EXTENSION SEQUENCES FOR DIABODIES

[0001] The present application is being filed along with a Sequence Listing in electronic format. The Sequence Listing is provided as a file entitled IGNAB043WOSEQLIST.TXT, created on January 10, 2018, which is 61,429 bytes in size. The information in the electronic format of the Sequence Listing is incorporated herein by reference in its entirety.

BACKGROUND

Field

[0002] Embodiments described herein relate generally to extension sequences.

Description of the Related Art

[0003] Various antigen binding constructs exist. Some such constructs include diabodies. Diabodies contain a V _L domain associated with a V _H domain.

SUMMARY OF THE INVENTION

[0004] In some embodiments, a diabody is provided that comprises a heavy chain variable domain, a light chain variable domain, a linker that links the heavy chain variable domain to the light chain variable domain, and an extension sequence. The extension sequence can be selected from the group consisting of: EPKSX _n 5DKTHTCX _n iXn2CX _n 3Xn4C (SEQ ID NO: 1), (SEQ ID NO: 2),

ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCX _n iXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, wherein X _nl , X _n2 , Xn3, Xn4, and X _n5 can be any amino acid. The linker connects V _H to V _L through its peptide backbone, while the extension sequence can connect VH to VH or VL to VL through a disulfide bond. [0005] In some embodiments, a diabody comprising a heavy chain variable domain, a light chain variable domain a linker that links the heavy chain variable domain to the light chain variable domain, and an extension sequence attached to either the heavy chain variable domain or the light chain variable domain is provided. The extension sequence comprises CPPCPPCPPC (SEQ ID NO: 6).

[0006] In some embodiments, a method of manufacturing a diabody as provided herein can comprise providing yeast or a mammalian cell comprising a nucleic acid sequence encoding a diabody; and expressing the diabody as described herein.

[0007] In some embodiments, an extension sequence configured for use within an antigen binding construct is provided. The extension sequence is selected from the group consisting of: EPKSXn5DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1), ERKX _n5 CXniXn2CXn3Xn4C (SEQ ID NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, wherein X _n i, X _n2 , Xn3, X _N 4, and X _N 5 can be any amino acid.

[0008] In some embodiments, a diabody is provided. The diabody can comprise a first heavy chain variable domain, a first light chain variable domain, a first linker that connects the first heavy chain variable domain and the first light chain variable domain, a second heavy chain variable domain, a second light chain variable domain, a second linker that connects the second heavy and second light chain variable domains, and at least two extension sequences that covalently connect either a) the first heavy chain variable domain to the second heavy chain variable or b) the first light chain variable domain to the second light chain variable domain. The extension sequence can be selected from the group consisting of:

EPKSXn ₅ DKTHTCXnlXn ₂ CXn3Xn4C (SEQ ID NO: 1), ERKXn ₅ CXnlXn ₂ CXn3Xn4C (SEQ ID

NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9. X _n i, X _n2 , Xn3, Xn4, and X _n5 can be any amino acid. The linker connects V _H to V _L through its peptide backbone, while the extension sequence can connect VH to VH or VL to VL through a disulfide bond. [0009] In some embodiments, a cell line is provided that produces any of the diabodies disclosed herein.

[0010] In some embodiments, a kit is provided that comprises any of the diabodies disclosed herein and a detectable marker.

[0011] In some embodiments, a method of manufacturing any of the diabodies disclosed herein is provided comprising providing yeast or mammalian cells comprising a nucleic acid encoding the diabody and expressing the diabody.

[0012] In some embodiments, an extension sequence is provided that is configured for use within an antigen binding construct, wherein the extension sequence is selected from the group consisting of: EPKSXn5DKTHTCX _n iXn2CX _n 3Xn4C (SEQ ID NO: 1), ERKX _n5 CXniXn2CXn3Xn4C (SEQ ID NO: 2); ELKTPLGDTTHTCX _n iXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, wherein X _n i, X _n2 , Xn3, X _n 4, and X _n 5 can be any amino acid.

[0013] In some embodiments, a method of detecting a presence or absence of a marker is provided, the method comprising: applying any of the diabodies disclosed herein to a sample; and detecting the presence or absence of the marker.

[0014] In some embodiments, a pharmaceutical composition is provided comprising any of the extension sequences disclosed herein. In some embodiments, a pharmaceutical composition is provided comprising any of the diabodies disclosed herein.

[0015] In some embodiments, a method of treatment is provided comprising: administering a therapeutically effective amount of any pharmaceutical composition disclosed herein.

[0016] In some embodiments, a nucleic acid is provided that encodes for any diabody described herein. In some embodiments, a nucleic acid is provided that encodes for any extension sequence described herein.

[0017] In some embodiments, a vector comprising any of the nucleic acids disclosed herein is provided.

[0018] In some embodiments, a diabody comprising two chains is provided. The first chain comprises a first heavy chain variable domain, a first light chain variable domain, a first linker that connects the first heavy chain variable domain and the first light chain variable domains, and a first extension sequence. The diabody further comprises a second chain that comprises a second heavy chain variable domain, a second light chain variable domain, a second linker that connects the second heavy and second light chain variable domains, and a second extension sequence. The first extension sequence and the second extension sequence are covalently connected to one another. The first extension sequence and the second extension sequence are selected from the group consisting of: EPKSX _n5 DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1), ERKXn5CXniXn2CXn3Xn4C (SEQ ID NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, wherein X _nl , X _n2 , Xn3, Xn4, andX _n5 can be any amino acid. The linker connects V _H to V _L through its peptide backbone, while the extension sequence can connect VH to VH or VL to VL through a disulfide bond.

[0019] In some embodiments, diabodies comprising one or more of the extension sequences can be used in the treatment of a subject in need of treatment with a diabody directed to a specific target.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 depicts a Cys-diabody that contains a single Cys-Cys bridge at the C-terminus.

[0021] FIG. 2A depicts the structure of the original Cys-diabody in which a (PPC)n motif has been added.

[0022] FIG. 2B depicts the structure of the original Cys-diabody.

[0023] FIG. 2C depicts the structure of a Cys-diabody in which a (PPC) motif has been added.

[0024] FIG. 2D depicts the structure of a Cys-diabody in which a (PPC) ₂ motif has been added.

[0025] FIG. 2E depicts the structure of a Cys-diabody in which a (PPQ3 motif has been added. [0026] FIG. 3A depicts HPLC that shows peaks that corresponding to both an intact Cys-diabody and single chain fragment variable.

[0027] FIG. 3B depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable. Samples used for analysis were derived both from mammalian and yeast cells.

[0028] FIG. 4A depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB lC-1 construct.

[0029] FIG. 4B depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB lC-2 construct.

[0030] FIG. 4C depicts an SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody from the IAB lC-3 construct with no detectable scFV.

[0031] FIG. 5A depicts peaks showing binding of the IAB lC-1 , IAB lC-2, and IAB lC-3 constructs to PSCA expressed on SW780 bladder cancer cells.

[0032] FIG. 5B depicts a graph that compares binding of the IAB lC-1, IAB lC-2, and IAB lC-3 constructs to PSCA at different concentrations of the constructs.

[0033] FIG. 6A depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB2C-1 construct.

[0034] FIG. 6B depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB2C-2 construct.

[0035] FIG. 6C depicts an SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody from the IAB2C-3 construct with no detectable scFv.

[0036] FIG. 7A depicts peaks showing binding of the IAB2C- 1, IAB2C-2, and IAB2C-3 constructs to PSMA expressed on the surface of PC3-PSMA cells.

[0037] FIG. 7B depicts a graph that compares binding of the IAB2C-1, IAB2C-2, and IAB2C-3 constructs to PSMA at different concentrations of the constructs. [0038] FIG. 8A depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB22C-1 construct.

[0039] FIG. 8B depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB22C-2 construct.

[0040] FIG. 8C depicts an SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody from the IAB22C-3 construct with no detectable scFv.

[0041] FIG. 9A depicts peaks showing binding of the IAB22C-1, IAB22C-2, and IAB22C-3 constructs to CD8 expressed on the surface of HPB-ALL cells.

[0042] FIG. 9B depicts a graph that compares binding of the IAB22C-1, IAB22C- 2, and IAB22C-3 constructs to CD8 at different concentrations of the constructs.

[0043] FIG. 10A depicts an SDS-PAGE gel that shows bands that correspond to both an intact Cys-diabody and a single chain fragment variable derived from the IAB8C-1 construct.

[0044] FIG. 10B depicts an SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody from the IAB8C-3 construct with no detectable scFv.

[0045] FIG. IOC depicts an SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody from the IAB8C-4 construct with no detectable scFv.

[0046] FIG. 11A depicts peaks showing binding of the IAB8C-1 , IAB8C-3, and IAB8C-4 constructs to Her2/neu expressed on the surface of NCI-N87 gastric cancer cells.

[0047] FIG. 11B depicts a graph that compares binding of the IAB2C-1, IAB2C- 2, and IAB2C-3 constructs to Her2/neu at different concentrations of the constructs.

[0048] FIG. 12A depicts a SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody and a single chain fragment variable derived from the bC-PSMAxCD3-l construct.

[0049] FIG. 12B depicts a SDS-PAGE gel that shows bands that correspond to an intact Cys-diabody derived from the bC-PSMAxCD3-3 construct with no detectable scFv.

[0050] FIG. 12C depicts levels of cell cytotoxicity on PSMA-PC3 cells when treated with various constructs. [0051] FIG. 13 depicts SDS-PAGE gels that summarize expression of intact Cys- diabodies and single chain fragment variables across various constructs.

[0052] FIG. 14A depicts Mass Spectrometry analysis of the full and half molecule of IAB lC-1.

[0053] FIG. 14B depicts Mass Spectrometry analysis of the full and half molecule of IAB20C-1.

[0054] FIG. 14C depicts an SDS-PAGE gel that shows bands that correspond to the full size diabody of the IAB lC-1 construct.

[0055] FIG. 14D depicts and SDS-PAGE get that shows bands that correspond to the full size diabody of the IAB20C- 1 construct.

[0056] FIG. 15A depicts Mass Spectrometry analysis of the IAB2C-3 intact diabody.

[0057] FIG. 15B depicts Mass Spectrometry analysis of the relevant expanded region of the IAB2C-3 intact diabody.

[0058] FIG. 15C depicts Mass Spectrometry analysis of the IAB2C-3 single chain fragment variable.

[0059] FIG. 16A depicts Mass Spectrometry analysis of the IAB22C-3 intact diabody.

[0060] FIG. 16B depicts Mass Spectrometry analysis of the relevant expanded region of the IAB22C-3 intact diabody.

[0061] FIG. 16C depicts Mass Spectrometry analysis of the IAB22C-3 single chain fragment variable.

[0062] FIG. 17A depicts Mass Spectrometry of the intact bC-5T4xCD3 diabody.

[0063] FIG. 17B depicts Mass Spectrometry of the reduced form of the bC- 5T4xCD3 diabody showing 2 distinct protein peaks.

[0064] FIG. 18 depicts a SDS-PAGE gel showing bands that correspond to intact Cys-diabodies and single chain fragment variables after site-specific conjugation of single and multi-IAB8C Cys diabody proteins. [0065] FIG. 19A depicts images showing distribution of ⁸⁹ Zr-DF-IABDBC- 1 , ⁸⁹ Zr-DF-IABDBC-l-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-10kPEG, and ⁸⁹ Zr-DF-IABDBC-4- 20kPEG 4 hours after injection of the construct.

[0066] FIG. 19B depicts images showing distribution ⁸⁹ Zr-DF-IABDBC- 1 , ⁸⁹ Zr- DF-IABDBC-l-lOkPEG, ⁸⁹ Zr-DF-IABDBC-4-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-20kPEG 24 hours after injection of the construct.

[0067] FIG. 19C depicts images showing distribution ⁸⁹ Zr-DF-IABDBC- 1 , ⁸⁹ Zr- DF-IABDBC-l-lOkPEG, ⁸⁹ Zr-DF-IABDBC-4-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-20kPEG 48 hours after injection.

[0068] FIG. 20 depicts a graph showing biodistribution across various tissues of ⁸⁹ Zr-DF-IABDBC-l, ⁸⁹ Zr-DF-IABDBC-l-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-10kPEG, ⁸⁹ Zr-DF- IABDBC-4-20kPEG 48 hours after injection.

[0069] FIG. 21 depicts a graph showing blood clearance of ⁸⁹ Zr-DF-IABDBC- 1 , ⁸⁹ Zr-DF-IABDBC-l-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-10kPEG, ⁸⁹ Zr-DF-IABDBC-4-20kPEG at different time points after injection.

[0070] FIG. 22 is an amino acid sequence of a diabody construct of IAB22C-1, having a sequence comprising GGC.

[0071] FIG. 23 is an amino acid sequence of a diabody construct of IAB22C-2, having a sequence comprising CPPC.

[0072] FIG. 24 is an amino acid sequence of a diabody construct of IAB22C-3, having a sequence comprising CPPCPPC.

DETAILED DESCRIPTION

[0073] Described herein are components of antigen binding constructs, including, for example, diabodies. These diabodies can include a heavy chain variable domain, a light chain variable domain, a linker, and an extension sequence. The linker connects V _H to V _L through its peptide backbone, while the extension sequence can connect V _H to V _H or V _L to V _L through a (meaning one or more) disulfide bond(s). In some embodiments, specific extension sequences are employed in diabodies. In some embodiments, the extension sequences provide various benefits when they are associated with diabodies. In some embodiments, the benefits of extension sequences can include one or more of, but are not limited to, (i) increasing the stability of diabodies, (ii) reducing the impurities consisting of the single chain fragment variable, and (iii) increasing the proper assembly of bispecific diabodies. Also described herein are extension sequences that are associated with antigen binding constructs. In some embodiments, the extension sequence allows for additional cysteines for attaching moieties such as cytotoxic drugs, chelators and/or PEGs while maintaining the overall stability and characteristics of the protein.

Definitions

[0074] The term "diabody" denotes a dimer that comprises heavy chain (V _H ) domains and light-chain variable (V _L ) domains. Each heavy chain domain is connected to a light chain domain through a linker.

[0075] The term "linker" denotes a peptide sequence that connects the V _H and V _L domains. Linkers can orient the VH and VL domains in either a VL-VH or VH-VL orientation. The linker connects V _H to V _L through its peptide backbone.

[0076] The term "extension sequence" denotes a region that connects a first V _H domain to a second V _H domain or a first V _L to a second V _L domain, in for example, a diabody. Extension sequences can connect the domains through the C-terminus of each domain. In some embodiments, extension sequences connect the domains through covalent bonds. In some embodiments, the extension sequence will include one or more cysteine, allowing for one or more disulfide bonds to be formed between two such extension sequences. An example of a pair of extension sequences is shown as the line with two cysteines connecting either the two heavy chain domains or the two light chain domains. While the extension sequence will be towards the C-terminus of the constructs in FIG. 1 , it need not be the absolute last amino acid in the variable domain. That is, the linker can be positioned slightly N-terminal to the C-terminus. For example, the extension sequence can be placed within the 10 amino acids at the C-terminus. Similarly, additional sequence can be placed between the native C-terminus and where the extension sequence starts. The extension sequence can connect VH to VH or VL to VL through a disulfide bond [0077] The term "treating" or "treatment" of a condition can include preventing the condition, slowing the onset and/or rate of development of the condition, reducing the risk of developing the condition, preventing and/or delaying the development of symptoms associated with the condition, reducing or ending symptoms associated with the condition, generating a complete or partial regression of the condition, or some combination thereof. The term "prevent" does not require the absolute prohibition of the disorder or disease.

[0078] A "therapeutically effective amount" or a "therapeutically effective dose" is an amount that produces a desired therapeutic effect in a subject, such as preventing, treating a target condition, delaying the onset of the disorder and/or symptoms, and/or alleviating symptoms associated with the condition. This amount will vary depending upon a variety of factors, including but not limited to the characteristics of the therapeutic compound (including activity, pharmacokinetics, pharmacodynamics, and bioavailability), the physiological condition of the subject (including age, sex, disease type and stage, general physical condition, responsiveness to a given dosage, and type of medication), the nature of the pharmaceutically acceptable carrier or carriers in the formulation, and/or the route of administration. One skilled in the clinical and pharmacological arts will be able to determine a therapeutically effective amount through routine experimentation, for example by monitoring a subject's response to administration of a compound and adjusting the dosage accordingly, given the present disclosure. For additional guidance, see Remington: The Science and Practice of Pharmacy 21st Edition, Univ. of Sciences in Philadelphia (USIP), Lippincott Williams & Wilkins, Philadelphia, PA, 2005.

[0079] The term "antigen binding construct" includes all varieties of antibodies, including binding fragments thereof. Further included are constructs that include 1 , 2, 3, 4, 5, and/or 6 CDRs. In some embodiments, tandem scFvs can be provided, which can provide two arms with bivalent binding. In some embodiments, these CDRs can be distributed between their appropriate framework regions in a traditional antibody. In some embodiments, the CDRs can be contained within a heavy and/or light chain variable region. In some embodiments, the CDRs can be within a heavy chain and/or a light chain. In some embodiments, the CDRs can be within a single peptide chain. Unless otherwise denoted herein, the antigen binding constructs described herein bind to the noted target molecule. The term "target" or "target molecule" denotes the protein to which the antigen binding construct binds.

[0080] The term "antibody" includes, but is not limited to, genetically engineered or otherwise modified forms of immunoglobulins, such as intrabodies, chimeric antibodies, fully human antibodies, humanized antibodies, antibody fragments, scFv, and heteroconjugate antibodies (for example, bispecific antibodies, diabodies, triabodies, tetrabodies, etc.). The term "antibody" includes scFv and minibodies. Thus, each and every embodiment provided herein in regard to "antibodies" is also envisioned as scFv and/or minibody embodiments, unless explicitly denoted otherwise. The term "antibody" includes a polypeptide of the immunoglobulin family or a polypeptide comprising fragments of an immunoglobulin that is capable of noncovalently, reversibly, and in a specific manner binding a corresponding antigen. An exemplary antibody structural unit comprises a tetramer. In some embodiments, a full length antibody can be composed of two identical pairs of polypeptide chains, each pair having one "light" and one "heavy" chain (connected through a disulfide bond). The recognized immunoglobulin genes include the kappa, lambda, alpha, gamma, delta, epsilon, hinge, and mu constant region genes, as well as the myriad immunoglobulin variable region genes. For full length chains, the light chains are classified as either kappa or lambda. For full length chains, the heavy chains are classified as gamma, mu, alpha, delta, or epsilon, which in turn define the immunoglobulin classes, IgG, IgM, IgA, IgD, and IgE, respectively. The N-terminus of each chain defines a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VL) and variable heavy chain (VH) refer to these regions of light and heavy chains respectively. As used in this application, an "antibody" encompasses all variations of antibody and fragments thereof. Thus, within the scope of this concept are full length antibodies, chimeric antibodies, humanized antibodies, single chain antibodies (scFv), Fab, Fab', and multimeric versions of these fragments (for example, F(ab')2) with the same binding specificity. In some embodiments, the antibody binds specifically to a desired target.

[0081] An "antibody variable light chain" or an "antibody variable heavy chain" as used herein refers to a polypeptide comprising the VL or VH, respectively. The endogenous VL is encoded by the gene segments V (variable) and J (junctional), and the endogenous VH by V, D (diversity), and J. Each of VL or VH includes the CDRs as well as the framework regions. In this application, antibody variable light chains and/or antibody variable heavy chains may, from time to time, be collectively referred to as "antibody chains." These terms encompass antibody chains containing mutations that do not disrupt the basic structure of VL or VH, as one skilled in the art will readily recognize. In some embodiments, full length heavy and/or light chains are contemplated. In some embodiments, only the variable region of the heavy and/or light chains are contemplated as being present.

[0082] Antibodies can exist as intact immunoglobulins or as a number of fragments produced by digestion with various peptidases. Thus, for example, pepsin digests an antibody below the disulfide linkages in the hinge region to produce F(ab)'2, a dimer of Fab' which itself is a light chain (VL-CL) joined to VH-CH1 by a disulfide bond. The F(ab)'2 can be reduced under mild conditions to break the disulfide linkage in the hinge region, thereby converting the F(ab)'2 dimer into an Fab' monomer. The Fab' monomer is a Fab with part of the hinge region. (Paul, W. E., "Fundamental Immunology," 3d Ed., New York: Raven Press, 1993). While various antibody fragments are defined in terms of the digestion of an intact antibody, one of skill will appreciate that such fragments can be synthesized de novo either chemically or by using recombinant DNA methodology. Thus, the term "antibody," as used herein, also includes antibody fragments either produced by the modification of whole antibodies, or those synthesized de novo using recombinant DNA methodologies (for example, single chain Fv) or those identified using phage display libraries {see, for example, McCafferty, J. et al., "Phage antibodies: filamentous phage displaying antibody variable domains," Nature, Vol. 348, No. 66301 , pp. 552-554, 1990).

[0083] Antibodies further include one or more immunoglobulin chains that are chemically conjugated to, or expressed as, fusion proteins with other proteins. It also includes bispecific antibodies. A bispecific or bifunctional antibody is an artificial hybrid antibody having two different heavy/light chain pairs and two different binding sites.

[0084] Other antigen-binding fragments or antibody portions of the invention include, bispecific scFv antibodies where the antibody molecule recognizes two different epitopes, single binding domains (sdAb or nanobodies), and minibodies. [0085] The term "antibody fragment" includes, but is not limited to one or more antigen binding fragments of antibodies alone or in combination with other molecules, including, but not limited to Fab', F(ab')2, Fab, Fv, rlgG (reduced IgG), scFv fragments, single domain fragments (nanobodies), peptibodies, minibodies. The term "scFv" refers to a single chain Fv ("fragment variable") antibody in which the variable domains of the heavy chain and of the light chain of a traditional two chain antibody have been joined to form one chain.

[0086] A pharmaceutically acceptable carrier can be a pharmaceutically acceptable material, composition, or vehicle that is involved in carrying or transporting a compound of interest from one tissue, organ, or portion of the body to another tissue, organ, or portion of the body. For example, the carrier can be a liquid or solid filler, diluent, excipient, solvent, or encapsulating material, or some combination thereof. Each component of the carrier is "pharmaceutically acceptable" in that it is be compatible with the other ingredients of the formulation. It also must be suitable for contact with any tissue, organ, or portion of the body that it may encounter, meaning that it must not carry a risk of toxicity, irritation, allergic response, immunogenicity, or any other complication that excessively outweighs its therapeutic benefits. The pharmaceutical compositions described herein may be administered by any suitable route of administration. A route of administration can refer to any administration pathway known in the art, including but not limited to aerosol, enteral, nasal, ophthalmic, oral, parenteral, rectal, transdermal (for example, topical cream or ointment, patch), or vaginal. "Transdermal" administration can be accomplished using a topical cream or ointment or by means of a transdermal patch. "Parenteral" refers to a route of administration that is generally associated with injection, including infraorbital, infusion, intraarterial, intracapsular, intracardiac, intradermal, intramuscular, intraperitoneal, intrapulmonary, intraspinal, intrasternal, intrathecal, intrauterine, intravenous, subarachnoid, subcapsular, subcutaneous, transmucosal, or transtracheal. In some embodiments, the antigen binding construct can be delivered intraoperatively as a local administration during an intervention or resection.

[0087] The term "nucleic acid" or "polynucleotide" refers to deoxyribonucleic acids (DNA) or ribonucleic acids (RNA) and polymers thereof in either single- or doublestranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (for example, degenerate codon substitutions), alleles, orthologs, SNPs, and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions can be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer, M. A. et al., "Enhanced evolutionary PCR using oligonucleotides with inosine at the 3'-terminus," Nucleic Acid Res., Vol. 19, No. 18, pp. 5081, 1991 ; Ohtsuka, E. et al., "An alternative approach to deoxyoligonucleotides as hybridization probes by insertion of deoxyinosine at ambiguous codon positions," J. Biol. Chem., Vol. 260, No. 5, pp. 2605-2608, 1985; Rossolini, G. M. et al., "Use of deoxyinosine containing primers vs degenerate primers for polymerase chain reaction based on ambiguous sequence information," Mol. Cell. Probes, Vol. 8, No. 2, pp. 91-98, 1994).

[0088] The terms "polypeptide," "peptide," and "protein" are used interchangeably herein to refer to a polymer of amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residue is an artificial chemical mimetic of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers and non-naturally occurring amino acid polymer.

[0089] The term "amino acid" refers to naturally occurring and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function in a manner similar to the naturally occurring amino acids. Naturally occurring amino acids are those encoded by the genetic code, as well as those amino acids that are later modified, for example, hydroxyproline, gamma-carboxyglutamate, and O-phosphoserine. Amino acid analogs refer to compounds that have the same basic chemical structure as a naturally occurring amino acid, for example, an alpha-carbon that is bound to a hydrogen, a carboxyl group, an amino group, and an R group, for example, homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. Such analogs have modified R groups (for example, norleucine) or modified peptide backbones, but retain the same basic chemical structure as a naturally occurring amino acid. Amino acid mimetics refers to chemical compounds that have a structure that is different from the general chemical structure of an amino acid, but that functions in a manner similar to a naturally occurring amino acid.

[0090] The term "conservatively modified variants" applies to both amino acid and nucleic acid sequences. With respect to particular nucleic acid sequences, conservatively modified variants refers to those nucleic acids which encode identical or essentially identical amino acid sequences, or where the nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given protein. For instance, the codons GCA, GCC, GCG and GCU all encode the amino acid alanine. Thus, at every position where an alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are "silent variations," which are one species of conservatively modified variations. Every nucleic acid sequence herein which encodes a polypeptide also describes every possible silent variation of the nucleic acid. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine, and TGG, which is ordinarily the only codon for tryptophan) can be modified to yield a functionally identical molecule. Accordingly, each silent variation of a nucleic acid that encodes a polypeptide is implicit in each described sequence.

[0091] As to amino acid sequences, one of skill will recognize that individual substitutions, deletions or additions to a nucleic acid, peptide, polypeptide, or protein sequence which alters, adds or deletes a single amino acid or a small percentage of amino acids in the encoded sequence is a "conservatively modified variant" where the alteration results in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. Such conservatively modified variants are in addition to and do not exclude polymorphic variants, interspecies homologs, and alleles of the invention.

[0092] The following eight groups each contain amino acids that are conservative substitutions for one another: 1) Alanine (A), Glycine (G); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); 7) Serine (S), Threonine (T); and 8) Cysteine (C), Methionine (M) (see, for example, Creighton, T. E., "Proteins - Structures and Molecular Properties," W. H. Freeman & Co. Ltd., 1984).

[0093] The term "percentage of sequence identity" can be determined by comparing two optimally aligned sequences over a comparison window, wherein the portion of the polynucleotide sequence in the comparison window can comprise additions or deletions (i.e., gaps) as compared to the reference sequence (for example, a polypeptide of the invention), which does not comprise additions or deletions, for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid base or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison and multiplying the result by 100 to yield the percentage of sequence identity.

[0094] The terms "identical" or percent "identity," in the context of two or more nucleic acids or polypeptide sequences, refer to two or more sequences or subsequences that are the same sequences. Two sequences are "substantially identical" if two sequences have a specified percentage of amino acid residues or nucleotides that are the same (for example, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% sequence identity over a specified region, or, when not specified, over the entire sequence of a reference sequence), when compared and aligned for maximum correspondence over a comparison window, or designated region as measured using one of the following sequence comparison algorithms or by manual alignment and visual inspection. Optionally, the identity exists over a region that is at least about 15, 25 or 50 nucleotides in length, or more preferably over a region that is 100 to 500 or 1000 or more nucleotides in length, or over the full length of the reference sequence. With respect to amino acid sequences, identity or substantial identity can exist over a region that is at least 5, 10, 15 or 20 amino acids in length, optionally at least about 25, 30, 35, 40, 50, 75 or 100 amino acids in length, optionally at least about 150, 200 or 250 amino acids in length, or over the full length of the reference sequence. With respect to shorter amino acid sequences, for example, amino acid sequences of 20 or fewer amino acids, in some embodiments, substantial identity exists when one or two amino acid residues are conservatively substituted, according to the conservative substitutions defined herein.

[0095] For sequence comparison, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are entered into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. Default program parameters can be used, or alternative parameters can be designated. The sequence comparison algorithm then calculates the percent sequence identities for the test sequences relative to the reference sequence, based on the program parameters.

[0096] A "comparison window", as used herein, includes reference to a segment of any one of the number of contiguous positions selected from the group consisting of from 20 to 600, usually about 50 to about 200, more usually about 100 to about 150 in which a sequence can be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned. Methods of alignment of sequences for comparison are well known in the art. Optimal alignment of sequences for comparison can be conducted, for example, by the local homology algorithm of Smith and Waterman (1970) Adv. Appl. Math. 2:482c, by the homology alignment algorithm of Needleman, S. B. et al., "A general method applicable to the search for similarities in the amino acid sequence of two proteins," J. Mol. Biol., Vol. 48, No. 3, pp. 443-453, 1970, by the search for similarity method of Pearson, W. R. et al., "Improved tools for biological sequence comparison," Proc. Natl. Acad. Sci. U.S.A., Vol. 85, No. 8, pp. 2444-2448, 1988, by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection (see, for example, Ausubel, F. M. et al., Current Protocols in Molecular Biology, Supplement, 1995).

[0097] Two examples of algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul, S. F. et al., "Gapped BLAST and PSI-BLAST: a new generation of protein database search programs," Nucleic Acids Res., Vol. 25, No. 17, pp. 3389-3402, 1977, and Altschul, S. F. et al., "Basic local alignment search tool," J. Mol. Biol., Vol. 215, No. 3, pp. 403-410, 1990, respectively. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information. This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length Win the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul, S. F. et al., supra). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always>0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a word length (W) of 1 1, an expectation (E) or 10, M=5, N=-4 and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a wordlength of 3, and expectation (E) of 10, and the BLOSUM62 scoring matrix (see, Henikoff, S. et al., "Amino acid substitution matrices from protein blocks," Proc. Natl. Acad. Sci. U.S.A., Vol. 89, No. 22, pp. 10915-10919, 1992) alignments (B) of 50, expectation (E) of 10, M=5, N=-4, and a comparison of both strands.

[0098] The BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, for example, Karlin, S. et al., "Applications and statistics for multiple high-scoring segments in molecular sequences," Proc. Natl. Acad. Sci. U.S.A., Vol. 90, No. 12, pp. 5873-5787, 1993). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid to the reference nucleic acid is less than about 0.2, more preferably less than about 0.01 , and most preferably less than about 0.001.

[0099] An indication that two nucleic acid sequences or polypeptides are substantially identical is that the polypeptide encoded by the first nucleic acid is immunologically cross reactive with the antibodies raised against the polypeptide encoded by the second nucleic acid, as described below. Thus, in some embodiments, a polypeptide is typically substantially identical to a second polypeptide, for example, where the two peptides differ only by conservative substitutions. Another indication that two nucleic acid sequences are substantially identical is that the two molecules or their complements hybridize to each other under stringent conditions, as described below. Yet another indication that two nucleic acid sequences are substantially identical is that the same primers can be used to amplify the sequence.

[0100] The terms "subject," "patient," and "individual" interchangeably refer to an entity that is being examined and/or treated. This can include, for example, a mammal, for example, a human or a non-human primate mammal. The mammal can also be a laboratory mammal, for example, mouse, rat, rabbit, hamster. In some embodiments, the mammal can be an agricultural mammal (for example, equine, ovine, bovine, porcine, camelid) or domestic mammal (for example, canine, feline).

[0101] The term "co-administer" refers to the administration of two active agents in the blood of an individual or in a sample to be tested. Active agents that are coadministered can be concurrently or sequentially delivered.

Diabodies with Extension Sequences

[0102] Provided herein are diabodies that can include an extension sequence. In some embodiments, the diabody comprises a heavy chain variable domain a light chain variable domain, a linker, and an extension sequence. In some embodiments, the extension sequence can comprise or consist of at least one of the following: (a) EPKSX _n5 DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1),

(b) ERKX _n5 CXnlXn2CXn3Xn4C (SEQ ID NO: 2),

(c) ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3),

(d) ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4),

(e) CPPCPPC (SEQ ID NO: 5),

(f) CPPCPPCPPC (SEQ ID NO: 6), or

(g) GGC(PPC) _n (SEQ ID NO: 11), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Xni can be any amino acid. X _n2 can be any amino acid. X _N 3 can be any amino acid. X _N 4 can be any amino acid. X _n5 can be any amino acid. Each of these arrangements will form one half of the diabody. The linker connects a heavy chain variable domain to a light chain variable domain through its peptide backbone, while the extension sequence can connect V _H to V _H or V _L to V _L through a disulfide bond. Some embodiments of these extension sequences are shown in Table 0.1 below:

TABLE 0.1 - SEQUENCE LISTING

SEQ ID NO: 15 CXnlXn2CXn3Xn4CXn5Xn6CXn7Xn8CXn9 nloCXnllXnl2C

SEQ ID NO: 16 CXnlXn2CXn3Xn4C

SEQ ID NO: 17 GGC(XnlXn2C) _n

[0103] In some embodiments, the diabody comprises a first heavy chain variable domain, a first light chain variable domain, a first linker that connects the first heavy chain variable domain and the first light chain variable domains, a second heavy chain variable domain, a second light chain variable domain, a second linker that connects the second heavy and second light chain variable domains, and two extension sequences that covalently connect either a) the first heavy chain variable domain to the second heavy chain variable or b) the first light chain variable domain to the second light chain variable domain. The linker connects a heavy chain variable domain to a light chain variable domain through its peptide backbone. The connection between the two extension sequences can be achieved through crosslinking one or more of the cysteines within the extension sequences. As noted above, the extension sequence can be selected from the group consisting of: a) EPKSX _n5 DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1), b) ERKXn5CXniXn2CXn3Xn4C (SEQ ID NO: 2), c) ELKTPLGDTTHTCX _n iXn ₂ CXn3Xn4C (SEQ ID NO: 3), d) ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), e) CPPCPPC (SEQ ID NO: 5), and f) CPPCPPCPPC (SEQ ID NO: 6) and g) GGC(PPC) _n (SEQ ID NO: 11), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9. X _nl , Xn2, Xn3, Xn4, and X _n 5 can be any amino acid. Additional options for extension sequences are disclosed herein and can be combined with any one or more of the diabody arrangements provided herein.

[0104] In some embodiments, the diabody comprises a first chain and a second chain. The first chain comprises a first heavy chain variable domain, a first light chain variable domain, a first linker that connects the first heavy chain variable domain and the first light chain variable domain, and a first extension sequence. In some embodiments, the first chain comprises a single, continuous, peptide backbone. The diabody further comprises the second chain that comprises a second heavy chain variable domain, a second light chain variable domain, a second linker that connects the second heavy and second light chain variable domains, and a second extension sequence. In some embodiments, the second chain comprises a single, continuous, peptide backbone. The first extension sequence and the second extension sequence are covalently connected or bonded to one another. This connection can be through one or more of the cysteines in the first extension sequence forming one or more disulfide bonds with the cysteines in the second extension sequence. The linker connects a heavy chain variable domain to a light chain variable domain through its peptide backbone, while the extension sequence can connect V _H to V _H or V _L to V _L through a disulfide bond. The first extension sequence and the second extension sequence are selected from the group consisting of at least one of: EPKSX _n 5DKTHTCX _n iXn2CX _n 3Xn4C (SEQ ID NO: 1), ERKX _n5 CX _n iX _n2 CX _n3 X _n4 C (SEQ ID NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCX _n iXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPCPPC (SEQ ID NO: 5), and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein X _nl , X _n2 , Xn3, Xn4, andX _n5 can be any amino acid.

[0105] In some embodiments, the diabody is monospecific. In some embodiments, the diabody is bispecific. A bispecific diabody can be comprised of two different heavy/light chain pairs and/or it can recognize two different epitopes. Examples of targets to which the diabodies can bind include, but are not limited to, one or more of PCSA, PSMA, CD8, HER2, CD3, 5T4, PD-L1, folate receptor alpha, Mesothelin, CA19-9, CD19, CD20, and Her2/neu. In some embodiments, the first heavy chain variable domain and the second light chain variable domain are associated so as to form a first binding domain. In some embodiments, the second heavy chain variable domain and the first light chain variable domain are associated so as to form a second binding domain (e.g., as shown in FIG. 1). In some embodiments, the first light chain variable domain and the second heavy chain variable domain are associated so as to form a first binding domain.

[0106] In addition to the extension sequences noted above, other variations and subsets of extension sequences are contemplated as well. In some embodiments, amino acid sequences of extension sequences within diabodies are provided. Any of the diabodies described herein can comprise any of the extension sequences described herein.

[0107] In some embodiments, the extension sequence is EPKSXn ₅ DKTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 1). X _NL can be any amino acid. X _n2 can be any amino acid. X _N 3 can be any amino acid. X _N 4 can be any amino acid. X _n5 can be any amino acid. In some embodiments, any of X _nl , X _n2 , Xn3, Xn4, and X _n5 are P (SEQ ID NO: 18). In some embodiments, at least one of X _nl , X _n2 , Xn3, Xn4, and X _n5 is P (SEQ ID NO: 19). In some embodiments, X _nl is P (SEQ ID NO: 20). In some embodiments X _n2 is P (SEQ ID NO: 21). In some embodiments, X _n3 is P (SEQ ID NO: 22). In some embodiments, X _n 4 is P (SEQ ID NO: 23). In some embodiments, X _n5 is P (SEQ ID NO: 24). The remaining positions can be any amino acid (SEQ ID NO: 18 - SEQ ID NO: 24).

[0108] In some embodiments, at least any two of X _nl , X _n2 , Xn3, Xn4, and X _n5 are P (SEQ ID NO: 25) in EPKSXn ₅ DKTHTCXniXn ₂ CXn ₃ Xn4C (SEQ ID NO: 1). In some embodiments the X _nl and X _n2 are P (SEQ ID NO: 26). In some embodiments, X _nl and X _n3 are P (SEQ ID NO: 27). In some embodiments, X _nl and X _n4 are P (SEQ ID NO: 28). In some embodiments, X _nl and X _n5 are P (SEQ ID NO: 29). In some embodiments, X _n2 and X _n3 are P (SEQ ID NO: 30). In some embodiments, X _n2 and X _n4 are P (SEQ ID NO: 31). In some embodiments, X _n2 and X _n5 are P (SEQ ID NO: 32). In some embodiments, X _n3 and X _n 4 are P (SEQ ID NO: 33). In some embodiments, X _n3 and X _n5 are P (SEQ ID NO: 34). In some embodiments, X _n 4 and X _n5 are P (SEQ ID NO: 35). The remaining positions can be any amino acid (SEQ ID NO: 25 - SEQ ID NO: 35).

[0109] In some embodiments, at least any three of X _nl , X _n2 , Xn ₃ , Xn4, and X _n5 are P (SEQ ID NO: 36) in EPKSXn ₅ DKTHTCXniXn ₂ CXn ₃ Xn4C (SEQ ID NO: 1). In some embodiments, X _nl , X _n2 , Xn ₃ are P (SEQ ID NO: 37). In some embodiments, X _n2 , Xn ₃ and X _n 4 are P (SEQ ID NO: 38). In some embodiments, X _n3 , Xn4, and X _n5 are P (SEQ ID NO: 39). In some embodiments, X _nl , X _n2 , and X _n 4 are P (SEQ ID NO: 40). In some embodiments, X _nl , X _n2 , and X _n 5 are P (SEQ ID NO: 41). In some embodiments, X _nl , X _n3 , and X _n 4 are P (SEQ ID NO: 42). In some embodiments, X _nl , X _n 4, and X _n5 are P (SEQ ID NO: 43). In some embodiments, X _n2 , X _n3 , and X _n5 are P (SEQ ID NO: 44). In some embodiments, X _n2 , X _n 4, and Xns are P (SEQ ID NO: 45). In some embodiments, X _n i, X _n3 , and X _n5 are P (SEQ ID NO: 46). The remaining positions can be any amino acid (SEQ ID NO: 36 - SEQ ID NO: 46).

[0110] In some embodiments, at least any four of X _nl , X _n2 , Xn ₃ , Xn4, and X _n5 are P (SEQ ID NO: 47) in EPKSXn ₅ DKTHTCXniXn ₂ CXn ₃ Xn4C (SEQ ID NO: 1). In some embodiments, X _nl , X _n2 , Xn ₃ , and X _n 4 are P (SEQ ID NO: 48). In some embodiments, X _n2 , Xn3, Xn4, and X _n 5 are P (SEQ ID NO: 49). In some embodiments, X _nl , X _n3 , Xn4, and X _n5 are P (SEQ ID NO: 50). In some embodiments, X _n i, X _n2 , Xn4, and X _n5 are P (SEQ ID NO: 51). The remaining positions can be any amino acid (SEQ ID NO: 47 - SEQ ID NO: 51).

[0111] In some embodiments all of X _nl , X _n2 , Xn3, Xn4, and X _n5 are P (SEQ ID NO: 52) in EPKSXn ₅ DKTHTCXniXn ₂ CXn ₃ Xn4C (SEQ ID NO: 1).

[0112] In some embodiments, the extension sequence comprises greater than 70% sequence identity to the EPKSXn5DKTHTCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 1) sequence, for example, 75%, 85%, or 95%.

[0113] In some embodiments, a nucleic acid sequence is provided that encodes for EPKSXn5DKTHTCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 1) . The nucleic acid sequence can comprise conservative substitutions of EPKSXn5DKTHTCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 1), which results in expression of a conservatively modified variant of the sequence.

[0114] In some embodiments the extension sequence is ERKXn5CXniXn ₂ CXn ₃ Xn4C (SEQ ID NO: 2). Xni can be any amino acid. X _n2 can be any amino acid. X _n3 can be any amino acid. X _n 4 can be any amino acid. X _n5 can be any amino acid. In some embodiments, any of X _nl , X _n2 , Xn ₃ , Xn4, and X _n5 are P (SEQ ID NO: 53). In some embodiments, at least one of X _nl , X _n2 , Xn ₃ , Xn4, and X _n5 is P (SEQ ID NO: 54). In some embodiments, X _nl is P (SEQ ID NO: 55). In some embodiments X _n2 is P (SEQ ID NO: 56). In some embodiments, X _n3 is P (SEQ ID NO: 57). In some embodiments, X _n 4 is P (SEQ ID NO: 58). In some embodiments, X _n5 is P. The remaining positions can be any amino acid (SEQ ID NO: 53 - SEQ ID NO: 58).

[0115] In some embodiments, at least any two of X _nl , X _n2 , Xn ₃ , Xn4, and X _n5 are P (SEQ ID NO: 59) in ERKXn5CXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 2). In some embodiments the Xni and X _n2 are P (SEQ ID NO: 60). In some embodiments, X _nl and X _n3 are P (SEQ ID NO: 61). In some embodiments, X _nl and X _n 4 are P (SEQ ID NO: 62). In some embodiments, X _nl and Xns are P (SEQ ID NO: 63). In some embodiments, X _n2 and X _n3 are P (SEQ ID NO: 64). In some embodiments, X _n2 and X _n 4 are P (SEQ ID NO: 65). In some embodiments, X _n2 and Xns are P (SEQ ID NO: 66). In some embodiments, X _n3 and X _n4 are P (SEQ ID NO: 67). In some embodiments, X _n3 and X _n5 are P (SEQ ID NO: 68). In some embodiments, X _n 4 and X _n5 are P (SEQ ID NO: 69). The remaining positions can be any amino acid (SEQ ID NO: 59 - SEQ ID NO: 69).

[0116] In some embodiments, at least any three of X _nl , Xn2, Xn3, Xn4, and X _n5 are P (SEQ ID NO: 70) in ERKXn5CXniXn2CXn3Xn4C (SEQ ID NO: 2). In some embodiments, Xni, Xn2, Xn3 are P (SEQ ID NO: 71). In some embodiments, X _n2 , Xn3 and X _n4 are P (SEQ ID NO: 72). In some embodiments, X _n 3, Xn4, and X _n5 are P (SEQ ID NO: 73). In some embodiments, X _nl , X _n 2, and X _n 4 are P (SEQ ID NO: 74). In some embodiments, X _nl , X _n 2, and X _n 5 are P (SEQ ID NO: 75). In some embodiments, X _nl , X _n 3, and X _n 4 are P (SEQ ID NO: 76). In some embodiments, X _nl , X _n 4, and X _n5 are P (SEQ ID NO: 77). In some embodiments, X _n 2, Xn3, and X _n5 are P (SEQ ID NO: 78). In some embodiments, X _n 2, Xn4, and Xns are P (SEQ ID NO: 79). In some embodiments, X _n i, X _n 3, and X _n5 are P (SEQ ID NO: 80). The remaining positions can be any amino acid (SEQ ID NO: 70 - SEQ ID NO: 80).

[0117] In some embodiments, at least any four of X _nl , X _n 2, Xn3, Xn4, and X _n5 are P (SEQ ID NO: 81) in ERKX _n 5CX _n iXn2CX _n 3Xn4C (SEQ ID NO: 2). In some embodiments, Xni, Xn2, Xn3, and X _n 4 are P (SEQ ID NO: 82). In some embodiments, X _n 2, Xn3, Xn4, and X _n5 are P (SEQ ID NO: 83). In some embodiments, X _n i, X _n 3, Xn4, and X _n5 are P (SEQ ID NO: 84). In some embodiments, X _nl , Xn2, Xn4, and X _n5 are P (SEQ ID NO: 85). The remaining positions can be any amino acid (SEQ ID NO: 81 - SEQ ID NO: 85).

[0118] In some embodiments all of X _n i, Xn2, Xn3, Xn4, and X _n5 is P (SEQ ID NO:

86).

[0119] In some embodiments, the extension sequence comprises greater than 70% sequence identity to the ERKX _n 5CX _n iXn2CXn3Xn4C (SEQ ID NO: 2) sequence, for example, 75%, 85%, or 95%. In some embodiments, a nucleic acid sequence is provided that encodes for ERKXn5CXniXn2CXn3Xn4C (SEQ ID NO: 2). The nucleic acid sequence can comprise conservative substitutions of ERKX _n 5CX _n iXn2CXn3Xn4C (SEQ ID NO: 2), which results in expression of conservatively modified variant of the sequence.

[0120] In some embodiments the extension sequence is ELKTPLGDTTHTCXniXn2CXn ₃ Xn4C (SEQ ID NO: 3). X _nl can be any amino acid. X _n2 can be any amino acid. X _n 3 can be any amino acid. X _n 4 can be any amino acid. [0121] In some embodiments, any of X _nl , X _n2 , Xn3, and X _n4 are P (SEQ ID NO: 87) in ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3).

[0122] In some embodiments, at least one of X _nl , X _n2 , Xn3, and X _n4 is P (SEQ ID NO: 88) in ELKTPLGDTTHTCXn iX _n2 CX _n 3Xn4C (SEQ ID NO: 3). In some embodiments, Xni is P (SEQ ID NO: 89). In some embodiments, X _n2 is P (SEQ ID NO: 90). In some embodiments, X _n3 is P (SEQ ID NO: 91). In some embodiments, X _n4 is P (SEQ ID NO: 92). The remaining positions can be any amino acid (SEQ ID NO: 87 - SEQ ID NO: 92).

[0123] In some embodiments, at least any two of X _nl , X _n2 , Xn3, and X _n 4 are P (SEQ ID NO: 93) in ELKTPLGDTTHTCX _n iXn ₂ CX _n 3Xn4C (SEQ ID NO: 3). In some embodiments, X _nl and X _n2 are P (SEQ ID NO: 94). In some embodiments X _nl and X _n 3 are P (SEQ ID NO: 95). In some embodiments, X _nl and X _n4 are P (SEQ ID NO: 96). In some embodiments, X _n2 and X _n 3 are P (SEQ ID NO: 97). In some embodiments, X _n2 and X _n 4 are P (SEQ ID NO: 98). In some embodiments X _n3 and X _n4 are P (SEQ ID NO: 99). The remaining positions can be any amino acid (SEQ ID NO: 93 - SEQ ID NO: 99).

[0124] In some embodiments, at least any three of X _nl , X _n2 , Xn3, and X _n 4 are P (SEQ ID NO: 100) in ELKTPLGDTTHTCXn iX _n2 CXn3Xn4C (SEQ ID NO: 3). In some embodiments, X _nl , X _n2 , and X _n 3 are P (SEQ ID NO: 101). In some embodiments, X _nl , X _n2 , and X _n4 are P (SEQ ID NO: 102). In some embodiments, X _n i, X _n 3, and X _n4 are P (SEQ ID NO: 103). In some embodiments, X _n2 , X _n 3, and X _n4 are P (SEQ ID NO: 104).

[0125] In some embodiments all of X _nl , X _n2 , Xn3, and X _n 4 are P (SEQ ID NO: 105). The remaining positions can be any amino acid (SEQ ID NO: 100 -SEQ ID NO: 104).

[0126] In some embodiments, the extension sequence comprises greater than 70% sequence identity to the ELKTPLGDTTHTCXn iX _n2 CXn3Xn4C (SEQ ID NO: 3) sequence, for example, 75%, 85%, or 95%. In some embodiments, a nucleic acid sequence is provided that encodes for ELKTPLGDTTHTCXn iX _n2 CXn3Xn4C (SEQ ID NO: 3). The nucleic acid sequence can comprise conservative substitutions of ELKTPLGDTTHTCXn iX _n2 CXn3Xn4C (SEQ ID NO: 3), which results in expression of a conservatively modified variant of the sequence. [0127] In some embodiments the extension sequence is ESKYGPPCXniXn2CXn3Xn4C (SEQ ID NO: 4). X _nl can be any amino acid. X _n2 can be any amino acid. X _n3 can be any amino acid. X _n4 can be any amino acid.

[0128] In some embodiments, any of X _nl , X _n2 , Xn3, and X _n4 are P (SEQ ID NO: 106) in ESKYGPPCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 4).

[0129] In some embodiments, at least one of X _nl , X _n2 , Xn ₃ , and X _n 4 is P (SEQ ID NO: 107). In some embodiments, X _nl is P (SEQ ID NO: 108) in ESKYGPPCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 4). In some embodiments, X _n2 is P (SEQ ID NO: 109). In some embodiments, X _n3 is P (SEQ ID NO: 1 10). In some embodiments, X _n 4 is P (SEQ ID NO: 1 11). The remaining positions can be any amino acid (SEQ ID NO: 106 - SEQ ID NO: 111).

[0130] In some embodiments, at least any two of X _nl , X _n2 , Xn ₃ , and X _n 4 are P (SEQ ID NO: 112) in ESKYGPPCX _n iXn ₂ CX _n3 Xn4C (SEQ ID NO: 4). In some embodiments, Xni and X _n2 are P (SEQ ID NO: 1 13). In some embodiments X _nl and X _n3 are P (SEQ ID NO: 114). In some embodiments, X _nl and X _n 4 are P (SEQ ID NO: 1 15). In some embodiments, X _n2 and X _n3 are P (SEQ ID NO: 1 16). In some embodiments, X _n2 and X _n4 are P (SEQ ID NO: 1 17). In some embodiments X _n3 and X _n4 are P (SEQ ID NO: 118).

[0131] In some embodiments, at least any three of X _nl , X _n2 , Xn ₃ , and X _n 4 are P (SEQ ID NO: 119) in ESKYGPPCX _n iXn ₂ CX _n3 Xn4C (SEQ ID NO: 4). In some embodiments, Xni, Xn2, and X _n3 are P (SEQ ID NO: 120). In some embodiments, X _nl , X _n2 , and X _n 4 are P (SEQ ID NO: 121). In some embodiments, X _n i, X _n3 , and X _n 4 are P (SEQ ID NO: 122). In some embodiments, X _n2 , X _n3 , and X _n 4 are P (SEQ ID NO: 123).

[0132] In some embodiments all of X _nl , X _n2 , Xn ₃ , and X _n 4 are P (SEQ ID NO: 124) in ESKYGPPCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 4). The remaining positions can be any amino acid (SEQ ID NO: 112 - SEQ ID NO: 123).

[0133] In some embodiments, the extension sequence comprises greater than 70% sequence identity to the ESKYGPPCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 4) sequence, for example, 75%, 85%, or 95%. In some embodiments, a nucleic acid sequence is provided that encodes for ESKYGPPCXniXn ₂ CX _n3 Xn4C (SEQ ID NO: 4). The nucleic acid sequence can comprise conservative substitutions of ESKYGPPCX _n iXn2CX _n 3Xn4C (SEQ ID NO: 4), which results in expression of a conservatively modified variant of the sequence.

[0134] In some embodiments the extension sequence comprises the motif, XniXn2C. In some embodiments, this motif repeats 1, 2, 3, 4, 5, or 6 times. This can also be expressed as CX _n iX _n 2 in a repeating motif. X _n iX _n 2 can be any amino acid, but are preferably one or more proline.

[0135] In some embodiments, there is no C-terminus cysteine. In some embodiments, there is no N-terminus cysteine. In some embodiments, both terminal cysteines are removed.

[0136] In some embodiments, the extension sequence is CX _n iXn2CX _n 3Xn4C (SEQ ID NO: 16). X _nl can be any amino acid. X _n 2 can be any amino acid. X _n3 can be any amino acid. X _n 4 can be any amino acid. In some embodiments, any one of Xni, Xn2, Xn3, Xn4 are P (SEQ ID NO: 125). In some embodiments, any two of X _n i, X _n 2, X _n3 , Xn4 are P (SEQ ID NO: 126). In some embodiments, any three of X _nl , X _n 2, Xn ₃ , Xn4 are P (SEQ ID NO: 127). In some embodiments, the extension sequence is CPPCPPC (SEQ ID NO; 5). In some embodiments the C-terminus cysteine is removed. In some embodiments, the N-terminus cysteine is removed. In some embodiments, both terminal cysteines are removed.

[0137] In some embodiments, the extension sequence is CX _n iXn2CX _n3 Xn4CXn5Xn6C (SEQ ID NO: 12). Xni can be any amino acid. X _n 2 can be any amino acid. X _n3 can be any amino acid. X _n 4 can be any amino acid. X _n5 can be any amino acid. Xn6 can be any amino acid. In some embodiments, any one of X _nl , Xn2, Xn ₃ , Xn4, Xn5, Xn6 are P (SEQ ID NO: 128). In some embodiments, any two of X _nl , Xn2, Xn ₃ , Xn4, Xn5, Xn6 are P (SEQ ID NO: 129). In some embodiments, any three of Xni, Xn2, Xn ₃ , Xn4, Xn5, Xn6 are P (SEQ ID NO: 130). In some embodiments, any four of X _nl , X _n 2, Xn ₃ , Xn4, Xn5, Xn6 are P (SEQ ID NO: 131). In some embodiments, any five of X _nl , X _n 2, Xn ₃ , Xn4, Xn5, Xn6 are P (SEQ ID NO: 132). In some embodiments, the extension sequence is CPPCPPCPPC (SEQ ID NO: 6). In some embodiments, the C-terminus cysteine is removed. In some embodiments, the N-terminus cysteine is removed. In some embodiments, both terminal cysteines are removed. [0138] In some embodiments the extension sequence is CXniXn2CXn3Xn4CXn5Xn6CXn7Xn8C (SEQ ID NO: 13). X _n i can be any amino acid. X _n2 can be any amino acid. X _n3 can be any amino acid. X _n4 can be any amino acid. X _n5 can be any amino acid. X _n6 can be any amino acid. X _n7 can be any amino acid. X _n 8 can be any amino acid. In some embodiments, any one of X _nl , X _n2 , Xn3, Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 133). In some embodiments, any two of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 134). In some embodiments, any three of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 135). In some embodiments, any four of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 136). In some embodiments, any five of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 137). In some embodiments, any six of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 138). In some embodiments, any seven of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8 are P (SEQ ID NO: 139). In some embodiments, the extension sequence is CPPCPPCPPCPPC (SEQ ID NO: 8). In some embodiments, the C-terminus cysteine is removed. In some embodiments, the N-terminus cysteine is removed. In some embodiments, both terminal cysteines are removed.

[0139] In some embodiments, the extension sequence is CXniXn2CXn ₃ Xn4CXn ₅ Xn6CXn7Xn8CXn9XnioC (SEQ ID NO: 14). X _nl can be any amino acid. X _n2 can be any amino acid. X _n3 can be any amino acid. X _n 4 can be any amino acid. X _n5 can be any amino acid. X _n6 can be any amino acid. X _n 7 can be any amino acid. X _n s can be any amino acid. X _n 9 can be any amino acid. X _n io can be any amino acid. In some embodiments, any one of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 140). In some embodiments, any two of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, are P (SEQ ID NO: 141). In some embodiments, any three of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 142). In some embodiments, any four of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 143). In some embodiments, any five of X _nl , X _n2 , Xn ₃ , X _n 4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 144). In some embodiments, any six of Xni, Xn2, X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn ₉ , Xnio are P (SEQ ID NO: 145). In some embodiments, any seven of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 146). In some embodiments, any eight of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 147). In some embodiments, any nine of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio are P (SEQ ID NO: 148). In some embodiments, the extension sequence is CPPCPPCPPCPPCPPC (SEQ ID NO: 9). In some embodiments, the C-terminus cysteine is removed. In some embodiments, the N-terminus cysteine is removed. In some embodiments, both terminal cysteines are removed.

[0140] In some embodiments, the extension sequence is CXniXn2CXn3Xn4CXn ₅ Xn6CXn7Xn8CXn9XnioCXniiXni ₂ C (SEQ ID NO: 15). X _n i can be any amino acid. X _n2 can be any amino acid. X _n3 can be any amino acid. X _n4 can be any amino acid. X _n 5 can be any amino acid. X _n6 can be any amino acid. X _n7 can be any amino acid. X _n 8 can be any amino acid. X _n 9 can be any amino acid. X _n io can be any amino acid. X _{nl l} can be any amino acid. X _n i ₂ can be any amino acid. In some embodiments, any one of X _nl , X _n2 , X _n3 , Xn4, Xns, Xn6, Xn7, Xn8, Xn ₉ , Xnio, Xnii, Xni2 are P (SEQ ID NO: 149). In some embodiments, any two of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 150). In some embodiments, any three of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 151). In some embodiments, any four of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 152). In some embodiments, any five of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 153). In some embodiments, any six of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 154). In some embodiments, any seven of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 155). In some embodiments, any eight of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 156). In some embodiments, any nine of X _nl , X _n2 , Xn ₃ , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 157). In some embodiments, any ten of X _nl , X _n2 , X _n3 , Xn4, Xns, Xn6, Xn7, Xn8, Xn ₉ , Xnio, Xnii, Xni2 are P (SEQ ID NO: 158). In some embodiments, any eleven of X _nl , X _n2 , X _n3 , Xn4, Xn5, Xn6, Xn7, Xn8, Xn9, Xnio, Xnii, Xni2 are P (SEQ ID NO: 159). In some embodiments, the extension sequence is CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10). In some embodiments, the C-terminus cysteine is removed. In some embodiments, the N-terminus cysteine is removed. In some embodiments, both terminal cysteines are removed.

[0141] In some embodiments, the extension sequence comprises greater than 70% sequence identity to any one of the following extension sequences: CPPC (SEQ ID NO: 7), CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), or CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10), for example, 75%, 85%, or 95%. In some embodiments, a nucleic acid sequence is provided that encodes for one of the following extension sequences: CPPC (SEQ ID NO: 7), CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), or CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10). The nucleic acid sequence can comprise conservative substitutions, which provides a conservatively modified variant of the sequence.

[0142] In some embodiments, the extension sequence comprises GGC(PPC) _n (SEQ ID NO: 11), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9. In some embodiments, the extension sequence comprises GGC(X _n iXn2C) _n (SEQ ID NO: 17), wherein n is 1, 2, 3, 4, 5, 6, 7, 8, or 9, and wherein X _nl X _n2 can be any amino acid. In some embodiments, at least 50% of the amino acids within the X _nl and X _n2 are prolines. In some embodiments, at least 60, 70, 80, 90, or 100% of the amino acids within X _nl and X _n2 are prolines.

[0143] In some embodiments, the diabody comprises a cys-diabody comprising a heavy chain variable domain, a light chain variable domain and an extension sequence.

[0144] Extension sequences can associate the different chains and/or domains in different orientations. In some embodiments, the extension sequence (working as a pair of extension sequences) connects the C-terminus of the first VH domain to the C-terminus of the second VH variable domain via a covalent bond (e.g., one or more disulfide bonds). In some embodiments, the extension sequence (working as a pair of extension sequences) connects the C-terminus of the V _L domain to the C-terminus of the V _L domain via a covalent bond (e.g., one or more disulfide bonds). In some embodiments, the covalent bonds involve one or more disulfide bonds via the presence of the cysteines in the extension sequence. Any discussion herein of an extension sequence regarding one orientation also allows for the reverse orientation and both orientations. In some embodiments, 2, 3, 4, 5, 6, or more disulfide bonds are present in the assembled diabody.

[0145] In some embodiments, extension sequences work in pairs, as shown for example in FIGs. 2C, 2D, and 2E. Each extension sequence providing half of the cysteines needed for the targeted number of disulfide bonds. When these extension sequences are paired together, they can be termed "paired extension sequences" or other similar term. Not all of the cysteines need to be paired together in any one paired extension sequence within a diabody in order to obtain a benefit from the extension sequences. For example, unpaired cysteines allow for additional binding sites for other atoms or molecules, such as detectable markers, therapeutic agents, PEG, etc.

[0146] In some embodiments, the extension sequences within the diabodies provide the diabodies with additional functional characteristics. In some embodiments, the extension sequence increases the stability of the diabody, for example, through causing a diabody to retain its dimeric protein structure. Retention of the dimeric structure can result in reduced presence of unpaired scFv impurities after purification and analysis of the diabody.

[0147] In some embodiments, the extension sequences can impact the binding activity of a diabody by, for example, increasing the affinity of the diabody for an antigen. In some embodiments, the extension sequences have no impact on binding activity of the diabody. In some embodiments, the extension sequence increases the biological activity of the diabody by, for example, causing the diabody to retain its dimeric structure. Examples of increased biological activity include, but are not limited to, causing the diabody to more efficiently target tumors.

[0148] In some embodiments, any of the extension sequences described herein comprise at least 3 cysteines. In some embodiments, any of the extension sequences described herein comprise at least 4 cysteines. In some embodiments, any of the extension sequences described herein comprise at least 5 cysteines. In some embodiments, any of the extension sequences described herein comprise at least 6 cysteines. In some embodiments, any of the extension sequences described herein comprise at least 7 cysteines.

[0149] In some embodiments, the cysteine residues can be part of a PPC motif. In some embodiments, the extension sequence comprises a repeating PPC motif such as: CPPC (SEQ ID NO; 7), CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), or CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10). In some embodiments the C-terminus cysteine is removed. In some embodiments the N-terminus cysteine is removed. In some embodiments both the C-terminus and N-terminus cysteines are removed. Linker

[0150] In some embodiments, the heavy chain variable domain and light chain variable domain within a single chain can associate in different ways depending on how the linker connects the domains to form the single chain. Linker sequences can allow for a VL- VH or VH-VL orientation within the single chain. In some embodiments, the linker connects the C-terminus of the V _H domain to the N-terminus of the V _L domain. In some embodiments, the linker connects the C-terminus of the V _L domain to the N-terminus of the V _H domain. Any disclosure of a linker provided herein regarding one orientation also allows for the reverse orientation and both orientations. In some embodiments, the linker connects the heavy and light chain variable domains via a peptide backbone connection between the V _H and VL domains.

[0151] In some embodiments, the linker is about 1 to about 50 amino acids in length, for example, 2 to 15, 2-14, 3-13, 4-10, or 5 amino acids to 8 amino acids. In some embodiments, more than 1 linker is provided, for example, 2, 3, or 4 linkers. If more than 1 linker is provided, each of the linkers can be the same length or different lengths. In some embodiments, a modified amino acid can be used. Use of (i) different amounts of linkers, (i) different lengths of linkers, and (iii) different orientations of linkers allows for conformational flexibility and range-of-motion of the diabody to ensure formation of disulfide bonds. The linker connects the V _H domain to the V _L domain via the linker's peptide backbone. The linker will link the two domains as a continuous, single chain.

[0152] In some embodiments, the linker is a GlySer linker. The GlySer linker can be a polypeptide that is rich in Gly and/or Ser residues. In some embodiments, at least about 40% of the amino acid residues of the GlySer linker are Gly, Ser, or a combination of Gly and Ser, for example at least about 40%, 50%, 60%, 70%, 80%, or 90%. In some embodiments, the GlySer linker is at least about 2 amino acids long, for example at least about 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, or 40 amino acids long. In some embodiments, the linker comprises at least one threonine. In some embodiments, the linker is short enough to allow for cross-pairing between the domains in the diabody (such that the V _L and VH domains within a single chain do not form a binding domain, but instead the binding domains are formed between the two chains, e.g., a V _H from a first chain with a V _L from a second chain and a V _L from the first chain with the V _H from the second chain).

Method of making a diabody

[0153] In some embodiments methods of making the diabodies, antigen binding constructs, or extension sequences described herein are provided. In some embodiments cell lines are provided that produce any of the diabodies, antigen binding constructs, or extension sequences described herein. The cell lines can be a mammalian cell such as the CHO-K1 cell line. In some embodiments, a method of making a diabody in yeast is provided. The method comprises providing yeast comprising a nucleic acid encoding any of the diabodies described herein and expressing any of the diabodies described herein. In some embodiments, one or more of a wide variety of mammalian or non-mammalian expression systems are used to produce the diabodies, antigen binding constructs, or extension sequences disclosed herein including, but not limited to mammalian expression systems (for example, CHO-K1 cells), bacterial expression systems (for example, E. coli, B. subtilis) yeast expression systems (for example, Pichia, S. cerevisiae) or any other known expression system. Other systems can include insect cells and/or plant cells.

[0154] In some embodiments, any of the extension and/or linker sequences can be employed in one or more of the antigen binding constructs, e.g., diabody, provided herein. In some embodiment, the diabody has some or all of the amino acid sequence shown in FIGs. 22-24. In some embodiments, the diabody is at least 80% identical to any one or more of SEQ ID NO: 161-163, e.g., 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99%, or higher. In some embodiments, the percent identity is at least 80% identical to any one or more of SEQ ID NO: 161-163, e.g., 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99%, or higher but the extension sequence within the sequence is 100% identical to one or more of the sequences provided herein.

Method of use I diabody kit

[0155] In some embodiments kits are provided that comprise an antigen binding construct that comprises an extension sequence and a detectable marker. Any of the extension sequences provided herein can be employed. In some embodiments, the extension sequences include EPKSXn5DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1), ERKX _n5 CXniXn2CXn3Xn4C (SEQ ID NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPC (SEQ ID NO: 7), CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10), or GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, and wherein X _n i, Xn2, Xn3, Xn4, and X _n5 can be any amino acid. Detectable markers include, but are not limited to, a radioisotope, a fluorescent compound, a bioluminescent compound, a chemiluminescent compound, a metal chelator or an enzyme. The extension sequence can be on the end of a heavy or light chain variable region of a diabody.

[0156] In some embodiments kits are provided that comprise a diabody that comprise an extension sequence and a detectable marker. Any of the extension sequences provided herein can be employed. Extension sequences include

EPKSXn ₅ DKTHTCXnlXn ₂ CXn3Xn4C (SEQ ID NO: 1), ERKXn ₅ CXnlXn ₂ CXn3Xn4C (SEQ ID

NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPC (SEQ ID NO: 7) CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10), or GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, and wherein X _n i, X _n2 , Xn3, Xn4, andX _n 5 can be any amino acid. Detectable markers include, but are not limited to, a radioisotope, a fluorescent compound, a bioluminescent compound, a chemiluminescent compound, a metal chelator or an enzyme.

[0157] In some embodiments a method is provided for detecting the presence or absence of a marker. The method comprises applying any of the diabodies described herein to a sample and detecting the presence or absence of a marker. Markers (or targets) that can be employed include, but are not limited to, PCS A, PMSA, CD8, PDL-1, Her2/neu. In some embodiments, any target or marker can be selected.

[0158] In some embodiments, the diabody is incubated with the sample for no more than 20 hours. In some embodiments, the diabody is incubated with the sample for no more than 6 hours. In some embodiments, there is no time limit for how long the diabody is incubated with the sample.

Methods of treatment

[0159] In some embodiments, a method of treatment is provided comprising administering a therapeutically effective amount of the pharmaceutical composition of the diabody (which will include one or more of the disclosed extension sequences) to an individual in need thereof. The pharmaceutical compositions described herein can be administered by any suitable route of administration. A route of administration can refer to any administration pathway known in the art, including but not limited to aerosol, enteral, nasal, ophthalmic, oral, parenteral, rectal, transdermal (e.g., topical cream or ointment, patch), or vaginal. "Transdermal" administration can be accomplished using a topical cream or ointment or by means of a transdermal patch. "Parenteral" refers to a route of administration that is generally associated with injection, including infraorbital, infusion, intraarterial, intracapsular, intracardiac, intradermal, intramuscular, intraperitoneal, intrapulmonary, intraspinal, intrasternal, intrathecal, intrauterine, intravenous, subarachnoid, subcapsular, subcutaneous, transmucosal, or transtracheal. In some embodiments, the antigen binding construct can be delivered intraoperatively as a local administration during an intervention or resection.

[0160] In some embodiments any of the pharmaceutical compositions or therapeutic agents described herein can be used to target a therapeutic molecule, for example a cytotoxin, to a target positive cell, such as a cell expressing the target molecule. Thus, some embodiments include methods of targeting a therapeutic agent or a pharmaceutical composition to a target positive cell. The method can include administering a pharmaceutical composition or therapeutic agent to a subject. The subject can be a subject in need, for example a subject in need of elimination or neutralization of at least some target positive cells. In some embodiments, the therapeutic agent or pharmaceutical composition can be directly conjugated to the extension sequence, antigen binding construct, or diabody via a covalent bond, such as a disulfide bond. In some embodiments, the subject can benefit from the localization of a target molecule positive cell to another cell or agent. [0161] In some embodiments, before and/or after administration of the therapeutic agent or pharmaceutical composition, the number and/or localization of the target positive cells of the patient is determined. For example, determining the number and/or localization of target positive cells prior to administration can indicate whether the patient is likely to benefit from neutralization and/or elimination of the target positive cells. Determining the number and/or localization of the target positive cells after administration can indicate whether the target positive cells were eliminated in the patient.

[0162] In some embodiments, the disorder to be treated is one that expresses an elevated level of at least one of PSCA, PSMA, CD8, HER2/new and/or PSMA and CD3. In some embodiments, the disorder to be treated is one that can be targeted and/or detected by a diabody that binds to at least one of PSCA, PSMA, CD8, HER2/new and/or PSMA and CD3.

[0163] In some embodiments, diabody IAB1C (IABlC-1, IAB lC-2 and/or IABlC-3) can be used to target (including deliver a payload to) a PSCA expressing cell for treatment of a disorder related thereto.

[0164] In some embodiments, diabody IAB2C (IAB2C-1, IAB2C-2 and/or IAB2C-3) can be used to target (including deliver a payload to) a PSMA expressing cell for treatment of a disorder related thereto.

[0165] In some embodiments, diabody IAB22C (IAB22C-1, IAB22C-2 and/or IAB22C-3) can be used to target (including deliver a payload to) a CD8 expressing cell for treatment of a disorder related thereto.

[0166] In some embodiments, diabody IAB8C (IAB8C-1, IAB8C-3 and/or IAB8C-4) can be used to target (including deliver a payload to) a Her2/neu expressing cell for treatment of a disorder related thereto.

[0167] In some embodiments, diabody bC-PSMAxCD3-l bC-CD3xPSMA-l or bC-PSMAxCD3-3bC-CD3xPSMA-3 can be used to target (including deliver a payload to) a PSMAxCD3 expressing cell for treatment of a disorder related thereto.

[0168] In some embodiments, a method for reducing cells expressing PCSA, PSMA, CD8, HER2, CD3, 5T4, PD-L1, folate receptor alpha, Mesothelin, CA19-9, CD19, CD20, and/or Her2/neu is provided. The method comprises using one or more of the diabodies with the extension sequence(s) provided herein, with a therapeutic agent, cytotoxin, or other payload to deliver the payload to the cells expressing one or more of: PCSA, PSMA, CD8, HER2, CD3, 5T4, PD-Ll , folate receptor alpha, Mesothelin, CA19-9, CD19, CD20, and/or Her2/neu.

[0169] In some embodiments, a method of detecting a cell expressing or overexpressing one or more of PCSA, PSMA, CD8, HER2, CD3, 5T4, PD-Ll, folate receptor alpha, Mesothelin, CA19-9, CD19, CD20, and/or Her2/neu is provided. The method comprises using one or more of the diabodies with the extension sequence(s) provided herein, with a detectable marker to localize the detectable marker to the cells expressing one or more of: PCSA, PSMA, CD8, HER2, CD3, 5T4, PD-Ll, folate receptor alpha, Mesothelin, CA19-9, CD 19, CD20, and/or Her2/neu.

[0170] In some embodiments, the diabody or other antigen binding construct provided herein can be used in the treatment and/or prevention of one or more of: non-small cell lung cancer (NSCLC), Small Cell Lung Cancer (SCLC), Thymic Carcinoma, Lymphoma, Myxoid/Round Cell Liposarcoma, Liposarcoma, Synovial Sarcoma, Recurrent Adult Soft Tissue Sarcoma, Gliosarcoma, Astrocytoma, Acute Myelogenous Leukemia (AML), Malignant Solitary Fibrous Tumor of the Pleura (MSFT), Penile Cancer, Diffuse Intrinsic Pontine Glioma (DIPG), Thyroid Carcinoma, Head and neck Squamous Carcinoma (SCCHN), Adenocarcinoma of the Lung, Vulvar Cancer (squamous cell carcinoma), Bladder Cancer, Cervical Squamous Cell Carcinoma, Germ Cell Tumors, Testicular Cancer, Pancreatic Ductal Adenocarcinoma, Pancreatic Adenocarcinoma, Non-Melanoma Skin Cancers, Retroperitoneal and Peritoneal Carcinoma, Melanoma, Unresectable or Metastatic Melanoma, Mucosal Melanoma of the Head and Neck, Uveal Melanoma, Non-Cutaneous Melanoma, Cutaneous T-Cell Lymphoma, Occult Primary tumors, Biliary Cancer, Gastrointestinal Stromal Tumors (GIST), Mesothelioma, Biphasic Mesothelioma, Malignant Pleural Mesothelioma, Kidney cancer, Myelodysplasia syndrome, Liver Hepatocellular Carcinoma, Esophageal and Esophagogastric Junction Carcinoma, Extrahepatic Bile Duct Adenocarcinoma, Small Intestinal Malignancies, Gastric Adenocarcinoma, Cholangiocarcinoma, Intrahepatic ad extrahepatic Cholangiocarcinomas, Ovarian Surface Epithelial Carcinomas, Non-epithelial and epithelial Ovarian cancers, Breast Carcinoma, Triple Negative Breast Cancer, Endometrial carcinoma, Uterine sarcoma, Bone Cancers, Colorectal Adenocarcinoma, Prostatic Adenocarcinoma, Hormone-Resistant Prostate Cancer, Neuroendocrine tumors, Solid tumors, Follicular Lymphoma, Kaposi Sarcoma, Carcinoma of the Genitourinary Tract, Fallopian Tube Cancer, Malignant Glioma, Waldenstrom Macroglobulinemia, Richter Syndrome, Refractory Splenic Marginal Zone Lymphoma, Refractory Small Lymphocytic Lymphoma, Refractory Nodal Marginal Zone Lymphoma, Refractory Lymphoplasmacytic Lymphoma, Refractory Extranodal Marginal Zone Lymphoma of the Mucosa-Associated Lymphoid Tissue, Refractory Chronic Lymphocytic Leukemia, Multiple Myeloma, Hodgkin's Lymphoma, Non-Hodgkin's Lymphoma, Diffuse Large B-Cell Lymphoma, Nasopharyngeal Carcinoma, Gastroesophageal Junction Adenocarcinoma, renal cell carcinomas, colon carcinomas, Transitional cell carcinoma (TCC), urothelial carcinoma (UCC), glioblastoma multiforme (GBM), Gallbladder cancers, and Merkel Cell Carcinoma.

[0171] In some embodiments, the diabody or other antigen binding construct provided herein can be used in the treatment and/or prevention of one or more of: Prostate cancer, Lung cancers, Melanoma, Breast malignancies, CNS and brain Malignancies, Skin malignancies, Occult Primary tumors, Kidney cancers, Gastrointestinal malignancies, Ovarian Neoplasms, Renal Cancers, Biliary Cancer, Bladder cancer, Esophageal Neoplasms, Cervical cancers, Solid tumors, Head and neck cancers, Urogenital Neoplasms, Germ Cell Tumors, Testicular Cancer, Pancreatic cancers, Glioma, Liver cancers, Malignant Neoplasms of the Bone, Colorectal cancers, Thyroid Cancer, Thoracic and respiratory tumors, Lymphomas, Male and female genitourinary Malignancies, Bile duct cancers, Hematological Malignancies, Multiple Myeloma, Gallbladder cancers, endocrine tumors, ocular cancers, and Tumors of the hematopoietic and lymphoid tissues. In some embodiments, the diabody or other antigen binding construct provided herein can be used in the treatment and/or prevention of one or more of: Non-Small Cell Lung Cancer (NSCLC), Prostate Cancer, Melanoma, and Breast Cancer.

[0172] In some embodiments, any one or more of the methods of treatment noted above can instead be a method of preparing a medicament for the treatment of any one or more of the indications noted above, In some embodiments, any one or more of the diabodies and/or antigen binding constructs provided herein can be used as a composition for the treatment of any one or more of: non-small cell lung cancer (NSCLC), Small Cell Lung Cancer (SCLC), Thymic Carcinoma, Lymphoma, Myxoid/Round Cell Liposarcoma, Liposarcoma, Synovial Sarcoma, Recurrent Adult Soft Tissue Sarcoma, Gliosarcoma, Astrocytoma, Acute Myelogenous Leukemia (AML), Malignant Solitary Fibrous Tumor of the Pleura (MSFT), Penile Cancer, Diffuse Intrinsic Pontine Glioma (DIPG), Thyroid Carcinoma, Head and neck Squamous Carcinoma (SCCHN), Adenocarcinoma of the Lung, Vulvar Cancer (squamous cell carcinoma), Bladder Cancer, Cervical Squamous Cell Carcinoma, Germ Cell Tumors, Testicular Cancer, Pancreatic Ductal Adenocarcinoma, Pancreatic Adenocarcinoma, Non-Melanoma Skin Cancers, Retroperitoneal and Peritoneal Carcinoma, Melanoma, Unresectable or Metastatic Melanoma, Mucosal Melanoma of the Head and Neck, Uveal Melanoma, Non-Cutaneous Melanoma, Cutaneous T-Cell Lymphoma, Occult Primary tumors, Biliary Cancer, Gastrointestinal Stromal Tumors (GIST), Mesothelioma, Biphasic Mesothelioma, Malignant Pleural Mesothelioma, Kidney cancer, Myelodysplastic syndrome, Liver Hepatocellular Carcinoma, Esophageal and Esophagogastric Junction Carcinoma, Extrahepatic Bile Duct Adenocarcinoma, Small Intestinal Malignancies, Gastric Adenocarcinoma, Cholangiocarcinoma, Intrahepatic ad extrahepatic Cholangiocarcinomas, Ovarian Surface Epithelial Carcinomas, Non-epithelial and epithelial Ovarian cancers, Breast Carcinoma, Triple Negative Breast Cancer, Endometrial carcinoma, Uterine sarcoma, Bone Cancers, Colorectal Adenocarcinoma, Prostatic Adenocarcinoma, Hormone-Resistant Prostate Cancer, Neuroendocrine tumors, Solid tumors, Follicular Lymphoma, Kaposi Sarcoma, Carcinoma of the Genitourinary Tract, Fallopian Tube Cancer, Malignant Glioma, Waldenstrom Macroglobulinemia, Richter Syndrome, Refractory Splenic Marginal Zone Lymphoma, Refractory Small Lymphocytic Lymphoma, Refractory Nodal Marginal Zone Lymphoma, Refractory Lymphoplasmacytic Lymphoma, Refractory Extranodal Marginal Zone Lymphoma of the Mucosa-Associated Lymphoid Tissue, Refractory Chronic Lymphocytic Leukemia, Multiple Myeloma, Hodgkin's Lymphoma, Non-Hodgkin's Lymphoma, Diffuse Large B-Cell Lymphoma, Nasopharyngeal Carcinoma, Gastroesophageal Junction Adenocarcinoma, renal cell carcinomas, colon carcinomas, Transitional cell carcinoma (TCC), urothelial carcinoma (UCC), glioblastoma multiforme (GBM), Gallbladder cancers, Merkel Cell Carcinoma, Prostate cancer, Lung cancers, Melanoma, Breast malignancies, CNS and brain Malignancies, Skin malignancies, Occult Primary tumors, Kidney cancers, Gastrointestinal malignancies, Ovarian Neoplasms, Renal Cancers, Biliary Cancer, Bladder cancer, Esophageal Neoplasms, Cervical cancers, Solid tumors, Head and neck cancers, Urogenital Neoplasms, Germ Cell Tumors, Testicular Cancer, Pancreatic cancers, Glioma, Liver cancers, Malignant Neoplasms of the Bone, Colorectal cancers, Thyroid Cancer, Thoracic and respiratory tumors, Lymphomas, Male and female genitourinary Malignancies, Bile duct cancers, Hematological Malignancies, Multiple Myeloma, Gallbladder cancers, endocrine tumors, ocular cancers, and Tumors of the hematopoietic and lymphoid tissues. In some embodiments, the diabody or other antigen binding construct provided herein can be used in the treatment and/or prevention of one or more of: Non-Small Cell Lung Cancer (NSCLC), Prostate Cancer, Melanoma, and Breast Cancer.

[0173] In some embodiments, the diabody and/or antigen binding construct is present in an amount effective for reducing one or more symptom of any one or more of the disorders provided herein.[0169] In some embodiments, the diabody and/or antigen binding construct is conjugated to a therapeutic agent and/or cytotoxic agent for the therapy or therapeutic.

Nucleic acids

[0174] In some embodiments, a nucleic acid sequence is provided that encodes any of the diabodies disclosed herein. In some embodiments, a nucleic acid sequence is provided that encodes any of the extension sequences disclosed herein. In some embodiments, an expression vector is provided that comprises these nucleic acid sequences. In some embodiments, the expression vector includes pcDNA3.1™/myc-His (-) Version A vector for mammalian expression (Invitrogen, Inc.) or a variant thereof. The pcDNA3.1 expression vector features a CMV promoter for mammalian expression and both mammalian (Neomycin) and bacterial (Ampicillin) selection markers. In some embodiments, the expression vector includes a plasmid. In some embodiments, the vector includes a viral vector, for example a retroviral or adenoviral vector. In embodiments, the vector includes a cosmid, YAC, or BAC. [0175] Any of the extension sequences described herein can be configured for use within an antigen binding construct. In some embodiments, the extension sequence is located within an antibody fragment. In some embodiments, the extension sequence is located within antibody. The antibody can be mono-specific or bi-specific. Bi-specific antibodies can be assembled in a 1 : 1 ratio. In some embodiments, the extension sequence is part of a diabody. In some embodiments, the extension sequence is part of a diabody that is disclosed in Table 2.1.

[0176] In some embodiments a nucleic acid sequence is provided that encodes for any of the extension sequences described herein.

[0177] In some embodiments a vector is provided that comprises a nucleic acid that encodes for any of the extension sequences, antigen binding constructs, or diabodies described herein. In some embodiments, the vector includes pcDNA3.1™/myc-His (-) Version A vector for mammalian expression (Invitrogen, Inc.) or a variant thereof. The pcDNA3.1 expression vector features a CMV promoter for mammalian expression and both mammalian (Neomycin) and bacterial (Ampicillin) selection markers. In some embodiments, the expression vector includes a plasmid. In some embodiments, the vector includes a viral vector, for example a retroviral or adenoviral vector. In embodiments, the vector includes a cosmid, YAC, or BAC.

Therapeutic agent

[0178] In some embodiments any of the extension sequences, antibody binding constructs, or diabodies described herein can be covalently attached to one or more additional molecules, such as a therapeutic agent or detectable marker. A therapeutic agent as used herein is an atom, molecule, or compound that is useful in the treatment of a disorder related to a target molecule. Examples of therapeutic agents include, but are not limited to, drugs, chemotherapeutic agents, therapeutic antibodies and antibody fragments, toxins, radioisotopes, enzymes (for example, enzymes to cleave prodrugs to a cytotoxic agent at the site of the antigen binding construct binding), nucleases, hormones, immunomodulators, antisense oligonucleotides, chelators, boron compounds, photoactive agents and dyes, and nanoparticles. In some embodiments, the extension sequences can be connected to a therapeutic agent to a disorder associated with the expression of a target molecule. In some embodiments, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1, 12 or more molecules of therapeutic agents can be attached to each pair of extension sequences (for example 1, 2, 3, 4, 5, or 6 agents on each strand).

[0179] In some embodiments the agent is a cytotoxic agent. In some embodiments, the cytotoxic agent is one such as maytansine, auristatin, PBD, docetaxel, or etoposide. Additional embodiments of cytotoxic agents include ricin, doxorubicin, daunorubicin, taxol, ethiduim bromide, mitomycin, tenoposide, vincristine, vinblastine, colchicine, dihydroxy anthracin dione, actinomycin D, diphtheria toxin, Pseudomonas exotoxin (PE) A, PE40, abrin, and glucocorticoid and other chemotherapeutic agents, as well as radioisotopes. Embodiments of cytotoxins further include alkylating agents, antimetabolites, anti-tumor antibiotics, topoisomerase inhibitors, mitotic inhibitors hormone therapy, targeted therapeutics and immunotherapeutics. In some embodiments the chemotherapeutic agents that can be used as detectable markers in accordance with the embodiments of the disclosure include, but are not limited to, 13-cis- Retinoic Acid, 2- Chlorodeoxyadenosine, 5-Azacitidine, 5-Fluorouracil, 6-Mercaptopurine, 6- Thioguanine, actinomycin-D, adriamycin, aldesleukin, alemtuzumab, alitretinoin, alltransretinoic acid, alpha interferon, altretamine, amethopterin, amifostine, anagrelide, anastrozole, arabinosylcytosine, arsenic trioxide, amsacrine, aminocamptothecin, aminoglutethimide, asparaginase, azacytidine, bacillus calmette-guerin (BCG), bendamustine, bevacizumab, bexarotene, bicalutamide, bortezomib, bleomycin, busulfan, calcium leucovorin, citrovorum factor, capecitabine, canertinib, carboplatin, carmustine, cetuximab, chlorambucil, cisplatin, cladribine, cortisone, cyclophosphamide, cytarabine,darbepoetin alfa, dasatinib, daunomycin, decitabine, denileukin diftitox, dexamethasone,dexasone, dexrazoxane, dactinomycin, daunorubicin, decarbazine, docetaxel, doxorubicin,doxifluridine, eniluracil, epirubicin, epoetin alfa, erlotinib, everolimus, exemestane,estramustine, etoposide, filgrastim, fluoxymesterone, fulvestrant, flavopiridol, floxuridine, fludarabine, fluorouracil, flutamide, gefitinib, gemcitabine, gemtuzumab ozogamicin, goserelin, granulocyte - colony stimulating factor, granulocyte macrophage-colony stimulating factor, hexamethylmelamine, hydrocortisone hydroxyurea, ibritumomab, interferon alpha, interleukin - 2, interleukin- 1 1 , isotretinoin, ixabepilone, idarubicin, imatinib mesylate, ifosfamide, irinotecan, lapatinib, lenalidomide, letrozole, leucovorin, leuprolide, liposomal Ara-C, lomustine, mechlorethamine, megestrol, melphalan, mercaptopurine, mesna, methotrexate, methylprednisolone, mitomycin C, mitotane, mitoxantrone, nelarabine, nilutamide, octreotide, oprelvekin, oxaliplatin, paclitaxel, pamidronate, pemetrexed, panitumumab, PEG Interferon, pegaspargase, pegfilgrastim, PEG-L-asparaginase, pentostatin, plicamycin, prednisolone, prednisone, procarbazine, raloxifene, rituximab, romiplostim, ralitrexed, sapacitabine, sargramostim, satraplatin, sorafenib, sunitinib, semustine, streptozocin, tamoxifen, tegafur, tegafur-uracil, temsirolimus, temozolamide, teniposide, thalidomide, thioguanine, thiotepa, topotecan, toremifene, tositumomab, trastuzumab, tretinoin, trimitrexate, alrubicin, vincristine, vinblastine, vindestine, vinorelbine, vorinostat, maytansinoids, auristatins and pyrrolobenzodiazepines, or zoledronic acid.

[0180] In some embodiments a pharmaceutical composition is provided that comprises any of the extension sequences, antigen binding constructs, or diabodies described herein. In some embodiments, the pharmaceutical composition can also include a pharmaceutically acceptable carrier. A pharmaceutically acceptable carrier can be a pharmaceutically acceptable material, composition, or vehicle that is involved in carrying or transporting a compound of interest from one tissue, organ, or portion of the body to another tissue, organ, or portion of the body. For example, the carrier can be a liquid or solid filler, diluent, excipient, solvent, or encapsulating material, or some combination thereof. Each component of the carrier is "pharmaceutically acceptable" in that it is compatible with the other ingredients of the formulation. It is also suitable for contact with any tissue, organ, or portion of the body that it can encounter, meaning that, ideally it will not carry a significant risk of toxicity, irritation, allergic response, immunogenicity, or any other complication that excessively outweighs its therapeutic benefits.

[0181] In some embodiments, a therapeutic agent is provided that is covalently attached to any of the extension sequences, antigen binding constructs, or diabodies described herein. Examples of therapeutic agents include, but are not limited to, drugs, chemotherapeutic agents, therapeutic antibodies and antibody fragments, toxins, radioisotopes, enzymes (for example, enzymes to cleave prodrugs to a cytotoxic agent at the site of the antigen binding construct binding), nucleases, hormones, immunomodulators, antisense oligonucleotides, chelators, boron compounds, photoactive agents and dyes, and nanoparticles.

[0182] In some embodiments a pharmaceutical composition comprising any of the extension sequences described herein is provided. In some embodiments the pharmaceutical composition comprises a diabody that comprises an extension sequence or an antigen binding construct that comprises an extension sequence. In some embodiments a pharmaceutical composition comprising any one or more of the following sequences: EPKSX _n5 DKTHTCXniXn2CXn3Xn4C (SEQ ID NO: 1), ERKXn5CXniXn2CXn3Xn4C (SEQ ID NO: 2), ELKTPLGDTTHTCXniXn ₂ CXn3Xn4C (SEQ ID NO: 3), ESKYGPPCXniXn ₂ CXn3Xn4C (SEQ ID NO: 4), CPPC (SEQ ID NO: 7) CPPCPPC (SEQ ID NO: 5), CPPCPPCPPC (SEQ ID NO: 6), CPPCPPCPPCPPC (SEQ ID NO: 8), CPPCPPCPPCPPCPPC (SEQ ID NO: 9), CPPCPPCPPCPPCPPCPPC (SEQ ID NO: 10), or and GGC(PPC) _n (SEQ ID NO: 11), wherein n is 2, 3, 4, 5, 6, 7, 8, or 9, and wherein X _n i , X _n2 , X _n 3, Xn4, andX _n5 can be any amino acid.

[0183] In some embodiments, the pharmaceutical composition can also include a pharmaceutically acceptable carrier. A pharmaceutically acceptable carrier can be a pharmaceutically acceptable material, composition, or vehicle that is involved in carrying or transporting a compound of interest from one tissue, organ, or portion of the body to another tissue, organ, or portion of the body. For example, the carrier can be a liquid or solid filler, diluent, excipient, solvent, or encapsulating material, or some combination thereof. Each component of the carrier is "pharmaceutically acceptable" in that it is compatible with the other ingredients of the formulation. It is also suitable for contact with any tissue, organ, or portion of the body that it can encounter, meaning that, ideally it will not carry a significant risk of toxicity, irritation, allergic response, immunogenicity, or any other complication that excessively outweighs its therapeutic benefits.

Detectable marker

[0184] As used herein, a "detectable marker" includes an atom, molecule, or compound that is useful in diagnosing, detecting or visualizing a location and/or quantity of a target molecule, cell, tissue, organ and the like. Detectable markers that can be used in accordance with the embodiments herein include, but are not limited to, radioactive substances (e.g., radioisotopes, radionuclides, radiolabels or radiotracers), dyes, contrast agents, fluorescent compounds or molecules, bioluminescent compounds or molecules, enzymes and enhancing agents (e.g., paramagnetic ions). In addition, some nanoparticles, for example quantum dots and metal nanoparticles (described below) can be suitable for use as a detection agent. In some embodiments, the detectable marker is IndoCyanine Green (ICG) or one of the dyes that fluoresces in the near infrared region such as IR800 for surgical applications.

[0185] Exemplary radioactive substances that can be used as detectable markers in accordance with the embodiments herein include, but are not limited to, ¹⁸ F, ¹⁸ F-FAC, ³² P, ³³ P, ⁴⁵ Ti, ⁴⁷ Sc, ⁵² Fe, ⁵⁹ Fe, ⁶² Cu, ⁶⁴ Cu, ⁶⁷ Cu, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁵ Sc, ⁷⁷ As, ⁸⁶ Y, ⁹⁰ Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁴ Tc, ⁹⁴ Tc, "mTc, "Mo, ¹⁰⁵ Pd, ¹⁰⁵ Rh, ^m Ag, ^m In, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹³¹ I, ¹⁴² Pr, ¹⁴³ Pr, ¹⁴⁹ Pm, ¹⁵³ Sm, ^{154" 158} Gd, ¹⁶¹ Tb, ¹⁶⁶ Dy, ¹⁶⁶ Ho, ¹⁶⁹ Er, ¹⁷⁵ Lu, ¹⁷⁷ Lu, ¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁸⁹ Re, ¹⁹⁴ Ir, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Pb, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²²³ Ra and ²²⁵ Ac. Exemplary Paramagnetic ions substances that can be used as detectable markers include, but are not limited to ions of transition and lanthanide metals (e.g. metals having atomic numbers of 6 to 9, 21-29, 42, 43, 44, or 57-71). These metals include ions of Cr, V, Mn, Fe, Co, Ni, Cu, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0186] In some embodiments, the detectable marker can be a radionuclide such asYttrium-90, Lutetium-177, or Actinium-227. Additional embodiments of a radionuclide include Copper-67, Astatine-211, Lead-212/Bismuth-212, Actinium-225/ Bismuth-213, and Thorium. In some embodiments, treatment of a target cell with these radionuclides can result in cell damage and death to a target tissue.

[0187] In some embodiments, the detectable marker is a bioluminescence or fluorescent compound Examples include, fluorescein, fluorescein isothiocyanate (FITC), OREGON GREEN™, rhodamine, Texas red, tetrarhodimine isothiocynate (TRITC), Cy3, Cy5, and the like), fluorescent markers (e.g., green fluorescent protein (GFP), phycoerythrin, and the like), autoquenched fluorescent compounds that are activated by tumor-associated proteases, enzymes (e.g., luciferase, horseradish peroxidase, alkaline phosphatase, and the like), nanoparticles, biotin, digoxigenin or combination thereof.

[0188] In some embodiments, any of the detectable markers described herein can be conjugated to the diabody.

PEG

[0189] In some embodiments, any of the extension sequences, antigen binding constructs or diabodies described herein further comprise polyethylene glycol (PEG). PEG can be conjugated to a cysteine, lysine, histidine, arginine, aspartic acid, serine, or threonine of the extension sequence. In some embodiments, PEG is conjugated to a terminal cysteine of the diabody. The PEG can be a branched polyether or a linear polyether. The PEG can have terminal hydroxyl groups. In some embodiments, PEG increases the half-life of the diabody. In some embodiments, PEG controls the route of clearance. Examples of controlling the route of clearance include reducing blood clearance of the diabody and preventing clearance of the diabody through the kidney. In some embodiments, PEG results in higher tumor uptake of the diabody.

[0190] In some embodiments, any of the above options (therapeutic agents, detectable markers, PEG) or other options (such as carbohydrates) can be attached at one or more of the cysteines in the extension sequence(s). In some embodiments, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more such atoms or molecules are attached to the extension sequence(s). In some embodiments, different combinations of these molecules can be attached (for example, a detectable marker and a PEG and a therapeutic agent).

EXAMPLE 1

CYS-DIABODY CONSTRUCTS

[0191] The original Cys-diabody was designed to form a single Cys-Cys bridge at the C-terminus when the VL-linker-VH-GGC monomers assemble into a diabody. Cys- diabody can be assembled in both VL-linker-VH-GGC and VH-linker-VL-GGC configurations as shown in FIG. 1. Cys residues are added to the C-terminus of the construct with Gly-Gly spacer. The purpose of adding these GGC sequences is to enable site-specific conjugation. [0192] Studies showed that insertion of a repeating "PPC" (Pro-Pro-Cys) motif into a hinge of a human IgGl based minibody molecule results in stabilization of minibody dimers and proper disulfide pairing. (PPC) _n motifs were added to the C-terminus of the Cys- Db (FIGs. 2A and 2B) to determine if they could stabilize the diabody without introducing significant levels of aggregation. Experimentally n=l (two total cysteines; FIG. 2C), n=2 (three cysteines; FIG. 2D) and n=4 (four cysteines; FIG. 2E) motifs were tested. Additional cysteine residues were added to determine if they allowed for site-specific conjugation while maintaining the protein as an intact dimer.

[0193] Expression of the Cys-Db-vO (FIG. 2B) in a mammalian and/or yeast cells yielded a protein with approximately 10-50% of dimer protein that lacks a proper Cys-Cys bridge (variability was observed depending on the CDRs). When a Db containing a single Cys was run on a denaturing, non-reducing SDS-PAGE gel, a prominent 25 kDa band corresponding to the single chain was always present (FIG. 3B). The 25 kDa fragment is the single chain fragment variable (scFv) of the Cys-diabody (i.e. scFv dimer) that dissociated upon electrophoresis in the presence of SDS. A diabody containing a single Cys at the C- terminus maintained its intact dimeric form in solution based on noncovalent, inter-domain affinity of V _L and V _H chains as shown by SE-HPLC chromatography - a single, 50 kDa peak was usually detected on SEC (See FIG. 3A).

[0194] Uncoupled scFvs may arise during intracellular processing or post- secretion. The amount of scFv varies depending on the CDRs in the construct. It is reasonable to hypothesize that there is either a "strain" or an "excessive flexibility" at the C- termini of the individual scFv chains in the Cys-Db that contributes to heterogeneity during initial intracellular assembly or secretion into culture media.

EXAMPLE 2

SYNTHESIZING MONOSPECIFIC AND BI-SPECIFIC CYS-DIABODY PROTEINS

[0195] DNA expression constructs that encode for Cys-diabody proteins were synthesized that contain different CPPC (SEQ ID NO: 7) extension sequence motifs (Table 2.1). TABLE 2.1

EXAMPLE 3

NON-REDUCING SDS-PAGE ANALYSIS REVEALED THAT INCREASING THE CPPC (SEQ ID NO: 7) MOTIFS TO THE EXPRESSION CONSTRUCTS

RESULTED IN INCREASED STABILITY

[0196] Protein samples were evaluated for the presence of dimeric and scFvs using Sodium Dodecyl Sulfate (SDS) polyacrylamide gel electrophoresis (SDS-PAGE) under non-reducing conditions. Samples were prepared by dissolving 3-5 μg of each protein in l0μL· NuPAGE LDS sample buffer (Life Technologies). Each sample was loaded onto 1.0 mm, 12-well 4-12% Bis-Tris Protein Gel cassette (NuPAGE Novex), and the porteins separated after applying a constant potential of 198V for 35 minutes

[0197] The sizes of the half molecules were determined using SDS-PAGE analysis and reducing conditions. Briefly, a 1 : 100 dilutions of b-mercaptoethanol was added to the sample buffer. The samples were incubated at 70°C for 5 minutes prior to loading onto the gels. Each sample was loaded onto a 1.0 mm, 12- well 4-12% Bis-Tris Protein Gel cassette (NuPAGE No vex), and a constant potential of 198V was applied for 35 minutes.

[0198] The gels were removed from the plastic cassette and incubated in deionized water for 3 times for 5 minutes. The protein staining was completed by incubating the gel for 2 hours in a solution of Coomassie blue dye (GelCode Blue Safe Protein Stain, Thermo Scientific).

[0199] As shown in FIG. 4A, the IAB1 Cys-diabody containing 1 CPPC (SEQ ID NO: 7) motif produces a heterogeneous composition in which a 25kd band appears that represents the scFv. When 2 CPPC (SEQ ID NO: 7) motifs are present the intensity of this 25kd band decreases as shown in FIG. 4B resulting in a more homogeneous composition. When 3 CPPC (SEQ ID NO: 7) motifs are present there is no 25kd band as shown in FIG. 4C. Similar results are shown with (i) the IAB2C Cys-diabody (See FIGs. 6A, 6B, and 6C), (ii) the IAB22C Cys-diabody (See FIGs 8A, 8B, and 8C), (iii) the IAB8C Cys-diabody (See FIGs 10A, 10B, and IOC). In addition, FIGs. 12A and 12B show that the bispecific bC- PMSA construct that contains 1 CPPC (SEQ ID NO: 7) motif produces a 25kd band that represents the scFv, whereas when 3 CPPC (SEQ ID NO: 7) motifs are added the scFv band disappears. FIG. 13 shows a summary of the various Cys-diabody variants revealing improved homogeneity (reduced expression of the scFv band) when CPPC (SEQ ID NO: 7) motifs are added to the constructs.

[0200] In summary, adding one PPC with two total Cys is not enough to maintain dimeric protein through purification and analysis. However, adding two PPC with a total of three Cys results in a very homogeneous protein with no monomer. Adding three PPC with a total of four Cys results in a very homogeneous protein with no monomer. Thus, SDS-PAGE analysis of Cys diabodies with different PPC motifs shows benefit of adding cysteine residues. EXAMPLE 4

FACS ANALYSIS OF THE CONSTRUCTS SHOWS THAT ADDING CPPC (SEQ ID NO: 7) MOTIFS TO THE C-TERMINUS DOES NOT IMPACT BINDING

[0201] CPPC (SEQ ID NO: 7) motifs added to the C-terminus do not impact binding of IAB1C to PSCA expressed on SW780 cells. SW780 cells were cultured in Dulbecco's MEM and harvested by washing with sterile Dulbecco's phosphate buffer saline (without Calcium and Magnesium). The cells were detached with Accutase solution followed by centrifugation at 400 rpm for 5 minutes. The supernatant was removed and the cells were counted and re-suspended at a density of 1-2 xlO ⁶ cells/mL in the staining buffer (1% BSA in phosphate buffer saline, 0.09% sodium azide).

[0202] 50,000-200,000 cells were placed into each well of a 96 well conical bottom plate in a volume of lOOul. The respective protein samples were prepared at 2X the maximum concentration. 12 serial dilutions ranging from 100 nM-0.0006 nM were prepared by aliquoting 3X dilutions in 1% BSA in phosphate buffer saline, 0.09% sodium azide buffer. IOOUL of each of the diluted protein samples were combined with the cells and incubated at 4°C for 30 minutes. The cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. A working solution of 2 μg/mL Biotinylated protein was prepared according to the manufacturer's recommendation. IOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded.

[0203] A 1 :500 dilution of Strep-avidin conjugated with Allophycocyanine was prepared according to the manufacturer's recommendation. lOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. The cells were fixed by adding lOOul of 4% paraformaldehyde and incubated at room temperature for 10 minutes.

[0204] The cells were centrifuged at 400 rpm for 5 minutes, re-suspended in 200uL of cell staining buffer (1% BSA in phosphate buffer saline, 0.09% sodium azide). Data were acquired on the Attune Acoustic Focusing Cytometer (Applied Biosystems, Foster City, CA) (FIG. 5A) and Mean Fluorescent Intensity (MFI) values were plotted against concentration for each sample (FIG. 5B). Best fit binding curves and IC50 values were generated with four-parameter logistic nonlinear regression using GraphPad Prism version 6 for Windows (GraphPad Software, La Jolla, CA) and binding assessed on an Attune acoustic focusing cytometer (Applied Biosystems) (Table 4.1).

TABLE 4.1

[0205] CPPC (SEQ ID NO: 7) motifs added to the C-terminus do not impact binding of IAB2C to PSMA expressed on PC3-PSMA cells. PC3-PSMA cells were cultured in Dulbecco's MEM and harvested by washing with sterile Dulbecco's phosphate buffer saline (without Calcium and Magnesium). The cells were detached with Accutase solution followed by centrifugation at 400 rpm for 5 minutes. The supernatant was removed and the cells were counted and re-suspended at a density of 1-2 xlO ⁶ cells/mL in the staining buffer (1% BSA in phosphate buffer saline, 0.09% sodium azide).

[0206] 50,000-200,000 cells were placed into each well of a 96 well conical bottom plate in a volume of lOOul. The respective protein samples were prepared at 2X the maximum concentration. 12 serial dilutions ranging from 100 nM-0.0006 nM were prepared by aliquoting 3X dilutions in 1% BSA in phosphate buffer saline, 0.09% sodium azide buffer. IOOUL of each of the diluted protein samples were combined with the cells and incubated at 4°C for 30 minutes. The cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. A working solution of 2 μg/mL Biotinylated protein was prepared according to the manufacturer's recommendation. IOOuL of this solution was added to the cells and the plate

o

incubated at 4 C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded.

[0207] A 1 :500 dilution of Strep-avidin conjugated with Allophycocyanine was prepared according to the manufacturer's recommendation. lOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. The cells were fixed by adding lOOul of 4% paraformaldehyde and incubated at room temperature for 10 minutes.

[0208] The cells were centrifuged at 400 rpm for 5 minutes, re-suspended in 200uL of cell staining buffer (1 % BSA in phosphate buffer saline, 0.09% sodium azide). Data were acquired on the Attune Acoustic Focusing Cytometer (Applied Biosys terns, Foster City, CA) (FIG. 7A) and Mean Fluorescent Intensity (MFI) values were plotted against concentration for each sample (FIG. 7B). Best fit binding curves and IC50 values were generated with four-parameter logistic nonlinear regression using GraphPad Prism version 6 for Windows (GraphPad Software, La Jolla, CA) and binding assessed on an Attune acoustic focusing cytometer (Applied Biosystems) (Table 4.2).

TABLE 4.2

[0209] CPPC (SEQ ID NO: 7) motifs added to the C-terminus does not impact binding of IAB22C to CD8 expressed on HPB-ALL cells. HPB-ALL cells were cultured in RPMI medium and harvested by centrifugation at 400 rpm for 5 minutes. The supernatant was removed and the cells were counted and re-suspended at a density of 1-2

6

xlO cells/mL in the staining buffer (1 % BSA in phosphate buffer saline, 0.09% sodium azide).

[0210] 50,000-200,000 cells were placed into each well of a 96 well conical bottom plate in a volume of lOOul. The respective protein samples were prepared at 2X the maximum concentration. 12 serial dilutions ranging from 100 nM-0.0006 nM were prepared by aliquoting 3X dilutions in 1% BSA in phosphate buffer saline, 0.09% sodium azide buffer. IOOUL of each of the diluted protein samples were combined with the cells and incubated at 4°C for 30 minutes. The cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. A working solution of 2 μg/mL Biotinylated protein was prepared according to the manufacturer's recommendation. IOOUL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded.

[0211] A 1 :500 dilution of Strep-avidin conjugated with Allophycocyanine was prepared according to the manufacturer's recommendation. lOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. The cells were fixed by adding lOOul of 4% paraformaldehyde and incubated at room temperature for 10 minutes.

[0212] The cells were centrifuged at 400 rpm for 5 minutes, re-suspended in 200uL of cell staining buffer (1 % BSA in phosphate buffer saline, 0.09% sodium azide). Data were acquired on the Attune Acoustic Focusing Cytometer (Applied Biosys terns, Foster City, CA) (FIG. 9A) and Mean Fluorescent Intensity (MFI) values were plotted against concentration for each sample (FIG. 9B). Best fit binding curves and IC50 values were generated with four-parameter logistic nonlinear regression using GraphPad Prism version 6 for Windows (GraphPad Software, La Jolla, CA). and binding assessed on an Attune acoustic focusing cytometer (Applied Biosystems) (Table 4.3).

TABLE 4.3

[0213] CPPC (SEQ ID NO: 7) motifs added to the C-terminus do not impact binding of IAB8C to Her2/neu expressed on NCI-N87 cells. NCI-N87 cells were cultured in Dulbecco's MEM and harvested by washing with sterile Dulbecco's phosphate buffer saline (without Calcium and Magnesium). The cells were detached with Accutase solution followed by centrifugation at 400 rpm for 5 minutes. The supernatant was removed and the cells were counted and re-suspended at a density of 1-2 xlO ⁶ cells/mL in the staining buffer (1% BSA in phosphate buffer saline, 0.09% sodium azide). [0214] 50,000-200,000 cells were placed into each well of a 96 well conical bottom plate in a volume of lOOul. The respective protein samples were prepared at 2X the maximum concentration. 12 serial dilutions ranging from 100 nM-0.0006 nM were prepared by aliquoting 3X dilutions in 1% BSA in phosphate buffer saline, 0.09% sodium azide buffer. IOOUL of each of the diluted protein samples were combined with the cells and incubated at 4°C for 30 minutes. The cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. A working solution of 2 μg/mL Biotinylated protein was prepared according to the manufacturer's recommendation. IOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded.

[0215] A 1 :500 dilution of Strep-avidin conjugated with Allophycocyanine was prepared according to the manufacturer's recommendation. lOOuL of this solution was added to the cells and the plate incubated at 4°C for 30 minutes. Cells were centrifuged at 400 rpm for 5 minutes and the supernatant discarded. The cells were fixed by adding lOOul of 4% paraformaldehyde and incubated at room temperature for 10 minutes.

[0216] The cells were centrifuged at 400 rpm for 5 minutes, re-suspended in 200uL of cell staining buffer (1 % BSA in phosphate buffer saline, 0.09% sodium azide). Data were acquired on the Attune Acoustic Focusing Cytometer (Applied Biosys terns, Foster City, CA) (FIG. 11 A) and Mean Fluorescent Intensity (MFI) values were plotted against concentration for each sample (FIG. 11B). Best fit binding curves and IC50 values were generated with four-parameter logistic nonlinear regression using GraphPad Prism version 6 for Windows (GraphPad Software, La Jolla, CA) and binding assessed on an Attune acoustic focusing cytometer (Applied Biosystems) (Table 4.4).

EXAMPLE 5

BISPECIFIC BC-PSMA X CD3 CYS-DIABODIES BIND TO CD3 ON T CELLS AND PSMA ON TUMOR CELLS TO MEDIATE TARGET SPECIFIC CYTOTOXICITY.

[0217] The anti-tumor activity of the anti-CD3 x anti-PSMA bispecific Cys- diabodies was tested in T cell mediated cytotoxic assays using PC3-PSMA transfected cells. Freshly prepared human PBMCs or T cells isolated using MACs beads were incubated in 96 well plates together with PC3-PSMA expressing tumor cells in the presence or absence of the indicated concentration of cys-diabody. After incubation for 48 hours to allow time for killing, the metabolic indicator, WST, was added to each well. Incubation was continued for approximately 3 hours at 37°C. The absorbance at 450 nM in each well was determined using a plate reader. The result shown in FIG. 12C demonstrate that all anti-CD3 x anti-PSMA bispecific Cys-diabodies showed potent and specific killing of PC3-PSMA(+ve) cells at all doses tested when incubated with human T cells in vitro. However, incubation of the bispecific Cys-diabody with the target PC3-PSMA cells in the absence of T cells showed no cytotoxic activity. In addition, Incubation of PC3-PSMA cells in the presence of T cells without adding the bispecific Cys-Db had no activity. These results show bispecific diabodies with C terminal extension sequences can bring 2 different cell types in close contact to mediate killing of antigen expressing target cells. EXAMPLE 6

INTACT MASS SPECTROMETRY ANALYSIS CONFIRMS THAT INCREASING THE NUMBER OF DISULFIDE BONDS REDUCES THE LEVELS OF SCFV

[0218] The intact mass analyses were performed using LC-MS at the City of Hope Core Facility. Expressed Cys-Diabody proteins were desalted and separated using Waters nanoAcquity UPLC equipped with a C4 nanotile column (150μπι ID x 50mm, Waters) operated at 3μ1/ηιιη, with 0.1% formic acid in water and 0.1% formic acid in acetonitrile as mobile phases. The HPLC was coupled to Waters Synapt G2 HDMS fitted with a Trizaic nanoESI source. The samples were analyzed for intact mass and the amount of the half molecule by LC/MS. Representative deconvoluted mass spectra are shown in FIGs. 14A, 14B, 15A, 15B, 15C, 16A, 16B, 16C, 17A, and 17B.

[0219] The IAblC-1 and IAB20C diabodies that are linked by a single disulfide bond show high amounts of scFv or its Glutathione adduct when analyzed by mass spectrometry (FIGs. 14A and 14B). This result is confirmed when proteins are resolved on a non-reducing SDS-PAGE gel (FIGs. 14C and 14D). The IAB2C-3 and IAB22C-3 diabodies that are linked by three disulfides show only trace amounts of scFv (FIGs 15A, 15B, 15C, 16A, 16B, and 16C). Analysis of bC-5T4 x CD3 bispecific Cys diabody shows correct assembly of the bispecifc diabody and undetectable levels of scFv (FIG. 17A). Efficient assembly of the bispecific Cys diabody with a 1 : 1 ratio of both chains in which only one molecule of expected molecular weight is produced, which is broken down into 2 scFV arms corresponding to the molecular mass of 5T4 and CD3 scFv's respectively (FIG. 17B).

EXAMPLE 7

SCFV FORMATION AFTER SITE-SPECIFIC CONJUGATION OF SINGLE

AND MULTI-IAB8C CYS DIABODY PROTEINS

[0220] IAB8C Cys-diabody proteins were gently reduced using limiting TCEP and free thiol handles were quantified using the Ellman's assay, to yield approx. 2 free thiols. The resulting products were reacted with maleimido-Df chelate reagent (B-772, Macrocyclics, Dallas, TX) or Maleimido-PEGlOk (CreativePEGworks), purified and the amount of scFv was assessed by densitometry using non-reducing SDS-PAGE. The results are summarized in table 8.1 and FIG. 18. In FIG. 18, Molecular weight markers are shown in lane 1. Bottom arrow: scFv; middle arrow: intact Cys-Db; top arrow: major PEGylated product with 2 equivalents of PEG 10k. In summary, only small amounts of scFv are detectable after reduction and conjugation of Deferoxamine (Df) to cys residues in IAB8C-4 compared to conjugation on a single Cys in IAB8C-1 (FIG. 18 and Table 7.1).

TABLE 7.1

EXAMPLE 8

IN VIVO EVALULATION OF SINGLE AND MULTI-CYS IAB8C DIABODIES FOLLOWING CONJUGATION OF DF TO CYS AND PEGYLATION ON LYSINE

[0221] The 10 and 20 kDa PEGylated Cys-Diabodies IAB8C-1 and IAB8C-4 were generated by conjugating to cys residues. Respective proteins were reduced with TCEP, reacted with maleimido-PEG and the resulting products purified by SE HPLC from the excess PEG and non-pegylated Cys-Diabody using Acquity BEH 200 column (4.6 mm x 150 mm, Waters). The purified constructs were concentrated and buffer exchanged into borate buffer pH8.5. Deferoxamine (Df) was subsequently conjugated to lysine residues (isothiocyanate-Df, Macrocyclics). All conjugated diabodies were formulated in Hepes saline buffer pH7.0. The non-pegylated Cys-diabody, ⁸⁹ Zr-Df-IAB8C-1 was conjugated to cysteine residues using Maleimido-Df obtained from Macrocyclics. Table 8.1 summarizes this study design.

TABLE 8.1

[0222] The in vivo preclinical evaluation of Df-conjugated Cys-Db variants were conducted using female NOD SCID mice bearing human MCF7/HER2 breast cancer xenografts. To establish xenografts, mice were primed with 17P-estradiol in a biodegradable carrier-binder (1.7 mg estradiol/pellet) introduced subcutaneously (s.c). After 6 days, 10 million MCF7/HER2 cells (mixed with 1 : 1 matrigel) in 300 xL volume were implanted subcutaneously into the right flank. Tumors were allowed to grow for three weeks before being imaged. For PET imaging, Cys-Db variants were conjugated to desferoxamine (Df) and radiolabeled with the positron emitting radionuclide, Zirconium-89 ( ⁸⁹ Zr). Mice were divided into four groups of 3 mice each and - 10 μg of ⁸⁹ Zr-Df-IAB8C-l , ⁸⁹ Zr-Df-IAB8C-l- lOkPEG, ⁸⁹ Zr-Df-IAB8C-4-10kPEG or ⁸⁹ Zr-Df-IAB8C-l-20kPEG were administered intravenously. Mice were imaged at 4h, 24h and 48h, by PET for 10 minutes followed by a 2 minute CT scan for anatomical reference (FIGs. 19A, 19B, and 19C). All mice were sacrificed after the last scan at 48 hours and tumor, blood and organs of interest were harvested, weighted and counted in a gamma counter to determine the injected dose per gram (%ID/g) (FIG. 20 and Table 8.2). Blood samples were also collected throughout the imaging study and uptakes were plotted against time to determine the radioactive PK of the Cys-Db variants (FIG. 21).

Blood 0.04(0.01) 1.61(0.23) 8.37(2.46) 9.40(1.13)

Liver 1.27(0.13) 4.19(0.84) 5.70(0.55) 4.83(0.48)

Kidneys 71.20(2.74) 66.99(12.55) 9.52(0.37) 3.82(0.32)

Spleen 0.78(0.12) 2.26(0.45) 5.70(1.25) 3.45(0.35)

Lungs 0.23(0.01) 1.33(0.32) 3.78(0.95) 2.84(0.42)

Muscle 0.15(0.04) 0.51(0.10) 1.10(0.35) 1.02(0.14)

Bone 0.61(0.09) 2.48(0.39) 3.34(0.80) 7.41(1.95)

Tumor 1.37(0.07) 7.63(1.65) 12.31(3.16) 10.30(1.65)

Carcass 0.29(0.04) 1.16(0.16) 1.58(0.02) 2.04(0.11)

[0223] Results show that ⁸⁹ Zr-Df-IAB8C-4-10kPEG10 and ⁸⁹ Zr-Df-IAB8C-4- lOkPEGlO show higher tumor uptake. ⁸⁹ Zr-Df-IAB8C-4-10kPEG10 and ⁸⁹ Zr-Df-IAB8C-4- lOkPEGlO are not cleared primarily through the kidney due to the larger overall size of the proteins. Clearance of ⁸⁹ Zr-Df-IAB8C-l-10kPEG10 via the kidneys suggests that a diabody with a single cys bond dissociates into scFvs in vivo allowing for renal clearance similar to that observed for ⁸⁹ Zr-Df-IAB8C-l. ⁸⁹ Zr-Df-IAB8C-4- 10kPEG10 and ⁸⁹ Zr-Df-IAB8C-4- lOkPEGlO show longer circulating half-lives as expected from PEGylated proteins. ⁸⁹ Zr-Df- IAB8C-l-10kPEG10 has an intermediate blood clearance. ⁸⁹ Zr-Df-IAB8C-l clears very rapidly from the blood confirming results with other diabodies containing a single disulfide bond. EXAMPLE 9

[0224] A subject with a PSCA related disorder is identified. A diabody IAB1C (IABlC-1, IABlC-2 and/or in the alternative IABlC-3) is used to deliver a cytotoxic payload to a PSCA expressing cell to kill the PSCA expressing cell. The subject's health improves with the removal of at least some of the PSCA expressing cells.

EXAMPLE 10

[0225] A subject with a PSMA related disorder is identified. A diabody IAB2C (IAB2C-1, IAB2C-2 and/or in the alternative IAB2C-3) is used to deliver a cytotoxic payload to a PSMA expressing cell to kill the PSMA expressing cell. The subject's health improves with the removal of at least some of the PSMA expressing cells.

EXAMPLE 11

[0226] A subject with a CD 8 related disorder is identified. A diabody IAB22C (IAB22C-1, IAB22C-2 and/or in the alternative IAB22C-3) is used to deliver a cytotoxic payload to a CD8 expressing cell to kill the CD8 expressing cell. The subject's health improves with the removal of at least some of the CD8 expressing cells.

EXAMPLE 12

[0227] A subject with a Her2/neu related disorder is identified. A diabody IAB8C (IAB8C-1, IAB8C-2 and/or in the alternative IAB8C-3) is used to deliver a cytotoxic payload to a Her2/neu expressing cell to kill the Her2/neu expressing cell. The subject's health improves with the removal of at least some of the Her2/neu expressing cells.

EXAMPLE 13

[0228] A subject with a PSMAxCD3 related disorder is identified. A diabody bC-PSMAxCD3-l bC-CD3xPSMA-l or bC-PSMAxCD3-3bC-CD3xPSMA-3 is used to deliver a cytotoxic payload to a PSMAxCD3 expressing cell to kill the PSMAxCD3 expressing cell. The subject's health improves with the removal of at least some of the PSMAxCD3 expressing cells. [0229] In this application, the use of the singular can include the plural unless specifically stated otherwise or unless, as will be understood by one of skill in the art in light of the present disclosure, the singular is the only functional embodiment. Thus, for example, "a" can mean more than one, and "one embodiment" can mean that the description applies to multiple embodiments.

Incorporation By Reference

[0230] All references cited herein, including patents, patent applications, papers, text books, and the like, and the references cited therein, to the extent that they are not already, are hereby incorporated by reference in their entirety. In the event that one or more of the incorporated literature and similar materials differs from or contradicts this application; including but not limited to defined terms, term usage, described techniques, or the like, this application controls.

Equivalents

[0231] The foregoing description and Examples detail certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing may appear in text, the invention may be practiced in many ways and the invention should be construed in accordance with the appended claims and any equivalents thereof.