (CD38 + / CD138 + ). DOM11-3 / DOM12-45 did not bind substantially with the individual Raji positive cells (CD38 + / CD138-), or with the H647 cells (CD38- / CD138 +), or with the negative double cells (CCRF-CEM). Figures 5A-5C are photomicrographs showing that the Raji cell line (CD38 +) was labeled with a ligand that was linked to CD38 and CD138 (DOM11-3 / DOM12-45) (500 nM). The ligand was visualized using secondary and tertiary reagents (labeled with FTIC), and a confocal microscope (Zeiss LSM510 META). Cells were maintained at 4 ° C to inhibit internalization, or at 37 ° C to allow internalization. Figures 4A and 4B show that DOM11-3 / DOM12-45 bound to Raji cells, but were not substantially internalized at 4 ° C, as shown by the lack of acid-resistant fluorescence in Figure 4B. In contrast, Figure 4C shows acid-resistant fluorescence at 37 ° C, demonstrating that DOM11-3 / DOM12-45 was internalized. Figures 6A-6C are fluorescent histograms showing that a ligand that binds to CD38 and CD138 (DOM11-3 / DOM12-45), binds to the double positive myeloma cell line (OPM2, CD38 + / CD138 +). OPM2 cells were treated with DOM11-3 / DOM12-45 at 4 ° C or at 37 ° C, as described in Figures 5A-5C. The acid-resistant fluorescence was detected at 37 ° C, demonstrating that the ligand was internalized. In contrast, very little acid-resistant fluorescence was detected at 4 ° C, or in cells treated with a dAb that does not bind to CD38 or CD1 38 (false Vk), indicating that the ligand and dAb were not internalized. Figure 7 is a series of photomicrographs showing the co-localization of a ligand that bound to CD38 and CD 1 38 (DOM 1 1 -3 / DOM 1 2-45) (green fluorescence), with the lysosomal marker, cathepsin B (red fluorescence), in Raji cells, using the confocal microscope. The co-localized ligand and cathepsin B are shown in the overlay panels as the yellow fluorescence. Figures 8A-8E are fluorescence histograms showing that a ligand that binds CD38 and CD1 38 (DOM 1 1-3 / DOM 1 2-45; da-dAb), which were pegylated with the linear PEG of 5K (FIG. Figure 8B), 20K (Figure 8C), 30K (Figure 8D), or 40K (Figure 8E), was internalized to approximately the same degree as the non-pegylated ligand (Figure 8A) at 37 ° C. The Figures show the fluorescence of acid resistance for each ligand at 37 ° C, demonstrating that the ligands were internalized. Figures 9A-9D are fluorescence histograms showing that a ligand that bound to CD38 and CD1 38, and that contained a toxin (selenium) (DOM 1 1 -3 / DOM 1 2-45-Se), was internalized until the same degree as the corresponding ligand that did not contain a toxin (DOM 1 1 -3 / DOM 1 2-45) by the OPM2 cells. The figures show the fluorescence of acid resistance for DOM11-3 / DOM12-45-Se and DOM11-3 / DOM12-45 at 37 ° C, demonstrating that the ligands were internalized. In contrast, ligands that did not bind to CD38 or CD138 (Vk false / Vk false and Vk false / Vk false-Se) did not bind to the cells or become internalized. Figure 10 is a histogram showing apoptosis of the OPM2 MM cell line (CD38 + / CD138 +), and cells that did not express CD38 or CD138 (antigen -ve cell line) induced by camptothecin, a ligand that bound to CD38 and CD138, and containing a toxin (selenium) (DOM11-3 / DOM12-45-Se), a ligand that bound to CD38 and CD138 (DOM11-3 / DOM12-45), a ligand that did not bind to CD38 and CD138, and containing a toxin (selenium (Vkd Se), and a ligand that did not bind to CD38 and CD138 (Vkd) .The results show that DOM11-3 / DOM12-45- Cell line apoptosis was selectively induced OPM2 MM double positive, while camptothecin induced apoptosis of both cell lines, and DOM11-3 / DOM12-45, Vkd Se, and Vkd did not induce apoptosis in any cell line Figure 11 is a histogram showing that a ligand which was linked to CD38 and CD138, and which contained a toxin (selenium) (DOM11-3 / DOM12-45-Se; 38/138 Se), selectively induced cell death (reduced cell viability) of double positive OPM2 cells (CD38 + / CD138 +), but not of individual Raji positive cells (CD38 + / CD138) or double negative CEM cells (CD38- / CD138-). The corresponding ligand that did not contain a toxin (DOM11-3 / DOM12-45; 38 / 138-), a ligand that did not bind to CD38 or CD138 (VKD / VKD-), and a ligand that did not bind to CD38 or CD138 and containing a toxin (selenium) (VKD / VKD Se), did not reduce the cell viability of any of the cell lines. Figure 12 is a fluorescence histogram showing that a ligand that bound CEA and CD56 (DOM14-23 / DOM13-25), bound to double positive H69 cells (CEA + / CD56 +), but that the ligands that were bound to CD56 but not to CEA (DOM14-23 / false Vk), and a ligand that bound CEA but not CD56 (Vk false / DOM13-25), did not bind to H59 cells. Vk false is a dAb that does not bind to CEA or CD56. Figures 13A-13G illustrate the nucleotide sequences for several human anti-CD38 dAbs. Figures 14A-14G illustrate the nucleotide sequences for several human anti-CD138 dAbs. Figures 15A-15O illustrate the nucleotide sequences for various human anti-CEA dAbs. Figures 16A-16K illustrate the nucleotide sequences for several human anti-CD56 dAbs. Figures 17A-17F illustrate the amino acid sequences for several human anti-CD38 dAbs. Figures 18A-18F illustrate the amino acid sequences for several human anti-CD138 dAbs. Figures 19A-19G illustrate the amino acid sequences for various human anti-CEA dAbs. Figures 20A-20E illustrate the amino acid sequences for several human anti-CD56 dAbs. Figure 21A is an alignment of the three Vk amino acid sequences that bind to mouse serum albumin (MSA). The aligned amino acid sequences are from Vks designated as MSA16, which is also referred to as DOM7m-16 (SEQ ID NO: 541), MSA 12, which is also referred to as DOM7m-12 (SEQ ID NO: 542), and MSA 26, which is also referred to as DOM7m-26 (SEQ ID NO: 543). Figure 21B is an alignment of six Vk amino acid sequences that are linked to rat serum albumin (RSA). The aligned amino acid sequences are from Vks designated as DOM7r-1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO. : 547), DOM7r-7 (SEQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549). Figures 21C is an alignment of the six Vk amino acid sequences that bind to human serum albumin (HSA). The aligned amino acid sequences are from Vks designated as DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 554), and DOM7h-7 (SEQ ID NO: 555).

Figure 21D is an alignment of the amino acid sequences of seven VHs that bind to human serum albumin, and a sequence in consensus (SEQ ID NO: 556). The aligned sequences are from VHs designated as DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO. : 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), and DOM7h-27 (SEQ ID NO: 563). Figure 21E is an alignment of the three Vk amino acid sequences that bind to human serum albumin and to rat serum albumin. The aligned amino acid sequences are from Vks designated as DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566). Figure 22 is an illustration of the amino acid sequences of the Vks that bind to rat serum albumin (RSA). The illustrated sequences are from Vks designated as DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO. : 570), DOM7r-19 (SEQ ID NO: 571). Figures 23A-23B are an illustration of the amino acid sequences of VHs that are linked to rat serum albumin (RSA). The illustrated sequences are from VHs designated as DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO. : 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r- 28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). Figure 24 illustrates the amino acid sequence of several VHHS camelids that bind to mouse serum albumin, which are disclosed in International Publication Number WO 2004/041862. Sequence A (SEQ ID NO: 586), Sequence B (SEQ ID NO: 587), Sequence C (SEQ ID NO: 588), Sequence D (SEQ ID NO: 589), Sequence E (SEQ ID NO: 590), Sequence F (SEQ ID NO: 591), Sequence G (SEQ ID NO: 592), Sequence H (SEQ ID NO: 593), Sequence I (SEQ ID NO: 594), Sequence J (SEQ ID NO: 595), Sequence K (SEQ ID NO: 596), Sequence L (SEQ ID NO: 597), Sequence M (SEQ ID NO: 598), Sequence N (SEQ ID NO: 599), Sequence O (SEQ ID NO: 600), Sequence P (SEQ ID NO: 601), Sequence Q (SEQ ID NO: 602). Figure 25 is a graph illustrating the cell binding assay for dAb combinations on OMP2 multiple myeloma cells. The EC50 for DOM 11-3-1 / DOM 12-45-2 was 13.81, from 16.73 for DOM 11-3-15 / DOM 12-45-2, from 11.88 for SUN 11-3-20 / DOM 12- 45-2, from 11.0 for DOM 11-3-23 / DOM 12-45-2, and from 44.35 for DOM 11-3 / DOM 12-45. Figures 26A-26D illustrate the nucleic acid sequence for several affinity-matured human anti-CD38 dAbs. Figures 27A-27C illustrate the nucleic acid sequence for several affinity-matured human anti-CD38 dAbs. Figures 28A-28G illustrate the nucleic acid sequence for several affinity-matured human anti-CD1 38 dAbs. Figure 29 illustrates the anti-CD38 / anti-CD1 38 amino acid sequence (DOM 1 1 -3 / DOM 1 2-45) (SEQ ID NO: 677), the anti-CD38 / anti-CD1 nucleic acid sequence 38 (DOM 1 1 -3 / DOM 12-45) (SEQ ID NO: 678), the false Vk amino acid sequence (SEQ ID NO: 679), and the false Vk nucleic acid sequence (SEQ ID NO: 680) ). Figure 30 illustrates the nucleic acid sequences encoding several affinity-matured human anti-CEA dAbs. Figures 31 A-31 C illustrate the amino acid sequence and / or the nucleic acid sequence of several human dAbs. The three residues of alanine (AAA) in the C term of the amino acid sequence of dAb DOM 14-3A, are not part of the amino acid sequence of the real dAb, but are encoded by the cloning site. DETAILED DESCRIPTION OF THE INVENTION Within this specification, modalities have been described in a manner in which it is possible to write a clear and concise descriptive memory, but it is intended and appreciated that the modalities may be combined differently or separated. without departing from the invention. As used herein, the term "ligand" refers to a polypeptide comprising a first polypeptide domain having a binding site that has binding specificity for a first cell surface target, and a second polypeptide domain that it has a binding site that has link specificity for a second cell surface target. The first cell surface target and the second cell surface target are not the same (ie, they are different targets (eg, proteins)), but are both present (eg, co-expressed) in a cell, such as a pathogenic cell, as described herein. A ligand of the invention binds to a cell that contains the first cell surface target and the second cell surface target more strongly (eg, with greater avidity) than a cell that contains only one target. In accordance with the foregoing, a ligand of the invention can be selectively linked to a cell containing the first cell surface target and the second cell surface target. The ligands of the invention can bind to cell surface targets that are both present in normal cells, but that are present at higher levels in a pathogenic cell. Under these circumstances, the ligand can be used to preferentially deliver a therapeutic agent (eg, a toxin) to the pathogenic cell. For example, because of the higher level of cell surface targets on the pathogenic cell, more ligand will bind to the pathogenic cell and be internalized more than will be bound and internalized in the normal cell. Accordingly, an effective amount of toxin can be delivered preferentially to the pathogenic cell.

Ligands according to the invention preferably comprise immunoglobulin variable domains having different binding specificities, and which do not contain pairs of variable domains having the same specificity. Preferably, each domain has a binding site that has binding specificity for a cell surface target, is a single immunoglobulin variable domain (eg, a single immunoglobulin heavy chain variable domain (eg V, VH H). ), a single immunoglobulin light chain variable domain (e.g., VL)) that has binding specificity for a desired cell surface target (e.g., a membrane protein, such as a receptor protein). Each polypeptide domain having a binding site that has binding specificity for a cell surface target can also comprise one or more complementarity determining regions (CDRs) of an antibody or antibody fragment (eg, a single variable domain). of immunoglobulin), having binding specificity for a desired cell surface target in a suitable format, such that the binding domain has binding specificity for the cell surface target. For example, CDRs can be grafted onto a suitable protein scaffold or skeleton, such as an affibody, a SPA scaffold, a class A LDL receptor domain, or an EGF domain. In addition, the ligand may be bivalent (heterobivalent) or multivalent (heteromultivalent), as described herein. Therefore, "ligands" include polypeptides comprising two dAbs, wherein each dAb binds to a different cell surface target. The ligands also include polypeptides comprising at least two dAbs that bind to different cell surface targets (or the CDRs of a dAbs) in a suitable format, such as in an antibody format (e.g., IgG type format, scFv, Fab, Fab ', F (ab') 2), or a suitable protein scaffold or skeleton, such as an affibody, a SPA scaffold, a class A LDL receptor domain, an EGF domain, an avimer, and multispecific ligands, as described herein. The polypeptide domain having a binding site that has binding specificity for a cell surface target (ie, first or second cell surface target), can also be a protein domain comprising a binding site for a target desired protein, for example, a protein domain selected from an affibrant, a SPA domain, an LDL class A receptor domain, an avimer (see, for example, Patent Application Publications of the United States of America Numbers 2005). / 0053973, 2005/0089932, 2005/01 64301). As used herein, the phrase "objective" refers to a biological molecule (e.g., peptide, polypeptide, protein, lipid, carbohydrate), with which a polypeptide domain having a binding site can be linked . The target can be, for example, an intracellular target (e.g., an intracellular protein target), or a cell surface target (e.g., a membrane protein, a receptor protein). Preferably, an objective is a cell surface target, such as a cell surface protein. Preferably, the first cell surface target and the second cell surface target are both present in a pathogenic cell (eg, a cancer cell, a tumor cell). For example, the first cell surface target and the second cell surface target can be co-expressed in a cell (eg, a pathogenic cell). The first cell surface target and the second cell surface target may be individually present in certain normal cells, and may both be present in the pathogenic cells (e.g., are co-expressed in cancer cells, are co-expressed in tumor cells). Certain suitable targets (for example, certain first cell surface targets and certain second cell surface targets) could both be present in normal cells. In these situations, targets are expressed at low levels in normal cells, but are expressed at higher levels, for example, in pathogenic cells. For example, a first cell surface target and a second cell surface target may be present in a pathogenic cell at levels that are at least about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or at least about 10 times higher than the levels in normal cells. The level of an objective in a cell (for example, the amount of target on the surface of a cell) can be determined using a variety of suitable methods, such as antibody binding and flow cytometry. As used herein, the term "pathogenic cell" refers to a cell with an altered cellular physiology, which can produce or contribute to pathogenic production (eg, cancer). A pathogenic cell can be, for example, a cell that hosts one or more mutations that alter the regulation of normal cellular processes of division, proliferation, differentiation, senescence, and / or cell death. Particular pathogenic cells include cancer cells, such as carcinoma cells, lymphoma cells, myeloma cells, sarcoma cells, and the like. The phrase "single immunoglobulin variable domain" refers to a variable region of antibody (VH, VH H >; VL) that binds specifically to a target, antigen or epitope, independently of other V domains; however, as the term is used herein, a single immunoglobulin variable domain may be present in one format (eg, hetero-multimer) with other variable regions or variable domains, where the other regions or domains are not required. for antigen binding by the single immunoglobulin variable domain (ie, where the single immunoglobulin variable domain binds to the antigen independently of the additional variable domains). Each "single immunoglobulin variable domain" encompasses not only a single variable domain polypeptide of isolated antibody, but also larger polypeptides comprising one or more monomers of a single variable antibody domain polypeptide sequence. A "domain antibody" or "dAb" is the same as a "single variable immunoglobulin domain" polypeptide, as the term is used herein. A single immunoglobulin variable domain polypeptide, as used herein, refers to a variable single-domain polypeptide of mammalian immunoglobulin, preferably human, but also includes rodent (e.g., as given to know in the International Publication Number WO 00/29004, the content of which is incorporated herein by reference in its entirety), or the VH H camelid dAbs. As used herein, camelid dAbs are single-variable immunoglobulin domain polypeptides that are derived from species including camel, llama, alpaca, dromedary, and guanaco, and comprise heavy chain antibodies naturally devoid of light chain : (VH H) - Similar dAbs can be obtained for single-chain antibodies from other species, such as nurse shark. Preferred ligands comprise at least two different polypeptides from a single immunoglobulin variable domain, or at least two different dAbs. As used herein, "selectively binds" refers to the ligand capacity of the invention to preferentially bind with double positive cells on individual positive cells. For example, the ligand of the invention can bind to the double positive cells but does not bind substantially with the individual positive cells. A ligand "does not bind substantially" with individual positive cells when the amount of binding to individual positive cells is not greater than about 25 percent, about 24 percent, of about 23 percent, of about 22 percent, from about 21 percent, from about 20 percent, from about 1 percent, from about 1 percent, from about 1 percent, to about 1 percent; from about 1 5 percent, from about 14 percent, from about 1 3 percent, from about 12 percent, from about 1 1 percent, from about 1 0 percent, from about 9 percent percent, from about 8 percent, from about 7 percent, from about 6 percent, from about 5 percent, from about 4 percent, from about 3 percent, approximately 2 percent, or approximately 1 percent of the bond with double positive cells under the same binding conditions. The selective binding can be influenced, for example, by the affinity and avidity of the ligand, and by the concentration of the ligand. The person of ordinary skill in the art can determine the appropriate conditions under which the ligands of the invention selectively bind to the positive double cells using any suitable methods, such as titration of the ligand in a suitable cell binding assay. As used herein, the term "double positive" refers to a cell that contains two different cell surface targets (different target species) that are linked by a ligand of the invention. Ligands of the invention bind to double positive cells with high avidity. As used herein, the term "individual positive" refers to a cell that only contains a cell surface target that is linked by a ligand of the invention. As used herein, the terms "internalize", "internalized", and "internalization", and related variant terms, refer to the cellular processes by which the ligands are carried into the cell (e.g. endocytosis), after binding to the first cell surface target and to the second cell surface target. Internalization can be mediated by clathrin-coated orifice endocytosis followed by ligand-induced aggregation of cell surface targets. Once endocytogenated, the ligands can be delivered to the lysosomal compartment of the cell, where cellular enzymes, such as cathepsin B, can dissociate portions of the ligand (for example, they can dissociate a linker to release a toxin from the ligand). "Affinity" and "avidity" are terms of the technique that describe the strength of a bonding interaction. With respect to the ligands of the invention, avidity refers to the overall binding force between the targets (eg, first cell surface target and second cell surface target) on the cell and the ligand. Avidity is more than the sum of individual affinities for individual goals. As used herein, "toxin fraction" refers to a fraction comprising a toxin. A toxin is an agent that has detrimental effects on, or that alters cellular physiology (eg, causes cell necrosis, apoptosis, or inhibits cell division). As used herein, the term "dose" refers to the amount of ligand administered to a subject all at once (unit dose), or in two or more administrations for a defined time interval. For example, the dose may refer to the amount of ligand (e.g., the ligand comprising a single variable domain of immunoglobulin that binds to CEA, and a single variable domain of immunoglobulin that binds to CD56) administered to a subject during the course of 1 day (24 hours) (daily dose), two days, one week, two weeks, three weeks, or one or more months (for example, by a single administration, or by two or more administrations). The interval between the doses can be any desired amount of time. As used herein, "complementary" refers to when two immunoglobulin domains belong to families of structures that form pairs or cognate groups, or that are derived from such families and retain this feature. For example, a VH domain and a VL domain of an antibody are complementary; two VH domains are not complementary, and two V domains are not complementary. The complementary domains can be found in other members of the immunoglobulin super family, such as the Va and Vß domains (or y and d) of the T-cell receptor. Domains that are artificial, such as domains based on protein scaffolds that do not bind epitopes unless designed to do so, are not complementary. In the same way, two domains based (for example) on an immunoglobulin domain and a fibronectin domain, are not complementary. As used herein, "Immunoglobulin" refers to a family of polypeptides that retain the immunoglobulin fold characteristic of the antibody molecules, which contains two β-sheets, and usually, a conserved disulfide bond. Members of the immunoglobulin super family are involved in many aspects of cellular and non-cellular interactions in vivo, including the widely extended roles in the immune system (e.g., antibodies, T-cell receptor molecules, and the like), involvement in cell adhesion (e.g., ICAM molecules), and intracellular signaling (e.g., receptor molecules, such as the platelet-derived growth factor receptor). The present invention is applicable to all molecules of the immunoglobulin super family that have binding domains. Preferably, the present invention relates to antibodies. As used herein, "domain" refers to a folded protein structure that retains its tertiary structure independently of the rest of the protein. In general terms, the domains are responsible for the functional properties separated from the proteins, and in many cases they can be added, removed, or transferred to other proteins without loss of function of the rest of the protein and / or the domain. A single variable antibody domain means a folded polypeptide domain comprising characteristic sequences of the antibody variable domains. Accordingly, it includes the entire variable antibody domains and the modified variable domains, for example, wherein one or more cycles have been replaced by sequences that are not characteristic of the variable domains of antibody, or variable domains of antibody that have been truncated or comprising N- or C-terminal extensions, as well as the folded fragments of the variable domains that retain at least in part the binding activity and specificity of the full-length domain. Accordingly, each ligand comprises at least two different domains. "Repertoire". A collection of various variants, for example polypeptide variants, which differ in their primary structure. A library used in the present invention will encompass a repertoire of polypeptides comprising at least 1,000 members. "Library". The term "library" refers to a mixture of heterogeneous polypeptides or nucleic acids. The library is composed of members, each of which has a single polypeptide or nucleic acid sequence. To this degree, the library is synonymous with repertoire. The sequence differences between the members of the library are responsible for the diversity present in the library. The library can take the form of a simple mixture of polypeptides or nucleic acids, or it can be in the form of organisms or cells, for example bacteria, viruses, animal or plant cells, and the like, transformed with a nucleic acid library. Preferably, each individual organism or cell contains only one or a limited number of members of the library. Conveniently, the nucleic acids are incorporated into expression vectors, in order to allow expression of the polypeptides encoded by the nucleic acids. In a preferred aspect, therefore, a library can take the form of a population of host organisms, each organism containing one or more copies of an expression vector containing a single member of the library in the form of a nucleic acid, which can be expressed to produce its corresponding polypeptide member. Therefore, the population of host organisms has the potential to encode a large repertoire of genetically diverse polypeptide variants. As used herein, an antibody refers to IgG, IgM, IgA, Ig D or Ig E, or a fragment (such as a Fab, F (ab ') 2, Fv linked with disulfide, scFv, multispecific antibody of closed conformation, disulfide-linked scFv, diabody), either derived from any species that naturally produces an antibody, or created by recombinant DNA technology; either isolated from serum, B-cells, hybridomas, transfectomas, yeast, or bacteria. As described herein, an "antigen" is a molecule that is linked via a binding domain according to the present invention. Typically, the antigens are ligated by antibody ligands, and are capable of eliciting an antibody response in vivo. It can be a polypeptide, protein, nucleic acid, or other molecule. In general terms, the specific double ligands according to the invention are selected for the specificity of the target against two particular targets (e.g., antigen). In the case of conventional antibodies and fragments thereof, the antibody binding site by the variable cycles (L1, L2, L3, and H1, H2, H3) is capable of binding to the antigen. An "epitope" is a unit structure conventionally linked by an immunoglobulin VH / VL pair. The epitopes define the minimal binding site for an antibody, and therefore, represent the specificity target of an antibody. In the case of a single domain antibody, an epitope represents the unit structure linked by a variable domain in isolation. "Universal structure" refers to a single antibody structure sequence that corresponds to the regions of an antibody conserved in the sequence, as defined by Kabat ("Sequence of Proteins I mmunological I nterest", as defined by the Department of Health and Human Services of the United States), or corresponding to the immunoglobulin repertoire or structure of the human germinal line, as defined by Chothia and Lesk, J. Mol. Biol. 1 96:91 0-91 7 (1988). The invention provides the use of a single structure, or of a set of these structures, that has been found to allow the derivation of virtually any binding specificity through variation in hyper-variable regions alone. The phrase "half-life" refers to the time it takes for the serum concentration of the ligand to be reduced by 50 percent, in vivo, for example, due to degradation of the ligand and / or elimination or sequestration of the specific double ligand by natural mechanisms. The ligands of the invention are stabilized in vivo, and their life is increased by their binding to molecules that resist degradation and / or elimination or sequestration. Typically, these molecules are naturally occurring proteins, which themselves have a long half-life in vivo. The half-life of a ligand is increased if its functional activity persists, in vivo, for a longer period than a similar ligand that is not specific to the molecule that increases the half-life. Accordingly, a specific ligand for HSA and two target molecules are compared to the same ligand, where the specificity for HSA is not present, ie, it does not bind to HSA, but binds to another molecule. For example, you can link to a third objective on the cell. Typically, the half-life increases by 1 0 percent, 20 percent, 30 percent, 40 percent, 50 percent, or more. Increases in the range of 2x, 3x, 4x, 5x, 1 0x, 20x, 30x, 40x, 50x or more of the half-life are possible. Alternatively, or in addition, increases in the range of up to 30x, 40x, 50x, 60x, 70x, 80x, 90x, 1x, and 50x of the half-life are possible. As referred to herein, the term "competes" means that the link of a first target with its cognate target link domain is inhibited when a second target is linked to its cognate target link domain. For example, the link can be sterically inhibited, for example, by physically blocking a binding domain, or by altering the structure or environment of a binding domain, such that its affinity or avidity is reduced. for an objective.

As used herein, the terms "low restraint," "medium restraint," "high restraint," or "very high restraint conditions," describe the conditions for hybridization and washing of nucleic acids. A guide can be found to carry out the hybridization reactions in Current Protocols in Molecular Biology, John Wiley & Sons, N. Y. (1 989), 6.3.1 -6.3.6, which is incorporated herein by reference in its entirety. Aqueous and non-aqueous methods are described in that reference, and any of them can be used. The specific hybridization conditions referred to herein are as follows: (1) low-restriction hybridization conditions in 6X sodium chloride / sodium citrate (SSC) at about 45 ° C, followed by two washes in 0.2X SSC, SDS at 0.1 percent at least at 50 ° C (the temperature of the washings can be increased to 55 ° C for conditions of low restraint); (2) conditions of hybridization of medium restraint in 6X SSC at approximately 45 ° C, followed by one or more washes in 0.2X SSC, 0.1% SDS at 60 ° C; (3) conditions of high-restriction hybridization in 6X SSC, at approximately 45 ° C, followed by one or more washes in 0.2X SSC, 0.1 percent SDS at 65 ° C; and preferably (4) very high stringency hybridization conditions, which are with 0.5M sodium phosphate, 7% SDS at 65 ° C, followed by one or more washes in 0.2X SSC, 1% SDS at 65 ° C. The conditions of very high restriction (4) are the preferred conditions, and those that should be used, unless otherwise specified. Similar or homologous sequences (for example, with a sequence identity of at least about 70 percent) to the sequences disclosed herein are also part of the invention. In some embodiments, the sequence identity at the amino acid level can be about 80 percent, 85 percent, 90 percent, 91 percent, 92 percent, 93 percent, 94 percent, 95 percent, 96 percent, 97 percent, 98 percent, 99 percent or higher. At the level of the nucleic acid, the sequence identity can be about 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, 91 percent, 92 percent, the 93 percent, 94 percent, 95 percent, 96 percent, 97 percent, 98 percent, 99 percent or higher. Alternatively, there is a substantial identity when the nucleic acid segments are hybridized under selective hybridization conditions (eg, very high stringency hybridization conditions) to the chain complement. The nucleic acids can be present in whole cells, in a cellular list, or in a partially purified or substantially pure one. The calculations of "homology" or "sequence identity" or "similarity" between two sequences (the terms are used interchangeably in the present) are carried out as follows. The sequences are aligned for optimal comparison purposes (for example, gaps can be introduced into one or both of a first and second amino acid or nucleic acid sequence for optimal alignment, and non-homologous sequences are discarded for the purposes of the comparison). In a preferred embodiment, the length of an aligned reference sequence for comparison purposes is at least 30 percent, at least preferably 40 percent, more preferably at least 50 percent, still more preferable when less than 60 percent, and still most preferably at least 70 percent, 80 percent, 90 percent, 1 00 percent of the length of the reference sequence. The amino acid residues or nucleotides are then compared at the amino acid positions or at the corresponding nucleotide positions. When a position in a first sequence is occupied by the same amino acid or nucleotide residue as the corresponding position in the second sequence, then the molecules are identical in that position (as used herein, "homology" of amino acids or nucleic acid is equivalent to "identity" of amino acids or nucleic acid). The percent identity between the two sequences is a function of the number of identical positions shared by the sequences, taking into account the number of gaps, and the length of each gap, that need to be introduced for optimal alignment of the two sequences. Alignments of amino acid and nucleotide sequences, and homology, similarity, or identity, as defined herein, are preferably prepared and determined using the BLAST 2 sequence algorithm, using the default parameters (Tatusova, TA et al., FEMS Microbiol Lett, 1 74: 1 87-1 88 (1999)). In an alternative way, the BLAST algorithm (version 2.0) is used for the alignment of sequences, with the parameters established in the default values. BLAST (Basic Local Alignment Search Tool) is the heuristic search algorithm used by the blastp, blastn, blastx, tblastn, and tblastx programs; These programs ascribe meaning to their discoveries using the statistical methods of Karlin and Altschul, 1 990, Proc. Nati Acad. Sci. USA 87 (6): 2264-8. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art (eg, cell culture, molecular genetics, nucleic acid chemistry, hybridization techniques, and biochemistry). Conventional techniques are used for molecular, genetic, and biochemical methods (see generally, Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Edition (1989) Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N. . and Ausubel et al., Short Protocols in Molecular Biology (1 999) 4th Edition, John Wiley &Sons, I nc. which are incorporated herein by reference), and chemical methods. The invention relates to ligands that bind to two cell surface targets that are present on a cell. For example, the ligand may comprise a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and a second polypeptide domain having a binding site with a binding specificity for a second cell surface target. Preferably, the first polypeptide domain (eg, the single immunoglobulin variable domain) binds to the first cell surface target with low affinity, and the second polypeptide domain (single immunoglobulin variable domain) binds to the second cell surface target with low affinity. As described and exemplified herein, these ligands can be selectively linked to double positive cells that contain both the first cell surface target and the second cell surface target. In accordance with the above, polypeptides that bind to a desired low affinity cell surface antigen, such as antibodies and antigen binding fragments of antigens, can be formatted into ligands as described herein, to provide agents that can selectively bind to double positive cells. The ligands of the invention provide several advantages. For example, as described herein, ligands that bind to two different cell surface targets can be internalized into the cells after the binding of the two targets on the surface of a cell. Accordingly, the ligands can be used to deliver a therapeutic agent, such as a toxin, to a double positive cell expressing a first cell surface target and a second cell surface target, such as a cancer cell. Because the ligand can selectively bind to the positive double cells, possible undesirable effects that could result from the delivery of a therapeutic agent to an individual positive cell (e.g., side effects such as immunosuppression) can be eliminated, using the ligands of the invention. Ligands of the invention can bind to cell surface targets that are both present on normal cells, but that are present at higher levels on a pathogenic cell. Under these circumstances, the ligand can be used to preferentially deliver a therapeutic agent (eg, a toxin) to the pathogenic cell. For example, due to the higher level of cell surface targets on the pathogenic cell, more ligand will be bound and internalized with the pathogenic cell than it will be bound to and internalized in the normal cell. Accordingly, an effective amount of toxin can be delivered preferentially to the pathogenic cell. further, as described herein, the ligand can be tailored to have a desired in vivo serum half life. Accordingly, the ligands can be used to control, reduce, or eliminate the general toxicity of the therapeutic agents, such as the cytotoxin used to treat cancer. In general terms, both cell surface targets with which the ligand binds are present on a pathogenic cell, but are not both present on normal cells. As shown herein, in these situations, the ligand can be used in a concentration that results in selective binding to the pathogenic cells that contain both cell surface targets (at a concentration where the ligand does not substantially bind to the cell). individual positive normal cells). Certain normal cells can have both cell surface targets that are linked by a ligand of the invention present on their cell surfaces, but the targets are present at higher levels on the surface of a pathogenic cell (e.g., a cancer cell) . Preferably, both cell surface targets are not substantially present on the surface of normal cells. Under these circumstances, the ligand can be used in a concentration that results in selective binding to the pathogenic cells containing both cell surface targets (at a concentration where the ligand does not substantially bind to the normal cell containing low levels). of cell surface targets).

Preferred ligands comprise a first single immunoglobulin variable domain with binding specificity for a first cell surface target, and a second unique immunoglobulin domain with binding specificity for a second cell surface target. In preferred embodiments, the first single variable domain of immunoglobulin has a binding site with binding specificity for a cell surface target selected from the group consisting of CD38, CD1 38, carcinoembryonic antigen (CEA), CD56, factor vascular endothelial growth (VEGF), epidermal growth factor receptor (EGFR), and HER2. In particularly preferred embodiments, the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD1 38, CEA, CD56, VEGF, EG FR , and HER2, with the proviso that this first single variable domain of immunoglobulin and this second single variable domain of immunoglobulin do not bind to the same cell surface target. The ligand of the invention can be formatted as described herein. For example, the ligand of the invention can be formatted to tailor the serum half-life in vivo. If desired, the ligand may further comprise a toxin or a toxin moiety, as described herein. In some embodiments, the ligand comprises a toxin of surface activity, such as a free radical generator (eg, a toxin containing selenium), or a radionuclide. In other embodiments, the toxin or toxin fraction is a polypeptide domain (eg, a dAb) that has a binding site with a binding specificity for an intracellular target. Table 1 Target Specificities for Ligands Those skilled in the art will appreciate that the combinations of objectives provided in Table 1, and those provided in the Examples, represent a mere sample of the combinations suitable for use in accordance with the invention.

Table 2 Ligand Formats The ligand of the invention can be formatted as a double specific ligand, as described herein. The ligand can also be formatted as a multispecific ligand, for example, as described in International Publication Number WO 03/002609, the entire teachings of which are incorporated herein by reference. These specific double ligands comprise unique variable immunoglobulin domains having different binding specificities. These specific double ligands can comprise combinations of heavy and light chain domains. For example, the double specific ligand may comprise a VH domain and a VL domain, which may be linked together in the form of a scFv (e.g., using a suitable linker, such as Gly4Ser), or may be formatted in a bispecific antibody or in an antigen binding fragment thereof (eg, F (ab ') 2 fragment). The specific double ligands do not comprise complementary V H / V L pairs that form a conventional two-chain antibody antigen binding site that binds to the antigen or epitope in a cooperative manner. Instead, the double format ligands comprise a complementary VH / VL pair, wherein the V domains have different binding specificities. In addition, the specific double ligands may comprise one or more CH or C domains, if desired. A joint region domain can also be included if desired. These combinations of domains, for example, may mimic natural antibodies, such as IgG or IgM, or fragments thereof, such as Fv, scFv, or F (ab ') 2 molecules. Other structures are envisioned, such as a single arm of an IgG molecule comprising the VH domains, VL, VH1, and CL. Preferably, the double specific ligand of the invention comprises only two variable domains, although several of these ligands can be incorporated together in the same protein, for example, two of these ligands can be incorporated into an IgG or a multimeric immunoglobulin. , such as IgM. Alternatively, in another embodiment, a plurality of specific double ligands are combined to form a multimer. For example, two different double specific ligands are combined to create a tetra-specific molecule. One of ordinary skill in the art will appreciate that the variable regions liberated and weighted from a double specific ligand produced according to the method of the invention, may be on the same polypeptide chain, or alternatively, on different polypeptide chains. In case the variable regions are on different polypeptide chains, then they can be linked by means of a linker, generally a flexible linker (such as a polypeptide chain), a chemical linker group, or any other known method in this countryside. The ligands can be formatted as bi- or multi-specific antibodies or fragments of antibodies, or in structures other than bi- or multi-specific antibodies. Suitable formats include any suitable polypeptide structure, wherein an antibody variable domain or one or more of the CDRs thereof can be incorporated to confer antigen binding specificity on the structure. A variety of suitable antibody formats are known in the art, such as the bispecific IgG type formats (eg, chimeric antibodies, humanized antibodies, human antibodies, single chain antibodies, heavy chain heterodimers and / or light chains). antibodies, antigen binding fragments of any of the foregoing (e.g., an Fv fragment (e.g., single chain Fv (scFv), a disulfide linked Fv), a Fab fragment, a Fab 'fragment, a fragment F (ab ') 2), a single variable domain (e.g., VH, VL, VH H), a dAb, and modified versions of any of the above (e.g., modified by the covalent attachment of polyalkylene glycol (e.g. , polyethylene glycol, polypropylene glycol, polybutylene glycol), or other suitable polymer.) See PCT Publication Number PCT / G B03 / 002804, filed June 30, 2003, which is designated in the United States (Publication International No. WO 2004/081 026) with respect to the only PEGylated variable domains and dAbs, the methods suitable for their preparation, the longer in vivo half-life of the only PEGylated variable domains, and the monomers and multimers of dAb, the appropriate PEGs, the preferred hydrodynamic sizes of the PEGs, and the preferred hydrodynamic sizes of the only PEGylated variable domains and of dAb monomers and multimers. All teaching of the PCT Publication Number PCT / GB03 / 002804 (International Publication Number WO 2004/081 026), including the portions referred to above, are incorporated herein by reference. The ligand can be formatted using a suitable linker, such as (Gly Ser) n, where n = from 1 to 8, for example 2, 3, 4, 5, 6, or 7. If desired, the ligands, including The dAb monomers, dimers, and trimers can be linked to an antibody Fc region, comprising one or both of the CH2 and CH3 domains, and optionally a hinge region. For example, vectors encoding ligands linked as a single nucleotide sequence to an Fc region can be used to prepare these polypeptides. The ligands and monomers of dAb can also be combined and / or formatted into multiple ligand structures other than antibodies, to form multivalent complexes, which link the target molecules to the same epitope, thus providing a higher avidity. For example, natural bacterial receptors, such as SpA, can be used as scaffolds for the grafting of CDRs, in order to generate ligands that specifically bind to one or more epitopes. The details of this procedure are described in U.S. Patent No. US 5,831, 01 2. Other suitable scaffolds include those based on fibronectin and afibodies. Details of suitable procedures are described in International Publication Number WO 98/58965. Other suitable scaffolds include lipocalin and CTLA4, as described in van den Beuken et al., J. Mol. Biol. 31 0: 591-601 (2001), and scaffolds such as those described in International Publication Number WO 00/69907 (Medical Research Council), which are based, for example, on the ring structure of the Bacterial GroEL or other chaperone polypeptides. Protein scaffolds can be combined, for example, CDRs can be grafted onto a CTLA4 scaffold, and can be used together with the immunoglobulin VH and VL domains to form a ligand. In the same way, fibronectin, lipocalin, and other scaffolds can be combined. A variety of methods suitable for the preparation of any desired format are known in the art. For example, antibody chains and formats can be prepared (eg, bispecific IgG type formats, chimeric antibodies, humanized antibodies, human antibodies, single chain antibodies, homodimers, and heterodimers of heavy and / or light chains of antibodies). ), by expressing suitable expression constructs and / or culturing suitable cells (eg, hybridomas, heterohybridomas, recombinant host cells containing recombinant constructs encoding the format). In addition, formats such as antibody antigen binding fragment or antibody chains (eg, bispecific binding fragments, such as an Fv fragment (eg, single chain Fv (scFv), bound Fv) can be prepared. with disulfide), a Fab fragment, a Fab 'fragment, an F (ab') 2 fragment), by expression of suitable expression constructs, or by enzymatic digestion of the antibodies, for example using papain or pepsin.

The ligand can be formatted as a multispecific ligand, for example, as described in International Publication Number WO 03/002609, the entire teachings of which are incorporated herein by reference. This multispecific ligand possesses more than one epitope-binding specificity. In general terms, the multispecific ligand comprises two or more epitope binding domains, such as dAbs or non-antibody protein domain comprising a binding site for an epitope, for example an affibody, an SpA domain, a domain of LDL receptor class A, an EG F domain, an avimer. The multispecific ligands can be further formatted as described herein. In some embodiments, the ligand is in an IgG type format. These formats have the conventional structure of four chains of one molecule of IgG (two heavy chains and two light chains), where one or more of the variable regions (VH and VL) have been replaced with a dAb or with a single variable domain. of a desired specificity. Preferably, each of the variable regions (two VH regions and two VL regions) is replaced with a dAb or with a single variable domain. The dAb (s) or the only variable domains that are included in an IgG type format can have the same specificity or different specificities. In some embodiments, the IgG type format is tetravalent, and may have one, two, three, or four specificities. For example, the IgG type format can be monospecific, and comprises four dAbs that have the same specificity; bispecific, and comprises three dAbs that have the same specificity and another dAb that has a different specificity; bispecific and comprises two dAbs that have the same specificity and two dAbs that have a common but different specificity; trispecific and comprises first and second dAbs that have the same specificity, a third dAb with a different specificity, and a fourth dAb with a different specificity from the first, second, and third dAbs; or tetraespecific and comprises four dAbs each having a different specificity. Antigen binding fragments of IgG-like formats (eg, Fab, F (ab ') 2, Fab', Fv, scFv) can be prepared. The ligands of the invention can be formatted as a fusion protein containing a first single variable domain of immunoglobulin that is directly fused with a second single variable domain of immunoglobulin. If desired, this format can also comprise a fraction that extends the half-life. For example, the ligand may comprise a first single variable domain of immunoglobulin, which is directly fused with a second single immunoglobulin variable domain, which is directly fused to a single immunoglobulin variable domain that binds to serum albumin. In general, targeting the polypeptide domains having a binding site with binding specificity for a cell surface target, and if the ligand comprises a linker, is a matter of design choice. However, some orientations, with or without linkers, can provide better link characteristics than other orientations. All orientations (eg, dAb 1 -linker-dAb2; dAb2-linker-dAbl) are encompassed by the invention, and ligands containing an orientation that provides the desired link characteristics can be easily identified by screening. Formats that Extend the Average Life. The ligand, and the dAb monomers disclosed herein, can be formatted to extend their serum half life in vivo. The longer half-life in vivo is useful in the in vivo applications of immunoglobulins, especially antibodies, and more especially fragments of small-sized antibodies, such as dAbs. These fragments (Fvs, Fvs linked by disulfide, Fvs, Fabs, scFvs, dAbs) are rapidly eliminated from the body, which can limit the clinical applications. A ligand can be formatted as a larger antigen binding fragment of an antibody, or as an antibody (eg, formatted as a Fab, Fab ', F (ab) 2, F (ab') 2, IgG, scFv ), which has a larger hydrodynamic size. The ligands can also be formatted to have a larger hydrodynamic size, for example, by linking a polyalkylene glycol group (eg, a polyethylene glycol (PEG) group, polypropylene glycol, polybutylene glycol), serum albumin, transferrin, transferrin receptor. , or at least the transferrin binding portion thereof, an antibody Fc region, or by conjugation with an antibody domain. In some embodiments, the ligand is PEGylated. Preferably, the PEGylated ligand binds to a double positive cell with substantially the same avidity as the same ligand that is not PEGylated. For example, the ligand may be a PEGylated ligand comprising a dAb that binds to CD38, and a second dAb that binds to CD1 38, wherein the PEGylated ligand binds to a CD38 + CD 1 38+ cell with an avidity which differs from the avidity of the ligand in the non-PEGylated form by more than a factor of about 1,000, preferably not more than a factor of about 1 00, more preferably not more than a factor of about 1 0, or with a avidity substantially unchanged in relation to the non-PEGylated form. See TCP Publication No. PCT / GB03 / 002804, filed June 30, 2003, which designates the United States (International Publication Number WO 2004/081 026), with respect to the only PEGylated variable domains and dAbs, suitable methods for its preparation, the longer in vivo half-life of the only PEGylated variable domains and the dAb monomers and multimers, the appropriate PEGs, the preferred hydrodynamic sizes of the PEGs, and the preferred hydrodynamic sizes of the only PEGylated variable domains and the dAb monomers and multimers. All teaching of the PCT Publication Number PCT / GB03 / 002804 (International Publication Number WO 2004/081 026), including the portions referred to above, is incorporated herein by reference.

The hydrodynamic size of the ligands (e.g., dAb monomers and multimers) of the invention can be determined using methods that are well known in the art. For example, gel filtration chromatography can be used to determine the hydrodynamic size of a ligand. Gel filtration matrices suitable for determining hydrodynamic sizes of ligands, such as cross-linked agarose matrices, are well known and readily available. The size of a ligand format (e.g., the size of a PEG fraction attached to a dAb monomer) can be varied depending on the desired application. For example, when the ligand is intended to exit the circulation and enter the peripheral tissues, it is desirable to maintain the hydrodynamic size of the ligand low to facilitate extravasation from the bloodstream. Alternatively, when it is desired to cause the ligand to remain in the systemic circulation for a longer period of time, the size of the ligand can be increased, for example, by formatting as an Ig-like protein, or by the addition of a PEG fraction of 30 to 60 kDa (for example, linear or branched PEG of 30 to 40 kDa, such as the addition of two 20 kDa PEG fractions). The size of the ligand format can be tailored to achieve a desired in vivo serum half life, for example to control exposure to a toxin and / or to reduce the side effects of the toxic agents.

The hydrodynamic size of the ligand and its serum half-life can also be increased by conjugation or binding of the ligand to a binding domain that binds to an antigen or epitope that increases the half-life in vivo, as described in FIG. I presented. For example, the ligand (e.g., the dAb monomer) can be conjugated or linked to an antibody or an antibody or anti-Fc neonatal receptor fragment (e.g., an anti-SA or an anti-Fc receptor dAb). neonatal, Fab, Fab ', or scFv) or to an anti-SA poster or an anti-neonatal Fc receptor. Examples of albumin, albumin fragments, or albumin variants suitable for use in a ligand according to the invention are described in International Publication No. WO 2005 / 077042A2, which is incorporated herein by reference in its entirety. . In particular, the following albumins, albumin fragments, or albumin variants can be used in the present invention: SEQ ID NO: 1 as disclosed in International Publication Number WO 2005 / 077042A2, this sequence being explicitly incorporated herein disclosure by reference; Fragment or variant of albumin comprising or consisting of amino acids 1 to 387 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; Albumin, or fragment or variant thereof, comprising an amino acid sequence selected from the group consisting of: (a) amino acids 54 to 61 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (b) amino acids 76 to 89 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (c) amino acids 92 to 100 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (d) amino acids 170 to 176 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (e) amino acids 247 to 252 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (f) amino acids 266 to 277 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (g) amino acids 280 to 288 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (h) amino acids 362 to 368 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (i) amino acids 439 to 447 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (j) amino acids 462 to 475 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; (k) amino acids 478 to 486 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2; and (I) amino acids 560 to 566 of SEQ ID NO: 1 of International Publication Number WO 2005 / 077042A2. Other examples of albumins, fragments, and analogs suitable for use in a ligand according to the invention are described in International Publication Number WO 2005 / 077042A2, which is incorporated herein by reference in its entirety. In particular, the following albumins, fragments, or variants may be used in the present invention: Human serum albumin as described in International Publication Number WO 03 / 076567A2, for example in Figure 3 (this sequence information being incorporated explicitly to the present disclosure by reference); Human serum albumin (HA), which consists of a single non-glycosylated polypeptide chain of 585 amino acids, with a molecular weight of the formula of 66,500 (see Meloun, et al., FEBS Letters 55: 136 (1975); Behrens, and collaborators, Fed. Proc. 34: 591 (1975); Lawn, et al., Nucleic Acids Research 9: 6102-6114 (1981); Minghetti, et al., J. Biol Chem.261: 6141 (1986)); A polymorphic variant or an analogue or fragment of albumin, as described in Weitkamp, et al., Ann. Hum. Genet.37: 219 (1973); A fragment or variant of albumin as described in European Patent Number EP 322094, for example HA (1-373, HA (1-388), HA (1-389), HA (1-369), and HA (1 -419), and the fragments between 1-369 and 1-419 • A fragment or variant of albumin as described in European Patent Number EP 399666, for example HA (1-177) and HA (1-200), and the fragments between HA (1-X), where X is any number from 178 to 199. When one (one or more) fraction that prolongs the half-life is used (e.g., albumin, transferrin, and fragments and analogues of the same) in the ligands of the invention, this can be conjugated to the ligand using any suitable method, such as by direct fusion to the target binding moiety (eg, dAb or antibody fragment), for example, using a a single nucleotide construct encoding a fusion protein, wherein the fusion protein is encoded as a single polypeptide chain with a fraction that prolongs the localized N- or C-terminal half-life for the cell surface target binding fractions. Alternatively, conjugation can be achieved using a peptide linker between the fractions, for example, a peptide linker as described in International Publication Number WO 076567A2 or International Publication Number WO 2004/003019 (these linker disclosures are incorporated herein) by reference to the present disclosure to provide the Examples for use in the present invention). Typically, a polypeptide that improves serum half-life in vivo, is a polypeptide that occurs naturally in vivo, and that resists degradation or removal by endogenous mechanisms that remove undesired material from the organism (e.g., human) . For example, a polypeptide that improves serum half-life in vivo can be selected from extracellular matrix proteins, proteins found in the blood, proteins found in the blood-brain barrier, or neural tissue, proteins located in the kidney, liver, lung, heart, skin, or bone, stress proteins, disease-specific proteins, or proteins involved in the transport of Fc. Suitable polypeptides that improve serum half-life in vivo include, for example, transferrin-receptor-specific neuropharmaceutical ligand-fusion proteins (see U.S. Pat., 977, 307, the teachings of which are incorporated herein by reference), the brain capillary endothelial cell receptor, transferrin, transferrin receptor (eg, soluble transferrin receptor, insulin, insulin-like growth factor receptor-1). (IGF-1), insulin-like growth factor-2 receptor (IGF-2), insulin receptor, blood coagulation factor X, α1-antitrypsin, and HN F-1 a.Proper polypeptides that improve life serum media also include alpha-1 glycoprotein (orosomucoid; AAG), alpha-1 antichymotrypsin (ACT), alpha-1 microglobulin (HC protein, AI M), antithrombin III (AT III), apolipoprotein A-1 (Apo A-1), apolipoprotein B (Apo B), ceruloplasmin ( Cp), complement component C3 (C3), complement component C4 (C4), esterase inhibitors C1 (C 1 INH), C-reactive protein (CRP), ferritin (FER), hemopexin (HPX), lipoprotein (a ) (Lp (a)), mannose binding protein (MBP), myoglobin (Myo), prealbumin (transpiretin, PAL), retinol binding protein (RBP), and rheumatoid factor (RF). Suitable proteins from the extracellular matrix include, for example, collagens, laminins, integrins, and fibronectin. Collagens are the main proteins of the extracellular matrix. Approximately 1 5 types of collagen molecules are currently known, which are found in different parts of the body, for example type I collagen (which accounts for 90 percent of body collagen (found in bone, skin, tendon, ligaments, cornea, internal organs, or type II collagen found in cartilage, spinal disc, notochord, and vitreous humor of the eye, suitable proteins in the blood include, for example, plasma proteins (eg, fibrin, a-2). macroglobulin, serum albumin, fibrinogen (eg, fibrinogen A, fibrinogen B), serum amyloid protein A, haptoglobin, profilin, ubiquitin, uteroglobulin, and β-2 microglobulin), enzymes, and enzyme inhibitors (eg, plasminogen, lysozyme, cystatin C, anti-trypsin alpha-1, and pancreatic trypsin inhibitor), immune system proteins, such as immunoglobulin proteins (eg, IgA, IgD, IgE, IgG, IgM, lig chains) eras of immunoglobulin (kappa / lambda)), transport proteins (e.g., retinol binding protein, α-1 microglobulin), defensins (e.g., beta-defensin 1, neutrophil defensin 1, neutrophil defensin 2, and neutrophil defensin 3), and the like. Suitable proteins found in the blood-brain barrier or neural tissue include, for example, melanocortin receptor, myelin, ascorbate transporter, and the like. Suitable polypeptides that improve serum half-life in vivo also include proteins located in the kidney (eg, polycystin, type IV collagen, K1 organic anion transporter, Heymann antigen), proteins located in the liver ( for example, alcohol dehydrogenase, G250), proteins located in the lung (eg, secretory component, which binds to I GA), proteins located in the heart (eg, HSP27, which is associated with dilated cardiomyopathy ), proteins located in the skin (eg, keratin), bone-specific proteins, such as morphogenic proteins (BM Ps), which are a subset of the super-family of transforming growth factor-ß proteins, demonstrating osteogenic activity (e.g., BM P-2, BM P-4, BM P-5, BM P-6, BM P-7, BM P-8), tumor-specific proteins (e.g. trophoblasts, receptor herceptin, estrogen receptor, cathepsins (for example, cathepsin B, which can be found in the liver and spleen)). Suitable disease-specific proteins include, for example, antigens that are expressed only on activated T-cells, including LAG-3 (lymphocyte activation gene), osteoprotegerin ligand (OPGL, see Nature 402, 304-309 ( 1 999)), OX40 (a member of the TNF receptor family, expressed on activated T-cells, and specifically amplified on the cells producing the human T-cell type I leukemia virus (HTLV-I) see Immunol. 165 (1): 263-70 (2000)). Suitable disease-specific proteins also include, for example, metalloproteases (associated with arthritis / cancers), including CG6512 from Drosophila, human paraplegina, human FtsH, human AFG3L2, murine FtsH.; and angiogenic growth factors, including acid fibroblast growth factor (FGF-1), basic fibroblast growth factor (FGF-2), vascular endothelial growth factor / vascular permeability factor (VEGF / VPF), growth factor transformant-a (TGF-a), tumor necrosis factor-a (TNF-a), angiogenin, interleukin-3 (IL-3), interleukin-8 (IL-8), platelet-derived endothelial growth factor (PD) -ECGF), placental growth factor (PIGF), growth factor derived from midquina-BB platelets (PDGF), and fractalkine. Suitable polypeptides that improve serum half-life in vivo also include strain proteins, such as heat shock proteins (HSPs). Heat shock proteins are usually found intracellularly. When they are found extracellularly, this is an indicator that a cell has died and spilled its contents outward. This unscheduled cell death (necrosis) occurs when, as a result of trauma, disease, or injury, extracellular heat shock proteins trigger a response from the immune system. The binding to the extracellular heat shock protein may result in localization of the compositions of the invention at a disease site. Suitable proteins involved in Fc transport include, for example, the Brambell receptor (also known as FcRB). This Fc receiver has two functions, both of which are potentially useful for the supply. The functions are: (1) transport of IgG from the mother to the child through the placenta, (2) protection of IgG from degradation, thus prolonging its half-life in serum. It is thought that the receptor recycles IgG from the endosomes. (See Holliger et al., Nat. Biotechnol. 1 5 (7): 632-6 (1 997)). The methods for pharmacokinetic analysis and determination of the half-life of the ligand will be familiar to those skilled in the art. Details can be found in Kenneth, A et al., Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists, and in Peters et al., Pharmacokinetc analysis: A Practical Approach (1 996). Reference is also made to "Pharmacokinetics", M Gibaldi & D Perron, published by Marcel Dekker, Second Review, Extra Edition (1982), which describes pharmacokinetic parameters, such as the half-lives of t-alpha and t-beta, and the area under the curve (AUC). Ligands Containing a Fraction of Toxin or a Toxin The invention also relates to ligands comprising a toxin fraction or a toxin. Suitable toxin fractions comprise a toxin (e.g., surface activity toxin, cytotoxin). The toxin or toxin fraction can be linked or conjugated to the ligand using any suitable method. For example, the toxin or toxin fraction can be covalently linked to the ligand directly or through a suitable linker. Suitable linkers can include non-dissociable or dissociable linkers, for example, pH-releasable linkers that comprise a dissociation site for the cellular enzyme (e.g., cellular esterases, cellular proteases such as cathepsin B). These dissociable linkers can be used to prepare a ligand that can release a toxin or toxin fraction after the ligand is internalized. Conjugation A variety of methods can be employed to bind or conjugate a toxin or toxin moiety to a ligand. The particular method selected will depend on the fraction of toxin or toxin and the ligand to be bound or conjugated. If desired, linkers containing terminal functional groups can be used to bind the ligand and the toxin or toxin moiety. In general terms, conjugation is carried out by the reaction of the toxin or toxin fraction containing a reactive functional group (or that is modified to contain a reactive functional group) with a linker, or directly with a ligand. Covalent bonds may be formed by the reaction of a toxin or toxin moiety containing (or modifying to contain) a chemical moiety or functional group which, under the appropriate conditions, may react with a second chemical group, thereby forming a covalent bond. Many combinations of suitable reactive chemical groups are known in the art, for example, an amine group can react with an electrophilic group, such as tosylate, methylate, halogen (chlorine, bromine, fluorine, iodine), N-hydroxy-succinimidyl-ester (N HS), and the like. Thiols can react with maleimide, iodoacetyl, acryloyl, pyridyl disulfides, 5-thiol-2-nitro-benzoic acid thiol 8TNB-thiol), and the like. A functional aldehyde group can be coupled with molecules containing amine or hydrazide, and an azide group can react with a trivalent phosphorus group to form phosphoramidate or phosphorimide bonds. Suitable methods for introducing activating groups into molecules are known in this field (see, for example, Hermanson, G.T., Bioconjugate Techniques, Academic Press: San Diego, CA (1996)). The toxin conjugated ligand of the invention can be produced by the reaction of an appropriate ligand with a toxin comprising a chemical or reactive functional group, as described herein. For example, conjugation can be carried out by means of primary amine residues, carboxyl groups, and cysteine residues. The designed cysteine residues provide certain advantages as sites for conjugation of the toxin, because the conjugation of the toxin by means of an unpaired cysteine residue (eg, a cysteine residue designed in a ligand), provides a method to achieve site-specific conjugation, and reduces the possibility that conjugation will interfere with the antigen binding function. For example, unpaired cysteine can be incorporated into the carboxyl terminus of a dAb to provide a site-specific thiol conjugate residue. In addition, specific sites accessible to the solvent in the specific double ligand that are not naturally occurring cysteine residues can be mutated to a cysteine for toxin binding. Solvent-accessible residues in the specific double ligand can be determined using methods known in the art, such as analysis of the crystal structures of a ligand. For example, using the resolved crystal structure of the dkb Fake Vk (SEQ ID NO: 679), the residues Val-1 5, Pro-40, Gly-41, Ser-56, Gly-57, Ser-60 have been identified. , Pro-80, Glu-81, Gln-100, Lys-107, and Arg-108 as accessible to the solvent, and therefore, the residues in the corresponding positions on the specific double ligands described herein, are potential candidates for the mutation to a cysteine residue for conjugation of the toxin. Thiol conjugates can be prepared using any suitable method, such as well-known methods for the formation of disulfide bonds, or by reaction with a thiol-reactive group, such as maleimide, iodoacetyl, acryloyl, pyridyl disulfide , thiol of 5-thiol-2-nitro-benzoic acid (TNB-thiol), and the like. In certain embodiments, a toxin or a toxin fraction can be bound to the ligand in a non-site-specific manner, by the use of a chemical or functional group reactive with amine, for example, by the reaction of a ligand with an ester N HS of a toxin. The preferred conjugation is a site-specific conjugation, for example conjugation in a cysteine, in the amino terminus, or in the carboxyl terminus. The amino-terminal conjugation can be carried out using any suitable method, such as the methods described in European Patent Number EP 0 822 1 99 B 1. For example, a ligand can be reacted with a toxin or toxin fraction that reacts with an amine, under reducing alkylation conditions (eg, in the presence of sodium borohydride, sodium cyanoborohydride, dimethyl amine borate, trimethyl amine borate, or pyridine borate), at a suitable pH (eg, 4.0 to 6.0), to selectively activate the a-amino group at the amino terminus of the ligand, such that the toxin binds to the a-amino, thus obtaining the ligand-toxin conjugate. Suitable toxin fractions and toxins include, for example, a maytansinoid (eg, maytansinol, for example DM 1, DM4), a taxane, a calicheamicin, a duocarmycin, or derivatives thereof. The maytansinoid may be, for example, maytansinol an maytansinol analogue. Examples of the maytansinol analogues include those having a modified aromatic ring (eg, CD-19-dechloro, C-20-demethoxy-C-20-acyloxy), and those having modifications in other positions (eg. C-9-CH, -C14-alkoxymethyl, C-14-hydroxymethyl, or aceloxymethyl, C-15-hydroxyl / acyloxy, C-15-methoxy, C-18-N-demethyl, 4, 5-deoxy). Maytansinol and maytansinol analogs are described, for example, in U.S. Patent Nos. 5,208,020 and 6,333,410, the content of which is incorporated herein by reference. Maytansinol can be coupled with antibodies and antibody fragments using, for example, a N-succinimidyl 3- (2-pyridyl-dithio) -propionate (also known as 4- (2-pyridyl-dithio) -pentanoate of N- succinimidyl, or SPP), 4-succinimidyl-oxycarbonyl-a- (2-pyridyl-dithio) -toluene (SMPT), 3- (2-pyridyl-dithio) -butyrate-N-succinimidyl (SDPB), 2-imino- thiolane, or S-acetyl-succinic anhydride. The taxane can be, for example, a taxol, taxotere, or a novel taxane (see, for example, International Publication Number WO 01/38318). Calicheamicin can be, for example, a calicheamicin complexed with bromine (eg, an alpha-, beta-, or gamma-bromine complex), a calicheamicin complexed with iodine (eg, an alpha-, beta complex -, or gamma-iodine), or analogs and mimetics thereof. Calicheamicins forming complex with bromine include II-BR, I2-BR, I3-BR, I4-BR, J1-BR, J2-BR, and K1-BR. The calicheamicins forming complex include 11 -1, 12-1, 13-1, J 1 -I, J2-I, L1 -I, and K1 -BR. Calicheamicin and the mutants, analogs, and mimetics thereof are described, for example, in U.S. Patent Nos. 4,970, 198; 5,264,586; 5,550,246; 5,712,374, and 5,714,586, the content of each of which is incorporated herein by reference. The duocarmycin analogs (e.g., KW-2189, DC88, DC89 CB1 -TMI), and derivatives thereof, are described, for example, in U.S. Patent No. 5,070,092, in U.S. Pat. United States of America Number 5,187, 186, in U.S. Patent Number 5,641, 780, in U.S. Patent Number 5,641, 780, U.S. Patent Number 4,923,990, and in U.S. Patent No. 5,101,038, the contents of each of which is incorporated herein by reference. Examples of other toxins include, but are not limited to, anti-metabolites (e.g., methotrexate, 6-mercapto-purine, 6-thioguanine, cytarabine, 5-fluoro-uracil, decarbazine), alkylating agents (e.g., mechlorethamine, thiotepa-chlorambucil, CC-1065 (see U.S. Patent Nos. 5,475,092, 5,585,499, 5,846,545), melphalan, carmustine (BSNU), and lomustine (CCNU), cyclophosphamide, busulfan, dibromo-mannitol, streptozotocin , mitomycin C, and cis-dichloro-diamine / platinum (II) (DDP) cisplatin), anthracyclines (eg, daunorubicin (formerly daunomycin) and doxorubicin), antibiotics (eg, dactinomycin (formerly actinomycin), bleomycin, mithramycin, mitomycin, puromycin, anthramycin (AMC), duocarmycin and analogs or derivatives thereof, and anti-mitotic agents (eg, vincristine, vinblastine, taxol, auristatins (eg, auristatin E), and maytansinoids, and analogues or homologs of The toxin may also be a surface activity toxin, such as a toxin that is a generator of free radicals (eg, toxin fractions containing selenium), or a fraction containing radionuclide. Suitable radionuclide-containing fractions include, for example, fractions containing radioactive iodine (131l or 1 5l), yttrium (90Y), lutetium (177Lu), actinium (225Ac), praseodymium, astatin (1 At), rhenium (186R) ), bismuth (212Bi or 213Bi), indium (111ln), technetium ("mTc), phosphorus (3 P), rhodium (188Rh), sulfur (35S), carbon (14C), tritium (3H), chromium (51Cr) , chlorine (36CI), cobalt (57Co or 58Co), iron (59Fe), selenium (75Se), or gallium (67Ga) .The toxin can be a protein, a polypeptide, or a peptide, from bacterial sources, by example diphtheria toxin, Pseudomonas exotoxin (PE), and plant proteins, for example, ricin A chain (RTA), ribosome inactivating proteins (RIPs), gelonin, ivy antiviral protein, saporin, and dodecandron, which can be contemplated to be used as toxins, anti-sense nucleic acid compounds designed to bind, disable, and promote degradation or prevent oduction of the mRNA responsible for the generation of a particular target protein, can also be used as a toxin. Anti-sense compounds include anti-sense, single-stranded or double-stranded RNA or DNA, oligonucleotides, or analogs thereof, which can hybridize specifically to the individual mRNA species and prevent transcription and / or processing of RNA of the mRNA species, and / or translation of the encoded polypeptide, and thereby effect a reduction in the amount of the respective encoded polypeptide. Ching, et al., Proc. Nati Acad. Sci. USA. 86: 1 0006-1 001 0 (1,989); Broder, and collaborators, Ann. Int. Med. 1 1 3: 604-61 8 (1,990); Loreau, et al., FEBS Letters 214: 53-56 (1990); Useful anti-sense therapeutics include, for example: Veglin ™ R (VasGene) and OGX-01 1 (Oncogenix). Toxins can also be photoactive agents. Suitable photoactive agents include porphyrin-based materials, such as porfimer-sodium, green porphyrins, chlorin E6, the hematoporphyrin derivative itself, phthalocyanines, ethiopurpurines, texaphrine, and the like. The toxin can be an antibody or an antibody fragment (e.g., intrabody) that binds to an intracellular target, such as a dAb that binds to an intracellular target. These antibodies or antibody fragments (dAbs) can be directed to defined sub-cellular compartments or targets. For example, antibodies or antibody fragments (dAbs) can be linked to an intracellular target selected from erbB2, EGFR, BCR-ABL, p21Ras, Caspase 3, Caspase 7, Bcl-2, p53, Cyclin E, ATF- 1 / CREB, HPV16 E7, HPI, collagenase type IV, cathepsin L, as well as others described in Kontermann, RE, Methods, 34: 163-170 (2004), incorporated herein by reference in its entirety. Polypeptide Domains That Bind with CD38 The invention provides polypeptide domains (e.g., dAb) that have a binding site with binding specificity for CD38. In preferred embodiments, the polypeptide domain (e.g., dAb) binds to CD38 with a low affinity. Preferably, the polypeptide domain binds to CD38 with a Kd of between about 10 μM and about 10 nM, as determined by surface plasmon resonance. For example, the polypeptide domain can be linked to CD38 with an affinity of about 10 μM to about 300 nM, or about 10 μM to about 400 nM. In certain embodiments, the polypeptide domain binds to CD38 with an affinity of about 300 nM to about 10 nM, or from 200 nM to about 10 nM. In some embodiments, the polypeptide domain having a binding site with a binding specificity for CD38 competes for binding to CD38, with a dAb selected from the group consisting of: DOM11-14 (SEQ ID NO: 39 ), DOM11-22 (SEQ ID NO: 40), DOM11-23 (SEQ ID NO: 32), DOM11-25 (SEQ ID NO: 41), DOM11-26 (SEQ ID NO: 42), DOM11-27 ( SEQ ID NO: 43), DOM 11-29 (SEQ ID NO: 44), DOM11-3 (SEQ ID NO: 30), DOM11-30 (SEQ ID NO: 31), DOM11-31 (SEQ ID NO: 45 ), DOM11-32 (SEQ ID NO: 36), DOM11-36 (SEQ ID NO: 46), DOM11-4 (SEQ ID NO: 47), DOM11-43 (SEQ ID NO: 48), DOM11-44 ( SEQ ID NO: 49), DOM11-45 (SEQ ID NO: 50), DOM11-5 (SEQ ID NO: 51), DOM11-7 (SEQ ID NO: 33), DOM11-1 (SEQ ID NO: 52) , DOM11-10 (SEQ ID NO: 53), DOM11-16 (SEQ ID NO: 54), DOM11-2 (SEQ ID NO: 55), DOM11-20 (SEQ ID NO: 56), DOM11-21 (SEQ. ID NO: 57), DOM11-24 (SEQ ID NO: 38), DOM11-28 (SEQ ID NO: 58), DOM11-33 (SEQ ID NO: 59), DOM11-34 (SEQ ID NO: 60), DOM11-35 (SEQ ID NO: 61), DOM11-37 (SEQ ID NO: 37), DOM11-38 (SEQ ID NO: 34), DOM11-39 (SEQ I D NO: 35), DOM11-41 (SEQ ID NO: 62), DOM11-42 (SEQ ID NO: 63), DOM11-6 (SEQ ID NO: 64), DOM11-8 (SEQ ID NO: 65), and DOM11-9 (SEQ ID NO: 66). In other embodiments, the polypeptide domain having a binding site with a binding specificity for CD38 competes for binding to CD38, with a dAb selected from the group consisting of: DOM 11-3-1 (SEQ ID. NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272) DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274) DOM 11-3-10 (SEQ ID NO: 275), DOM 11-3- 11 (SEQ ID NO: 276) DOM 11-3-14 (SEQ ID NO: 277), DOM 11-3-15 (SEQ ID NO: 278) DOM 11-3-17 (SEQ ID NO: 279), DOM 11-3-19 (SEQ ID NO: 280), DOM 11-3-20 (SEQ ID NO: 281), DOM 11-3-21 (SEQ ID NO: 282), DOM 11-3-22 (SEQ ID NO: 283), DOM 11-3-23 (SEQ ID NO: 284), DOM 11-3-24 (SEQ ID NO: 285), DOM 11-3-25 (SEQ ID NO: 286), DOM 11- 3-26 (SEQ ID NO: 287), DOM 11-3-27 (SEQ ID NO: 288), DOM 11-3-28 (SEQ ID NO: 289), DOM 11-30-1 (SEQ ID NO: 290), DOM 11-30-2 (SEQ ID NO: 291), DOM 11-30-3 (SEQ ID NO: 292), DOM 11-30-5 (SEQ ID NO: 293), DOM 11- 30-6 (SEQ ID NO: 294), DOM 11-30-7 (SEQ ID NO: 295), DOM 11-30-8 (SEQ ID NO: 296), DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298), DOM 11-30-11 (SEQ ID NO: 299), DOM 11-30-12 (SEQ ID NO: 300), DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302), DOM 11-30-15 (SEQ ID NO: 303), DOM 11- 30-16 (SEQ ID NO: 304), and DOM 11-30-17 (SEQ ID NO: 305). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD38, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent , at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, at least about 95 percent, when less about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM11- 14 (SEQ ID NO: 261), DOM11-22 (SEQ ID NO: 262), DOM11-23 (SEQ ID NO: 9), DOM11-25 (SEQ ID NO: 263), DOM11-26 (SEQ ID NO: 264), DOM11-27 (SEQ ID NO: 265), DOM11-29 (SEQ ID NO: 266), DOM11-3 (SEQ ID NO: 1), DOM11-30 (SEQ ID NO: 2), DOM11-31 (SEQ ID NO: 267), DOM11-32 (SEQ ID NO: 7), DOM11-36 (SEQ ID NO: 268) ), DOM11-4 (SEQ ID NO: 269), DOM11-43 (SEQ ID NO: 270), DOM11-44 (SEQ ID NO: 271), DOM11-45 (SEQ ID NO: 272), DOM11-5 ( SEQ ID NO: 273), DOM11-7 (SEQ ID NO: 3), DOM11-1 (SEQ ID NO: 274), DOM11-10 (SEQ ID NO: 275), DOM11-16 (SEQ ID NO: 276), DOM11-2 (SEQ ID NO: 277), DOM11-20 (SEQ ID NO: 278), DOM11-21 (SEQ ID NO: 279), DOM11-24 (SEQ ID NO: 6), DOM11-28 (SEQ ID NO: 280), DOM11-33 (SEQ ID NO: 281), DOM11-34 (SEQ ID NO: 282), DOM11 -35 (SEQ ID NO: 283), DOM11-37 (SEQ ID NO: 8), DOM11-38 (SEQ ID NO: 4), DOM11-39 (SEQ ID NO: 5), DOM11-41 (SEQ ID NO: 284), DOM11-42 (SEQ ID NO: 285), DOM11-6 (SEQ ID NO: 286), DOM11 -8 (SEQ ID NO: 287), and DOM11-9 (SEQ ID NO: 288). In other embodiments, the polypeptide domain having a binding site with binding specificity for CD38, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent , at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, at least about 95 percent, when less about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM 11 -3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11-3-10 (SEQ ID NO: 275 DOM 11-3-11 (SEQ ID NO: 276 DOM 11-3-14 (SEQ ID NO: 277 DOM 11-3-15 (SEQ ID NO: 278 DOM 11-3-17 (SEQ ID NO: 279 SUN 11-3-19 (SEQ ID NO: 280 SUN 11-3-20 (SEQ ID NO: 281 DOM 11-3-21 (SEQ ID NO: 282 DOM 11-3-22 (SEQ ID NO: 283 DOM 11-3-23 (SEQ ID NO: 284 DOM 11-3-24 (SEQ ID NO: 285 DOM 11-3-25 (SEQ ID NO: 286 DOM 11-3-26 (SEQ ID NO: 287 DOM 11-3-27 (SEQ ID NO: 288 DOM 11-3-28 (SEQ ID NO. : 289 DOM 11-30-1 (SEQ ID NO: 290 DOM 11-30-2 (SEQ ID NO: 291 DOM 11-30-3 (SEQ ID NO: 292 DOM 11-30-5 (SEQ ID NO: 293 SUN 11-30-6 (SEQ ID NO: 294 SUN 11-30-7 (SEQ ID NO: 295 SUN 11-30-8 (SEQ ID NO: 296 SUN 11-30-9 (SEQ ID NO: 297 SUN 11 -30-10 (SEQ ID NO: 298 DOM 11-30-11 (SEQ ID NO: 299 DOM 11-30-12 (SEQ ID NO: 300 DOM 11-30-13 (SEQ ID NO: 301 DOM 11-30 -14 (SEQ ID NO: 302 DOM 11-30-15 (SEQ ID NO: 303 DOM 11-30-16 (SEQ ID NO: 304), and DOM 11-30-17 (SEQ ID NO: 305). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD38, competes with any of the dAbs disclosed herein for binding to CD38. In preferred embodiments, the polypeptide domain having a binding site with binding specificity for CD38 is selected from the group consisting of: DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254), DOM11-7 (SEQ ID NO: 238), DOM11-38 (SEQ ID NO: 262), DOM11-39 (SEQ ID NO: 263), DOM11-24 (SEQ ID NO: 248), DOM11-32 (SEQ ID NO: 256), DOM11-37 (SEQ ID NO: 261), and DOM11-23 (SEQ ID NO: 247). In other preferred embodiments, the polypeptide domain having a binding site with a binding specificity for CD38, is selected from the group consisting of: DOM11-3-1 (SEQ ID NO: 269), DOM11-3- 2 (SEQ ID NO: 270), DOM11-3-6 (SEQ ID NO: 273), DOM11-3-10 (SEQ ID NO: 275), DOM11-3-15 (SEQ ID NO: 278), DOM11- 3-20 (SEQ ID NO: 281), DOM11-3-23 (SEQ ID NO: 284), and DOM11-3-26 (SEQ ID NO: 287). In other preferred embodiments, the polypeptide domain having a binding site with a binding specificity for CD38 is selected from the group consisting of: DOM11-30-1 (SEQ ID NO: 290), DOM11-30-2 (SEQ ID NO: 291), DOM11-30-9 (SEQ ID NO: 297), DOM11-3-15 (SEQ ID NO: 303), and DOM11-30-16 (SEQ ID NO: 304).

The polypeptide domain having a binding site with binding specificity for CD38 may comprise any suitable immunoglobulin variable domain, and preferably comprises a human variable domain, or a variable domain comprising the human framework regions. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD38, comprises a universal structure, as described herein. The universal structure can be a V (V? Or VK) structure, such as a structure comprising the amino acid sequences of structure encoded by the segment of the immunoglobulin gene DPK1, DPK2, DPK3, DPK4, DPK5, DPK6, DPK7, DPK8 , DPK9, DPK1 0, DPK1 2, DPK1 3, DPK1 5, DPK1 6, DPK1 8, DPK1 9, DPK20, DPK21, DPK22, DPK23, DPK24, DPK25, DPK26, or DPK28 of the human germline. If desired, the VL structure may further comprise the amino acid sequence of structure encoded by the segment of the immunoglobulin gene J? 1, J? 2, J? 3, J? 4, or J? 5 of the human germinal line . In other embodiments, the universal structure can be a VH structure, such as a structure comprising the amino acid sequences of structure encoded by the segment of the immunoglobulin gene DP4, DP7, DP8, DP9, DP10, DP31, DP33, DP38, DP45 , DP46, DP47, DP49, DP50, DP51, DP53, DP54, DP65, DP66, DP67, DP68, or DP69 of the human germline. If desired, the VH structure may further comprise the amino acid sequence of structure encoded by the segment of the immunoglobulin gene JH1, J H2, JH3, JH4, JH4b, JH5, and JH6 of the human germline. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD38, comprises one or more structure regions comprising an amino acid sequence that is the same as the amino acid sequence of a corresponding structure region encoded by a genetic segment of human germline antibody, or the amino acid sequence of one or more of these structure regions collectively comprise up to three amino acid differences in relation to the amino acid sequence of this corresponding structure region encoded by a genetic segment of the human germline antibody. In other embodiments, the amino acid sequences of FW1, FW2, FW3, and FW4 of the polypeptide domain having a binding site with binding specificity for CD38, are the same as the amino acid sequences of the corresponding structure regions encoded by a genetic segment of the human germline antibody, or the amino acid sequences of FW1, FW2, FW3, and FW4 collectively contain up to 10 amino acid differences relative to the amino acid sequences of the corresponding structure regions encoded by that genetic segment of human germline antibody.

In other embodiments, the polypeptide domain having a binding site with binding specificity for CD38 comprises regions FW1, FW2, and FW3, and the amino acid sequence of these regions FW1, FW2, and FW3 are the same as the sequences of amino acids of the corresponding structure regions encoded by the genetic segments of the human germline antibody. In particular embodiments, the polypeptide domain having a binding site with binding specificity for CD38, comprises the VL DPK9 structure, or a VH structure selected from the group consisting of DP47, DP45, and DP38. The polypeptide domain having a binding site with binding specificity for CD38 may comprise a binding site for a generic ligand, such as protein A, protein L, and protein G. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD38 is substantially resistant to accumulation. For example, in some modalities, it accumulates less than about 10 percent, less than about 9 percent, less than about 8 percent, less than about 7 percent, less than about 6 percent, less than about 5 percent, less than about 4 percent, less than about 3 percent, less than about 2 percent, or less than about 1 percent of the polypeptide domain that has a binding site with specificity of binding for CD38, when a solution of 1 to 5 milligrams / milliliter, of 5 to 10 milligrams / milliliter, of 10 to 20 milligrams / milliliter, of 20 to 50 milligrams / milliliter, of 50 to 100 milligram / milliliter, of 100 to 200 milligrams / milliliter, or 200 to 500 milligrams / milliliter of ligand or dAb in a solvent that is routinely used for drug formulation, such as serum, regulated serum, citrate regulating serum, water, an emulsion, and any was of these solvents with an acceptable excipient, such as those approved by the FDA, is maintained at about 22 ° C, 22-25 ° C, 25-30 ° C, 30-37 ° C, 37-40 ° C, 40 -50 ° C, 50-60 ° C, 60-70 ° C, 70-80 ° C, 15-20 ° C, 10-15 ° C, 5-10 ° C, 2-5 ° C, 0-2 ° C, -10 ° C to 0 ° C, -20 ° C to -10 ° C, -40 ° C to -20 ° C, -60 ° C to -40 ° C, or -80 ° C ° C to -60 ° C, for a period of time, for example, of about 10 minutes, 1 hour, 8 hours, 24 hours, 2 days, 3 days, 4 days, 1 week, 2 weeks, 3 weeks, 1 month, 2 months, 3 months, 4 months, 6 months, 1 year, or 2 years. Accumulation can be evaluated using any suitable method, such as, by microscopy, evaluating the turbidity of a solution by visual inspection or spectroscopy, or by any other suitable method. Preferably, the accumulation is evaluated by dynamic light scattering. Polypeptide domains that have a binding site with binding specificity for CD38 that are resistant to accumulation provide several advantages. For example, these polypeptide domains having a binding site with binding specificity for CD38, can be easily produced in high yield as soluble proteins, by expression using a suitable biological production system, such as E. coli, and they can be formulated and / or stored at higher concentrations than conventional polypeptides, and with less accumulation and loss of activity. In addition, the polypeptide domain having a binding site with binding specificity for CD38 that is resistant to accumulation can be produced more economically than other antigen or epitope binding polypeptides (e.g. conventional). For example, in general terms, the preparation of the antigen or epitope binding polypeptides intended for in vivo applications includes proces(e.g., gel filtration) that remove accumulated polypeptides. Failure to remove these aggregates can result in a preparation that is not suitable for in vivo application, due, for example, to the fact that aggregates of an antigen binding polypeptide that is intended to act as an antagonist, can function as an agonist by induction of cross-linking or pooling of the target antigen. Protein aggregates can also reduce the efficacy of the therapeutic polypeptide by inducing an immune response in the subject to which it is administered. In contrast, the accumulation-resistant polypeptide domain having a binding site with a binding specificity for CD38 of the invention, can be prepared for in vivo applications, without the need to include process steps that remove the aggregates, and it can be used in in vivo applications without the aforementioned drawbacks caused by the polypeptide aggregates. In some embodiments, a polypeptide domain having a binding site with binding specificity for CD38, is deployed in a reversible manner when heated to a temperature (Ts), and cooled to a temperature (Te), where Ts is greater than the melting temperature (Tm) of the polypeptide domain having a binding site with binding specificity for CD38, and Te is lower than the fusion temperature of the polypeptide domain having a binding site with binding specificity for CD38. For example, the polypeptide domain having a binding site with binding specificity for CD38 can be displayed in a reversible manner when heated to 80 ° C and cooled to about room temperature. A polypeptide that is deployed in a reversible manner loses its function when it is deployed, but regains the function when it replicates. These polypeptides are distinguished from polypeptides that accumulate when they unfold, or that they replicate inappropriately (misfolded polypeptides), that is, they do not regain function.

The deployment and refolding of the polypeptide can be evaluated, for example, by directly or indirectly detecting the structure of the polypeptide, using any suitable method. For example, the structure of the polypeptide can be detected by circular dichroism (CD) (eg, UV-far CD, near-UV CD), fluorescence (eg, fluorescence of the side chains of tryptophan), susceptibility to proteolysis, nuclear magnetic resonance (NMR), or by detecting or measuring a polypeptide function that depends on an appropriate fold (e.g., binding to a target ligand, binding to a generic ligand). In one example, the deployment of the polypeptide is evaluated using a functional assay, wherein the loss of the binding function (e.g., the binding of a generic and / or target ligand, the binding of a substrate) indicates that the polypeptide is unfolded. The degree of unfolding and refolding of a polypeptide domain having a binding site with binding specificity for CD38, can be determined using a deployment and denaturation curve. A deployment curve can be produced by plotting the temperature as the ordinate, and the relative concentration of the folded polypeptide as the abscissa. The relative concentration of a folded polypeptide domain having a binding site with binding specificity for CD38 can be determined directly or indirectly using any suitable method (e.g., CD, fluorescence, binding assay). For example, a solution of a polypeptide domain having a binding site with binding specificity for CD38 can be prepared, and the ellipticity of the solution can be determined by circular dichroism. The ellipticity value obtained represents a relative concentration of the folded ligand or dAb monomer of 1 00 percent. The polypeptide domain having a binding site with binding specificity for CD38 in the solution is then deployed by increasing the temperature of the solution, and the ellipticity is determined in appropriate increments (eg, after each increment of one degree). in the temperature). The polypeptide domain having a binding site with binding specificity for CD38 in solution, is then refolded by increasingly reducing the temperature of the solution, and the ellipticity is determined in appropriate increments. The data can be plotted to produce a deployment curve and a fallback curve. The unfolding and folding curves have a characteristic sigmoid shape that includes a portion where molecules of the polypeptide domain that have a binding site with binding specificity for CD38 fold, a folding / unfolding transition, wherein the molecules of the polypeptide are folded. polypeptide domain having a binding site with binding specificity for CD38 are displayed to different degrees, and a portion where the polypeptide domain having a binding site with binding specificity for CD38 unfolds. The intercept of the y-axis of the refolding curve is the relative amount of the refolded polypeptide domain having a binding site with binding specificity for recovered CD38. A recovery of at least about 50 percent, or at least about 60 percent, or at least about 70 percent, or at least about 80 percent, or at least about 85 percent , or at least about 90 percent, or at least about 95 percent, indicates that the ligand or dAb monomer is displayed in a reversible manner. In a preferred embodiment, the reversibility of the deployment of a polypeptide domain having a binding site with binding specificity for CD38 is determined by preparing a solution of the polypeptide domain having a binding site with binding specificity for CD38., and graphing the curves of deployment and retreat with the heat. The solution of the polypeptide domain having a binding site with binding specificity for CD38 can be prepared in any suitable solvent, such as an aqueous buffer having a suitable pH to allow a polypeptide domain having a specific site to dissolve. bond with binding specificity for CD38 (for example, a pH that is approximately three units higher or lower than the isoelectric point (pl)). The solution of the polypeptide domain having a binding site with binding specificity for CD38 is sufficiently concentrated to allow deployment / folding to be detected. For example, the ligand or dAb monomer solution can be from about 0.1 μM to about 100 μM, or preferably from about 1 μM to about 10 μM. If the melting temperature (Tm) of the polypeptide domain having a binding site with binding specificity for CD38 is known, the solution can be heated to about 10 ° C below the Tm (Tm-10), and the fold can be assessed by ellipticity or fluorescence (eg, UV-distant CD scan from 200 nanometers to 250 nanometers, CD of fixed wavelength at 235 nanometers or at 225 nanometers; fluorescent emission spectra of tryptophan from 300 to 450 nanometers with excitation at 298 nanometers), to provide 1 00 percent ligand or relative folded dAb monomer. The solution is then heated to at least 10 degrees above the Tm (Tm + 10) in previously determined increments (e.g., increments of about 0.1 to about 1 degree), and ellipticity or fluorescence is determined at each increment. . Then, the polypeptide domain having a binding site with binding specificity for CD38 is refolded by cooling to at least Tm-1 0 in previously determined increments, and the ellipticity or fluorescence at each increment is determined. If the melting temperature of a polypeptide domain having a binding site with binding specificity for CD38 is not known, the solution can be deployed by heating increasingly from about 25 ° C to about 1000 ° C, and then folding back increasingly to at least about 25 ° C, and the ellipticity or fluorescence is determined at each increase in heating and cooling. The obtained data can be graphed to produce a deployment curve and a fallback curve, where the y-axis intercept in the fallback curve is the relative amount of recovered refolded protein. In some embodiments, the polypeptide domain having a binding site with binding specificity for CD38 does not comprise a variable domain of camelid immunoglobulin, or one or more structure amino acids that are unique to the immunoglobulin variable domains encoded by the Genetic segments of the camelid germ line antibody. Preferably, the polypeptide domain having a binding site with binding specificity for CD38 is secreted in an amount of at least about 0.5 milligrams / liter when expressed in E. coli, or in Pichia species (eg, P pastoris). In other preferred embodiments, a polypeptide domain having a binding site with binding specificity for CD38 is secreted in an amount of at least about 0.75 milligrams / liter, of at least about 1 milligram / liter, of at least about 4 milligrams / liter, of at least about 5 milligrams / liter, of at least about 10 milligrams / liter, of at least about 15 milligrams / liter, of at least about 20 milligrams / liter, of at least about 25 milligrams / liter, at least about 30 milligrams / liter, at least about 35 milligrams / liter, at least about 40 milligrams / liter, at least about 45 milligrams / liter, or at least about 50 milligrams / liter, or at least approximately 100 milligrams / liter, or at least approximately 200 milligrams / liter, or at least approximately 300 thousand igramos / liter, or at least approximately 400 milligrams / liter, or at least approximately 500 milligrams / liter, or at least approximately 600 milligrams / liter, or at least approximately 700 milligrams / liter, or at least approximately 800 milligrams / liter, at least approximately 900 milligrams / liter, or at least approximately 1 gram / liter, when expressed in E. coli or in Pichia species (for example, P. pastoris). In other preferred embodiments, a polypeptide domain having a binding site with binding specificity for CD38, is secreted in an amount of at least about 1 milligram / liter to at least about 1 gram / liter, of at least about 1 milligram / liter to at least about 750 milligrams / liter, from at least about 100 milligrams / liter to at least about 1 gram / liter, from at least about 200 milligrams / liter to at least about 1 gram / liter, from at least about 300 milligrams / liter to at least about 1 gram / liter, from at least about 400 milligrams / liter to at least about 1 gram / liter, from at least about 500 milligrams / liter to at least about 1 gram / liter liter, from at least about 600 milligrams / liter to at least about 1 gram / liter, from at least about 700 milligrams / liter to at least about 1 gram / liter, from at least about 800 milligrams / liter to at least about 1 gram / liter, or at least about 900 milligrams / liter to at least about 1 gram / liter, when expressed in E. coli or in Pichia species (eg, P. pastoris). Although a polypeptide domain having a binding site with binding specificity for D38 described herein can be secreted when expressed in E. coli or in Pichia species (eg, P. pastoris), it can be produced using any suitable method, such as synthetic chemical methods or biological production methods that do not employ E. coli or Pichia species. Polypeptide Domains That Bind with CD138 The invention provides polypeptide domains (e.g., dA), which have a binding site with binding specificity for CD1 38. In preferred embodiments, the polypeptide domain binds to CD 1 38 with a low affinity. Preferably, the polypeptide domain is linked to CD138 with a Kd of between about 1.0 μM and about 10 nM, as determined by surface plasmon resonance. For example, the polypeptide domain can be linked to CD138 with an affinity of about 10 μM to 300 nM, or 10 μM to about 400 nM. In certain embodiments, the polypeptide domain binds to CD138 with an affinity of about 300 nM to about 10 nM, or from 200 nM to about 10 nM. In some embodiments, the polypeptide domain having a binding site with binding specificity for CD138 competes for binding to CD138, with a dAb selected from the group consisting of: DOM12-1 (SEQ ID NO: 70), DOM12-15 (SEQ ID NO: 71), DOM12-17 (SEQ ID NO: 68), DOM12-19 (SEQ ID NO: 72), DOM12-2 (SEQ ID NO: 73), DOM12-20 (SEQ ID NO: 74), DOM12-21 (SEQ ID NO: 75), DOM12-22 (SEQ ID NO: 76), DOM12-3 (SEQ ID NO: 77), DOM12-33 (SEQ ID NO: 78), DOM12 -39 (SEQ ID NO: 79), DOM12-4 (SEQ ID NO: 80), DOM12-40 (SEQ ID NO: 81), DOM12-41 (SEQ ID NO: 82), DOM12-42 (SEQ ID NO: 83), DOM12-44 (SEQ ID NO: 84) ), DOM12-46 (SEQ ID NO: 85), DOM12-6 (SEQ ID NO: 86), DOM12-7 (SEQ ID NO: 87), DOM12-10 (SEQ ID NO: 88), DOM12-11 ( SEQ ID NO: 89), DOM12-18 (SEQ ID NO: 90), DOM12-23 (SEQ ID NO: 91), DOM12-24 (SEQ ID NO: 92), DOM12-25 (SEQ ID NO: 93), DOM12-26 (SEQ ID NO: 69), DOM12-27 (SEQ ID NO: 94), DOM12-28 (SEQ ID NO: 95), DOM12-29 (SEQ ID NO: 96), DOM12-30 (SEQ ID NO: 97), DOM12-31 (SEQ ID NO: 98), DOM12-32 (SEQ ID NO: 99), DOM12 -34 (SEQ ID NO: 100), DOM12-35 (SEQ ID NO: 101), DOM12-36 (SEQ ID NO: 102), DOM12-37 (SEQ ID NO: 103), DOM12-38 (SEQ ID NO. : 104), DOM12-43 (SEQ ID NO: 105), DOM12-45 (SEQ ID NO: 67), DOM12-5 (SEQ ID NO: 106), DOM12-8 (SEQ ID NO: 107), and DOM12 -9 (SEQ ID NO: 108). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD138 competes for binding to CD138, with a dAb selected from the group consisting of: DOM 12-45-1 (SEQ ID NO. : 348), DOM 12-45-2 (SEQ ID NO: 349 DOM 12-45-3 (SEQ ID NO: 350 DOM 12-45-4 (SEQ ID NO: 351 DOM 12-45-5 (SEQ ID NO: 352 DOM 12-45-6 (SEQ ID NO: 353 DOM 12-45-8 (SEQ ID NO: 354 DOM 12-45-9 (SEQ ID NO: 355 DOM 12-45-10 (SEQ ID NO: 356 DOM 12-45-11 (SEQ ID NO: 357 DOM 12-45-12 (SEQ ID NO: 358 DOM 12-45-13 (SEQ ID NO: 359 DOM 12-45-14 (SEQ ID NO: 360 DOM 12-45-15 (SEQ ID NO.361 DOM 12- 45-16 (SEQ ID NO: 362 DOM 12-45-17 (SEQ ID NO: 363, DOM 12-45-18 (SEQ ID NO: 364, DOM 12-45-19 (SEQ ID NO: 365, DOM 12-45-) 20 (SEQ ID NO: 366 DOM 12-45-21 (SEQ ID NO: 367 DOM 12-45-22 (SEQ ID NO: 368 DOM 12-45-23 (SEQ ID NO: 369 DOM 12-45-24 ( SEQ ID NO: 370 DOM 12-45-25 (SEQ ID NO: 371 DOM 12-45-26 (SEQ ID NO: 372 DOM 12-45-27 (SEQ ID NO: 373 DOM 12-45-28 (SEQ ID NO: 374 DOM 12-45-29 (SEQ ID NO: 375 DOM 12-45-30 (SEQ ID NO: 376 DOM 12-45-31 (SEQ ID NO: 377 DOM 12-45-32 (SEQ ID NO: 378 DOM 12-45-33 (SEQ ID NO: 379 DOM 12-45-34 (SEQ ID NO: 380 DOM 12-45-35 (SEQ ID NO: 381 DOM 12-45-36 (SEQ ID NO: 382 DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384). embodiments, the polypeptide domain having a binding site with binding specificity for CD138 comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent, of when less about 90 percent, from at least about 91 percent, from at least about 92 percent, from at least about 93 percent, from at least about 94 percent, from at least about 95 percent, to at least about 96 percent, of at least about 97 percent, of at least about 98 percent, or of at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM12-1 (SEQ ID NO: 289), DOM12-15 (SEQ ID NO: 290), DOM12-17 (SEQ ID NO: 11), DOM12-19 (SEQ ID NO: 291), DOM12-2 (SEQ ID NO: 292), DOM12-20 (SE Q ID NO: 293), DOM12-21 (SEQ ID NO: 294), DOM12-22 (SEQ ID NO: 295), DOM12-3 (SEQ ID NO: 296), DOM12-33 (SEQ ID NO: 297) , DOM12-39 (SEQ ID NO: 298), DOM12-4 (SEQ ID NO: 299), DOM12-40 (SEQ ID NO: 300), DOM12-41 (SEQ ID NO: 301), DOM12-42 (SEQ ID NO: 302), DOM12-44 (SEQ ID NO: 303), DOM12 -46 (SEQ ID NO: 304), DOM12-6 (SEQ ID NO: 305), DOM12-7 (SEQ ID NO: 306), DOM12-10 (SEQ ID NO: 307), DOM12-11 (SEQ ID NO. : 308), DOM12-18 (SEQ ID NO: 309), DOM12-23 (SEQ ID NO: 310), DOM12- 24 (SEQ ID NO: 311), DOM12-25 (SEQ ID NO.312), DOM12- 26 (SEQ ID NO: 12), DOM12-27 (SEQ ID NO: 313), DOM12-28 (SEQ ID NO: 314), DOM12-29 (SEQ ID NO: 315), DOM12-30 (SEQ ID NO: 316), DOM12-31 (SEQ ID NO: 317), DOM12-32 (SEQ ID NO: 318), DOM12-34 (SEQ ID NO: 319), DOM12-35 (SEQ ID NO: 320), DOM12-36 (I KNOW THAT ID NO: 321). DOM12-37 (SEQ ID NO: 322), DOM12-38 (SEQ ID NO: 323), DOM12-43 (SEQ ID NO: 324), DOM12-45 (SEQ ID NO: 310), DOM12-5 (SEQ ID NO: 325), DOM12-8 (SEQ ID NO: 326), and DOM12-9 (SEQ ID NO: 327). In some modalities, the polypeptide domain having a binding site with binding specificity for CD138, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent, of when less about 90 percent, from at least about 91 percent, from at least about 92 percent, from at least about 93 percent, from at least about 94 percent, from at least about 95 percent, to at least about 96 percent, of at least about 97 percent, of at least about 98 percent, or of at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM 12-45- 1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351) , DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353), DOM 12-45-8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355), DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357), DOM 12-45-12 (SEQ ID NO: 358) DOM 12-45-13 (SEQ ID NO: 359) DOM 12-45-14 (SEQ ID NO: 360) DOM 12-45-15 (SEQ ID NO.361) DOM 12-45 -16 (SEQ ID NO: 362) DOM 12-45-17 (SEQ ID NO: 363) DOM 12-45-18 (SEQ ID NO: 364) DOM 12-45-19 (SEQ ID NO: 365) DOM 12 -45-20 (SEQ ID NO: 366) DOM 12-45-21 (SEQ ID NO: 367) DOM 12-45-22 (SEQ ID NO: 368) DOM 12-45-23 (SEQ ID NO: 369) DOM 12-45-24 (SEQ ID NO: 370) DOM 12-45-25 (SEQ ID NO: 371) DOM 12-45-26 (SEQ ID NO: 372) DOM 12-45-27 (SEQ ID NO: 373) DOM 12-45-28 (SEQ ID NO: 374) DOM 12-45-29 (SEQ ID NO: 375) DOM 12-45-30 (SEQ ID NO: 376) DOM 12-45-31 (SEQ ID NO: 377) DOM 12-45-32 (SEQ ID NO: 378) DOM 12-45-33 (SEQ ID NO: 379) DOM 12-45-34 (SEQ ID NO: 380) DOM 12-45-35 ( SEQ ID NO.381) DOM 12-45-36 (SEQ ID NO: 382), DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD138, competes with any of the dAbs disclosed herein, for binding to CD138. In preferred embodiments, the polypeptide domain having a binding site with binding specificity for CD138, is selected from the group consisting of DOM12-45 (SEQ ID NO: 346), DOM12-17 (SEQ ID NO: 318), and DOM12-26 (SEQ ID NO: 327). In other preferred embodiments, the polypeptide domain having a binding site with binding specificity for CD1 38 is selected from the group consisting of DOM 1 2-45-1 (SEQ ID NO: 348), DOM 1 2- 45-2 (SEQ ID NO: 349), and DOM 1 2-45-5 (SEQ ID NO: 352). The polypeptide domain having a binding site with binding specificity for CD1 38 can comprise any suitable immunoglobulin variable domain, and preferably comprises a human variable domain or a variable domain comprising regions of human structure. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD 1 38 comprises a universal structure, as described herein. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD1 38 resists accumulation, is deployed in a reversible manner, and / or comprises a framework region, and is secreted as described above for the polypeptide domain having a binding site with binding specificity for CD38. Polypeptide Domains That Bind with CEA The invention provides polypeptide domains (e.g., dAb) that have a binding site with binding specificity for CEA. In preferred embodiments, the polypeptide domain binds to CEA with a low affinity. Preferably, the polypeptide domain binds CEA with a Kd of between about 10 μM and about 10 nM, determined by surface plasmon resonance. For example, the polypeptide domain can be linked to CEA with an affinity of about 10 μM to about 300 nM, or about 10 μM to about 400 nM. In certain embodiments, the polypeptide domain binds to CEA with an affinity of about 300 nM to about 10 nM, or 200 nM to about 10 nM. In some embodiments, the polypeptide domain having a binding site with binding specificity for CEA competes for the CEA binding, with a dAb selected from the group consisting of: DOM13-1 (SEQ ID NO: 385), DOM13-12 (SEQ ID NO: 393), DOM13-13 (SEQ ID NO: 394), DOM13-14 (SEQ ID NO: 395), DOM13-15 (SEQ ID NO: 396), DOM13-16 (SEQ ID NO: 397), DOM13-17 (SEQ ID NO: 398), DOM13-18 (SEQ ID NO: 399), DOM13-19 (SEQ ID NO: 400), DOM13-2 (SEQ ID NO: 386), DOM13 -20 (SEQ ID NO: 401), DOM13-21 (SEQ ID NO: 402), DOM13-22 (SEQ ID NO: 403), DOM13-23 (SEQ ID NO: 404), DOM13-24 (SEQ ID NO. : 405), DOM13-25 (SEQ ID NO: 406), DOM13-26 (SEQ ID NO: 407), DOM13-27 (SEQ ID NO: 408), DOM13-28 (SEQ ID NO: 409), DOM13-29 (SEQ ID NO: 410), DOM13-3 (SEQ ID NO: 387), DOM13-30 (SEQ ID NO: 411), DOM13-31 (SEQ ID NO: 412), DOM13-32 (SEQ ID NO: 413), DOM13-33 (SEQ ID NO: 414), DOM-13-34 (SEQ ID NO: 415), DOM13-35 ( SEQ ID NO: 416), DOM13-36 (SEQ ID NO: 417), DOM13-37 (SEQ ID NO-418), DOM13-4 (SEQ ID NO.388), DOM13-42 (SEQ ID NO: 419) , DOM13-43 (SEQ ID NO: 420), DOM13-44 (SEQ ID NO: 421), DOM13-45 (SEQ ID NO: 422), DOM13-46 (SEQ ID NO: 423), DOM13-47 (SEQ. ID NO: 424), DOM13-48 (SEQ ID NO: 425), DOM13-49 (SEQ ID NO: 426), DOM13-5 (SEQ ID NO: 389), DOM13-50 (SEQ ID NO: 427), DOM13-51 (SEQ ID NO: 428), DOM13-52 (SEQ ID NO: 429), DOM13-53 (SEQ ID NO: 430), DOM13-54 (SEQ ID NO: 431), DOM13-55 (SEQ ID NO: 432), DOM13-56 (SEQ ID NO: 433), DOM13-57 (SEQ ID NO: 434), DOM13-58 (SEQ ID NO: 435), DOM13-59 (SEQ ID NO: 436), DOM13 -6 (SEQ ID NO: 390), DOM13-60 (SEQ ID NO.437), DOM13-61 (SEQ ID NO: 438), DOM13-62 (SEQ ID NO: 439), DOM13-63 (SEQ ID NO: 440), DOM13-64 (SEQ ID NO: 441), DOM13-65 (SEQ ID NO: 442) ), DOM13-66 (SEQ ID NO: 443), DOM13-67 (SEQ ID NO: 444), DOM13-68 (SEQ ID NO: 445), DOM13-69 (SEQ ID NO: 446), DOM13-7 ( SEQ ID NO: 391), DOM13-70 (SEQ ID NO: 447), DOM13-71 (SEQ ID NO: 3448), DOM13-72 (SEQ ID NO: 449), DOM13-73 (SEQ ID NO: 450), DOM13-74 (SEQ ID NO: 451), DOM13-75 (SEQ ID NO: 452), DOM13 -76 (SEQ ID NO: 453), DOM13-77 (SEQ ID NO: 454), DOM13-78 (SEQ ID NO: 455), DOM13-79 (SEQ ID NO: 456), DOM13-8 (SEQ ID NO. : 392), DOM13-80 (SEQ ID NO: 457), DOM13-81 (SEQ ID NO: 458), DOM13-82 (SEQ ID NO: 459), DOM13-83 (SEQ ID NO: 460), DOM13- 84 (SEQ ID NO: 461), DOM13-85 (SEQ ID NO: 462), DOM13-86 (SEQ ID NO: 463), DOM13-87 (SEQ ID NO: 464), DOM13-88 (SEQ ID NO: 465), DOM13-89 (SEQ ID NO: 466), DOM13-90 (SEQ ID NO: 467), DOM13-91 (SEQ ID NO: 468), DOM13-92 (SEQ ID NO: 469), DOM13-93 (SEQ ID NO: 470), DOM13-94 (SEQ ID NO: 471), and DOM13-95 (SEQ ID NO: 472). In certain embodiments, the polypeptide domain having a binding site with binding specificity for CEA competes for the CEA binding, with a dAb selected from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). In some embodiments, the polypeptide domain having a binding site with binding specificity for CEA, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent , at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, at least about 95 percent, when less about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM13- 1 (SEQ ID NO: 385), DOM13-12 (SEQ ID NO: 393), DOM13-13 (SEQ ID NO: 394), DOM13-14 (SEQ ID NO: 395), DOM13-15 (SEQ ID NO: 3396), DOM13-16 (SEQ ID NO: 397), DOM13-17 (SEQ ID NO: 398), DOM13-18 (SEQ ID NO: 399), DOM13-19 (SEQ ID NO: 400), DOM13-2 (SEQ ID NO: 386), DOM13-20 (SEQ ID NO: 401), DOM13-21 (SEQ ID NO: 402), DOM13-22 (SEQ ID NO: 403), DOM13-23 (SEQ ID NO: 404), DOM13 -24 (SEQ ID NO: 3405), DOM13-25 (SEQ ID NO: 406), DOM13-26 (SEQ ID NO: 407), DOM13-27 (SEQ ID NO: 408), DOM13-28 (SEQ ID NO: 409), DOM13-29 (SEQ ID NO: 410), DOM13-3 (SEQ ID NO: 387), DOM13-30 (SEQ ID NO: 411), DOM13-31 (SEQ ID NO: 412), DOM13-32 (SEQ ID NO: 413), DOM13-33 (SEQ ID NO: 414), DOM-13-34 (SEQ ID NO: 415). DOM13-35 (SEQ ID NO: 416), DOM13-36 (SEQ ID NO: 417), DOM13-37 (SEQ ID NO: 418), DOM13-4 (SEQ.

ID NO: 388), DOM13-42 (SEQ ID NO: 419), DOM13-43 (SEQ ID NO: 420), DOM13-44 (SEQ ID NO: 421), DOM13-45 (SEQ ID NO: 422), DOM13-46 (SEQ ID NO: 423), DOM13-47"(SEQ ID NO: 424), DOM13-48 (SEQ ID NO: 425), DOM13-49 (SEQ ID NO: 426), DOM13-5 (SEQ. ID NO: 389), DOM13-50 (SEQ ID NO: 427), DOM13-51 (SEQ ID NO: 428), DOM13-52 (SEQ ID NO: 429), DOM13-53 (SEQ ID NO: 430), DOM13-54 (SEQ ID NO: 431), DOM13-55 (SEQ ID NO: 432), DOM13 -56 (SEQ ID NO: 433), DOM13-57 (SEQ ID NO: 434), DOM13-58 (SEQ ID NO: 435), DOM13-59 (SEQ ID NO: 436), DOM13-6 (SEQ ID NO. : 390), DOM13-60 (SEQ ID NO: 437), DOM13-61 (SEQ ID NO: 438), DOM13-62 (SEQ ID NO: 439), DOM13-63 (SEQ ID NO: 440), DOM13-64 (SEQ ID NO: 441), DOM13-65 (SEQ ID NO: 442), DOM13-66 (SEQ ID NO: 443), DOM13-67 (SEQ ID NO: 444), DOM13-68 (SEQ ID NO: 445), DOM13-69 (SEQ ID NO: 446), DOM13-7 (SEQ ID NO: 391), DOM13-70 (SEQ ID NO: 447), DOM13-71 (SEQ ID NO: 3448), DOM13-72 (SEQ ID NO: 449), DOM13-73 (SEQ. ID NO: 450), DOM13-74 (SEQ ID NO: 451), DOM13-75 (SEQ ID NO: 452), DOM13-76 (SEQ ID NO: 453), DOM13-77 (SEQ ID NO: 454), DOM13-78 (SEQ ID NO: 455), DOM13-79 (SEQ ID NO: 456), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO: 457), DOM13-81 (SEQ ID NO: 458), DOM13-82 (SEQ ID NO: 459), DOM13-83 (SEQ ID NO: 460), DOM13-84 (SEQ ID NO: 461), DOM13-85 (SEQ ID NO: 462), DOM13 -86 (SEQ ID NO: 463), DOM13-87 (SEQ ID NO: 464), DOM13-88 (SEQ ID NO: 465), DOM13-89 (SEQ ID NO: 466), DOM13-90 (SEQ ID NO. : 467), DOM13-91 (SEQ ID NO: 468), DOM13-92 (SEQ ID NO: 469), DOM13-93 (SEQ ID NO: 470), DOM13-94 (SEQ ID NO: 471), and DOM13 -95 (SEQ ID NO: 472). In other embodiments, the polypeptide domain having a binding site with binding specificity for CEA, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent , at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, at least about 95 percent, when less about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM 13 - 25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). In preferred embodiments, the polypeptide domain having a binding site with binding specificity for CEA is selected from the group consisting of: DOM13-25 (SEQ ID NO: 80), DOM13-57 (SEQ ID NO: 81), DOM13-58 (SEQ ID NO: 82), DOM13-59 (SEQ ID NO: 83), DOM13-64 (SEQ ID NO: 84), DOM13-65 (SEQ ID NO: 85), DOM13-74 (SEQ ID NO: 86), DOM13-93 (SEQ ID NO: 87), and DOM13-95 (SEQ ID NO: 88). In some embodiments, the link domain that has a binding site with binding specificity for CEA competes with any of the dAbs disclosed herein by the CEA link. The polypeptide domain having a binding site with binding specificity for CEA can comprise any suitable immunoglobulin variable domain, and preferably comprises a human variable domain or a variable domain comprising regions of human structure. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CEA comprises a universal structure, as described herein. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CEA resists accumulation, is deployed in a reversible manner, and / or comprises a region of structure, and is secreted, as described above for the polypeptide domain having a binding site with binding specificity for CD38. Polypeptide Domains That Bind with CD56 The invention provides polypeptide domains (e.g., dAb) that have a binding site with binding specificity for CD56. In preferred embodiments, the polypeptide domain binds to CD56 with a low affinity. Preferably, the polypeptide domain binds to CD56 with a Kd of between about 10 μM and about 10 nM, determined by surface plasmon resonance. For example, the polypeptide domain can be linked to CD56 with an affinity of about 10 μM to about 300 nM, or about 10 μM to about 400 nM. In certain embodiments, the polypeptide domain binds to CD56 with an affinity of about 300 nM to about 10 nM, or from 200 nM to about 10 nM. In some modalities, the polypeptide domain having a binding site with binding specificity for CD56 competes for binding to CD56, with a dAb selected from the group consisting of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14 -16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO. : 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14- 24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507) ), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 ( SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ.

ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14 -60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO. : 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO.536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD56, comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, at least about 85 percent , at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, at least about 95 percent, when less about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM14- 1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483 ), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487), DOM14-17 ( I KNOW THAT ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14 -33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO. : 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14- 41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (I KNOW THAT ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525) DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO. : 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). In preferred embodiments, the polypeptide domain having a binding site with binding specificity for CD56, is selected from the group consisting of: DOM14-23 (SEQ ID NO: 494), DOM14-48 (SEQ ID NO. : 517), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO: 526), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14- 68 (SEQ ID NO: 537), and DOM14-70 (SEQ ID NO: 539). In some embodiments, the polypeptide domain having a binding site with binding specificity for CD56, competes with any of the dAbs disclosed herein for binding to CD56.

The polypeptide domain having a binding site with binding specificity for CD56 may comprise any suitable immunoglobulin variable domain, and preferably comprises a human variable domain or a variable domain comprising regions of human structure. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD56, comprises a universal structure, as described herein. In certain embodiments, the polypeptide domain having a binding site with binding specificity for CD56 resists accumulation, is deployed in a reversible manner, and / or comprises a region of structure, and is secreted, as described above for the polypeptide domain having a binding site with binding specificity for CD38. Ligands with dAb Monomers That Bind with Serum Albumin The ligands of the invention may further comprise a dAba monomer that binds with serum albumin (SA) at a kd of 1 nM to 500 μM (i.e., 1 x 10" 9 to 5x1 0"4), preferably 100 nM to 10 μM. Preferably, for a ligand comprising an anti-SA dAb, the linkage (e.g., Kd and / or KdeSactave measured by surface plasmon resonance (e.g., using BiaCore)) of the ligand with its targets, is from 1 to 1 00,000 times (preferably from 1 00 to 1 00,000, more preferably from 1,000 to 1,000,000, or from 1,000,000 to 1,000,000 times) stronger than for serum albumin. Preferably, serum albumin is human serum albumin (HSA). In one embodiment, the first dAb (or a dAb monomer) is linked to serum albumin (e.g., HSA), with a Kd of about 50, preferably 70, and more preferably 100, 1 50, or 200 nM . In certain embodiments, the dAb monomer that binds to the serum albumin resists accumulation, unfolds in a reversible manner, and / or comprises a region of structure, as described above for the dAb monomers that bind to CD38. . In particular embodiments, the antigen binding fragment of an antibody that binds to serum albumin is a dAb that binds to human serum albumin. In certain embodiments, dAb binds to human serum albumin, and competes for binding to albumin with a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-1 2 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 (SEQ ID NO-.544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477 ), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 ( SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560) DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577) ), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 ( SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). In certain embodiments, dAb binds to human serum albumin, and comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, or at least about 85 percent, or at least about 90 percent, or at least about 91 percent, or at least about 92 percentor at least about 93 percent, or at least about 94 percent, or at least about 95 percent, or at least about 96 percent, or at least about 97 percent, or at least about 98 percent, or at least about 99 percent, with the amino acid sequence of a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542) ), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 ( SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551) , DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h- 25 (SEQ ID NO: 560), DOM 7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7M8 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r -27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO. : 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). For example, the dAb that binds to human serum albumin can comprise an amino acid sequence having an amino acid sequence identity of at least about 90 percent, or at least about 95 percent, or when less about 96 percent, or at least about 97 percent, or at least about 98 percent, or at least about 99 percent with DOM7h-2 (SEQ ID NO: 550), DOM7h- 3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 554), DOM7h-7 (SEQ ID NO: 555), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), and DOM7h-27 (SEQ ID NO: 563). The identity of amino acid sequences is preferably determined using a suitable sequence alignment algorithm, and the default parameters, such as BLAST P (Karlin and Altschul, Proc. Nati. Acad. Sci. USA 87 (6): 2264- 2268 (1990)). In the most particular embodiments, dAb is a VK that binds to human serum albumin, and has an amino acid sequence selected from the group consisting of: DOM7h-2 (SEQ ID NO: 550), DOM7h-3 ( SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 554), DOM7h-7 (SEQ ID NO: 555) , DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), or a VH dAb having an amino acid sequence selected from the group which consists of: DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h- 25 (SEQ ID NO: 560), DOM7h- 26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563). In other embodiments, the antigen binding fragment of an antibody that binds to serum albumin is a dAb that binds to human serum albumin, and comprises the CDRs of any of the above amino acid sequences. Suitable camelid VH H that binds to serum albumin includes those disclosed in International Publication Number WO 2004/041 862 (Ablynx N. V.), and in this Sequence A (SEQ ID NO: 586) , Sequence B (SEQ ID NO: 587), Sequence C (SEQ ID NO: 588), Sequence D (SEQ ID NO: 589), Sequence E (SEQ ID NO: 590), Sequence F (SEQ ID NO: 591) , Sequence G (SEQ ID NO: 592), Sequence H (SEQ ID NO: 593), Sequence I (SEQ ID NO: 594), Sequence J (SEQ ID NO: 595), Sequence K (SEQ ID NO: 596) , Sequence L (SEQ ID NO: 597), Sequence M (SEQ ID NO: 598), Sequence N (SEQ ID NO: 599), Sequence O (SEQ ID NO: 600), Sequence P (SEQ ID NO: 601) , Sequence Q (SEQ ID NO: 602). In certain embodiments, camelid VH H binds to human serum albumin, and comprises an amino acid sequence having an amino acid sequence identity of at least about 80 percent, or at least about 85 percent, or at least about 90 percent, or at least about 95 percent, or at least about 96 percent, or at least about 97 percent, or at least about 98 percent, or at least about the 99 percent with any of SEQ ID NOs: 586-602. The identity of amino acid sequences is preferably determined using a suitable sequence alignment algorithm and the default parameters, such as BLAST P (Karlin and Altschul, Proc. Nati. Acad. Sci. USA 87 (6): 2264-2268 ( 1990)). In some modalities, the ligand comprises an anti-serum albumin dAb that competes with any anti-serum albumin dAb as disclosed herein for binding to serum albumin (e.g., human serum albumin). Nucleic Acid Molecules, Vectors, and Host Cells. The invention also provides isolated and / or recombinant nucleic acid molecules that encode ligands (specific double ligands and multispecific ligands), as described herein. In certain embodiments, the isolated and / or recombinant nucleic acid comprises a nucleotide sequence encoding a ligand as described herein, comprising an amino acid sequence that is at least about 80 percent, at least about 85 percent. percent, at least about 90 percent, at least about 95 percent, at least about 96 percent, at least about 97 percent, at least about 98 percent, at least about 99 percent homologous to the amino acid sequence selected from the group consisting of: DOM11-14 (SEQ ID NO: 242), DOM11-22 (SEQ ID NO: 246), DOM11-23 (SEQ ID NO: 247), DOM11-25 (SEQ ID NO: 249), DOM11-26 (SEQ ID NO: 250), DOM11-27 (SEQ ID NO: 251), DOM 11-29 (SEQ ID NO: 253), DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254) , DOM11-31 (SEQ ID NO: 255), DOM11-32 (SEQ ID NO: 256), DOM11-36 (SEQ ID NO: 260), DOM11-4 (SEQ ID NO: 235), DOM11-43 (SEQ ID NO: 266), DOM11-44 (SEQ ID NO: 267), DOM11-45 (SEQ ID NO: 268), DOM11-5 (SEQ ID NO: 236), DOM11-7 (SEQ ID NO: 238), DOM11-1 (SEQ ID NO: 232), DOM11-10 (SEQ ID NO: 241), DOM11 -16 (SEQ ID NO: 243), DOM11-2 (SEQ ID NO: 233), DOM11-20 (SEQ ID NO: 244), DOM11-21 (SEQ ID NO: 245), DOM11-24 (SEQ ID NO. : 248), DOM11-28 (SEQ ID NO: 252), DOM11-33 (SEQ ID NO: 257), DOM11-34 (SEQ ID NO: 258), DOM11-35 (SEQ ID NO: 259), DOM11- 37 (SEQ ID NO: 261), DOM11-38 (SEQ ID NO: 262), DOM11-39 (SEQ ID NO: 293), DOM11-41 (SEQ ID NO: 264), DOM11-42 (SEQ ID NO: 265), DOM11-6 (SEQ ID NO: 237), DOM11-8 (SEQ ID NO: 239), DOM11-9 (SEQ ID NO: 240), DOM12-1 (SEQ ID NO: 306), DOM12-15 (SEQ ID NO: 317), DOM12-17 (SEQ ID NO: 318), DOM12-19 (SEQ ID NO: 320), DOM12-2 (SEQ ID NO: 307), DOM12-20 (SEQ ID NO: 321), DOM12 -21 (SEQ ID NO: 322), DOM12-22 (SEQ ID NO: 323), DOM12-3 (SEQ ID NO: 308), DOM12-33 (SEQ ID NO: 334), DOM12-39 (SEQ ID NO. : 340), DOM12-4 (SEQ ID NO: 309), DOM12-40 (SEQ ID NO: 341), DOM12-41 (SEQ ID NO: 342), DOM12-42 (SEQ ID NO: 343), DOM12- 44 (SEQ ID NO: 345), DOM12-46 (SEQ ID NO: 347), DOM12-6 (SEQ ID NO: 311), DOM12-7 (SEQ ID NO: 312), DOM12-10 (SEQ ID NO: 315), DOM12-11 (SEQ ID NO: 316), DOM12-18 (SEQ ID NO: 319), DOM12-23 (SEQ ID NO: 324), DOM12-24 (SEQ ID NO: 325), DOM12-25 (SEQ ID NO: 326), DOM12-26 (SEQ ID NO: 327), DOM12-27 (SEQ ID NO: 328), DOM12-28 (SEQ ID NO: 329), DOM12-29 (SEQ ID NO: 330), DOM12-30 (SEQ ID NO: 331), DOM12-31 (SEQ ID NO: 332), DOM12-32 (SEQ ID NO: 333), DOM12-34 (SEQ ID NO: 335), DOM12-35 (SEQ ID NO: 336), DOM12 -36 (SEQ ID NO: 337), DOM12-37 (SEQ ID NO: 338), DOM12-38 (SEQ ID NO: 339), DOM12-43 (SEQ ID NO: 344), DOM12-45 (SEQ ID NO. : 346), DOM12-5 (SEQ ID NO: 310), DOM12-8 (SEQ ID NO: 313), DOM12-9 (SEQ ID NO: 314), DOM13-1 (SEQ ID NO: 385), DOM13- 12 (SEQ ID NO: 393), DOM13-13 (SEQ ID NO: 394), DOM13-14 (SEQ ID NO: 395), DOM13-15 (SEQ ID NO: 396), DOM13-16 (SEQ ID NO: 397), DOM13-17 (SEQ ID NO: 398), DOM13-18 (SEQ ID NO: 399), DOM13-19 (SEQ ID NO: 400), DOM13-2 (SEQ ID NO: 386), DOM13-20 (SEQ ID NO: 401), DOM13-21 (SEQ ID NO: 402), DOM13-22 (SEQ ID NO: 403), DOM13-23 (SEQ ID NO: 404), DOM13-24 (SEQ ID NO: 3405), DOM13 -25 (SEQ ID NO: 406), DOM13-26 (SEQ ID NO: 407), DOM13-27 (SEQ ID NO: 408), DOM13-28 (SEQ ID NO: 409), DOM13-29 (SEQ ID NO: 410), DOM13-3 (SEQ ID NO: 387), DOM13 -30 (SEQ ID NO: 411), DOM13-31 (SEQ ID NO: 412), DOM13-32 (SEQ ID NO: 413), DOM13-33 (SEQ ID NO: 414), DOM-13-34 (SEQ. ID NO: 415), DOM13-35 (SEQ ID NO: 416), DOM13-36 (SEQ ID NO: 417), DOM13-37 (SEQ ID NO: 418), DOM13-4 (SEQ ID NO: 388), DOM13-42 (SEQ ID NO: 419), DOM13-43 (SEQ ID NO: 420), DOM13-44 (SEQ ID NO: 421), DOM13-45 (SEQ ID NO: 422), DOM13-46 (SEQ ID NO: 423), DOM13-47 (SEQ ID NO: 424), DOM13-48 (SEQ ID NO: 425), DOM13-49 (SEQ ID NO: 426), DOM13-5 (SEQ ID NO: 389), DOM13 -50 (SEQ ID NO: 427), DOM13-51 (SEQ ID NO: 428), DOM13-52 (SEQ ID NO: 429), DOM13-53 (SEQ ID NO: 430), DOM13-54 (SEQ ID NO: 431), DOM13-55 (SEQ ID NO: 432), DOM13-56 (SEQ ID NO: 433), DOM13-57 (SEQ ID NO: 434), DOM13-58 (SEQ ID NO: 435), DOM13-59 (SEQ ID NO: 436), DOM13-6 (SEQ ID NO: 390), DOM13-60 (SEQ ID NO: 437), DOM13-61 (SEQ ID NO: 438), DOM13-62 (SEQ ID NO: 439), DOM13 -63 (SEQ ID NO: 440), DOM13-64 (SEQ ID NO: 441), DOM13-65 (SEQ ID NO: 442), DOM13-66 (SEQ ID NO: 443), DOM13-67 (SEQ ID NO. : 444), DOM13-68 (SEQ ID NO: 445), DOM13-69 (SEQ ID NO: 446), DOM13-7 (SEQ ID NO: 391), DOM13-70 (SEQ ID NO: 447), DOM13-71 (SEQ ID NO: 448), DOM13-72 (SEQ ID NO: 449), DOM13-73 (SEQ ID NO: 450), DOM13-74 (SEQ ID NO: 451), DOM13-75 (SEQ ID NO: 452), DOM13-76 (SEQ ID NO: 453), DOM13-77 (SEQ ID NO: 454), DOM13-78 (SEQ ID NO: 455), DOM13-79 (SEQ ID NO: 456), DOM13 -8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO: 457), DOM13-81 (SEQ ID NO: 458), DOM13-82 (SEQ ID NO: 459), DOM13-83 (SEQ ID NO. : 460), DOM13-84 (SEQ ID NO: 461), DOM13-85 (SEQ ID NO: 462), DOM13-86 (SEQ ID NO: 463), DOM13-87 (SEQ ID NO: 464), DOM13-88 (SEQ ID NO: 465), DOM13-89 (SEQ ID NO: 466), DOM13-90 (SEQ ID NO: 467), DOM13-91 (SEQ ID NO: 468), DOM13-92 (SEQ ID NO: 469) ), DOM13-93 (SEQ ID NO: 470), DOM13-94 (SEQ ID NO: 471), DOM13-95 (SEQ ID NO: 472), DOM14-1 (SEQ ID NO: 477), DOM14-10 ( SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484) , DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14 -2 (SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO. : 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO.498), DOM 14 -28 (SEQ ID NO: 499), DOM 14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505). DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14 -53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO. : 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14- 62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). In certain embodiments, the isolated and / or recombinant nucleic acid comprises a nucleotide sequence encoding a ligand, as described herein, wherein this nucleotide sequence has a nucleotide sequence identity of at least about 80 percent , at least about 85 percent, at least about 90 percent, at least about 91 percent, at least about 92 percent, at least about 93 percent, at least about 94 percent, when less about 95 percent, at least about 96 percent, at least about 97 percent, at least about 98 percent, or at least about 99 percent with a nucleotide sequence selected from the group that consists of: DOM11-14 (SEQ ID NO: 10), DOM11-22 (SEQ ID NO: 11), DOM11-23 (SEQ ID NO: 3), DOM11-25 (SEQ ID NO: 12), DOM11-26 (SEQ ID NO: 13), DOM11-27 (SEQ ID NO: 14), DOM 11-29 (SEQ ID NO: 15), DOM11-3 (SEQ ID NO: 1), DOM11-30 (SEQ ID NO: 2), DOM11-31 (SEQ ID NO: 16), DOM11-32 (SEQ ID NO: 7), DOM11-36 (SEQ ID NO: 17), DOM11-4 (SEQ ID NO: 18), DOM11-43 (SEQ ID NO: 19), DOM11-44 (SEQ ID NO: 20), DOM11-45 (SEQ ID NO: 21), DOM11-5 (SEQ ID NO: 22), DOM11 -7 (SEQ ID NO: 4), DOM11-1 (SEQ ID NO: 23), DOM11-10 (SEQ ID NO: 24), DOM11-16 (SEQ ID NO: 25), DOM11-2 (SEQ ID NO. : 26), DOM11-20 (SEQ ID NO: 27), DOM11-21 (SEQ ID NO: 28), DOM11-24 (SEQ ID NO: 9), DOM11-28 (SEQ ID NO: 29), DOM11-33 (SEQ ID NO: 30), DOM11-34 (SEQ ID NO: 31), DOM11-35 (SEQ ID NO: 32), DOM11-37 (SEQ ID NO: 8), DOM11-38 (SEQ ID NO: 5), DOM11-39 (SEQ ID NO: 6), DOM11-41 (SEQ ID NO: 33), DOM11 -42 (SEQ ID NO: 34), DOM11-6 (SEQ ID NO: 35), DOM11-8 (SEQ ID NO: 36), DOM11-9 (SEQ ID NO: 37), DOM12-1 (SEQ ID NO: 41), DOM12-15 (SEQ ID NO: 42), DOM12-17 (SEQ ID NO: 39), DOM12-19 (SEQ ID NO: 43), DOM12-2 (SEQ ID NO: 44), DOM12-20 (SEQ ID NO: 45), DOM12-21 (SEQ ID NO: 46), DOM12-22 (SEQ ID NO: 47) ), DOM12-3 (SEQ ID NO: 48), DOM12-33 (SEQ ID NO: 49), DOM12-39 (SEQ ID NO: 50), DOM12-4 (SEQ ID NO: 51), DOM12-40 (SEQ ID NO: 52), DOM12-41 (SEQ ID NO: 53), DOM12-42 (SEQ ID NO: 54), DOM12 -44 (SEQ ID NO: 55), DOM12-46 (SEQ ID NO: 56), DOM12-6 (SEQ ID NO: 57), DOM12-7 (SEQ ID NO: 58), DOM12-10 (SEQ ID NO. : 59), DOM12-11 (SEQ ID NO: 60), DOM12-18 (SEQ ID NO: 61), DOM12-23 (SEQ ID NO: 62), DOM12-24 (SEQ ID NO: 63), DOM12-25 (SEQ ID NO: 64), DOM12-26 (SEQ ID NO: 40), DOM12-27 (SEQ ID NO: 65) ), DOM12-28 (SEQ ID NO: 66), DOM12-29 (SEQ ID NO: 67), DOM12-30 (SEQ ID NO: 68), DOM12-31 (SEQ ID NO: 69), DOM12-32 (SEQ. ID NO: 70), DOM12-34 (SEQ ID NO: 71), DOM12-35 (SEQ ID NO: 72), DOM12-36 (SEQ ID NO: 73), DOM12-37 (SEQ ID NO: 74), DOM12-38 (SEQ ID NO: 75), DOM12-43 (SEQ ID NO: 76), DOM12-45 (SEQ ID NO: 38), DOM12-5 (SEQ ID NO: 77), DOM12-8 (SEQ ID NO: 78), DOM12-9 (SEQ ID NO: 79), DOM13-1 (SEQ ID NO: 89), DOM13-12 (SEQ ID NO: 90), DOM13-13 (SEQ ID NO: 91), DOM13 -14 (SEQ ID NO: 92), DOM13-15 (SEQ ID NO: 93), DOM13-16 (SEQ ID NO: 94), DOM13-17 (SEQ ID NO: 95), DOM13-18 (SEQ ID NO. : 96), DOM13-19 (SEQ ID NO: 97), DOM13-2 (SEQ ID NO: 98), DOM13-20 (SEQ ID NO: 99), DOM13-21 (SEQ ID NO: 100), DOM13- 22 (SEQ ID NO: 101), DOM13-23 (SEQ ID NO: 102), DOM13-24 (SEQ ID NO: 103), DOM13-25 (SEQ ID NO: 80), DOM13-26 (SEQ ID NO: 104), DOM13-27 (SEQ ID NO: 105), DOM13-28 (SEQ ID NO: 106), DOM13-29 (SEQ ID NO: 104), DOM13-3 (SEQ ID NO: 108), DOM13-30 (SEQ ID NO: 109), DOM13-31 (SEQ ID NO: 110), DOM13-32 (SEQ ID NO. : 111), DOM13-33 (SEQ ID NO: 112), DOM-13-34 (SEQ ID NO: 113), DOM13-35 (SEQ ID NO: 114), DOM13-36 (SEQ ID NO: 115), DOM13-37 (SEQ ID NO: 116), DOM13-4 (SEQ ID NO: 117), DOM13-42 (SEQ ID NO: 118) ), DOM13-43 (SEQ ID NO: 119), DOM13-44 (SEQ ID NO: 120), DOM13-45 (SEQ ID NO: 121), DOM13-46 (SEQ ID NO: 122), DOM13-47 ( SEQ ID NO: 123), DOM13-48 (SEQ ID NO: 124), DOM13-49 (SEQ ID NO: 125), DOM13-5 (SEQ ID NO: 126), DOM13-50 (SEQ ID NO: 127), DOM13-51 (SEQ ID NO: 128), DOM13-52 (SEQ ID NO: 129), DOM13-53 (SEQ ID NO: 130), DOM13-54 (SEQ ID NO: 131), DOM13-55 (SEQ ID NO: 132), DOM13-56 (SEQ ID NO: 133), DOM13-57 (SEQ ID NO: 81) ), DOM13-58 (SEQ ID NO: 82), DOM13-59 (SEQ ID NO: 83), DOM13-6 (SEQ ID NO: 134), DOM13-60 (SEQ ID NO: 135), DOM13-61 ( SEQ ID NO: 136), DOM13-62 (SEQ ID NO: 137), DOM13-63 (SEQ ID NO: 138), DOM13-64 (SEQ ID NO: 84), DOM13-65 (SEQ ID NO: 85) , DOM13-66 (SEQ ID NO: 139), DOM13-67 (SEQ ID NO: 140), DOM13-68 (SEQ ID NO: 141), DOM13-69 (SEQ ID NO: 142), DOM13-7 (SEQ. ID NO: 143), DOM13-70 (SEQ ID NO: 144), DOM13-71 (SEQ ID NO: 145), DOM13-72 (SEQ ID NO: 146), DOM13-73 (SEQ ID NO: 147), DOM13-74 (SEQ ID NO: 86), DOM13-75 (SEQ ID NO: 148), DOM13-76 (SEQ ID NO: 149), DOM13-77 (SEQ ID NO: 150), DOM13-78 (SEQ ID NO: 151), DOM13-79 (SEQ ID NO: 152), DOM13-8 (SEQ ID NO: 153), DOM13-80 (SEQ ID NO: 154), DOM13-81 (SEQ ID NO: 155), DOM13-82 (SEQ ID NO: 156), DOM13-83 (SEQ ID NO: 157), DOM13-84 (SEQ ID NO: 158), DOM13-85 (SEQ ID NO: 159), DOM13-86 (SEQ ID NO: 160), DOM13-87 (SEQ ID NO: 161), DOM13-88 (SEQ ID NO: 162), DOM13-89 (SEQ ID NO: 163), DOM13-90 (SEQ ID NO: 164), DOM13-91 (SEQ ID NO: 165), DOM13-92 (SEQ ID NO: 166), DOM13-93 (SEQ ID NO: 87), DOM13-94 (SEQ ID NO: 167), DOM13-95 (SEQ ID NO: 88), DOM14-1 (SEQ ID NO: 176), DOM14-10 (SEQ ID? O: 177), DOM14-100 (SEQ ID NO: 178), DOM14-11 (SEQ ID NO: 179), DOM14-12 (SEQ ID NO: 180), DOM14-13 (SEQ ID NO: 181), DOM14-14 (SEQ ID NO: 182), DOM14-15 (SEQ ID NO: 183), DOM14-16 (SEQ ID NO: 184), DOM14-17 (SEQ ID NO: 185), DOM14-18 (SEQ ID NO: 186), DOM14-19 (SEQ ID NO: 187), DOM14-2 (SEQ ID NO: 188), DOM14-20 (SEQ ID NO: 189), DOM14-21 (SEQ ID NO: 190), DOM14 -22 (SEQ ID NO: 191), DOM14-23 (SEQ ID NO: 168), DOM14-24 (SEQ ID NO: 192), DOM14-25 (SEQ ID NO: 193), DOM14-26 (SEQ ID NO. : 194), DOM14-27 (SEQ ID NO: 195), DOM14-28 (SEQ ID NO: 196), DOM14-3 (SEQ ID NO: 197), DOM14-31 (SEQ ID NO: 198), DOM14- 32 (SEQ ID NO: 199), DOM14-33 (SEQ ID NO: 200), DOM14-34 (SEQ ID NO: 201), DOM14-35 (SEQ ID NO: 202), DOM14-36 (SEQ ID NO: 203), DOM14-37 (SEQ ID NO: 204), DOM14-38 (SEQ ID NO: 205), DOM14-39 (SEQ ID NO: 206), DOM14-4 (SEQ ID NO: 207), DOM14-40 (SEQ ID NO: 208), DOM14-41 (SEQ ID NO: 209), DOM14-42 (SEQ ID NO: 210), DOM14-43 (SEQ ID NO: 211), DOM14-44 (SEQ ID NO: 212), DOM14-45 (SEQ ID NO: 213), DOM14-46 (SEQ ID NO: 214), DOM14-47 (SEQ ID NO: 215), DOM14-48 (SEQ ID NO: 169), DOM14-49 (SEQ ID NO: 216), DOM14-50 (SEQ ID NO: 217), DOM14-51 (SEQ ID NO: 218), DOM14-52 (SEQ ID NO: 219), DOM14-53 (SEQ ID NO: 220), DOM14-54 (SEQ ID NO: 221), DOM14-55 (SEQ ID NO: 222) ), DOM14-56 (SEQ ID NO: 170), DOM14-57 (SEQ ID NO: 171), DOM14-58 (SEQ ID NO: 223), DOM14-59 (SEQ ID NO: 224), DOM14-60 (SEQ ID NO: 225), DOM14-61 (SEQ ID NO: 226), DOM14-62 (SEQ ID NO: 172), DOM14-63 (SEQ ID NO: 173), DOM14-64 (SEQ ID NO: 227), DOM14-65 (SEQ ID NO: 228), DOM14-66 (SEQ ID NO: 229), DOM14 -67 (SEQ ID NO: 230), DOM14-70 (SEQ ID NO: 175), DOM14-68 (SEQ ID NO: 174), and DOM14-69 (SEQ ID NO: 231). The invention also provides a vector comprising a recombinant nucleic acid molecule of the invention. In certain embodiments, the vector is an expression vector that comprises one or more expression control elements, or sequences that are operably linked to the recombinant nucleic acid of the invention. The invention also provides a recombinant host cell comprising a recombinant nucleic acid molecule or a vector of the invention. Vectors (e.g., plasmids, phagemids), expression control elements, host cells, and methods suitable for producing the recombinant host cells of the invention, are well known in the art, and the examples are further described herein. Suitable expression vectors may contain a number of components, for example, a replication origin, a selectable marker gene, one or more expression control elements, such as a transcription control element (e.g., promoter, enhancer, terminator), and / or one or more translation signals, a signal sequence, or a leader sequence, and the like. The expression control elements and a signal sequence, if present, may be provided by the vector or another source. For example, transcriptional and / or translational control sequences of a cloned nucleic acid encoding an antibody chain can be used to direct expression. A promoter can be provided for expression in a desired host cell. The promoters can be constitutive or inducible. For example, a promoter can be operably linked to a nucleic acid encoding an antibody, an antibody chain, or a portion thereof, such that it directs the transcription of the nucleic acid. A variety of suitable promoters are available for prokaryotic hosts (e.g., lac, tac, T3, T7 promoters for E. coli), and eukaryotes (e.g., early or late promoter from simian virus 40, long terminal repeat promoter). of Rous sarcoma virus, cytomegalovirus promoter, adenovirus late promoter). In addition, expression vectors typically comprise a selectable marker for selection of host cells bearing the vector, and in the case of a replicable expression vector, a replication origin. Genes that encode products that confer resistance to antibiotics or drugs are common selectable markers, and can be used in prokaryotic cells (eg, lactamase gene (ampicillin resistance), Tet gene for tetracycline resistance), and in eukaryotic cells (e.g., genes for resistance to neomycin (G418 or geneticin), gpt (mycophenolic acid), ampicillin, or hygromycin). The dihydrofolate reductase marker genes allow selection with methotrexate in a variety of hosts. Genes encoding the genetic product of host auxotrophic markers (eg, LEU2, URA3, HIS3) are often used as selectable markers in yeast. The use of viral (e.g., baculovirus) or phage vectors, and vectors that are capable of integrating into the genome of the host cell, such as retroviral vectors, is also contemplated. Expression vectors suitable for expression in mammalian cells and in prokaryotic cells (E. coli), insect cells (Schnieder S2 cells from Drosophila, Sf9), and in yeast (P. methanolica, P. pastoris, S. cerevisiae ), are well known in this field. Suitable host cells can be prokaryotic, including bacterial cells, such as E. coli, B. subtilis, and / or other suitable bacteria; eukaryotic cells, such as fungal or yeast cells (e.g., Pichia pastoris, Aspergillus sp., Saccharomyces cerevisiae, Schizosaccharomyces pombe, Neurospora crassa), and other lower eukaryotic cells, and higher eukaryotic cells, such as those of insects (e.g., Schnieder S2 cells from Drosophila, S9 insect cells (International Publication Number WO 94/26087 (O'Connor)) , of mampherics (eg, COS cells, such as COS-1 (ATCC, Accession Number CRL-1 650), and COS-7 (ATCC, Accession Number CRL-1 651), CHO (eg, ATTC , Accession number CRL-9096, CHO DG44 (Uriaub, G. and Chasin, LA, Proc. Nati. Acad. Sci. USA, 77 (7): 421 6-4220 (1 980))), 293 (ATCC, Accession Number CRL-1 573), HeLa (ATCC Accession Number CCL-2), CV1 (ATCC Accession Number CCL-70), WOP (Dailey, L., et al., J. Virol., 54 : 739-749 (1985), 3T3, 293T (Pear W. S., Et al., Proc. Nati, Acad. Sci. USA, 90: 8392-8396 (1993)), NSO cells, SP2 / 0, cells HuT 78, and the like, or plants (for example, tobacco) (See, for example, Ausubel, F. M. Et al., Editors, Curren t Protocols in Molecular Biology, Greene Publishing Associates and John Wiley & Sons Inc. (1993)). In some embodiments, the host cell is an isolated host cell and is not part of a multicellular organism (e.g., plant or animal). In preferred embodiments, the host cell is a non-human host cell. The invention also provides a method for producing a ligand (e.g., specific double ligand, multispecific ligand) of the invention, which comprises maintaining a recombinant host cell comprising a recombinant nucleic acid of the invention, under conditions suitable for the expression of the recombinant nucleic acid, whereby, the recombinant nucleic acid is expressed, and a ligand is produced. In some embodiments, the method further comprises isolating the ligand. Preparation of Immunoglobulin-based Ligands. Ligands (for example, specific double ligands, multispecific) according to the invention, can be prepared according to previously established techniques, used in the field of antibody engineering, for the preparation of scFv, "phage" antibodies. , and other designed antibody molecules. Techniques for the preparation of antibodies, for example, are described in the following reviews and references cited therein: Winter and Milstein, (1 991) Nature 349: 293-299; Pluckthun (1 992) Immunological Reviews 1 30: 1 51 -1 88 Wright et al. (1 992) Crit. Rev. Immunol. 1 2: 1 25-1 68 Holliger, P. and Winter, G. (1993) Curr. Op. Biotechn. 4, 446-449 Carter, and collaborators (1 995) J. Hematother. 4, 463-470; Chester, K. A. and Hawkins, R. E. (1995) Trends Biotechn. 13, 294-300; Hoogenboom, H. R. (1997) Nature Biotechnol. 15, 125-126; Fearon, D. (1997) Nature Biotechnol. 15, 618-619; Plückthun, A. and Pack, P. (1997) Immunotechnology 3, 83-105; Cárter, P. and Merchant, A. M. (1997) Curr. Opin. Biotechnol. 8, 449-454; Holliger, P. and Winter, G. (1997) Cancer Immunol. Immunother.45,128-130. Suitable techniques employed for the selection of variable domains of antibodies with a desired specificity employ libraries and selection procedures that are known in the art. Natural libraries (Marks et al. (1991) J. Mol. Biol, 222: 581; Vaughan et al. (1996) Nature Biotech., 14: 309), using reconfigured V genes harvested from human B-cells, are well known by the experts in the field. Synthetic libraries (Hoogenboom and Winter (1992) J. Mol. Biol, 227: 381; Barbas et al. (1992) Proc. Nati. Acad. Sci. USA, 89: 4457; Nissim et al. (1994) EMBO J, 13 : 692; Griffiths et al. (1994) EMBO J., 13: 3245; De Kruif et al. (1995) J. Mol Biol, 248: 97), are prepared by cloning immunoglobulin V genes, usually using chain reaction of the polymerase. Errors in the polymerase chain reaction process can lead to a high degree of random selection. The VH and / or V libraries can be screened against the target antigens or epitopes separately, in which case, the single-domain link is directly selected, or together.

Library Vectors Systems A variety of selection systems are known in the art, which are suitable for use in the present invention. The examples of these systems are described below. The bacteriophage lambda expression systems can be screened directly as bacteriophage plaques or as colonies of lysogens, as previously described (Huse et al. (1989; Science, 246: 1 275; Cato and Koprowski (1990) Proc. Nati Acad. Sci. USA, 87; Mullinax and collaborators (1 990) Proc. Nati, Acad. Sci. USA, 87: 8095; Persson et al. (1991) Proc. Nati. Acad. Sci. USA, 88: 2432 ), as they are for use in the invention, although these expression systems can be used to track up to 1 06 different members of a library, they are not really suitable for tracking larger numbers (more than 1 06 members). Particular use in the construction of libraries is the selection display systems, which make it possible for a nucleic acid to be linked to the polypeptide that it expresses.As used herein, a selection display system is a system that allows to make the selection, by m suitable exhibition days, of the individual members of the library, through the link of the generic and / or the objective. Selection protocols for the isolation of desired members of large libraries are known in this field, as typified by phage display techniques. These systems, in which various peptide sequences are displayed on the surface of the filamentous bacteriophage (Scott and Smith (1990) Science, 249: 386), have proven to be useful for the creation of libraries of antibody fragments (and the sequences of nucleotides encoding them), for the in vitro selection and amplification of specific antibody fragments that bind to a target antigen (McCafferty et al., International Publication No. WO 92/01 047). The nucleotide sequences encoding the variable regions are linked to the genetic fragments encoding the leader signals that direct them towards the periplasmic space of E. coli, and as a result, the resulting antibody fragments are displayed on the surface of the bacteriophage, typically as fusions with the bacteriophage coating proteins (eg, pl II or pVI II). Alternatively, antibody fragments are externally displayed on capsids of lambda phages (phagobodies). An advantage of phage-based display systems is that, due to their biological systems, selected members of the library can be amplified simply by growing the phage containing the selected member of the library, in bacterial cells. Additionally, because the nucleotide sequence encoding the polypeptide member of the library is contained on a phage or phagemid vector, sequencing, expression, and subsequent genetic manipulation are relatively straightforward. Methods for the construction of bacteriophage antibody libraries and lambda phage display libraries are well known in the art (McCafferty et al. (1990) Nature, 348: 552; Kang et al. (1991) Proc. Nati). Acad Sci USA, 88: 4363, Clackson et al. (1991) Nature, 352: 624, Lowman et al. (1991) Biochemistry, 30: 10832, Burton et al. (1991) Proc. Nati. Acad. Sci. , 88: 10134; Hoogenboom et al. (1991) Nucleic Acids Res., 19: 4133; Chang et al. (1991) J. Immunol, 147: 3610; Breitling et al. (1991) Gene, 104: 147; Marks et al. 1991) supra, Barbas et al. (1992) supra, Hawkins and Winter (1992) J. Immunol, 22: 867, Marks et al., 1992, J. Biol. Chem., 267: 16007, Lerner et al. (1992) Science. , 258: 1313, incorporated herein by reference). A particularly convenient approach has been the use of scFv phage libraries (Huston et al., 1988, Proc. Nati, Acad. Sci. USA, 85: 5879-5883.; Chaudhary et al. (1990) Proc. Nati Acad. Sci. USA, 87: 1066-1070; McCafferty et al. (1990) supra; Clackson et al. (1991) Nature, 352: 624; Marks et al. (1991) J. Mol. Biol, 222: 581; Chiswell et al. (1992) Trends Biotech., 10:80; Marks et al. (1992) J. Biol. Chem., 267). Different modalities of scFv libraries displayed on bacteriophage coating proteins have been described. Refinements of the phage display approaches are also known, for example, as described in International Publications Nos. WO WO96 / 0621 3 and WO92 / 01 047 (Medical Research Council et al.), And WO97 / 08320 (Morphosys) , which are incorporated herein by reference. Other systems for generating polypeptide libraries involve the use of cell-free enzymatic machine for the in vitro synthesis of the members of the library. In one method, RNA molecules are selected by alternating rounds of selection against a target, and amplification with polymerase chain reaction (Tuerk and Gold (1990) Science, 249: 505; Ellington and Szostak (1990) Nature, 346: 81 8). A similar technique can be used to identify DNA sequences that bind to a previously determined human transcription factor (Thiesen and Bach (1990) Nucleic Acids Res., 1 8: 3203; Beaudy and Joyce (1992) Science , 257: 635, International Publications Nos. WO 92/05258 and WO92 / 14843). In a similar manner, in vitro translation can be used to synthesize polypeptides as a method to generate large libraries. These methods, which generally comprise stabilized polysome complexes, are further described in International Publications Nos. WO88 / 08453, WO90 / 05785, WO90 / 07003, WO91 / 02076, WO91 / 05058, and WO92 / 02536. Alternative display systems that are not phage-based, such as those disclosed in International Publication Numbers WO95 / 22625 and WO95 / 1 1922 (Affymax), use polysomes to display polypeptides for selection. A still further category of techniques involves the selection of repertoires in artificial compartments, which allow the linking of a gene with its genetic product. For example, a selection system is described wherein nucleic acids encoding desirable gene products can be selected in microcapsules formed by water-in-oil emulsions, in International Publications Nos. WO99 / 02671, WO00 / 4071 2, and in Tawfik and Griffiths (1 998) Nature Biotechnol. 1 6 (7), 652-6. Genetic elements that encode a gene product having a desired activity are compartmentalized into microcapsules, and then transcribed and / or translated to produce their respective gene products (RNA or protein) within the microcapsules. Subsequently, the genetic elements that produce the genetic product that has the desired activity are classified. This approach selects the genetic products of interest by detecting the desired activity by a variety of means. Library Construction The libraries intended for selection can be built using techniques known in this field, for example, as stipulated above, or can be purchased from commercial sources. Libraries that are useful in the present invention are described, for example, in International Publication No. WO99 / 20749. Once a vector system is selected, and one or more nucleic acid sequences encoding the polypeptides of interest are cloned into the library vector, diversity can be generated within the cloned molecules by undertaking mutagenesis prior to expression.; in an alternative manner, the encoded proteins can be expressed and selected, as described above, before mutagenesis, and additional rounds of selection are carried out. The mutagenesis of nucleic acid sequences encoding structurally optimized polypeptides is carried out by conventional molecular methods. Particularly useful is the polymerase chain reaction, or PCR (Mullis and Faloona (1987) Methods Enzymol, 1 55: 335, incorporated herein by reference). The polymerase chain reaction, which utilizes multiple cycles of DNA replication catalyzed by a thermostable DNA-dependent DNA polymerase to amplify the target sequence of interest, is well known in the art. The construction of different antibody libraries has been discussed in Winter et al. (1 994) Ann. Rev. Immunology 1 2, 433-55, and references cited therein. The polymerase chain reaction is carried out using template DNA (at least 1 fg, more usefully 1 to 1,000 ng), and at least 25 picomoles of oligonucleotide primers; it may be convenient to use a larger amount of primer when the pool of primers is heavily heterogeneous, because each sequence is represented only by a small fraction of the molecules in the pool, and the quantities become limiting in subsequent amplification cycles. . A typical reaction mixture includes: 2 microliters of DNA, 25 picomoles of oligonucleotide primer, 2.5 microliters of 1XX 1 PCR regulator (Perkin-Elmer, Foster City, CA), 0.4 microliters of dNTP 1.25 μM, 0.1 5 microliters (or 2.5 units) of Taq DNA polymerase (Perkin-Elmer, Foster City, CA), and deionized water to a total volume of 25 microliters. Mineral oil is superposed, and the polymerase chain reaction is carried out using a programmable thermal cycler. The duration and temperature of each step of a polymerase chain reaction cycle, as well as the number of cycles, are adjusted according to the current restriction requirements. The tempering temperature and time are both determined by the efficiency with which a primer is expected to quench a template, and the degree of mismatching that will be tolerated; obviously, when nucleic acid molecules are amplified and mutated simultaneously, a mismatch is required, at least in the first round of synthesis. The ability to optimize the restriction of the priming conditions of primers is well within the knowledge of a moderate expert in this field. A tempering temperature of between 30 ° C and 72 ° C is used. The initial denaturation of the template molecules normally occurs between 92 ° C and 99 ° C for 4 minutes, followed by 20 to 40 cycles consisting of denaturation (from 94 ° C to 99 ° C for 1 5 seconds to 1 minute), tempered (the temperature is determined as discussed above, from 1 to 2 minutes), and extension (72 ° C for 1 to 5 minutes, depending on the length of the amplified product). The final extension is usually for 4 minutes at 72 ° C, and can be followed by an indefinite step (from 0 to 24 hours) at 4 ° C. Combination of Single Variable Domains The domains useful in the invention, once selected, can be combined by a variety of methods known in the art, including covalent and non-covalent methods. Preferred methods include the use of polypeptide linkers, as described, for example, in relation to scFv molecules (Bird et al. (1988) Science 242: 423-426). Discussion of suitable linkers is provided in Bird et al., Science 242, 423-426; Hudson et al., Journal Immunol Methods 231 (1 999) 1 77-1 89; Hudson et al., Proc. Nat. Acad. Sci. E UA 85, 5879-5883. The linkers are preferably flexible, allowing the two unique domains to interact. An example of a linker is a linker (Gly4Ser) n, where n = from 1 to 8, for example 2, 3, 4, 5, or 7. The linkers used in diabodies, which are less flexible, can also be employ (Holliger et al. (1 993) Proc. Nat. Acad. Sci. USA 90: 6444-6448). In one embodiment, the linker employed is not an immunoglobulin articulation region.

Variable domains can be combined using methods other than linkers. For example, the use of disulphide bridges, provided through naturally occurring or designed cysteine residues, can be exploited to stabilize the VH-VH, VL-V, or VH-V dimer (Reiter et al. (1 994) Protein Eng. 7: 697-704) or by remodeling the interface between the variable domains to improve the "fit", and therefore, the stability of the interaction (Ridgeway et al. (1996) Protein. Eng. 7: 61 7-621; Zhu et al. (1 997) Protein Science 6: 781-788). Other techniques can be employed to bind or stabilize the variable immunoglobulin domains, and in particular the VH domains of antibodies, as appropriate. Characterization of Ligands The binding of a specific double ligand to the cell, or the binding of each binding domain to each specific target, can be tested by methods that will be familiar to those skilled in the art, and include ELISA. In a preferred embodiment of the invention, the binding is tested using the monoclonal phage ELISA. The phage ELISA can be carried out according to any suitable procedure: an exemplary protocol is stipulated below. Phage populations produced in each round of selection can be screened for binding by ISA with the selected antigen or epitope, in order to identify "polyclonal" phage antibodies. The phage from the individual infected bacterial colonies can then be screened from these populations by ELISA to identify "monoclonal" phage antibodies. It is also desirable to screen the soluble antibody fragments for binding to the antigen or epitope, and this can also be undertaken by ELISA, using reagents, for example, against a C- or N-terminal tag (see, for example, Winter and collaborators, (1 994) Ann. Rev. Immunology 1 2, 433-55, and references cited therein). The diversity of the selected phage monoclonal antibodies can also be evaluated by gel electrophoresis of the polymerase chain reaction products (Marks et al., 1 991, supra; Nissim et al., 1994, supra), probing ( Tomlinson et al. (1992) J. Mol. Biol. 227, 776), or by sequencing the vector DNA. Structure of Ligands In the case that each variable domain is selected from the V-gene repertoires, for example, using the phage display technology as described in the preend, then these variable domains comprise a region of universal structure, such that they can be recognized by a specific generic double specific ligand, as defined herein. The use of universal structures, generic ligands, and the like is described in International Publication Number WO99 / 20749.

When V-gene repertoires are used, the variation in the polypeptide sequence is preferably located within the structural cycles of the variable domains. The polypeptide sequences of any variable domain can be altered by mixing the DNA or by mutation, in order to improve the interaction of each variable domain with its complementary pair. The DNA mixture is known in the art, and is taught, for example, by Stemmer, 1994, Nature 370: 389-391, and in the United States Patent of North America No. 6,297,053, both of which are they are incorporated herein by reference. Other methods of mutagenesis are well known to those skilled in the art.

In general, nucleic acid molecules and vector constructs required for the selection, preparation, and formatting of the specific double ligands can be constructed and manipulated as stipulated in conventional laboratory manuals., such as Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, USA. The manipulation of the nucleic acids useful in the present invention is typically carried out in recombinant vectors. As used herein, "vector" refers to a separate element that is used to introduce heterologous DNA into the cells for the expression and / or replication thereof. The methods by which they are selected and constructed, and subsequently these vectors are used, are well known to one of ordinary skill in the art. Numerous vectors are publicly available, including bacterial plasmids, bacteriophages, artificial chromosomes, and episomal vectors. These vectors can be used for simple cloning and mutagenesis; in an alternative way, the gene expression vector is used. A useful vector according to the invention can be selected to accommodate a polypeptide coding sequence of a desired size, typically 0.25 kilobases (kb) to 40 kilobases or more in length. A suitable host cell is transformed with the vector after the in vitro cloning manipulations. Each vector contains different functional components, which generally include a cloning site (or "polylinker"), a replication origin, and at least one selectable marker gene. If a given vector is an expression vector, it additionally possesses one or more of the following: an enhancer, promoter, transcription termination, and signal sequences, each placed in the vicinity of the cloning site, such that they are operatively linked to the gene encoding a specific double ligand according to the invention. Both the cloning and expression vectors generally contain nucleic acid sequences that make it possible for the vector to replicate in one or more selected host cells. Typically, in cloning vectors, this sequence is one that makes it possible for the vector to replicate independently of the chromosomal DNA of the host, including replication origins or sequences that replicate autonomously. These sequences are well known for a variety of bacteria, yeast, and viruses. The replication origin of plasmid pB R322 is suitable for most of the gram-negative bacteria, the origin of the plasmid of 2 micras is suitable for the yeast, and different viral origins (eg SV 40, adenovirus) are useful for the cloning vectors in mammalian cells. In general terms, the origin of replication for mammalian expression vectors is not needed, unless they are used in mammalian cells capable of replicating high levels of DNA, such as COS cells. Conveniently, a cloning or expression vector may contain a selection gene, also referred to as a selectable marker. This gene encodes a protein necessary for the survival or growth of transformed host cells cultured in a selective culture medium. Accordingly, host cells not transformed with the vector containing the selection gene will not survive in the culture medium. Typical selection genes encode proteins that confer resistance to antibiotics and other toxins, eg, ampicillin, neomycin, methotrexate, or tetracycline, auxotrophic complement deficiencies, or provide critical nutrients not available in the culture medium. Because the replication of the vectors encoding a specific double ligand according to the present invention is most conveniently carried out in E. coli, a selectable marker of E. coli, for example, the β-lactamase that confers resistance to the antibiotic ampicillin. These can be obtained from E. coli plasmids, such as pB R322, or a pUC plasmid, such as pUC1 8 or pUC1 9. Expression vectors usually contain a promoter that is recognized by the host organism, and binds operatively with the coding sequence of interest. This promoter can be inducible or constitutive. The term "operably linked" refers to a juxtaposition wherein the described components are in a relationship that allows them to function in their intended manner. A control sequence "operably linked" with a coding sequence is ligated such that expression of the coding sequence is achieved under conditions compatible with the control sequences. Promoters suitable for use with prokaryotic hosts include, for example, β-lactamase and lactose promoter systems, alkaline phosphatase, the tryptophan (trp) promoter system, and the hybrid promoters, such as the tac promoter. Promoters for use in bacterial systems will also generally contain a Shine-Delgarno sequence operably linked to the coding sequence. Preferred vectors are expression vectors that make possible the expression of a nucleotide sequence corresponding to a member of the polypeptide library. Accordingly, selection with the first and / or the second antigen or epitope can be carried out by separate propagation and expression of a single clone expressing the member of the polypeptide library, or by using any system of selection exhibition. As described above, the preferred screening display system is the display of bacteriophages. Therefore, phage or phagemid vectors can be used, for example, plT1 or plT2. The leader sequences useful in the invention include pelB, stll, ompA, phoA, bla, and pelA. An example is phagemid vectors that have a replication origin of E. coli (for double-stranded replication), and also a replication origin of phage (for the production of single-stranded DNA). The manipulation and expression of these vectors are well known in the art (Hoogenboom and Winter (1992) supra).; N issim et al. (1 994) supra). Briefly stated, the vector contains a β-lactamase gene to confer selectivity to the phagemid, and a lac current promoter arrives from an expression cassette consisting (N- to C-terminal) in a leader sequence of pelB. (which directs the expressed polypeptide to the peri-plasmic space), a multiple cloning site (for the cloning of the nucleotide version of the library member), optionally one or more peptide tags (for detection), optionally one or more more stop codons TAG, and phage protein pl ll. Accordingly, using different suppressor and non-suppressor strains of E. coli, and with the addition of glucose, isopropyl thio-β-D-galactoside (I PTG), or of an auxiliary phage, such as VCS M 1 3, the The vector can be replicated as a plasmid without expression, can produce large amounts of the polypeptide library member alone, or can produce phages, some of which contain at least one copy of the polypeptide-pll fusion on its surface. The construction of vectors encoding double specific ligands according to the invention employs conventional ligation techniques. Isolated vectors or DNA fragments are dissociated, tailored, and religated in the desired form to generate the required vector. If desired, an analysis can be carried out to confirm that the correct sequences are present in the constructed vector, in a known manner. Suitable methods for constructing expression vectors, for the preparation of in vitro transcripts, for the production of DNA in host cells, and for carrying out the analyzes in order to evaluate expression and function, are known to the experts. in this field. The presence of a genetic sequence in a sample is detected, or its amplification and / or expression is quantified, by conventional methods, such as Southern or Northern analysis, Western blot, staining of DNA, RNA or protein spots, in situ hybridization, immunocytochemistry, or sequence analysis of nucleic acid or protein molecules. Those skilled in the art will readily foresee the manner in which these methods can be modified, if desired.

Skeletons Skeletons can be based on immunoglobulin molecules, or can be of a non-immunoglobulin origin, as stipulated above. Each domain of the specific double ligand can be a different skeleton. Preferred immunoglobulin backbones, as defined herein, include any one or more of those selected from the following: an immunoglobulin molecule comprising at least: (i) the CL domain (kappa or lambda subclass) of an antibody; or (ii) the CH 1 domain of an antibody heavy chain; an immunoglobulin molecule comprising the CH1 and CH2 domains of an antibody heavy chain; an immunoglobulin molecule comprising the CH 1, CH 2, and CH 3 domains of an antibody heavy chain; or any of the subset (ii) in conjunction with the CL domain (kappa or lambda subclass) of an antibody. A joint region domain can also be included. These combinations of domains, for example, can mimic natural antibodies, such as IgG or IgM, or fragments thereof, such as Fv, scFv, Fab, or F (ab ') 2 molecules. Experts in this field will be aware that this list is not intended to be exhaustive. Protein Scaffolds Each binding domain comprises a protein scaffold and one or more CDRs that are involved in the domain-specific interaction with one or more epitopes. Conveniently, an epitope binding domain according to the present invention comprises three complementarity determining regions. Suitable protein scaffolds include any of those selected from the group consisting of the following: those based on immunoglobulin domains, those based on fibronectin, those based on affibodies, those based on CTLA4, those based on chaperones, such as GroEL , those based on lipocalin, and those based on the bacterial Fc receptors SpA and SpD. Those skilled in the art will appreciate that this list is not intended to be exhaustive. Scaffolds for Use in the Construction of Ligands Selecting the Conformation of the Primary Chain Members of the immunoglobulin superfamily all share a similar fold for their polypeptide chain. For example, although the antibodies are highly diverse in terms of their primary sequence, the comparison of the sequences and crystallographic structures has revealed that, contrary to expectation, five of the six antigen binding cycles of the antibodies (H 1, H2 , L 1, L2, L3) adopt a limited number of conformations of the main chain, or canonical structures (Chothia and Lesk (1987) J. Mol. Biol, 1 96: 901; Chothia et al., (1989) Nature , 342: 877). The analysis of the lengths of the cycles and the key residues has made it possible, therefore, to predict the conformations of the main chain of H 1, H 2, L 1, L 2, and L 3 found in most of the antibodies humans (Chothia et al. (1992) J. Mol. Biol, 227: 799; Tomlinson et al. (1,995) EMBO J, 1 4: 4628; Williams et al. (1 996) J. Mol. Biol., 264: 220). Although the H3 region is much more diverse in terms of sequence, length, and structure (due to the use of the D segments), it also forms a limited number of conformations of the main chain for short cycle lengths, which depend on the length and the presence of particular residues, or types of residues, in the key positions in the cycle and in the structure of the antibody (Martin et al., (1 996) J. Mol. Biol, 263: 800; Shirai et al., (1996) FEBS Letters, 399: 1). Ligand libraries and / or binding domains can be designed, where certain cycle lengths and key residues have been chosen, to ensure that the conformation of the main chain of the members is known. Conveniently, these are actual conformations of the immunoglobulin super-family molecules found in nature, to minimize the chances of them not being functional, as discussed in the foregoing. The segments of the germline V gene serve as a basic structure suitable for constructing libraries of antibodies or T-cell receptors.; other sequences are also useful. Variations can occur at a low frequency, so that a small number of functional members can have a conformation of the altered main chain, which does not affect its function.

The canonical structure theory is also useful to evaluate the number of different conformations of the main chain encoded by the ligands, to predict the conformation of the main chain based on the sequences of the specific double ligands, and to choose the residues for the diversification that does not affect the canonical structure. It is known that, in the V? Domain, the L1 cycle can adopt one of four canonical structures, the L2 cycle has a single canonical structure, and that 90 percent of the V? humans adopt one of four or five canonical structures for the L3 cycle (Tomlinson et al. (1995) supra); therefore, in the V domain? only, different canonical structures can be combined to create a range of different conformations of the main chain. Since the domain V? codifies a different range of canonical structures for the cycles L 1, L2, and L3, and that the V domains? and V? can be paired with any VH domain that can encode various canonical structures for the H 1 and H2 cycles, the number of combinations of canonical structures observed for these five cycles is very large. This implies that the generation of diversity in the conformation of the main chain can be essential for the production of a wide range of binding specificities. However, by building an antibody library based on a single conformation of the known backbone, it has been found that, contrary to expectation, diversity in the shaping of the backbone is not required to generate sufficient diversity to address substantially all antigens. Still more surprisingly, the individual conformation of the main chain does not need to be a consensus structure - a single conformation that naturally occurs as the basis for the entire library can be used. Accordingly, in a preferred aspect, the ligands of the invention possess a conformation of a single known backbone. The only conformation of the main chain that is selected is preferably a common place among the molecules of the immunoglobulin super family type in question. A conformation is a common place when it is observed that a significant number of molecules that occur naturally adopt it. In accordance with the above, in a preferred aspect of the invention, the natural presentation of the different conformations of the main chain for each binding cycle of an immunoglobulin domain is considered separately, and then a variable domain that is present is selected. naturally, which possesses the desired combination of main chain conformations for the different cycles. If none are available, you can choose the nearest equivalent. It is preferable that the desired combination of main chain conformations for the different cycles be created by selecting the germ line genetic segments that encode the desired main chain conformations. It is more preferable that the selected germline genetic segments are frequently expressed in nature, and it is highly preferable that they are those that are most frequently expressed from all the natural germline genetic segments. In the design of ligands (for example, ds-dAbs) or libraries thereof, the incidence of the different conformations of the main chain for each of the six antigen binding cycles can be considered separately. For H 1, H 2, L 1, L 2, and L 3, a given conformation is chosen that is adopted between 20 percent and 100 percent of the antigen binding cycles of the naturally occurring molecules. Typically, its observed incidence is greater than 35 percent (that is, between 35 percent and 100 percent), and ideally, greater than 50 percent, or even greater than 65 percent. Because the vast majority of H3 cycles do not have canonical structures, it is preferable to select a conformation of the main chain that is a commonplace between these cycles, which do exhibit canonical structures. For each of the cycles, therefore, the conformation most frequently observed in the natural repertoire is selected. In human antibodies, the most popular canonical structures (CS) for each cycle are as follows: Hl -CS 1 (79 percent of the expressed repertoire), H2-CS 3 (46 percent), L1 - CS 2 of VK ( 39 percent), L2 - CS 1 (1 00 percent), L3 - CS 1 of V? (36 percent) (the calculation assumes a?:? Ratio of 70:30, Hood et al. (1967) Cold Spring Harbor Symp. Quant. Biol, 48: 133). For the H3 cycles that have canonical structures, a length of the CDR3 (Kabat et al. (1 991) Sequences of proteins of immunological interest, from the United States Department of Health and Human Services) of seven residues with a salt bridge from the residue 94 to residue 01, seems to be the most common. There are at least 16 human antibody sequences in the EM BL data library with the required length of H3 and key residues to form this conformation, and at least two crystallographic structures in the protein data bank that can be used as a basis for the modeling of the antibodies (2cgr and 1 tet). The germline genetic segments most frequently expressed in this combination of canonical structures are segment VH 3-23 8DP-47), segment JH J H4b, segment V? O2 / O1 2 (DPK9), and the segment J? J? 1. The segments VH DP45 and DP38 are also suitable. These segments, therefore, can be used in combination as a basis to build a library with the conformation of the desired individual main chain. In an alternative way, instead of deselecting the conformation of the individual main chain based on the natural presentation of the different conformations of the main chain for each of the link cycles in isolation, the natural presentation of the conformation combinations of the main chain as the basis for choosing the conformation of the individual main chain. In the case of antibodies, for example, one can determine the natural presentation of combinations of canonical structures for any two, three, four, five, or six cycles of antigen binding. Here, it is preferable that the selected conformation be a common site in naturally occurring antibodies, and more preferably that it is more frequently observed in the natural repertoire. Therefore, in human antibodies, for example, when considering natural combinations of the five antigen binding cycles, H1, H2, L1, L2, and L3, the most frequent combination of canonical structures is determined, and then They combine with the most popular conformation for the H3 cycle, as a basis for selecting the conformation of the individual main chain. Diversification of the Canonical Sequence Having selected several known main chain conformations, or preferably a single conformation of the known backbone, specific double ligands (eg, ds-dAbs) or libraries can be constructed for use in the invention, varying each binding site of the molecule, in order to generate a repertoire with structural and / or functional diversity. This means that variants are generated, in such a way that they have sufficient diversity in their structure and / or in their function, in such a way that they are able to provide a range of activities. The desired diversity is typically generated by varying the selected molecule in one or more positions. The positions to be changed can be randomly selected, or selected in a preferable manner. Then the variation can be achieved either by random selection, during which the resident amino acid is replaced by any amino acid or analog thereof, natural or synthetic, producing a very large number of variants, or by replacing the resident amino acid with one or more of a defined subset of amino acids, producing a more limited number of variants. Different methods have been reported to introduce this diversity. Polymerase chain reaction susceptible to error can be used (Hawkins et al. (1992) J. Mol. Biol, 226: 889), chemical mutagenesis (Deng et al., (1994) J. Biol. Chem., 269: 9533). ), or bacterial mutant strains (Low et al. (1996) J. Mol. Biol., 260: 359), to introduce random mutations in the genes encoding the molecule. Methods for mutating the selected positions are also well known in the art, and include the use of mismatched oligonucleotides or degenerate oligonucleotides, with or without the use of the polymerase chain reaction. For example, several libraries of synthetic antibodies have been created by directing the mutations toward the antigen binding cycles. The H3 region of a human tetanus toxoid binding Fab has been randomly selected to create a range of novel binding specificities (Barbas et al. (1992) Proc. Nati. Acad. Sci. USA, 89: 4457). The random or semi-random H3 and L3 regions have been appended to the germline V gene segments to produce large libraries with unmutated structure regions (Hoogenboom and Winter (1992) J. Mol. Biol, 227: 381; Barbas et al. (1992) Proc. Nati Acad. Sci. USA, 89: 4457; Nissim et al. (1 994) EMBO J, 1 3: 692; Griffiths et al. (1 994) EMBO J, 1 3: 3245; De Kruif et al. (1995) J. Mol. Biol, 248: 97). This diversification has been extended to include some or all of the other antigen binding sites (Crameri et al. (1 996) Nature Med., 2: 1 00; Riechmann et al. (1 995) Bio / Technology, 1 3: 475; Morphosys, International Publication Number WO97 / 08320, supra). Because the random selection of cycles has the potential to create approximately more than 1 01 5 structures for H3 only, and similarly a large number of variants for the other five cycles, it is not feasible, using the current transformation technology, or even using systems without cells, produce a library that represents all possible combinations. For example, in one of the largest libraries constructed to date, 6x101 0 different antibodies were generated, which is only a fraction of the potential diversity for a library of this design (Griffiths et al. (1 994), supra). Preferably, only residues that are directly involved in the creation or modification of the desired function of each domain of the double specific ligand molecule are diversified. For many molecules, the function of each domain will be linked to an objective, and therefore, diversity must be concentrated in the target binding site, while shifting residues that are crucial for the overall packaging of the molecule are avoided, or to maintain the conformation of the main chain selected. Diversification of the Canonical Sequence as it is applied to the Antibody Domains. In the case of antibody-based ligands (e.g., ds-dAbs), the binding site for each target is most often the antigen binding site. Accordingly, preferably only the residues at the antigen binding site are varied. These residues are extremely diverse in the repertoire of human antibodies, and are known to make contacts in the high resolution antibody / antigen complexes. For example, in L2, positions 50 and 53 are known to be diverse in naturally occurring antibodies, and it is observed that they make contact with the antigen. In contrast, the conventional approach would have been to diversify all the residues in the corresponding complementarity determining region (CDR1), as defined by Kabat et al. (1991), some seven residues, comparing with the two diversified in the library for used according to the invention. This represents a significant improvement in terms of the functional diversity required to create a range of antigen binding specificities. In nature, the diversity of antibodies is the result of two processes: somatic recombination of the genetic segments of the germ line V, D, and J, to create a pure primary repertoire (the so-called diversity of the germinal line and of union), and somatic hyper-mutation of the resulting reconfigured V genes. The analysis of human antibody sequences has shown that the diversity in the primary repertoire is focused on the center of the antigen binding site, while the somatic hyper-mutation extends the diversity to regions at the periphery of the binding site of the antigen. antigen, which are highly conserved in the primary repertoire (see Tomlinson et al., (1996) J. Mol. Biol., 256: 81 3). This complementarity has probably evolved as an efficient strategy to search for sequence space, and, although apparently unique to antibodies, it can be easily applied to other polypeptide repertoires. The wastes that are varied are a subset of those that form the liaison site for the objective. Different subsets (including overlaps) of waste at the target link site, they are diversified in different stages during the selection, if desired. In the case of an antibody repertoire, an initial "pure" repertoire can be created, where some, but not all, residues at the antigen binding site are diversified. As used herein in this context, the term "pure" refers to antibody molecules that do not have a previously determined purpose. These molecules resemble those that are encoded by the immunoglobulin genes of an individual who has not undergone immune diversification, as is the case with fetal and newborn individuals whose immune systems have not yet been assaulted by a wide variety of antigenic stimuli. Then this repertoire is selected against a range of antigens or epitopes. If required, additional diversity can then be introduced outside the diversified region in the initial repertoire. This mature repertoire can be selected for a modified function, specificity, or affinity. The pure repertoires of binding domains for the construction of double specific ligands, wherein some or all of the residues at the antigen binding site are varied are known in the art. (See International Publications Numbers WO 2004/058821, WO 2004/003019, and WO 03/002609). The "primary" library mimics the natural primary repertoire, with the diversity restricted to residues at the center of the antigen binding site that are diverse in the V-gene segments of the germ line (germline diversity), or they diversify during the recombination process (binding diversity). These diversifying residues include, but are not limited to, H50, H52, H52a, H53, H55, H56, H58, H95, H96, H97, H98, L50, L53, L91, L92, L93, L94 and L96. In the "somatic" library, diversity is restricted to residues that are diversified during the recombination process (union diversity), or that are highly somatically mutated. These diversifying residues include, but are not limited to: H31, H33, H35, H95, H96, H97, H98, L30, L31, L32, L34 and L96. It is known that all the residues listed above as suitable for diversification in these libraries make contacts in one or more antibody-antigen complexes. Because in both libraries not all residues of the antigen binding site are varied, additional diversity is incorporated during selection by varying the remaining residues, if desired to do so in this manner. It will be apparent to one skilled in the art that any subset of any of these residues (or additional residues comprising the antigen binding site) can be used for the initial and / or subsequent diversification of the antigen binding site. In the construction of the libraries for use in the invention, the diversification of the selected positions is typically achieved at the level of the nucleic acid, by altering the coding sequence that specifies the polypeptide sequence, so that a number of possible amino acids (the 20 or a subset thereof) in that position. Using the I U PAC nomenclature, the most versatile codon is NNK, which codes for all amino acids, as well as the stop codon TAG. The N NK codon is preferably used in order to introduce the required diversity. Other codons that achieve the same ends are also useful, including the NNN codon, which leads to the production of the additional stop codons TGA and TAA.

A characteristic of the side chain diversity at the antigen binding site of human antibodies is a pronounced tilt that favors certain amino acid residues. If the amino acid composition of the 10 most diverse positions is added in each of the VH, V? And V? Regions, more than 76 percent of the side chain diversity comes from only seven different residues, these being serine (24 percent), tyrosine (1.4 percent), asparagine (1.1 percent), glycine (9 percent), alanine (7 percent), aspartate (6 percent), and threonine (6 percent) ). This bias towards hydrophilic residues and towards small residues that can provide flexibility of the main chain, reflects the evolution of surfaces that are predisposed to link with a wide range of antigens or epitopes, and may help to explain the required promiscuity of the antibodies in the primary repertoire. Because it is preferable to mimic this amino acid distribution, the amino acid distribution at the positions to be varied preferably mimics that seen at the antigen binding site of the antibodies. This bias in amino acid substitution that allows the selection of certain polypeptides (not only antibody polypeptides) against a range of target antigens is easily applied to any repertoire of polypeptides. There are different methods to vary the inclination of the amino acid distribution in the position (including the use of tri-nucleotide mutagenesis, see International Publication Number WO97 / 08320), of which the preferred method, due to the ease of synthesis , is the use of conventional degenerate codons. By comparing the amino acid profile encoded by all combinations of degenerate codons (with individual, double, triple, and quadruple degeneration in equal proportions in each position) with the use of natural amino acids, it is possible to calculate the most representative codon. The codons (AGT) (AGC) T, (AGT) (AGC) C, and (AGT) (AGC) (CT) - that is, DVT, DVC, and DVY, respectively, using the I UPAC nomenclature - are those that they are closer to the desired amino acid profile: they encode 22 percent serine and 1 1 percent tyrosine, asparagine, glycine, alanine, aspartate, threonine, and cysteine. Accordingly, libraries are preferably constructed using any of the DVT, DVC, or DVY codons in each of the diversified positions. Therapeutic and Diagnostic Compositions, and Uses. The invention provides compositions comprising the ligands of the invention, and a pharmaceutically acceptable carrier, diluent, or excipient, and therapeutic and diagnostic methods employing the ligands or compositions of the invention. The ligands according to the method of the present invention can be used in therapeutic and prophylactic applications in vivo, in in vivo diagnostic applications, and the like.

The therapeutic and prophylactic uses of the ligands of the invention involve the administration of the ligands according to the invention to a recipient mammal, such as a human. The ligands bind to the targets with a high avidity. In some embodiments, the ligands may allow the cross-linking of two targets, for example in the recruitment of cytotoxic T-cells to mediate the killing of tumor cell lines. Substantially pure ligands, for example ds-dAbs, of a homogeneity of at least 90 to 95 percent are preferred for administration to a mammal, and a homogeneity of 98 to 99 percent or more is preferred for pharmaceuticals, especially when the mammal is a human being. Once purified, partially or until homogeneity as desired, the ligands can be used diagnostically or therapeutically (including extracorporeally), or in the development and performance of assay procedures, immunofluorescent staining, and the like Lefkovite and Pernis, (1979 and 1981) Immunological Methods, Volumes I and I I, Academic Press, NY). For example, the ligands of the present invention will typically find use in the prevention, suppression, or treatment of disease states. For example, the ligands may be administered to treat, suppress, or prevent a chronic inflammatory disease, allergic hypersensitivity, cancer, bacterial or viral infection, autoimmune disorders (which include, but are not limited to, type I diabetes, asthma, sclerosis multiple, rheumatoid arthritis, juvenile rheumatoid arthritis, psoriatic arthritis, spondylarthropathy (eg, ankylosing spondylitis), systemic lupus erythematosus, inflammatory bowel disease (eg, Crohn's disease, ulcerative colitis), myasthenia gravis, and Behcet's syndrome), psoriasis, endometriosis, and abdominal adhesions (for example, after abdominal surgery). Ligands are particularly useful for the treatment of infectious diseases wherein cells infected with an infectious agent contain higher levels of cell surface targets than uninfected cells, or which contain one or more cell surface targets that are not present in uninfected cells, such as a protein that is encoded by the infectious agent (e.g., bacteria, virus). Ligands according to the invention that are capable of binding to extracellular targets, can be endocytosed, and can deliver therapeutic agents (e.g., a toxin) intracellularly (e.g., they can deliver a dAb that is linked to an intracellular target) . In addition, the ligands provide a means whereby each binding domain (e.g., a dAb monomer) that is capable of specifically binding to an intracellular target can be delivered to an intracellular environment. This strategy requires, for example, a link domain with physical properties that make it possible to remain functional within the cell. Alternatively, if the intracellular compartment of final destination is oxidant, a good fold ligand may not be required to be free of disulfide. In the present application, the term "prevention" involves the administration of the protective composition prior to the induction of the disease. "Suppression" refers to the administration of the composition after an inductive event, but before the clinical appearance of the disease. "Treatment" involves the administration of the protective composition after the symptoms of the disease become manifest. The treatment includes the improvement of the symptoms associated with the disease, and also the prevention or delay of the establishment of the disease, and also the reduction of the severity or frequency of the symptoms of the disease. The term "cancer" refers to, or describes, the physiological condition in mammals that is typically characterized by poorly regulated proliferation or cell survival. Examples of cancer include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia, and lymphoid malignancies. More particular examples of cancers include squamous cell cancer (e.g., squamous epithelial cell cancer), lung cancer (e.g., microcellular lung carcinoma, non-microcellular lung cancer, lung adenocarcinoma, squamous cell carcinoma of the lung), cancer of the lung. peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, rectal cancer, colorectal cancer rectal, multiple myeloma, chronic myeloid leukemia, acute myelogenous leukemia, endometrial or uterine carcinoma, salivary gland carcinoma, kidney or kidney cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, anal carcinoma, carcinoma of the penis, cancer of the head and neck, and Similar. Animal model systems that can be used to evaluate the efficacy of the ligands of the invention for preventing, treating, or suppressing the disease (eg, cancer) are available. Suitable cancer models include, for example, models of human xenograft and orthotopic cancers in animal models, such as the SCI D-hu myeloma model (Epstein J, and Yaccoby, S., Methods Mol. Med. 1 1 3: 1 83-90 (2005), Tassone P, et al., Clin Cancer Res. 1 1 (11): 4251-8 (2005)), mouse models of human lung cancer (e.g., Meuwissen R. et al. Berns A, Genes Dev. 1 9 (6): 643-64 (2005)), and mouse models of metastatic cancers (eg, Kubota T., J. Cell Biochem. 56 (1): 4-8 (1 994)). In general terms, the present ligands will be used in a purified form together with pharmacologically appropriate vehicles. Typically, these vehicles include solutions, emulsions, or aqueous or alcoholic / aqueous suspensions, including serum and / or regulated media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, and lactated Ringer. Suitable physiologically acceptable adjuvants, if necessary to maintain a polypeptide complex in suspension, may be selected from thickeners, such as carboxymethyl cellulose, polyvinyl pyrrolidone, gelatin, and alginates. Intravenous vehicles include fluid and nutrient replenishers and electrolyte replenishers, such as those based on Ringer's dextrose. There may also be preservatives and other additives, such as antimicrobials, antioxidants, chelating agents, and inert gases present (Mack (1982) Remington's Pharmaceutical Sciences, 16th Edition). A variety of suitable formulations, including sustained release formulations, can be used. The ligand of the present invention can be used as compositions administered separately, or in conjunction with other agents. The ligands can be administered and / or formulated together with one or more additional therapeutic or active agents. When a ligand is administered with an additional therapeutic agent, the ligand can be administered before, simultaneously with, or after administration of the additional agent. In general terms, the ligand and the additional agent are administered in a manner that provides an overlap of the therapeutic effect. Additional agents that can be administered or formulated with the ligand of the invention include, for example, different immunotherapeutic drugs, such as cyclosporin, methotrexate, adriamycin, or cisplatin, antibiotics, antifungals, antiviral agents, and immunotoxins. For example, when the antagonist is administered to prevent, suppress, or treat lung inflammation or a respiratory disease, it may be administered in conjunction with phosphodiesterase inhibitors (eg, phosphodiesterase 4 inhibitors), bronchodilators (eg, beta2 agonists, anticholinergics). , theophylline), short-acting beta-agonists (eg, albuterol, salbutamol, bambuterol, fenoterol, isoeterin, isoproterenol, levalbuterol, metaproterenol, pirbuterol, terbutaline, and telolate), long-acting beta-agonists (eg, formoterol and salmeterol ), short-acting anticholinergics (eg, ipratropium bromide and oxitropium bromide), long-acting anticholinergics (eg, tiotropium), theophylline (eg, short-acting formulations, long-acting formulations), inhaled steroids (eg, example, beclomethasone, budesonide, flunisolide, fluticasone propionate, and triamcinolone), oral steroids (e.g., methylprednisolone, prednisolone, prednisolone, and prednisone), short-acting beta-agonists with combined anticholinergics (eg, albuterol / salbutamol / ipratropium, and fenoterol / ipratropium), long-acting beta agonists with combined inhaled steroids (eg, salmeterol / fluticasone, and formoterol / budesonide), and mucolytic agents (eg, erdostein, acetyl cysteine, bromheccin, carbocysteine, guiafenesin, and iodized glycerol.) The ligands of the invention can be co-administered (eg, to treat cancer ) with a variety of suitable co-therapeutic agents, including cytokines, analgesics / antipyretics, antiemetics, and chemotherapeutics Suitable co-therapeutic agents include cytokines, which include, without limitation, a lymphokine, tumor necrosis factor, factor-type cytokine of tumor necrosis, lymphotoxin, interferon, inflammatory protein of macrophages, stimulating factor of monocyte colonies granulocyte cough, interleukin (including, without limitation, interleukin-1, interleukin-2, interleukin-6, interleukin-12, interleukin-15, interleukin-18), growth factors, which include, without limitation (eg, growth hormone, insulin-like growth factor 1 and 2 (IGF-1 and IGF-2), granulocyte colony-stimulating factor (GCSF), platelet-derived growth factor (PGDF), epidermal growth factor (EGF), and agents for the stimulation of erythropoiesis, for example recombinant human erythropoietin (Epoetin alfa), EPO, a hormonal agonist, hormone antagonists (e.g., flutamide, tamoxifen, leuprolide acetate (LUPRON), and steroids (e.g., dexamethasone, retinoid, betamethasone, cortisol, cortisone, prednisone, dehydrotestosterone, glucocorticoid, mineralocorticoid, estrogen, testosterone, progestin). Analgesics / antipyretics may include, without limitation, aspirin, acetaminophen, ibuprofen, naproxen-sodium, buprenorphine hydrochloride, propoxyphene hydrochloride, propoxyphene napsylate, meperidine hydrochloride, hydromorphone hydrochloride, morphine sulfate, oxycodone hydrochloride, phosphate codeine, dihydrocodeine bitartrate, pentazocine hydrochloride, hydrocodone bitartrate, levorphanol tartrate, diflunisal, trolamine salicylate, nalbuphine hydrochloride, mefenamic acid, butorphanol tartrate, choline salicylate, butalbital, phenyl-toloxamine citrate, diphenhydramine citrate , methotrimeprazine, cinamedrin hydrochloride, meprobamate, and the like. Antiemetics can also be co-administered to prevent or treat nausea and vomiting, for example, suitable antiemetics include meclizine hydrochloride, nabilone, prochlorperazine, dimenhyd rinate, promethazine hydrochloride, triethylperazine, scopolamine, and the like. Chemotherapeutic agents, as this term is used herein, include, but are not limited to, for example, anti-microtubule agents, e.g., taxol (paclitaxel), taxotere (docetaxel); alkylating agents, for example, cyclophosphamide, carmustine, lomustine, and chlorambucil; cytotoxic antibiotics, for example dacti nomicin, doxorubicin, mitomycin C, and bleomycin; anti-metabolites, for example cytarabine, gemcitabine, methotrexate, and 5-fluoro-uracil; antimitotics, for example, vincristine, vinca alkaloids, e.g. etoposide, vinblastine, and vincristine; and others, such as cisplatin, dacarbazine, procarbazine, and hydroxy urea; and combinations thereof. The ligands of the invention can be used to treat cancer in combination with another therapeutic agent. For example, a ligand of the invention can be administered in combination with a chemotherapeutic agent. In a convenient manner, in this therapeutic approach, the amount of chemotherapeutic agent that must be administered to be effective can be reduced. Accordingly, the invention provides a method for the treatment of cancer, which comprises administering to a patient in need, a therapeutically effective amount of a ligand of the invention and a chemotherapeutic agent, wherein the chemotherapeutic agent is administered in a dose low. In general terms, the amount of chemotherapeutic agent that is coadministered with a ligand of the invention is about 80 percent, or about 70 percent, or about 60 percent, or about 50 percent, or about 40 percent, or about 30 percent, or about 20 percent, or about 10 percent or less, of the dose of chemotherapeutic agent alone that is normally administered to a patient. Accordingly, co-therapy is particularly convenient when the chemotherapeutic agent causes harmful or undesirable side effects, which can be reduced or eliminated at a lower dose. The pharmaceutical compositions may include "cocktails" of different cytotoxic agents or other agents in conjunction with the ligands of the present invention, or even combinations of ligands according to the present invention having different specificities, such as the ligands selected using different antigens or target epitopes, whether they are clustered or not before administration. The route of administration of the pharmaceutical compositions according to the invention can be any suitable route, such as any of those commonly known to those of ordinary skill in the art. For therapy, including, without limitation, immunotherapy, the ligands of the invention can be administered to any patient according to conventional techniques. The administration can be by any appropriate mode, including parenterally (eg, intravenous, intramuscular, intraperitoneal, intra-articular, intrathecal), transdermally, by the pulmonary route, or also, appropriately, by direct infusion with a catheter. The dosage and frequency of administration will depend on the age, sex, and condition of the patient, the concurrent administration of other drugs, contraindications and other parameters that should be taken into account by the clinician. Administration may be local (eg, local delivery to the lung by pulmonary administration (eg, intranasal administration) or local injection directly into a tumor), or systemic, as indicated. The ligands of this invention can be lyophilized for storage, and can be reconstituted in a suitable vehicle before use. This technique has been shown to be effective with conventional immunoglobulins, and lyophilization and reconstitution techniques known in the art can be employed. It will be appreciated by those skilled in the art that lyophilization and reconstitution can lead to different degrees of loss of antibody activity (e.g., with conventional immunoglobulins, IgM antibodies tend to have a greater loss of activity than IgG antibodies), and that levels of use may have to be adjusted upward to compensate. The compositions containing the ligands can be administered for prophylactic and / or therapeutic treatments. In certain therapeutic applications, an amount suitable to carry out at least a partial inhibition, suppression, modulation, annihilation, or some other measurable parameter, of a population of selected cells, is defined as a "therapeutically effective dose". The amounts necessary to achieve this dosage will depend on the severity of the disease and the general health of the patient, but in general will be in the range of 0.005 to 5.0 milligrams of ligand per kilogram of body weight, most commonly using doses of 0.05 to 2.0 milligrams / kilogram / dose. For prophylactic applications, compositions containing the present ligands or cocktails thereof at similar or slightly lower dosages may also be administered to prevent, inhibit, or delay the establishment of the disease (e.g., to sustain remission or passivity, or to prevent the acute phase). The skilled clinician will be able to determine the appropriate dosage range to treat, suppress, or prevent the disease. When a ligand is given to treat, suppress, or prevent a disease, it can be administered up to four times a day, twice a week, once a week, once every two weeks, once a month, or once every two. months, in a dose, for example, from about 10 micrograms / kilogram to about 80 milligrams / kilogram, from about 100 micrograms / kilogram to about 80 milligrams / kilogram, from about 1 milligram / kilogram to about 80 milligrams / kilogram, of about 1 milligram / kilogram to about 70 milligrams / kilogram, from about 1 milligram / kilogram to about 60 milligrams / kilogram, from about 1 milligram / kilogram to about 50 milligrams / kilogram, from about 1 milligram / kilogram to about 40 milligrams / kilogram, from about 1 milligram / kilogram to about 30 milligrams / kilogram, from about 1 milligram / kilogram to approximate 20 milligrams / kilogram, from about 1 milligram / kilogram to about 10 milligrams / kilogram, from about 10 micrograms / kilogram to about 10 milligrams / kilogram, from about 10 micrograms / kilogram to about 5 milligrams / kilogram, of about 10 micrograms / kilogram -Kilogram to about 2.5 milligrams / kilogram, of about 1 milligram / kilogram, of about 2 milligrams / kilogram, of about 3 milligrams / kilogram, of about 4 milligrams / kilogram, of about 5 milligrams / kilogram, of about 6 milligrams / kilogram , about 7 milligrams / kilogram, about 8 milligrams / kilogram, about 9 milligrams / kilogram, or about 10 milligrams / kilogram. In particular embodiments, the specific double ligand is administered to treat, suppress, or prevent a chronic inflammatory disease once every two weeks or once a month, in a dose of about 10 micrograms / kilogram to about 10 milligrams / kilogram ( for example, from about 10 micrograms / kilogram, about 1000 micrograms / kilogram, about 1 milligram / kilogram, about 2 milligrams / kilogram, about 3 milligrams / kilogram, about 4 milligrams / kilogram, about 5 milligrams / kilogram, approximately 6 milligrams / kilogram, approximately 7 milligrams / kilogram, approximately 8 milligrams / kilogram, approximately 9 milligrams / kilogramor about 1 milligrams / -kilogram). In particular embodiments, the invention is administered in a dose that provides selective binding to the positive double cells in vivo. As described in the preamble, selective binding to double positive cells can be achieved when the ligand is used in a concentration of about 1 pM to about 150 nM. A dose that is sufficient to reach a serum concentration of the ligand that is from about 1 pM to about 150 nM may be administered. The skilled physician can determine the appropriate dosage to reach this concentration in serum, for example, by titrating the ligand and monitoring the serum concentration of the ligand. Therapeutic regimens involving the administration of a therapeutic agent to achieve a desired serum concentration of the agent are common in the art, particularly in the field of oncology. The treatment or therapy carried out using the compositions described herein is considered to be "effective" if one or more symptoms are reduced (for example, by at least 10%, or at least one point on the evaluation scale). clinic), in relation to these symptoms present before treatment, or in relation to these symptoms in an individual (human or animal model) not treated with the composition or other suitable control. The symptoms will obviously vary depending on the disease or the targeted disorder, they can be measured by an ordinarily skilled clinician or technician. These symptoms can be measured, for example, by monitoring the level of one or more biochemical indicators of the disease or disorder (for example, the levels of an enzyme or metabolite correlated with the disease, the number of affected cells, etc.). , by monitoring the physical manifestations (for example, inflammation, tumor size, etc.), or by a accepted clinical evaluation scale, for example, the Scale of I ncapacity Expanded (for multiple sclerosis), the I rvine Inflammatory Disease I-Inflammatory Disease Questionnaire (32-point evaluation assesses quality of life with respect to bowel function, systemic symptoms, social function, and emotional state - the rating is in the range of 32 to 224, indicating the highest grades a better quality of life), the Rheumatoid Arthritis Scale of Quality of Life, or another scale of accepted clinical evaluation, as it is known in this field. A sustained reduction (for example, a day or more, preferably more time) in the symptoms of the disease or disorder by at least 10 percent, or by one or more points on a given clinical scale, indicates a "effective" treatment. In a similar manner, prophylaxis carried out using a composition as described herein, is "effective" if the establishment or severity of one or more symptoms in relation to these symptoms is delayed, reduced, or eliminated. a similar individual (human or animal model) not treated with the composition. A composition containing the ligands according to the present invention can be used in prophylactic and therapeutic settings to aid in the alteration, inactivation, annihilation, or removal of a selected target population of cells in a mammal. In addition, selected ligands and repertoires of polypeptides described herein, may be used extracorporeally or in vitro selectively to effectively kill, consume, or otherwise remove a population of target cells from a heterogeneous collection of cells. The blood of a mammal can be combined extracorporeally with the ligands, for example the antibodies, the cell surface receptors, or the binding proteins thereof, where the unwanted cells are annihilated or otherwise removed from the blood., to return to the animal according to conventional techniques. EXAMPLES In the Examples described herein, CD38 is also referred to as DOM 1 1, CD 1 38 is also referred to as DOM 1 2, CEA is also referred to as DOM 1 3, and CD56 is also referred to as DOM 1 4. Selections and Tracing dAbs that Link with CD38, CD138, CEA, or CD56. The dAbs were selected using antigens that were expressed as Fc fusion proteins in mammalian cells. Three rounds of selection were carried out using dAb libraries for CD38, CD 1 38, CEA, and CD56 captured alternately on magnetic beads of protein G (Dynal) and anti-human Fc (Novagen). The selection productions were tested in ELISA to determine specificity as phage and as soluble dAbs in rounds 2 and 3 on the cognate antigen, but not on the non-cognate antigen. For soluble ELI SAs, all dAbs Vk were cross-linked with the L protein. For each antigen, the positive clones were sequenced for the soluble ELISA, showing that the selections have diverse productions. Link assays to determine the positive clones for the dAb. Positive ELISA clones were expressed in 50 milliliter cultures, and purified on protein A (VH clones) or on L protein (Vk clones) as appropriate. Briefly stated, a phage display plasmid (pDOM 5) that encoded the dAb was transformed into HB21 51 from E. coli, and the cells were applied on TYE plates containing 50 micrograms / ml liter of carbenicillin and glucose 5 percent, and incubated overnight at 37 ° C. The expression of dAb in the culture supernatant was made using self-induction according to the following method: the following components were added to a 250 milliliter screen flask: 50 milliliters of TB, 1000 micrograms / milliliter of carbenicillin, 1 drop of antifoam A204 (Sigma), 1 milliliter of Solution 1, 2.5 milliliters of Solution 2, and 0.05 milliliter of Solution 3 of the Novagen Overnight Express Autoinduction Kit, and a single colony of transformed E. coli cells. The flasks were covered with Milliwrap PTFE membrane, and the culture was allowed to grow and express the protein for 48 hours at 250 revolutions per minute at 30 ° C. The protein was purified directly from the culture supernatant using protein A or L. All dAbs were analyzed by FACS on the positive and negative cell lines for the antigen, using the following method. The determination of the cell link by FACS was carried out as follows: the cells were centrifuged at 250g for 5 minutes, and the culture medium was removed. The cells were resuspended in the FACS incubation buffer at 4 ° C, at a density of 2x1 06 cells / milliliter. The cells were blocked by incubation for 1 5 minutes at 4 ° C in the FACS incubation buffer. 50 microliters of 2x primary antibody supply (FITC anti-CD38, FITC anti-CD1 38, or control isotypo conjugated with FITC m lgG 1 (all from B. D. Biosciences) were added.; or the dAb was added to the cells in the FACS incubation buffer, and incubated for 30 to 60 minutes at 4 ° C. The cells were then washed once in the FACS incubation buffer. One thousand microliters of secondary antibody (rabbit anti-Vk) was added to the cells in the FACS incubation buffer, and incubated for 30 to 60 minutes at 4 ° C. The cells were washed once in the FACS incubation buffer. Then 1 00 microliter of 1 x tertiary antibody was added to the cells in the FACS incubation buffer, and incubated for 30 to 60 minutes at 4 ° C (for dAbs, the tertiary antibody is FITC anti-rabbit (Sigma)). The cells were washed twice in the FACS incubation buffer. The cell granule was resuspended in 200 microliters of FACS + Incubation Regulator marker for viable cells (BD Viaprobe). The cells were then analyzed by flow cytometry. The cell lines described in Table 3 were used for the FACS analysis. The phenotypes of the cell lines were determined by FACS. Suitable cells that have a phenotype suitable for the evaluation of binding specificity of ligands can be obtained from cell depositories, such as the American Type Culture Collection (eg, accession numbers CCL-155, CRL 9068, CCL-86, CRL1929, TIB 196, CRL 1730, CRL2408, HTB 173, HTB 119, CRL 5834), and from the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (for example, access numbers ACC50, ACC31). Table 3 Phenotype of Cell Lines Used in the FACS Analysis 04 Results In this study, dAbs DOM11-3, DOM11-30, DOM12-45, DOM13-25, and DOM14-23 were identified by FACS analysis for having good link characteristics for CD36, CD38, CD138, CEA, and CD56, respectively. See Figures 1A-1H.

Table 4 Properties of anti-CD38 and anti-CD138 dAbs by FACS Analysis = The dAb is linked. X = The dAb is not linked.

BIACORE Analysis The anti-CD38, anti-CEA, and anti-CD56 dAbs that were identified as positive clones for FACS were analyzed in addition by Biacore using the following procedure. The surface of the CM5 chip was activated by flooding with 1: 1 EDC / N HS (0.4M-1-ethyl-3- (3-dimethyl-amino-propyl) -carbodi-imide in water; 0.1M N-hydroxy-succinimide in water), at a flow rate of 5 microliters / minute during a contact time of 10 minutes. CD38 was immobilized in 500 nM acetate buffer, pH 4, at 5 microliters / minute, and this was repeated until the RUs reached between 500 and 1,000 (low density). The CEA and CD56 were coupled in acetate buffer, pH 4.5. Any excess of reactive groups was deactivated by passing 1 M-HCI ethanolamine on the CM5 chip (again 5 microliters / minute for 7 minutes). The affinities of the anti-CD38, anti-CEA, and anti-CD56 dAbs were measured in the Biacore as described above. For each objective, dAbs were found to bind with an affinity in the range of 100 to 200 nM. Figure 2 shows the results of two anti-CD38 dAbs (DOM11-30 and DOM11-3) that were measured to determine affinity in the Biacore. DOM11-30 had an affinity (KD) of 150 nM, and DOM11-2 had an affinity of 250 nM. Epitope Mapping of anti-CD38 dAbs Epitope mapping was carried out to determine whether the anti-CD38 dAbs were linked to different epitopes on CD38. The assay was carried out in the Biacore as described above, using a chip coated at medium density (RUs of approximately 2,000). CD38 was coated on a CM5 chip at medium density as described above. Using the co-injection function, the first anti-CD38 dAbs were injected at a concentration of 500 nM. Both the first and the second anti-CD38 dAbs were co-injected at the same concentration (500 nM). Because both dAbs bind to different epitopes, the RUs during the second injection increase beyond the level of binding of the first dAb. The results showed that the anti-CD38 dAbs DOM113, DOM11-30, and DOM11-23 bind with different epitopes on CD38. See Figures 3A-3D.

Table 5 Properties of anti-CEA dAbs + + Strong link. + It is linked.

It does not link. NT It was not tested. Table 6 Properties of anti-CD56 dAbs + + Strong link. + It is linked. It does not link.

Ligands that contain an anti-CD38 dAb and an anti-CD138 dAb Low-affinity dAbs that bind to CD38 or CD1 38 have been identified. These dAbs have been linked by means of in-line fusion to create double specific dAbs (ligands) that specifically bind to cells expressing antigen by FACS. All dAbs were expressed in E. coli, and purified using L protein agarose, followed by Resource S cation chromatography when required. It has been shown that all dAbs bind as monomers to the cell lines that express the antigen, but not to the cell lines negative for the antigen. The anti-CD38 dAbs and the anti-CD 1 38 dAbs were paired as in-line fusions, and examined for binding by FACS on the positive and negative cell lines, as described above. The optimal double specific dAb pairings were DOM 1 1 -3 / DOM 1 2-45 and DOM 1 1 -30 / DOM 1 2-45. At the optimal concentration (25 to 50 nM), these pairings were strongly bound to double positive cell lines (CD38 + / CD 1 38+), but not to individual positive or negative cell lines. See Figures 4A-4D.

INTERNALIZATION Method The cells were washed once in RPM I 1 640+ FCS at 1 0 percent (internalization regulator). The cell pellet was resuspended in the required volume of internalization buffer, and divided between the appropriate number of tubes (50 microliters per tube). The cells were incubated for 1 5 minutes in the internalization buffer to block. Then 50 microliters of 2x supply of previously mixed primary and secondary antibodies (dAb + rabbit anti-Vk) were added to the cells in the internalization buffer, and incubated for 60 minutes at 4 ° C. The cells were washed once in the internalization buffer. One thousand microliters of 1 x tertiary antibody (anti-rabbit FITC) was added to the cells in the internalization buffer, and incubated for 30 to 60 minutes at 4 ° C. The cells were washed once in the internalization buffer. The relevant samples were incubated at 37 ° C for 1.5 hours to allow internalization. Two sets of duplicate samples were kept in polypeptide at 4 ° C. To differentiate between surface-bound and internalized dAbs, a sample of cells that had been incubated at 4 ° C only, and cells that had been incubated at 37 ° C, were washed with acid, removing only the dAb from the cell surface . The cells were then washed twice in acid wash buffer, and then twice in phosphate buffered serum. The cells were resuspended in 200 microliters of phosphate-buffered + 10 microliters of BD Viaprobe, and analyzed by flow cytometry. The proportion of labeled cells was evaluated at 4 ° C only (bound to cell surface), compared to the acid wash treatment at 37 ° C (internalized) by FACS. Alternatively, for the confocal microscope, the cells are fixed in a 4 percent paraformaldehyde solution, and mounted on coverslips.

Results It was demonstrated that both anti-CD38 / anti-CD138 double specific ligands (DOM11-3 / DOM12-45 and DOM11-30 / DOM12-45) are internalized in the CD38 + Raji cell line by FACS and confocal microscope. Figures 5A-5C show that the cell line positive for CD38 was labeled with DOM 11-3 / DOM11-45 (500 nM, and visualized with FITC staining in a Zeiss LSM510 META confocal microscope). Internalization was revealed as acid-resistant fluorescence at 37 ° C.

It has also been shown that the specific double ligands anti-CD38 / anti-CD138, DOM11-3 / DOM12-45 and DOM11-30 / DOM12-45, are internalized in the dual-expression multiple myeloma cell line OPM2 (DSMZ ACC50) . See Figures 6A and 6B.

Table 7 A determination of the proportion of specific double dAbs internalized Intracellular Localization In this study the intracellular localization of the internalized double specific dAbs was investigated. Method Briefly, the intracellular localization of the specific internalized double dAbs (ds-dAbs) was investigated. The dAbs internalized by the Raji 8CD38 + cells), as described above, were counter-stained with magic red according to the manufacturer's instructions (Serotec). Magical red is a marker for cathepsin B, which is located in the lysosomal compartment.

Both DOM 1 1-30 / DOM 1 2-45 have shown a co-localization with this marker. RESULTS Figure 7 shows the co-localization of CD38 / CD1 38 with the lysosomal marker, Cathepsin B, in the Raji cells, visualized by the confocal microscope. Both DOM 1 1 -30 / DOM 1 2-45 and DOM 1 1 -3 / DOM 1 2-45 have shown a co-localization with that marker. These results show that a ligand can be internalized in the lysosomal compartment, where the ligand can be processed, for example by proteolytic cleavage (dissociation of cathepsin B), for example, to release a toxin.

Conjugates of Double-Polyethylene Glycol Specific Ligand (PEG) Method The specific double ligands anti-CD38 / anti-CD1 38, DOM 1 1 -3 / DOM 1 2-45 and DOM 1 1 -30 / DOM 1 2-45, were pegilated by means of a C-terminal cysteine residue, with PEGS of 5K, 20K, 30K, or 40K . The cysteine designed in the C-terminus of dAb, allows the specific binding of the MAL-PEG site. Glycerol was added to the dAb protein solution to a final concentration of 20 percent (volume / volume), and dithioerythritol at 5 mM. The solution was incubated at room temperature for 20 minutes to allow reduction of the surface thiol. The volume of the sample was reduced to 2.5 milliliters using a centrifugal concentrator (Vivascience) (4,500 revolutions per minute). The regulator of the protein solution was exchanged to remove the reducing agent, using a PD-1 0 column (Amersham). The PD-1 0 column was equilibrated with 25 milliliters of coupling regulator (20 mM BIS-Tris, pH 6.5, 5 mM EDTA, and 10 percent glycerol [volume / volume]), before applying the 2.5 milliliters of reduced protein. The protein solution was allowed to enter completely to the resin bed before eluting the dAb by the addition of an additional 3.5 milliliters of coupling buffer. Then the protein was coupled immediately. The protein concentration (milligrams / milliliter) was determined by measuring the absorbance at 280 nanometers. The amount of protein was converted from milligrams / milliliter to a molar concentration. A 3 molar excess of the MAL-PEG was added. The reaction was allowed to proceed overnight at room temperature. The sample regulator was exchanged using a PD-10 desalting column to remove the uncoupled MAL-PEG. The FACS analysis of the pegylated samples was carried out as described above for the binding and internalization of the dAbs. Results The results show that, when pegylated, the specific double ligands bind to their targets to a degree similar to the specific non-pegylated double ligands. Some reduction in binding was seen, in particular with the larger PEGs for the specific double ligands anti-CD38 / anti-CD138, DOM11 -30 / DOM12-45. In addition, the pegylated forms of the anti-CD38 (DOM1 1) were internalized by the OPM2 multiple myeloma cells to a degree similar to that of the non-pegylated ligand (see Figures 8A-8E).

Conjugate of Double Specific Ligand anti-CD38 / anti-CD138 -Toxin Preparation of specific double ligands anti-CD38 / anti-CD138 (DOM 1 1 -3 / DOM 12-45) A specific double ligand anti-CD38 / anti-CD138 ( DOM 1 1 - 3 / DOM 12-45) was expressed in E. coli, and purified using L protein agarose, followed by Resource S cation chromatography. The false Vk / Vk false homodimer was also expressed, and purified to be used as a negative control. Conjugation of Toxin-Selenium with anti-CD38 / anti-CD138 (DOM11-3 / 12-45) Selenium was conjugated with the anti-CD38 / anti-CD138 double specific ligand, using a 3-carbon-carbon acid linker or an amine linker of 3 carbon atoms. (See U.S. Patent No. 5,783,454, the teachings of which are incorporated herein by reference). On average, two selenium molecules were coupled to each specific double anti-CD38 / anti-CD138 ligand. Internalization of Selenium-Conjugated Double Specific Ligands The internalization of the selenium-conjugated dAbs by OPM2 cells was examined by FACS, as described above. The specific double ligand anti-CD38 / anti-CD138 (DOM1 1 -3 / DOM12-45) conjugated to selenium was internalized to the same degree as the unconjugated dAbs, whereas the dAb Vk false unconjugated or conjugated to selenium, not It was internalized. See Figures 9A-9D. Anti-CD38 / anti-CD138 Cell Annihilation Assays In order to determine the effect of conjugates of specific double-Se ligands on apoptosis and cell death, double staining was carried out with Annexin V alexa-fl uor 488 and propidium iodide (Pl) (Vybrant apoptosis assay kit # 2, Molecular Probes). 1 x1 05 multiple positive myeloma cells for CD38 / CD 1 38 OPM2 (ATCC), or cells negative for CD 38 / CD38 antigen, were incubated with the double specific dAb or with the false Vk with and without conjugation with selenium for 24 hours. As a positive control, the cells were incubated with camptothecin (Sigma) for 6 hours. After treatment, the cells were washed with FACS regulator, and resuspended in the binding buffer containing annexin V and propidium iodide, according to the manufacturer's instructions. Following a 1.5 minute incubation, the cells were assayed by FACS for the presence of apoptotic and dead cell populations. (As shown in Figure 10). The results shown in Figure 10 show that the conjugation of selenium with the dAb specific double anti-CD38 / anti-CD 1 38, provided a selective cell annihilation of the double positive cells (CD38 + / CD1 38+). An increase in apoptosis was observed in multiple myeloma cells expressing both CD38 and CD1 38, compared to the specific double dAb without conjugation with selenium. Moreover, this increase in apoptosis was specific for multiple myeloma cells that expressed both CD38 and CD1 38. No increase in apoptosis was observed with a negative control dAb conjugated with selenium, on any of the positive or negative cell lines. negative for CD38 / CD1 38. The effect of the ligand-Se conjugates on cell viability was analyzed in 1 x 10 5 multiple myeloma cells (CD38 + / CD1 38+) OPM2. Raji cells (positive for CD38 / negative for CD1 38), or negative cells for CD1 38- / CD38-, were incubated with the double specific ligand or with the false Vk, with and without conjugation with selenium for 24 hours, as described above. The cells were washed and stained with propidium iodide, and cell viability was determined by FACS. The results show that conjugation of selenium with the double specific ligand results in a reduction in cell viability in the double positive multiple myeloma cells, whereas the double positive and single negative cell lines were not affected. See Figure 1 1. In some studies, the specific double ligands or false Vk were incubated with and without conjugation, with the cells for 24 to 96 hours. Ligands Containing an anti-CD138 dAb and an anti-CD56 dAb Low affinity dAbs have been identified that bind to CD1 38 or CD56. The dAbs DOM 1 2-45 and DOM 14-23 were linked to create double specific dAbs that specifically bind to the cells expressing the target, by FACS. All dAbs were expressed in E. coli, and purified using L protein agarose, followed by Resource S cation chromatography, when required. A specific double ligand anti-CD1 38 / anti-CD56 was made (DOM 1 2-45 / DOM 14-23) as an online merger. This is an alternative pairing to the anti-CD38 / anti-CD1 38 ligands, for the treatment of multiple myeloma. It has been shown by FACS to bind strongly to double positive cell lines (CD 1 38 + / CD56 +), but not to individual positive or negative cell lines. DOM 14-23 / DOM 12-45 has been shown to be internalized in the double positive multiple myeloma cell line OPM2 (see Table 7). Ligands Containing an Anti-CEA dAb and an Anti-CD56 dAb Low affinity dAbs were identified that bind CEA or CD56. The dAbs (DOM 13-25 and DOM 14-23) were linked to create double specific dAbs, which bind specifically to the cells expressing the target, by means of FACS. All dAbs were expressed in E. coli, and purified using L protein agarose, followed by Resource S cation chromatography, when required. A specific anti-CEA / anti-CD56 double ligand (DOM 1 3-25 / DOM 1 4-23) was made in an on-line fusion. The ligand can be used to treat microcellular lung carcinoma. It has been shown by FACS that it binds strongly to the positive double cell line (H69, a microcellular lung carcinoma that is CEA + / CD56 +), but not to the individual positive or negative cell lines. In addition, DOM 1 3-25 and DOM 14-23 were paired with false Vk (a dAb comprising an amino acid sequence of the germinal line that does not bind to CD38, CD 1 38, CEA, or CD56). When paired with the false Vk, no dAb shows a significant binding to the H69 cells, and only when paired together as a specific double dAb did they bind effectively with the H69 cells. Ligands Containing an Anti-CEA dAb and an Anti-CD56 dAb (DOM13 / DOM14) Methods The anti-CEA dAb, DOM 1 3-25, and the anti-CD56 dAb, DOM 1 4-23, were formatted as a fusion online . This ligand is indicated for the microcellular pulmonary carcinoma. It has been shown by FACS, which binds strongly to the double positive cell lines for the antigen (H69, microcellular pulmonary carcinoma, ATCC), but not with the individual positive cell lines for the antigen or negative. In addition, DOM 1 3-25 and DOM 14-23 were paired with the false Vk. When paired with the false Vk, no dAb showed a significant binding to the H69 cells, and only when paired together as a double-address dAb did they bind effectively with the H69 cells. dAbs anti-CD38 (DOM11) Matured by affinity Affinity maturing libraries were created for the anti-CD38 dAbs DOM11-3 and DOM11-30, by polymerase chain reaction susceptible to error. Three rounds of selection were carried out on the CD38-Fc antigen. The dAbs of rounds 2 and 3 were shown to bind specifically by phage ELISA, and subsequently by soluble ELISA (as described above). The initial screening was carried out by Biacore (as described above), and then by FACS. Some clones that showed a better binding to the antigen were identified by Biacore and FACS. Table 8 and Table 9 show the affinity (KD) observed for the parental dAbs, and for several affinity-matured anti-CD38 dAbs (DOM11-3-1, DOM11-3-2, DOM11-30-1, DOM11- 30-2, DOM11-30-3, and DOM11-30-4). Affinity matured dAbs from DOM11-30 showed a better binding affinity of up to about ten fold. Table 8 Table 9 Anti-CD138 dAbs Matured by Affinity An affinity maturation library was created for the anti-CD1 dAb 38 DOM 1 2-45, by polymerase chain reaction susceptible to error. Three rounds of selection were carried out on the CD 1 38-Fc antigen. It was shown that the dAbs of rounds 2 and 3 are specifically linked by phage ELISA, and subsequently by soluble ELISA. The initial screening was carried out using FACS. Guiding clones were identified that showed a better binding with the antigen in FACS. The affinity matured dAbs showed a better binding affinity of up to about 10 fold. Double Specific Ligands anti-CD38lanti-CD138 Maturated by Affinity The affinity-matured dAbs anti-CD38 and anti-CD1 38 were paired to create double specific ligands, by cloning an anti-CD38 dAb and an anti-CD 1 38 dAb into a double expression vector. In order to determine if the higher affinity of the monomers was reflected in a higher binding affinity of the specific double ligand, a number of the affinity-matured anti-CD38 dAbs were paired with the anti-CD 1 38 DOM 1 2 -45, a number of anti-CD1 dAbs 38 matured by affinity with the anti-CD38 dAbs were paired, and a number of affinity-matured anti-CD38 dAbs and affinity-matured anti-CD1 dAbs 38 were paired. All the specific double ligands were expressed in E. coli, and purified using L-protein agarose, followed by Resource S cation exchange chromatography when required. The binding affinity of the specific double ligands was evaluated by FACS as described above. In this study, a range of concentrations was used to allow determination of the EC50. The results of some of the pairings are shown in Figure 25. Although this invention has been shown and described particularly with reference to its preferred embodiments, it will be understood by those skilled in the art that different changes may be made in form and details thereof, without departing from the scope of the invention encompassed by the appended claims.

Claims

REVIVAL DICTION EN 1 . A ligand comprising a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and a second polypeptide domain having a binding site with a binding specificity for a second binding target. cell surface, wherein the first cell surface target and the second cell surface target are different, and the first cell surface target and the second cell surface target are present in a pathogenic cell; wherein said ligand binds to the first cell surface target and to the second cell surface target in the pathogenic cell; and where this ligand is internalized by this pathogenic cell.
2. The ligand of claim 1, wherein said ligand is preferentially internalized by the aforementioned pathogenic cell.
3. The ligand of claim 1 or 2, wherein this ligand is not substantially internalized by the individual or normal positive cells.
4. The ligand of any of claims 1 to 3, wherein this ligand is selectively linked to the aforementioned pathogenic cell.
5. The ligand of any of claims 1 to 4, wherein the first polypeptide domain binds to the first cell surface target with a low affinity, and the second polypeptide domain binds to the second cell surface target with a low affinity The ligand of claim 5, wherein the first polypeptide domain and the second polypeptide domain each bind to their respective cell surface targets with an affinity (KD) that is between about 1.0 μM and about 1 μM. 0 nM, as determined by surface plasmon resonance. The ligand of claim 4, wherein this ligand selectively binds to the pathogenic cell when this ligand is present at a concentration that is between about 1 pM and about 150 nM. The ligand of any of claims 1 to 7, wherein the first polypeptide domain having a binding site with binding specificity for a first cell surface target, and the second polypeptide domain having a binding site with a binding specificity for a second cell surface target, they are a first single variable domain of immunoglobulin, and a second single variable domain of immunoglobulin, respectively. The ligand of claim 8, wherein the first single immunoglobulin variable domain and / or the second unique immunoglobulin variable domain is a VH H-10. The ligand of claim 8, wherein the first single variable domain of immunoglobulin and the second single variable domain of immunoglobulin are independently selected from the group consisting of a human VH, and a human V. eleven . The ligand of claim 8 or claim 10, wherein the first single immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38.CD1 38 , carcinoembryonic antigen (CEA), CD56, vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), and H ER2. The ligand of claim 1, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD1 38, CEA, CD56, VEGF, EGFR, and HER2, with the proviso that this first single variable domain of immunoglobulin and this second single variable domain of immunoglobulin do not bind to the same cell surface target. The ligand of claim 1 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD38, and compete for binding with CD38, with a domain antibody (FIG. dAb) anti-CD38 selected from the group consisting of:DOM11-14 (SEQ ID NO: 242), DOM11-22 (SEQ ID NO: 246), DOM11-23 (SEQ ID NO: 247), DOM11-25 (SEQ ID NO: 249), DOM11-26 (SEQ ID NO: 250), DOM11-27 (SEQ ID NO: 251), DOM11-29 (SEQ ID NO: 253), DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254), DOM11 -31 (SEQ ID NO: 255), DOM11-32 (SEQ ID NO: 256), DOM11-36 (SEQ ID NO: 260), DOM11-4 (SEQ ID NO: 235), DOM11-43 (SEQ ID NO. : 266), DOM11-44 (SEQ ID NO: 267), DOM11-45 (SEQ ID NO: 268), DOM11-5 (SEQ ID NO: 236), DOM 11-7 (SEQ ID NO: 238), DOM11 -1 (SEQ ID NO: 232), DOM11-10 (SEQ ID NO: 241), DOM11-16 (SEQ ID NO: 243), DOM11-2 (SEQ ID NO: 233), DOM11-20 (SEQ ID NO: 244), DOM11-21 (SEQ ID NO: 245), DOM11-24 (SEQ ID NO: 248), DOM11-28 (SEQ ID NO: 252), DOM11-33 (SEQ ID NO: 257), DOM11 -34 (SEQ ID NO: 258), DOM11-35 (SEQ ID NO: 259), DOM11-37 (SEQ ID NO: 261), DOM11-38 (SEQ ID NO: 262), DOM11-39 (SEQ ID NO. : 293), DOM11-41 (SEQ ID NO: 264), DOM11-42 (SEQ ID NO: 265), DOM11-6 (SEQ ID NO: 237), DOM11-8 (SEQ ID NO: 239), and DOM11-9 (SEQ ID NO: 240). The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD38, and competes for binding with CD38, with an anti-domain (dAb) antibody. -CD38 selected from the group consisting of: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11-3- 10 (SEQ ID NO: 275), DOM 11-3-11 (SEQ ID NO: 276), DOM 11-3-14 (SEQ ID NO: 277), DOM 11-3- 15 (SEQ ID NO: 278) , DOM 11-3-17 (SEQ ID NO: 279), DOM 11-3-19 (SEQ ID NO: 280), DOM 11-3-20 (SEQ ID NO: 281), DOM 11-3-21 ( SEQ ID NO: 282), DOM 11-3-22 (SEQ ID NO: 283), DOM 11-3-23 (SEQ ID NO: 284), DOM 11-3-24 (SEQ ID NO: 285), DOM 11-3-25 (SEQ ID NO: 286), DOM 11-3-26 (SEQ ID NO: 287), DOM 11-3-27 (SEQ ID NO: 288), DOM 11-3- 28 (SEQ ID NO: 289), DOM 11-30-1 (SEQ ID NO: 290), DOM 11-30-2 (SEQ ID NO: 291), DOM 11-30-3 (SEQ ID NO: 292) , DOM 11-30- 5 (SEQ ID NO: 293), DOM 11-30-6 (SEQ ID NO: 294), DOM 11-30-7 (SEQ ID NO: 295), DOM 11-30-8 (SEQ ID NO: 296), DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298), DOM 11-30- 11 (SEQ ID NO: 299), DOM 11-30-12 (SEQ ID NO: 300), DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302) , DOM 11-30-15 (SEQ ID NO: 303), DOM 11-30-16 (SEQ ID NO: 304), and DOM 11-30-17 (SEQ ID. NO: 305). 15. The ligand of claim 13, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM11-14 (SEQ ID NO: 242), DOM11-22 (SEQ ID NO: 246), DOM11-23 (SEQ ID NO: 247), DOM11-25 (SEQ ID NO: 249), DOM11-26 (SEQ ID NO: 250), DOM11-27 (SEQ ID NO: 251), DOM 11-29 (SEQ ID NO: 253), DOM11-3 (SEQ ID NO: 234), DOM11-30 (SEQ ID NO: 254), DOM11-31 (SEQ ID NO: 255), DOM11-32 (SEQ ID NO: 256), DOM11-36 (SEQ ID NO: 260), DOM11-4 (SEQ ID NO: 235), DOM11-43 (SEQ ID NO: 266), DOM11-44 (SEQ ID NO: 267), DOM11-45 (SEQ ID NO: 268), DOM11-5 (SEQ ID NO: 236) ), DOM11-7 (SEQ ID NO: 238), DOM11-1 (SEQ ID NO: 232), DOM11-10 (SEQ ID NO: 241), DOM11-16 (SEQ ID NO: 243), DOM11-2 (SEQ ID NO: 233), DOM11-20 (SEQ ID NO: 244), DOM11-21 (SEQ ID NO: 245), DOM11-24 (SEQ ID NO: 248), DOM11-28 (SEQ ID NO: 252), DOM11-33 (SEQ ID NO: 257), DOM11 -34 (SEQ ID NO: 258), DOM11-35 (SEQ ID NO: 259), DOM11-37 (SEQ. ID NO: 261), DOM11-38 (SEQ ID NO: 262), DOM11-39 (SEQ ID NO: 293), DOM11-41 (SEQ ID NO: 264), DOM11-42 (SEQ ID NO: 265), DOM11-6 (SEQ ID NO: 237), DOM11-8 (SEQ ID NO: 239), and DOM11-9 (SEQ ID NO: 240). The ligand of claim 13, wherein the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent to the sequence of amino acids of a dAb selected from the group consisting of: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11 -3-10 (SEQ ID NO: 275), DOM 11-3-11 (SEQ ID NO: 276), DOM 11-3-14 (SEQ ID NO: 277), DOM 11-3-15 (SEQ ID NO. : 278), SUN 11-3-17 (SEQ ID NO: 279), SUN 11-3-19 (SEQ ID NO: 280) DOM 11-3-20 (SEQ ID NO: 281) DOM 11-3-21 (SEQ ID NO: 282) DOM 11-3-22 (SEQ ID NO: 283) DOM 11-3-23 (SEQ ID NO: 284) DOM 11-3-24 (SEQ ID NO: 285) DOM 11-3-25 (SEQ ID NO: 286) DOM 11-3-26 (SEQ ID NO: 287) DOM 11-3-27 (SEQ ID NO: 288) DOM 11-3-28 (SEQ ID NO: 289) DOM 11-30-1 (SEQ ID NO: 290) DOM 11-30-2 (SEQ ID NO: 291) DOM 11-30-3 (SEQ ID NO: 292) DOM 11-30-5 (SEQ ID NO: 293) DOM 11-30-6 (SEQ ID NO: 294) DOM 11-30-7 (SEQ ID NO: 295) DOM 11-30-8 (SEQ ID NO: 296) DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298), DOM 11 -30-11 (SEQ ID NO: 299), DOM 11-30-12 (SEQ ID NO: 300), DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302), DOM 11-30-15 (SEQ ID NO: 303), DOM 11-30-16 (SEQ ID NO: 304), and DOM 11-30-17 (SEQ ID NO: 305). The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD138, and competes for binding to CD138, with an anti-domain (dAb) antibody. - CD138 selected from the group consisting of: DOM12-1 (SEQ ID NO: 306), DOM12-15 (SEQ ID NO: 317), DOM12-17 (SEQ ID) NO: 318), DOM12-19 (SEQ ID NO: 320), DOM12-2 (SEQ ID NO: 307), DOM12-20 (SEQ ID NO: 321), DOM12-21 (SEQ ID NO: 322), DOM12-22 (SEQ ID NO: 323), DOM12-3 (SEQ ID NO: 308), DOM12-33 (SEQ. ID NO: 334), DOM12-39 (SEQ ID NO: 340), DOM12-4 (SEQ ID NO: 309), DOM12-40 (SEQ ID NO: 341), DOM12-41 (SEQ ID NO: 342), DOM12-42 (SEQ ID NO.343), DOM12-44 (SEQ ID NO: 345), DOM12-46 (SEQ ID NO: 347), DOM12-6 (SEQ ID NO: 311), DOM12-7 (SEQ ID NO.312), DOM12-10 (SEQ ID NO: 315), DOM12-11 (SEQ ID NO: 316), DOM12-18 (SEQ ID NO.319), DOM12-23 (SEQ ID NO: 324), DOM12 -24 (SEQ ID NO: 325), DOM12-25 (SEQ ID NO: 326), DOM12-26 (SEQ. ID NO: 327), DOM12-27 (SEQ ID NO: 328), DOM12-28 (SEQ ID NO: 329), DOM12-29 (SEQ ID NO: 330), DOM12-30 (SEQ ID NO: 331), DOM12-31 (SEQ ID NO: 332), DOM12-32 (SEQ ID NO: 333), DOM12-34 (SEQ ID NO.335), DOM12-35 (SEQ ID NO: 336), DOM12-36 (SEQ ID NO.337), DOM12-37 (SEQ ID NO: 338), DOM12-38 (SEQ ID NO: 339), DOM12-43 (SEQ ID NO: 344), DOM12-45 (SEQ ID NO: 346), DOM12-5 (SEQ ID NO: 310), DOM12-8 (SEQ ID NO: 313), and DOM12-9 (SEQ ID NO: 314). The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD138, and competes for binding to CD138, with an anti-domain (dAb) antibody. -CD138 selected from the group consisting of: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351), DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353), DOM 12-45-8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355), DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357), DOM 12-45-12 (SEQ ID NO: 358), DOM 12-45-13 (SEQ. ID NO: 359), DOM 12-45-14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ ID NO: 361), DOM 12-45-16 (SEQ ID NO: 362), DOM 12 -45-17 (SEQ ID NO: 363), DOM 12-45-18 (SEQ ID NO: 364), DOM 12-45-19 (SEQ ID NO: 365), DOM 12-45-20 (SEQ ID NO. : 366), DOM 12-45-21 (SEQ ID NO: 367), DOM 12-45-22 (SEQ ID NO: 368), DOM 12-45-23 (SEQ ID NO: 369), DOM 12-45 -24 (SEQ ID NO: 370), DOM 12-45-25 (SEQ ID NO: 371), DOM 12-45-26 (SEQ ID NO: 372), DOM 12-45-27 (SEQ ID NO: 373), DOM 12-45-28 (SEQ ID NO: 374), DOM 12-45-29 (SEQ ID NO: 375), DOM 12-45-30 (SEQ ID NO: 376), DOM 12-45-31 (SEQ ID NO: 377), DOM 12-45-32 (SEQ ID NO: 378), DOM 12-45-33 (SEQ. ID NO: 379), DOM 12-45-34 (SEQ ID NO: 380), DOM 12-45-35 (SEQ ID NO: 381), DOM 12-45-36 (SEQ ID NO: 382), DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384). The ligand of claim 17, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM12-1 (SEQ ID NO: 306), DOM12-15 (SEQ ID NO: 317), DOM12-17 (SEQ ID NO: 318), DOM12-19 (SEQ ID NO: 320), DOM12-2 (SEQ ID NO: 307), DOM12-20 (SEQ ID NO: 321), DOM12-21 (SEQ ID NO: 322), DOM12-22 (SEQ ID NO: 323), DOM12-3 (SEQ ID NO: 308) ), DOM12-33 (SEQ ID NO: 334), DOM12-39 (SEQ ID NO: 340), DOM12-4 (SEQ ID NO: 309), DOM12-40 (SEQ ID NO: 341), DOM12-41 ( SEQ ID NO: 342), DOM12-42 (SEQ ID NO: 343), DOM12-44 (SEQ ID NO: 345), DOM12-46 (SEQ ID NO: 347), DOM12-6 (SEQ ID NO: 311) , DOM12-7 (SEQ ID NO: 312), DOM12-10 (SEQ ID NO.315), DOM12-11 (SEQ ID NO: 316), DOM12-18 (SEQ ID NO: 319), DOM12-23 (SEQ. ID NO: 324), DOM12-24 (SEQ ID NO: 325), DOM12-25 (SEQ ID NO: 326), DOM12-26 (SEQ ID NO: 327), DOM 12-27 (SEQ ID NO: 328) , DOM 12-28 (SEQ ID NO: 329), DOM12-29 (SEQ ID NO: 330), DOM12-30 (SEQ ID NO: 331), DOM12-31 (SEQ ID NO: 332), DOM12-32 (SEQ ID NO: 333), DOM12-34 (SEQ ID NO: 335), DOM12-35 (SEQ ID NO: 336), DOM12-36 (SEQ ID NO: 337), DOM12-37 (SEQ ID NO: 338), DOM12-38 (SEQ ID NO: 339), DOM12-43 (SEQ ID NO: 344), DOM12-45 (SEQ ID NO: 346), DOM12-5 (SEQ ID NO: 310), DOM12-8 (SEQ ID NO: 313), and DOM12-9 (SEQ ID NO: 314). The ligand of claim 17, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349) DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351) DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353) DOM 12-45-8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355) DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357) DOM 12-45-12 (SEQ ID NO: 358), DOM 12-45- 13 (SEQ ID NO: 359) DOM 12-45-14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ ID NO: 361) DOM 12-45-16 (SEQ ID NO: 362) DOM 12 -45-17 (SEQ ID NO: 363), DOM 12-45-18 (SEQ ID NO: 364) DOM 12-45-19 (SEQ ID NO: 365), DOM 12-45-20 (SEQ ID NO: 366) DOM 12-45-21 (SEQ ID NO: 367), DOM 12-45-22 (SEQ ID NO: 368) DOM 12-45-23 (SEQ ID NO: 369), DOM 12-45-24 ( SEQ ID NO: 370) DOM 12-45-25 (SEQ ID NO: 371), DOM 12-45-26 (SEQ ID NO: 372) DOM 12-45-27 (SEQ ID NO: 373), DOM 12- 45-28 (SEQ ID NO: 374) DOM 12-45-29 (SEQ ID NO: 375), DOM 12-45-30 (SEQ ID NO: 376) DOM 12-45-31 (SEQ ID NO: 377) , DOM 12-45-32 (SEQ ID NO: 378) DOM 12-45-33 (SEQ ID NO: 379), DOM 12-45-34 (SEQ ID NO: 380) DOM 12-45-35 (SEQ ID NO: 381), DOM 12-45-36 (SEQ ID NO: 382) DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO. : 384). The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second unique immunoglobulin variable domain binds to CEA, and competes for CEA binding, with an anti-domain (dAb) antibody. -CEA selected from the group consisting of: DOM13-1 (SEQ ID NO: 385), DOM13-12 (SEQ ID NO: 393), DOM13-13 (SEQ ID NO: 394), DOM13-14 (SEQ ID) NO: 395); DOM13-15 (SEQ ID NO: 396), DOM13-16 (SEQ ID NO: 397), DOM13-17 (SEQ ID NO: 398), DOM13-18 (SEQ ID NO: 399), DOM13-19 (SEQ ID NO: 400), DOM13-2 (SEQ ID NO: 386), DOM13-20 (SEQ ID NO: 401), DOM13-21 (SEQ ID NO: 402), DOM13-22 (SEQ ID NO: 403), DOM13 -23 (SEQ ID NO: 404), DOM13-24 (SEQ ID NO: 3405), DOM13-25 (SEQ ID NO: 406), DOM13-26 (SEQ ID NO: 407), DOM13-27 (SEQ ID NO. : 408), DOM13-28 (SEQ ID NO: 409), DOM13-29 (SEQ ID NO: 410), DOM13-3 (SEQ ID NO: 387), DOM13-30 (SEQ ID NO: 411), DOM13- 31 (SEQ ID NO: 412), DOM13-32 (SEQ ID NO: 413), DOM13-33 (SEQ ID NO: 414), DOM-13-34 (SEQ ID NO: 415), DOM13-35 (SEQ ID NO: 416), DOM13-36 (SEQ ID NO: 417), DOM13-37 (SEQ ID NO: 418), DOM13-4 (SEQ ID NO: 388), DOM13-42 (SEQ ID NO: 419), DOM13-43 (SEQ ID NO: 420), DOM13-44 (SEQ ID NO: 421), DOM13-45 (SEQ ID W): 422), DOM13-46 (SEQ ID NO: 423), DOM13-47 (SEQ ID NO: 424), DOM13-48 (SEQ ID NO: 425), DOM13-49 (SEQ ID NO: 426), DOM13-5 (SEQ ID NO: 389), DOM13-50 (SEQ ID NO: 427), DOM13-51 (SEQ ID NO: 428), DOM13- 52 (SEQ ID NO: 429), DOM13-53 (SEQ ID NO: 430), DOM13-54 (SEQ ID NO: 431), DOM13-55 (SEQ ID NO: 432), DOM13-56 (SEQ ID NO: 433), DOM13-57 (SEQ ID NO: 434), DOM13-58 (SEQ ID NO: 435), DOM13 -59 (SEQ ID NO: 436), DOM13-6 (SEQ ID NO: 390), DOM13-60 (SEQ ID NO: 437), DOM13-61 (SEQ ID NO: 438), DOM13-62 (SEQ ID NO: 439), DOM13-63 (SEQ ID NO: 440), DOM13-64 (SEQ ID NO: 441), DOM13-65 (SEQ ID NO: 442), DOM13-66 (SEQ ID NO: 443), DOM13 -67 (SEQ ID NO: 444), DOM13-68 (SEQ ID NO: 445), DOM13-69 (SEQ ID NO: 446), DOM13-7 (SEQ ID NO: 391), DOM13-70 (SEQ ID NO. : 447), DOM13-71 (SEQ ID NO: 3448), DOM13-72 (SEQ ID NO: 449), DOM13-73 (SEQ ID NO: 450), DOM13-74 (SEQ ID NO: 451), DOM13-75 (SEQ ID NO: 452), DOM13-76 (SEQ ID NO: 453), DOM13 -77 (SEQ ID NO: 454), DOM13-78 (SEQ ID NO: 455), DOM13-79 (SEQ ID NO: 456), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO. : 457), DOM13-81 (SEQ ID NO: 458), DOM13-82 (SEQ ID NO: 459), DOM13-83 (SEQ ID NO: 460), DOM13-84 (SEQ ID NO: 461), DOM13- 85 (SEQ ID NO: 462), DOM13-86 (SEQ ID NO: 463), DOM13-87 (SEQ ID NO: 464), DOM13-88 (SEQ ID NO: 465), DOM13-89 (SEQ ID NO: 466), DOM13-90 (SEQ ID NO: 467), DOM13-91 (SEQ ID NO: 468), DOM13-92 (SEQ ID NO: 469), DOM13-93 (SEQ ID NO: 470), DOM13-94 (SEQ ID NO: 471), and DOM13-95 (SEQ ID NO: 472). The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CEA, and competes for binding with CEA, with an anti-domain (dAb) antibody. -CEA selected from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). 23. The ligand of claim 21, wherein the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM13-1 (SEQ ID NO: 385), DOM13-12 (SEQ ID NO: 393), DOM13-13 (SEQ ID NO: 394), DOM13-14 (SEQ ID NO: 395), DOM13-15 (SEQ ID NO: 396), DOM13-16 (SEQ ID NO: 397), DOM13-17 (SEQ ID NO: 398), DOM13-18 (SEQ ID NO: 399) ), DOM13-19 (SEQ ID NO: 400), DOM13-2 (SEQ ID NO: 386), DOM13-20 (SEQ ID NO: 401), DOM13-21 (SEQ ID NO: 402), DOM13-22 ( SEQ ID NO: 403), DOM13-23 (SEQ ID NO: 404), DOM13-24 (SEQ ID NO: 405), DOM13-25 (SEQ ID NO: 406), DOM13-26 (SEQ ID NO: 407) , DOM13-27 (SEQ ID NO: 408), DOM13-28 (SEQ ID NO: 409), DOM13-29 (SEQ ID NO: 410), DOM13-3 (SEQ ID NO: 387), DOM13-30 (SEQ. ID NO: 411), DOM13-31 (SEQ ID NO: 412), DOM13-32 (S EQ ID NO: 413), DOM13-33 (SEQ ID NO: 414), DOM-13-34 (SEQ ID NO: 415), DOM13-35 (SEQ ID NO: 416), DOM13-36 (SEQ ID NO: 417), DOM13-37 (SEQ ID NO: 418) , DOM13-4 (SEQ ID NO: 388), DOM13-42 (SEQ ID NO: 419), DOM13-43 (SEQ ID NO: 420), DOM13-44 (SEQ ID NO: 421), DOM13-45 (SEQ ID NO: 422), DOM13-46 (SEQ ID NO: 423), DOM13-47 (SEQ ID NO: 424), DOM13-48 (SEQ ID NO: 425), DOM13-49 (SEQ ID NO: 426), DOM13-5 (SEQ ID NO: 389), DOM13-50 (SEQ ID NO: 427), DOM13-51 (SEQ ID NO: 428), DOM13-52 (SEQ ID NO: 429), DOM13-53 (SEQ ID NO: 430), DOM13-54 (SEQ ID NO: 431), DOM13-55 (SEQ ID NO: 432), DOM13-56 (SEQ ID NO: 433), DOM13-57 (SEQ ID NO: 434), DOM13 -58 (SEQ ID NO: 435), DOM13-59 (SEQ ID NO: 436), DOM13-6 (SEQ ID NO: 390), DOM13-60 (SEQ ID NO: 437), DOM13-61 (SEQ ID NO: 438), DOM13-62 (SEQ ID NO: 439), DOM13-63 (SEQ ID NO: 440), DOM13-64 (SEQ ID NO: 441), DOM13-65 (SEQ ID NO: 442), DOM13-66 (SEQ ID NO: 443), DOM13-67 (SEQ ID NO: 444), DOM13-68 (SEQ ID NO: 445), DOM13-69 (SEQ ID NO: 446), DOM13-7 (SEQ ID NO: 391), DOM13-70 (SEQ ID NO: 447), DOM13-71 (SEQ ID NO: 3448), DOM13 -72 (SEQ ID NO: 449), DOM13-73 (SEQ ID NO: 450), DOM13-74 (SEQ ID NO: 451), DOM13-75 (SEQ ID NO: 452), DOM13-76 (SEQ ID NO. : 453), DOM13-77 (SEQ ID NO: 454), DOM13-78 (SEQ ID NO: 455), DOM13-79 (SEQ ID NO: 456), DOM13-8 (SEQ ID NO: 392), DOM13- 80 (SEQ ID NO: 457), DOM13-81 (SEQ ID NO: 458), DOM13-82 (SEQ ID NO: 459), DOM13-83 (SEQ ID NO: 460), DOM13-84 (SEQ ID NO: 461), DOM13-85 (SEQ ID NO: 462), DOM13-86 (SEQ ID NO: 463), DOM13-87 (SEQ ID NO: 464), DOM13-88 (SEQ ID NO: 465), DOM13-89 (I KNOW THAT ID NO: 466), DOM13-90 (SEQ ID NO: 467), DOM13-91 (SEQ ID NO: 468), DOM13-92 (SEQ ID NO: 469), DOM13-93 (SEQ ID NO: 470), DOM13-94 (SEQ ID NO: 471), and DOM13-95 (SEQ ID NO: 472). The ligand of claim 21, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). 25. The ligand of claim 11 or 12, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD56, and competes for binding with CD56, with an anti-domain (dAb) antibody. -CD56 selected from the group consisting of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482); DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14 -20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO. : 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14 -41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO.511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO. : 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO.517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14 -57 (SEQ ID NO: 52), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO. : 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14- 66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO. : 538). The ligand of claim 25, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ. ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO.499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14 -35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO. : 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14- 43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14-55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525) ), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14 -63 (SEQ ID NO.532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO. : 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). The ligand of any of claims 8 to 26, wherein the first single immunoglobulin variable domain has a binding site with a binding specificity for CD38.; and the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD138, CEA, CD56, VEGF, EGFR, and HER2. 28. The ligand of claim 27, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD138. 29. The ligand of any of claims 8 to 26, wherein the first single immunoglobulin variable domain has a binding site with a binding specificity for CD138; and the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CEA, CD56, VEGF, EGFR, and H ER2. 30. The ligand of claim 29, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CEA. 31 The ligand of any of claims 8 to 26, wherein the first single variable domain of immunoglobulin has a binding site with a binding specificity for CEA; and the second unique variable domain of immunoglobulin has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD38, CEA, VEGF, EGFR, and H ER2. 32. The ligand of claim 31, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD56. 33. The ligand of any of claims 1 to 32, wherein this ligand further comprises a toxyna. 34. The ligand of claim 33, wherein said toxin is a surface activity toxin. 35. The ligand of claim 34, wherein said surface activity toxin comprises a free radical generator or a radionuclide. 36. The ligand of claim 35, wherein said toxin is a cytotoxin, a surface activity toxin, a free radical generator, anti-metabolite, protein, polypeptide, peptide, photoactive agent, anti-sense compound, chemotherapeutic product , radionuclide, or intrabodies. 37. The ligand of any of claims 1 to 36, wherein this ligand further comprises a fraction that prolongs the half-life. 38. The ligand of claim 37, wherein the fraction that prolongs the aforementioned half-life is a polyalkylene glycol fraction, serum albumin or a fragment thereof, transferrin receptor or a transferrin binding portion thereof, or a antibody or antibody fragment comprising a binding site for a polypeptide that improves the half-life in vivo. 39. The ligand of claim 38, wherein the fraction that prolongs the aforementioned half-life is a polyethylene glycol fraction. 40. The ligand of claim 39, wherein the fraction that prolongs the aforementioned half-life is an antibody or an antibody fragment comprising a binding site for the serum albumin or neonatal Fc receptor. 41 The ligand of claim 38, wherein the antibody or antibody fragment is an antibody fragment, and the antibody fragment is a single immunoglobulin variable domain. 42. The ligand of claim 41, wherein the single immunoglobulin variable domain competes for binding to human serum albumin with a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570) ), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r-29 (SEQ ID NO: 581), DOM7r -30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). 43. The ligand of claim 42, wherein the single variable domain of immunoglobulin that binds to human serum albumin, comprises an amino acid sequence having an amino acid sequence identity of at least 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 ( SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477), DOM7h- 8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h- 21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7M8 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r -29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). 44. A ligand comprising a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, a second polypeptide domain having a binding site with a binding specificity for a second target of cell surface, and at least a fraction of toxin; wherein the first cell surface target and the second cell surface target are different, and the first cell surface target and the second cell surface target are present in a pathogenic cell; wherein this ligand binds to the first cell surface target and to the second cell surface target on the aforementioned pathogenic cell with an avidity of between about 1 0"6M and about 10 ~ 12, and wherein this ligand is internalized by the pathogenic cell 45. The ligand of claim 44, wherein said ligand is preferentially internalized by the aforementioned pathogenic cell 46. The ligand of claim 44 or 45, wherein said ligand is not substantially internalized by the cells. positive individual or normal 47. The ligand of any of claims 44 to 46, wherein this ligand is selectively linked to the aforementioned pathogenic cell 48. The ligand of any of claims 44 to 47, wherein the toxin fraction mentioned comprises a cytotoxin, surface activity toxin, free radical generator, anti-metabolite, protein, polypeptide, peptide gone, photoactive agent, anti-sense compound, chemotherapeutic product, radionuclide, or intrabodies. 49. The ligand of any of claims 44 to 47, wherein said toxin fraction comprises a toxin of surface activity. 50. The ligand of claim 49, wherein said surface activity toxin comprises a free radical generator or a radionuclide. 51 The ligand of any of claims 44 to 50, wherein the first polypeptide domain binds to the first cell surface target with low affinity, and the second polypeptide domain binds to the second cell surface target with one low affinity 52. The ligand of claim 51, wherein the first polypeptide domain and the second polypeptide domain each bind to their respective cell surface targets with an affinity (KD) that is between about 1.0 μM and about 1 0 nM, as determined by surface plasmon resonance. 53. The ligand of claim 47, wherein this ligand selectively binds to the pathogenic cell when the ligand is present at a concentration that is between about 1 pM and about 150 nM. 54. The ligand of any of claims 44 to 53, wherein the first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and the second polypeptide domain having a site. of binding with a binding specificity for a second cell surface target, are a first single variable domain of immunoglobulin and a second single variable domain of immunoglobulin, respectively. 55. The ligand of claim 54, wherein the first single immunoglobulin variable domain and / or the second unique immunoglobulin variable domain is a VH H-56. The ligand of claim 54, wherein the first single variable domain of immunoglobulin and the second single variable domain of immunoglobulin are independently selected from the group consisting of a human VH and a human VL. 57. The ligand of claim 54 or claim 56, wherein the first single immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38. , CD 1 38, carci noembryonic antigen (CEA), CD56, vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EG FR), and H ER2. 58. The ligand of claim 57, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD1 38, CEA, CD56, VEGF, EG FR, and H ER2, with the proviso that this first single variable domain of immunoglobulin and this second single variable domain of immunoglobulin do not bind to the same cell surface target. 59. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD38, and competes for binding with CD38, with an anti-CD38 domain (dAb) antibody selected from the group consisting of : DOM11-14 (SEQ ID NO: 261), DOM11-22 (SEQ ID NO: 262), DOM11-23 (SEQ ID NO: 9), DOM11-25 (SEQ ID NO: 263), DOM11-26 (SEQ. ID NO: 264), DOM11-27 (SEQ ID NO: 265), DOM 11-29 (SEQ ID NO: 266), DOM11-3 (SEQ ID NO: 1), DOM11-30 (SEQ ID NO: 2), DOM11-31 (SEQ. ID NO: 267), DOM11-32 (SEQ ID NO: 7), DOM11-36 (SEQ ID NO: 268), DOM11-4 (SEQ ID NO: 269), DOM11-43 (SEQ ID NO: 270), DOM11-44 (SEQ ID NO: 271), DOM11-45 (SEQ ID NO: 272), DOM11-5 (SEQ ID NO: 273), DOM11-7 (SEQ ID NO: 3), DOM11-1 (SEQ ID NO: 274), DOM11-10 (SEQ ID NO: 275), DOM11-16 (SEQ ID NO: 276), DOM11 -2 (SEQ ID NO: 277), DOM11-20 (SEQ ID NO: 278), DOM11-21 (SEQ ID NO: 279), DOM11-24 (SEQ ID NO: 6), DOM11-28 (SEQ ID NO : 280), DOM11-33 (SEQ ID NO: 281), DOM11-34 (SEQ ID NO: 282), DOM11-35 (SEQ ID NO: 283), DOM11-37 (SEQ ID NO: 8), DOM11- 38 (SEQ ID NO: 4), DOM11-39 (SEQ ID NO: 5), DOM11-41 (SEQ ID NO: 284), DOM11-42 (SEQ ID NO: 285), DOM11-6 (SEQ ID NO: 286), DOM11-8 (SEQ ID NO: 287), and DOM11-9 (SEQ ID NO: 288). 60. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD38, and competes for binding to CD38, with an anti-domain (dAb) antibody. -CD38 selected from the group consisting of: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO: 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ IDNO: 274), DOM 11- 3-10 (SEQ ID NO: 275), DOM 11-3-11 (SEQ ID NO: 276), DOM 11-3-14 (SEQ ID NO: 277), DOM 11-3- 15 (SEQ ID NO: 278), DOM 11-3-17 (SEQ ID NO: 279), DOM 11-3-19 (SEQ ID NO: 280), DOM 11-3-20 (SEQ ID NO: 281), DOM 11-3-21 (SEQ ID NO: 282), DOM 11-3-22 (SEQ ID NO: 283), DOM 11-3-23 (SEQ ID NO: 284), DOM 11-3- 24 (SEQ ID NO: 285), DOM 11-3-25 (SEQ ID NO: 286), DOM 11-3-26 (SEQ ID NO: 287), DOM 11-3-27 (SEQ ID NO: 288) , DOM 11-3-28 (SEQ ID NO: 289), DOM 11-30-1 (SEQ ID NO: 290), DOM 11-30-2 (SEQ ID NO: 291), DOM 11-30-3 (SEQ ID NO: 292), DOM 11-30-5 (SEQ ID NO: 293), DOM 11-30-6 (SEQ ID NO: 294), DOM 11-30- 7 (SEQ ID NO: 295), DOM 11-30-8 (SEQ ID NO: 296), DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298) , DOM 11-30-11 (SEQ ID NO: 299), DOM 11-30-12 (SEQ ID NO: 300), DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302), DOM 11-30-15 (SEQ ID NO: 303), DOM 11-30-16 (SEQ ID NO: 304), and DOM 11-30 -17 (SEQ ID NO: 305). 61. The ligand of claim 59, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM11-14 (SEQ ID NO: 261), DOM11-22 (SEQ ID NO: 262), DOM11-23 (SEQ ID NO: 9), DOM11-25 (SEQ ID NO: 263), DOM11-26 (SEQ ID NO: 264), DOM11-27 (SEQ ID NO: 265), DOM11-29 (SEQ ID NO: 266), DOM11-3 (SEQ ID NO: 1 ), DOM11-30 (SEQ ID NO: 2), DOM11-31 (SEQ ID NO: 267), DOM11-32 (SEQ ID NO: 7), DOM11-36 (SEQ ID NO: 268), DOM11-4 ( SEQ ID NO: 269), DOM11-43 (SEQ ID NO: 270), DOM11-44 (SEQ ID NO: 271), DOM11-45 (SEQ ID NO: 272), DOM11-5 (SEQ ID NO: 273), DOM11-7 (SEQ ID NO: 3), DOM11 -1 (SEQ ID NO: 274), DOM11-10 (SEQ ID NO: 275), DOM11-16 (SEQ ID NO: 276), DOM11-2 (SEQ ID NO: 277), DOM11-20 (SEQ ID NO. : 278), DOM11-21 (SEQ ID NO: 279), DOM11-24 (SEQ ID NO: 6), DOM11-28 (SEQ ID NO: 280), DOM11-33 (SEQ ID NO: 281), DOM11-34 (SEQ ID NO: 282), DOM11-35 (SEQ ID NO: 283), DOM11-37 (SEQ ID NO: 8) ), DOM11-38 (SEQ ID NO: 4), DOM11-39 (SEQ ID NO: 5), DOM11-41 (SEQ ID NO: 284), DOM11-42 (SEQ ID NO: 285), DOM11-6 ( SEQ ID NO: 286), DOM11-8 (SEQ ID NO: 287), and DOM11-9 (SEQ ID NO: 288). 62. The ligand of claim 59, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM 11-3-1 (SEQ ID NO: 269), DOM 11-3-2 (SEQ ID NO: 270), DOM 11-3-3 (SEQ ID NO : 271), DOM 11-3-4 (SEQ ID NO: 272), DOM 11-3-6 (SEQ ID NO: 273), DOM 11-3-9 (SEQ ID NO: 274), DOM 11-3 -10 (SEQ ID NO: 275), DOM 11-3-11 (SEQ ID NO: 276), DOM 11-3-14 (SEQ ID NO: 277), DOM 11-3-15 (SEQ ID NO: 278), DOM 11-3-17 (SEQ ID NO: 279), DOM 11-3-19 (SEQ ID NO: 280), DOM 11-3-20 (SEQ ID NO: 281), DOM 11-3-21 (SEQ ID NO: 282), DOM 11-3-22 (SEQ ID NO: 283), DOM 11-3-23 (SEQ. ID NO: 284), DOM 11-3-24 (SEQ ID NO: 285), DOM 11-3-25 (SEQ ID NO: 286), DOM 11 -3-26 (SEQ ID NO: 287), DOM 11-3-27 (SEQ ID NO: 288), DOM 11-3-28 (SEQ ID NO: 289), DOM 11-30-1 (SEQ ID NO: 290), DOM 11-30-2 (SEQ ID NO: 291), DOM 11-30- 3 (SEQ ID NO: 292), DOM 11-30-5 (SEQ ID NO: 293), DOM 11-30-6 (SEQ. ID NO: 294), DOM 11-30-7 (SEQ ID NO: 295), DOM 11-30-8 (SEQ ID NO: 296), DOM 11-30-9 (SEQ ID NO: 297), DOM 11-30-10 (SEQ ID NO: 298), DOM 11-30-11 (SEQ ID NO: 299), DOM 11-30-12 (SEQ ID NO: 300), DOM 11-30-13 (SEQ ID NO: 301), DOM 11-30-14 (SEQ ID NO: 302), DOM 11-30-15 (SEQ ID NO: 303), DOM 11-30-16 (SEQ. ID NO: 304), and DOM 11-30-17 (SEQ ID NO: 305). 63. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD138, and competes for binding to CD138, with an anti-domain (dAb) antibody. -CD138 selected from the group consisting of: DOM12-1 (SEQ ID NO: 289), DOM12-15 (SEQ ID NO: 290), DOM12-17 (SEQ ID NO: 11), DOM12-19 (SEQ ID NO: 291), DOM12-2 (SEQ ID NO: 292), DOM12-20 (SEQ ID NO: 293), DOM12-21 (SEQ ID NO: 294), DOM12-22 (SEQ ID NO: 295), DOM12 -3 (SEQ ID NO: 296), DOM12-33 (SEQ ID NO: 297), DOM12-39 (SEQ ID NO: 298), DOM12-4 (SEQ ID NO: 299), DOM12-40 (SEQ ID NO: 300), DOM12-41 (SEQ ID NO: 301), DOM12-42 (SEQ ID NO: 302), DOM12-44 (SEQ ID NO: 303), DOM12 -46 (SEQ ID NO: 304), DOM12-6 (SEQ ID NO: 305), DOM12-7 (SEQ ID NO: 306), DOM12-10 (SEQ ID NO: 307), DOM12-11 (SEQ ID NO. : 308), DOM12-18 (SEQ ID NO: 309), DOM12-23 (SEQ ID NO: 310), DOM12- 24 (SEQ ID NO: 311), DOM12-25 (SEQ ID NO: 312), DOM12- 26 (SEQ ID NO: 12), DOM12-27 (SEQ ID NO: 313), DOM12-28 (SEQ ID NO.314), DOM12-29 (SEQ ID NO: 315), DOM12-30 (SEQ ID NO: 316), DOM12-31 (SEQ ID NO: 317), DOM12-32 (SEQ ID NO: 318), DOM12-34 (SEQ ID NO: 319), DOM12-35 (SEQ ID NO: 320), DOM12-36 (I KNOW THAT ID NO: 321), DOM12-37 (SEQ ID NO: 322), DOM12-38 (SEQ ID NO: 323), DOM12-43 (SEQ ID NO: 324), DOM12-45 (SEQ ID NO: 310), DOM12-5 (SEQ ID NO: 325), DOM12-8 (SEQ ID NO: 326), and DOM12-9 (SEQ ID NO: 327). 64. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD138, and competes for binding to CD138, with an anti-domain (dAb) antibody. -CD138 selected from the group consisting of: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351), DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353), DOM 12-45- 8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355), DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357) , DOM 12-45-12 (SEQ ID NO: 358), DOM 12-45-13 (SEQ ID NO: 359) DOM 12-45-14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ. ID NO: 361) DOM 12-45-16 (SEQ ID NO: 362), DOM 12-45-17 (SEQ ID NO: 363) DOM 12-45-18 (SEQ ID NO: 364), DOM 12-45 -19 (SEQ ID NO: 365) DOM 12-45-20 (SEQ ID NO: 366), DOM 12-45-21 (SEQ ID NO: 367) DOM 12-45-22 (SEQ ID NO: 368), DOM 12-45-23 (SEQ ID NO: 369) DOM 12-45-24 (SEQ ID NO: 370), DOM 12-45-25 (SEQ ID NO: 371) DOM 12-45-26 (SEQ ID NO: 372), DOM 12-45-27 (SEQ ID NO: 373) DOM 12 -45-28 (SEQ ID NO: 374), DOM 12-45-29 (SEQ ID NO: 375) DOM 12-45-30 (SEQ ID NO: 376), DOM 12-45-31 (SEQ ID NO: 377) DOM 12-45-32 (SEQ ID NO: 378), DOM 12-45-33 (SEQ ID NO: 379) DOM 12-45-34 (SEQ ID NO: 380), DOM 12-45-35 (SEQ ID NO: 381) DOM 12-45-36 (SEQ ID NO: 382), DOM 12-45-37 (SEQ ID NO: 383), and DOM 12-45-38 (SEQ ID NO: 384). 65. The ligand of claim 63, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM12-1 (SEQ ID NO: 289), DOM12-15 (SEQ ID NO: 290), DOM12-17 (SEQ ID NO: 11), DOM12- 19 (SEQ ID NO: 291), DOM12-2 (SEQ ID NO: 292), DOM12-20 (SEQ ID NO: 293), DOM12-21 (SEQ ID NO: 294), DOM12-22 (SEQ ID NO: 295), DOM12-3 (SEQ ID NO: 296), DOM12-33 (SEQ ID NO: 297), DOM12-39 (SEQ ID NO: 298), DOM12-4 (SEQ ID NO: 299), DOM12-40 (SEQ ID NO: 300), DOM12-41 (SEQ ID NO: 301), DOM12-42 (SEQ ID NO: 302), DOM12-44 (SEQ ID NO: 303), DOM12-46 (SEQ ID NO: 304), DOM12-6 (SEQ ID NO: 305), DOM12 -7 (SEQ ID NO: 306), DOM12-10 (SEQ ID NO: 307), DOM12-11 (SEQ ID NO: 308), DOM12-18 (SEQ ID NO: 309), DOM12-23 (SEQ ID NO. : 310), DOM12-24 (SEQ ID NO: 311), DOM12-25 (SEQ ID NO: 312), DOM12-26 (SEQ ID NO: 12), DOM12-27 (SEQ ID NO: 313), DOM12- 28 (SEQ ID NO: 314), DOM12-29 (SEQ ID NO: 315), DOM12-30 (SEQ ID NO: 316), DOM12-31 (SEQ ID NO: 317), DOM12-32 (SEQ ID NO: 318), DOM12-34 (SEQ ID NO: 319), DOM12-35 (SEQ ID NO: 320), DOM12-36 (SEQ ID NO: 321), DOM12-37 (SEQ ID NO: 322), DOM12-38 (I KNOW THAT ID NO: 323), DOM12-43 (SEQ ID NO: 324), DOM12-45 (SEQ ID NO: 310), DOM12-5 (SEQ ID NO: 325), DOM12-8 (SEQ ID NO: 326), and DOM12-9 (SEQ ID NO: 327). 66. The ligand of claim 63, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM 12-45-1 (SEQ ID NO: 348), DOM 12-45-2 (SEQ ID NO: 349), DOM 12-45-3 (SEQ ID NO: 350), DOM 12-45-4 (SEQ ID NO: 351) DOM 12-45-5 (SEQ ID NO: 352), DOM 12-45-6 (SEQ ID NO: 353) DOM 12-45 -8 (SEQ ID NO: 354), DOM 12-45-9 (SEQ ID NO: 355) DOM 12-45-10 (SEQ ID NO: 356), DOM 12-45-11 (SEQ ID NO: 357) DOM 12-45-12 (SEQ ID NO: 358), DOM 12-45-13 (SEQ ID NO: 359) DOM 12-45- 14 (SEQ ID NO: 360), DOM 12-45-15 (SEQ ID NO: 361) DOM 12-45-16 (SEQ ID NO: 362), DOM 12-45-17 (SEQ ID NO: 363) DOM 12-45-18 (SEQ ID NO: 364) DOM 12-45-19 (SEQ ID NO: 365) DOM 12-45-20 (SEQ ID NO: 366) DOM 12-45-21 (SEQ ID NO: 367) DOM 12-45-22 (SEQ ID NO: 368) DOM 12-45-23 (SEQ ID NO: 369) DOM 12-45-24 (SEQ ID NO: 370) DOM 12-45-25 (SEQ ID NO: 371) DOM 12-45-26 (SEQ ID NO: 372) DOM 12-45-27 (SEQ ID NO: 373) DOM 12-45-28 (SEQ ID NO: 374) DOM 12-45-29 ( SEQ ID NO: 375) DOM 12-45-30 (SEQ ID NO: 376) DOM 12-45-31 (SEQ ID NO: 377) DOM 12-45-32 (SEQ ID NO: 378) DOM 12-45- 33 (SEQ ID NO: 379) DOM 12-45-34 (SEQ ID NO: 380) DOM 12-45-35 (SEQ ID NO: 381) DOM 12-45-36 (SEQ ID NO: 382) DOM 12- 45-37 (SEQ ID NO: 383) and DOM 12-45-38 (SEQ ID NO: 384). 67. The ligand of claim 54 or 56, wherein the first single immunoglobulin variable domain or the second unique immunoglobulin variable domain binds to CEA, and competes for CEA binding, with an anti-domain (dAb) antibody. -CEA selected from the group consisting of: DOM13-1 (SEQ ID NO: 328), DOM13-12 (SEQ ID NO: 329), DOM13-13 (SEQ ID NO: 330), DOM13-14 (SEQ ID) NO: 331), DOM13-15 (SEQ ID NO: 332), DOM13-16 (SEQ ID NO: 333), DOM13-17 (SEQ ID NO: 334), DOM13-18 (SEQ ID NO: 335), DOM13 -19 (SEQ ID NO: 336), DOM13-2 (SEQ ID NO: 337), DOM13-20 (SEQ ID NO: 338), DOM13-21 (SEQ ID NO: 339), DOM13-22 (SEQ ID NO. : 340), DOM13-23 (SEQ ID NO: 341), DOM13-24 (SEQ ID NO: 342), DOM13-25 (SEQ ID NO: 13), DOM13-26 (SEQ ID NO: 343), DOM13-27 (SEQ ID NO: 344), DOM13-28 (SEQ ID NO: 345), DOM13-29 (SEQ ID NO: 346), DOM13-3 (SEQ ID NO: 347), DOM13-30 (SEQ ID NO: 348), DOM13-31 (SEQ ID NO: 349), DOM13-32 (SEQ ID NO: 350), DOM13-33 (SEQ ID NO: 351), DOM-13-34 ( SEQ ID NO: 352), DOM13-35 (SEQ ID NO: 353), DOM13-36 (SEQ ID NO: 354), DOM13-37 (SEQ ID NO: 355), DOM13-4 (SEQ ID NO: 356), DOM13-42 (SEQ ID NO: 357), DOM13-43 (SEQ ID NO: 358), DOM13 -44 (SEQ ID NO: 359), DOM13-45 (SEQ ID NO: 360), DOM13-46 (SEQ ID NO.361), DOM13-47 (SEQ ID NO: 362), DOM13-48 (SEQ ID NO. : 363), DOM13-49 (SEQ ID NO: 364), DOM13-5 (SEQ ID NO: 365), DOM13-50 (SEQ ID NO: 366), DOM13-51 (SEQ ID NO: 367), DOM13-52 (SEQ ID NO: 368), DOM13-53 (SEQ ID NO: 369), DOM13-54 (SEQ ID NO: 370), DOM13-55 (SEQ ID NO: 371), DOM13-56 (SEQ ID NO: 372), DOM13-57 (SEQ ID NO: 14), DOM13-58 (SEQ ID NO: 15), DOM13 -59 (SEQ ID NO: 16), DOM13-6 (SEQ ID NO: 373), DOM13-60 (SEQ ID NO: 374), DOM13-61 (SEQ ID NO: 375), DOM13-62 (SEQ ID NO: 376), DOM13-63 (SEQ ID NO: 377), DOM13-64 (SEQ ID NO: 17 ), DOM13-65 (SEQ ID NO: 18), DOM13-66 (SEQ ID NO: 378), DOM13-67 (SEQ ID NO: 379), DOM13-68 (SEQ ID NO: 380), DOM13-69 (SEQ ID NO: 381), DOM13-7 (SEQ. ID NO: 382), DOM13-70 (SEQ ID NO: 383), DOM13-71 (SEQ ID NO: 384), DOM13-72 (SEQ ID NO: 385), DOM13-73 (SEQ ID NO: 386), DOM13-74 (SEQ ID NO: 19), DOM13-75 (SEQ ID NO: 387), DOM13-76 (SEQ ID NO: 388), DOM13-77 (SEQ ID NO: 389), DOM13-78 (SEQ ID NO: 390), DOM13-79 (SEQ ID NO: 391), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ ID NO: 393), DOM13-81 (SEQ ID NO: 394), DOM13 -82 (SEQ ID NO: 395), DOM13-83 (SEQ ID NO: 396), DOM13-84 (SEQ ID NO: 397), DOM13-85 (SEQ ID NO: 398), DOM13-86 (SEQ ID NO. : 399), DOM13-87 (SEQ ID NO: 400), DOM13-88 (SEQ ID NO: 401), DOM13-89 (SEQ ID NO: 402), DOM13-90 (SEQ ID NO: 403), DOM13- 91 (SEQ ID NO: 404), DOM13-92 (SEQ ID NO: 405), DOM13-93 (SEQ ID NO: 20), DOM13-94 (SEQ ID NO: 406), and DOM13-95 (SEQ ID NO: 21). 68. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CEA, and competes for binding with CEA, with an anti-domain (dAb) antibody. -CEA selected from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). 69. The ligand of claim 67, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM13-1 (SEQ ID NO: 328), DOM13-12 (SEQ ID NO: 329), DOM13-13 (SEQ ID NO: 330), DOM13-14 (SEQ ID NO: 331), DOM13-15 (SEQ ID NO: 332), DOM13-16 (SEQ ID NO: 333), DOM13-17 (SEQ ID NO: 334), DOM13-18 (SEQ ID NO: 335) ), DOM13-19 (SEQ ID NO: 336), DOM13-2 (SEQ ID NO: 337), DOM13-20 (SEQ ID NO: 338), DOM13-21 (SEQ ID NO: 339), DOM13-22 (SEQ ID NO: 340), DOM13-23 (SEQ ID NO: 341), DOM13-24 (SEQ ID NO: 342), DOM13-25 (SEQ ID NO: 13), DOM13-26 (SEQ ID NO: 343), DOM13-27 (SEQ ID NO: 344), DOM13-28 (SEQ ID NO: 345), DOM13-29 (SEQ ID NO: 346), DOM13 -3 (SEQ ID NO: 347), DOM13-30 (SEQ ID NO: 348), DOM13-31 (SEQ ID NO: 349), DOM13-32 (SEQ ID NO: 350), DOM13-33 (SEQ ID NO: 351), DOM-13-34 (SEQ ID NO: 352), DOM13-35 (SEQ ID NO. : 353), DOM13-36 (SEQ ID NO: 354), DOM13-37 (SEQ ID NO: 355), DOM13-4 (SEQ ID NO: 356), DOM13-42 (SEQ ID NO: 357), DOM13- 43 (SEQ ID NO: 358), DOM13-44 (SEQ ID NO: 359), DOM13-45 (SEQ ID NO: 360), DOM13-46 (SEQ ID NO: 361), DOM13-47 (SEQ ID NO: 362), DOM13-48 (SEQ ID NO: 363), DOM13-49 (SEQ ID NO: 364), DOM13-5 (SEQ ID NO: 365), DOM13-50 (SEQ ID NO: 366), DOM13-51 (SEQ ID NO: 367), DOM13-52 (SEQ ID NO: 368), DOM13-53 (SEQ ID NO: 369), DOM13 -54 (SEQ ID NO: 370), DOM13-55 (SEQ ID NO: 371), DOM13-56 (SEQ ID NO: 372), DOM13-57 (SEQ ID NO: 14), DOM13-58 (SEQ ID NO. : 15), DOM13-59 (SEQ ID NO: 16), DOM13-6 (SEQ ID NO: 373), DOM13-60 (SEQ ID NO: 374), DOM13-61 (SEQ ID NO: 375), DOM13- 62 (SEQ ID NO: 376), DOM13-63 (SEQ ID NO: 377), DOM13-64 (SEQ ID NO: 17), DOM13-65 (SEQ ID NO: 18), DOM13-66 (SEQ ID NO: 378), DOM13-67 (SEQ ID NO: 379), DOM13-68 (SEQ ID NO: 380), DOM13-69 (SEQ ID NO: 381), DOM13-7 (SEQ ID NO: 382), DOM13-70 (SEQ ID NO: 383), DOM13-71 (SEQ ID NO: 384), DOM13-72 (SEQ ID NO: 385), DOM13-73 (SEQ ID NO: 386), DOM13-74 (SEQ ID NO: 19 ), DOM13-75 (SEQ ID NO: 387), DOM13-76 (SEQ ID NO: 388), DOM13-77 (SEQ ID NO: 389), DOM13-78 (SEQ ID NO: 390), DOM13-79 ( SEQ ID NO: 391), DOM13-8 (SEQ ID NO: 392), DOM13-80 (SEQ. ID NO: 393), DOM13-81 (SEQ ID NO: 394), DOM13-82 (SEQ ID NO: 395), DOM13-83 (SEQ ID NO: 396), DOM13-84 (SEQ ID NO: 397), DOM13-85 (SEQ ID NO: 398), DOM13-86 (SEQ ID NO: 399), DOM13-87 (SEQ. ID NO: 400), DOM13-88 (SEQ ID NO: 401), DOM13-89 (SEQ ID NO: 402), DOM13-90 (SEQ ID NO: 403), DOM13-91 (SEQ ID NO: 404), DOM13-92 (SEQ ID NO: 405), DOM13-93 (SEQ ID NO: 20), DOM13-94 (SEQ ID NO: 406), and DOM13-95 (SEQ ID NO: 21). 70. The ligand of claim 67, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM 13-25-3 (SEQ ID NO: 473), DOM 13-25-23 (SEQ ID NO: 474), DOM 13-25-27 (SEQ ID NO: 475), and DOM 13-25-80 (SEQ ID NO: 476). 71. The ligand of claim 54 or 56, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin binds to CD56, and competes for binding with CD56, with an anti-domain (dAb) antibody. -CD56 selected from the group consisting of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486), DOM14-16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 (SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14 -21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO. : 496), DOM14-26 (SEQ ID NO: 497), DOM14-27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14- 31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO: 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ. ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14-37 (SEQ ID NO: 506), DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO: 511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14-46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO: 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14 -55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO. : 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14- 64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ. ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). 72. The ligand of claim 71, wherein the first single variable domain of immunoglobulin or the second single variable domain of immunoglobulin comprises an amino acid sequence having an amino acid sequence similarity of at least about 90 percent with the sequence of amino acids of a dAb selected from the group consisting of: DOM14-1 (SEQ ID NO: 477), DOM14-10 (SEQ ID NO: 481), DOM14-100 (SEQ ID NO: 540), DOM14-11 (SEQ ID NO: 482), DOM14-12 (SEQ ID NO: 483), DOM14-13 (SEQ ID NO: 484), DOM14-14 (SEQ ID NO: 485), DOM14-15 (SEQ ID NO: 486) ), DOM14-16 (SEQ ID NO: 487), DOM14-17 (SEQ ID NO: 488), DOM14-18 (SEQ ID NO: 489), DOM14-19 (SEQ ID NO: 490), DOM14-2 ( SEQ ID NO: 478), DOM14-20 (SEQ ID NO: 491), DOM14-21 (SEQ ID NO: 492), DOM14-22 (SEQ ID NO: 493), DOM14-23 (SEQ ID NO: 494), DOM14-24 (SEQ ID NO: 495), DOM14-25 (SEQ ID NO: 496), DOM14-26 (SEQ ID NO: 497), DOM14 -27 (SEQ ID NO: 498), DOM14-28 (SEQ ID NO: 499), DOM14-3 (SEQ ID NO: 479), DOM14-31 (SEQ ID NO: 500), DOM14-32 (SEQ ID NO. : 501), DOM14-33 (SEQ ID NO: 502), DOM14-34 (SEQ ID NO: 503), DOM14-35 (SEQ ID NO: 504), DOM14-36 (SEQ ID NO: 505), DOM14- 37 (SEQ ID NO: 506) ,. DOM14-38 (SEQ ID NO: 507), DOM14-39 (SEQ ID NO: 508), DOM14-4 (SEQ ID NO: 480), DOM14-40 (SEQ ID NO: 509), DOM14-41 (SEQ ID NO: 510), DOM14-42 (SEQ ID NO.511), DOM14-43 (SEQ ID NO: 512), DOM14-44 (SEQ ID NO: 513), DOM14-45 (SEQ ID NO: 514), DOM14 -46 (SEQ ID NO: 515), DOM14-47 (SEQ ID NO: 516), DOM14-48 (SEQ ID NO: 517), DOM14-49 (SEQ ID NO: 518), DOM14-50 (SEQ ID NO. : 519), DOM14-51 (SEQ ID NO: 520), DOM14-52 (SEQ ID NO: 521), DOM14-53 (SEQ ID NO: 522), DOM14-54 (SEQ ID NO: 523), DOM14- 55 (SEQ ID NO: 524), DOM14-56 (SEQ ID NO: 525), DOM14-57 (SEQ ID NO: 526), DOM14-58 (SEQ ID NO: 527), DOM14-59 (SEQ ID NO: 528), DOM14-60 (SEQ ID NO: 529), DOM14-61 (SEQ ID NO: 530), DOM14-62 (SEQ ID NO: 531), DOM14-63 (SEQ ID NO: 532), DOM14-64 (SEQ ID NO: 533), DOM14-65 (SEQ ID NO: 534), DOM14-66 (SEQ ID NO: 535), DOM14-67 (SEQ ID NO: 536), DOM14-70 (SEQ ID NO: 539), DOM14-68 (SEQ ID NO: 537), and DOM14-69 (SEQ ID NO: 538). 73. The ligand of any of claims 54 to 72, wherein the first single variable domain of immunoglobulin has a binding site with a binding specificity for CD38; and the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD138, CEA, CD56, VEGF, EGFR, and HER2. 74. The ligand of claim 73, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD 1 38. 75. The ligand of any of claims 54 to 72, wherein the first single variable domain of immunoglobulin has a binding site with a binding specificity for CD1 38; and the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CEA, CD56, VEGF, EVGFR, and H ER2. 76. The ligand of claim 75, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CEA. 77. The ligand of any of claims 54 to 72, wherein the first single variable domain of immunoglobulin has a binding site with a binding specificity for CEA; and the second unique immunoglobulin variable domain has a binding site with a binding specificity for a cell surface target selected from the group consisting of CD38, CD38, CEA, VEGF, EGFR, and HER2. 78. The ligand of claim 77, wherein the second unique immunoglobulin variable domain has a binding site with a binding specificity for CD56. 79. The ligand of any of claims 44 to 78, wherein this ligand further comprises a fraction that prolongs the half-life. 80. The ligand of claim 79, wherein the fraction that prolongs the aforementioned half-life is a polyalkylene glycol fraction, serum albumin or a fragment thereof, a transferrin receptor or a transferrin binding portion thereof, or an antibody or antibody fragment comprising a binding site for a polypeptide that improves the half-life in vivo. 81 The ligand of claim 80, wherein the fraction that extends the aforementioned half-life is a polyalkylene glycol moiety. 82. The ligand of claim 80, wherein the fraction that prolongs the aforementioned half-life is an antibody or antibody fragment comprising a binding site for a serum albumin or neonatal Fc receptor. 83. The ligand of claim 80, wherein the antibody or antibody fragment is an antibody fragment, and the antibody fragment is a single immunoglobulin variable domain. 84. The ligand of claim 83, wherein the single immunoglobulin variable domain mentioned competes for binding to human serum albumin, with a dAb selected from the group consisting of: DOM7m-1 6 (SEQ ID NO: 541), DOM7m-1 2 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r-1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r- 4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (S EQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h -7 (SEQ ID NO: 477), DOM7h-8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558), DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h- 21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r -20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO. : 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580), DOM7r- 29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). 85. The ligand of claim 84, wherein the single immunoglobulin variable domain that binds to human serum albumin, comprises an amino acid sequence having an amino acid sequence identity of at least 90 percent with the amino acid sequence of a dAb selected from the group consisting of: DOM7m-16 (SEQ ID NO: 541), DOM7m-12 (SEQ ID NO: 542), DOM7m-26 (SEQ ID NO: 543), DOM7r- 1 (SEQ ID NO: 544), DOM7r-3 (SEQ ID NO: 545), DOM7r-4 (SEQ ID NO: 546), DOM7r-5 (SEQ ID NO: 547), DOM7r-7 (SEQ ID NO: 548), and DOM7r-8 (SEQ ID NO: 549), DOM7h-2 (SEQ ID NO: 550), DOM7h-3 (SEQ ID NO: 551), DOM7h-4 (SEQ ID NO: 552), DOM7h-6 (SEQ ID NO: 553), DOM7h-1 (SEQ ID NO: 555), DOM7h-7 (SEQ ID NO: 477), DOM7h- 8 (SEQ ID NO: 564), DOM7r-13 (SEQ ID NO: 565), and DOM7r-14 (SEQ ID NO: 566), DOM7h-22 (SEQ ID NO: 557), DOM7h-23 (SEQ ID NO: 558) , DOM7h-24 (SEQ ID NO: 559), DOM7h-25 (SEQ ID NO: 560), DOM7h-26 (SEQ ID NO: 561), DOM7h-21 (SEQ ID NO: 562), DOM7h-27 (SEQ ID NO: 563), DOM7r-15 (SEQ ID NO: 567), DOM7r-16 (SEQ ID NO: 568), DOM7r-17 (SEQ ID NO: 569), DOM7r-18 (SEQ ID NO: 570), DOM7r-19 (SEQ ID NO: 571), DOM7r-20 (SEQ ID NO: 572), DOM7r-21 (SEQ ID NO: 573), DOM7r-22 (SEQ ID NO: 574), DOM7r-23 (SEQ ID NO: 575), DOM7r-24 (SEQ ID NO: 576), DOM7r-25 (SEQ ID NO: 577), DOM7r-26 (SEQ ID NO: 578), DOM7r-27 (SEQ ID NO: 579), DOM7r-28 (SEQ ID NO: 580) ), DOM7r-29 (SEQ ID NO: 581), DOM7r-30 (SEQ ID NO: 582), DOM7r-31 (SEQ ID NO: 583), DOM7r-32 (SEQ ID NO: 584), and DOM7r-33 (SEQ ID NO: 585). 86. A ligand of any of claims 1 to 85, for use in therapy or diagnostics. 87. A ligand of any of claims 1 to 85, for use in the treatment of cancer. 88. The use of the ligand of any of claims 1 to 85, for the manufacture of a medicament for the treatment of cancer. 89. A method for delivering a toxin internally to a cell, which comprises contacting this cell with a ligand of any of claims 44 to 85, wherein the ligand is internalized, and the toxin is supplied internally. 90. A method for the treatment of cancer, which comprises administering to a subject in need thereof, a therapeutically effective amount of a ligand of any of claims 1 to 85. 91. The method of claim 90, wherein the cancer is multiple myeloma. 92. The method of claim 91, wherein the cancer is lung carcinoma. 93. A composition comprising a ligand of any of claims 1 to 85, and a physiologically acceptable carrier. 94. The composition of claim 93, wherein said composition comprises a vehicle for intravenous, intramuscular, intraperitoneal, intra-arterial, intrathecal, intra-articular, or subcutaneous administration. 95. The composition of claim 93, wherein said composition comprises a vehicle for pulmonary, intranasal, vaginal, or rectal administration. 96. A drug delivery device, which comprises the composition of claim 93. 97. The drug delivery device of claim 96, wherein said drug delivery device is selected from the group consisting of a parenteral delivery device, an intravenous delivery device, an intramuscular delivery device, an intraperitoneal delivery device, a transdermal delivery device, a pulmonary delivery device, an intra-arterial delivery device, an intrathecal delivery device , an intra-articular delivery device, a subcutaneous delivery device, an intranasal delivery device, a vaginal delivery device, and a rectal delivery device. 98. The drug delivery device of claim 96, wherein said device is selected from the group consisting of a syringe, a transdermal delivery device, a capsule, a tablet, a nebulizer, an inhaler, an atomizer, an aerosolizer, a fine mist nebulizer, a dry powder inhaler, a metered dose inhaler, a metered dose sprayer, a metered dose nebulizer, a metered dose sprayer, or a catheter. 99. The use of the ligand of any of claims 1 to 85, for the manufacture of a medicament for selectively killing cancer cells on normal cells. 1 00. The use of the ligand of any of claims 1 to 85, for the manufacture of a medicament for delivering a therapeutic agent intracellularly. 1 01. The use of the ligand of any of claims 1 to 85, for the manufacture of a medicament for delivering a therapeutic agent to a compartment of cathepsin B in a cell. 02. of the ligand of any of claims 1 to 85, for the manufacture of a medicament for locating this ligand in a compartment of cathepsin B in a cell. 1 03. An isolated or recombinant nucleic acid encoding a ligand of any one of claims 1 to 85. 1 04. A vector comprising the recombinant nucleic acid of claim 1 03. 1 05. A host cell comprising the acid recombinant nucleic acid of claim 1 03, or the vector of claim 1 04. 1 06. A method for producing a ligand, which comprises maintaining the host cell of claim 1 under conditions suitable for the expression of this nucleic acid or vector, whereby it is produced a ligand 1 07. The method of claim 1 06, which further comprises isolating the ligand. 1 08. A method for the treatment of cancer, which comprises administering to a subject in need thereof, a therapeutically effective amount of the ligand of any of claims 1 to 85, and a chemotherapeutic agent, wherein the chemotherapeutic agent is administered at a low dose SUMMARY Disclosed are ligands comprising a first polypeptide domain having a binding site with a binding specificity for a first cell surface target, and a second polypeptide domain having a binding site for a second cell surface target. , where each goal is different and is on the same cell. In some embodiments, the ligands described further comprise a toxin. In other embodiments, the ligands further comprise fractions that prolong the half-life. Methods for using these ligands are also disclosed. In particular, the use of these ligands for cancer therapy is described. * * * * *