Patent Publication Number: US-2021188945-A1

Title: Mesothelin-targeted trail trimer

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application No. 62/500,377, filed May 2, 2017, and U.S. provisional application No. 62/527,598, filed Jun. 30, 2017, each of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure provides constructs that comprise (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer comprising three consecutive extracellular TRAIL domains fused together in a head-to-tail configuration; (b) an epitope binding agent, and (c) optionally one or more additional components, wherein the epitope binding agent competitively inhibits binding of P4-TR3 or HN1-TR3 to full-length, cell surface human mesothelin. Constructs of the present disclosure induce apoptosis in cells expressing full-length, human mesothelin and a death receptor (DR4 or DR5) on the cell&#39;s surface. 
     REFERENCE TO SEQUENCE LISTING 
     This application contains a Sequence Listing that has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. The ASCII copy, created on May 1, 2018, is named 594973_SequenceListing_ST25.txt, and is 56 KB in size. 
     BACKGROUND OF THE INVENTION 
     Various forms of TNF-related apoptosis-inducing ligand (fusion protein format, in which the 3 extracellular domains of TRAIL are covalently linked. These fusion proteins have been successfully tethered to antibodies or antibody fragments to achieve specific targeting with the aim to enrich the therapeutic protein at the tumor site. For example, Tatzel et al. ( Scientific Reports  2016, 6: 22661) described a mesothelin-targeted TR3 variant referred to as SS-TR3. However, it has been reported that cell death proceeded exclusively via a bystander mechanism and protected the mesothelin-positive targets from apoptosis rather than leading to their elimination. As such, there remains a need in the art for effective TRAIL-based therapies. 
     SUMMARY OF THE INVENTION 
     In an aspect, the present disclosure encompasses a construct comprising (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer comprising three extracellular TRAIL domains fused together in a head-to-tail configuration that substantially retains the killing capacity of TRAIL; (b) an epitope binding agent, wherein the epitope binding agent competitively inhibits binding of P4 or HN1 to cell surface human mesothelin; and (c) optionally a spacer. The epitope binding agent is an antibody that has a heavy chain variable region comprising SEQ ID NO: 13, SEQ ID NO: 14, and/or SEQ ID NO: 15; and/or a light chain variable region comprising SEQ ID NO: 10, SEQ ID NO: 11, and/or SEQ ID NO: 12; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain; and wherein the first peptide is attached to the second peptide by an amino acid linker, and the second peptide is attached to the third peptide by an amino acid linker. 
     In another aspect, the present disclosure encompasses a construct comprising (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer comprising three extracellular TRAIL domains fused together in a head-to-tail configuration that substantially retains the killing capacity of TRAIL; (b) an epitope binding agent, wherein the epitope binding agent competitively inhibits binding of P4 or HN1 to cell surface human mesothelin; and (c) optionally a spacer. The epitope binding agent is an antibody that a heavy chain variable region comprising SEQ ID NO: 20, SEQ ID NO: 21, and/or SEQ ID NO: 22; and/or a light chain variable region comprising SEQ ID NO: 18, the amino acid sequence KAS, and/or SEQ ID NO: 19; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain; and wherein the first peptide is attached to the second peptide by an amino acid linker, and the second peptide is attached to the third peptide by an amino acid linker. 
     Other aspects and iterations of the invention are described more thoroughly below. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The application file contains at least one photograph executed in color. Copies of this patent application publication with color photographs will be provided by the Office upon request and payment of the necessary fee. 
         FIG. 1  shows the amino acid sequence of SEQ ID NO: 1, which is human TRAIL. The light grey shading identifies TRAIL 108-281 . The combination of the dark grey shading and the light grey shading identifies TRAIL 91-281 . 
         FIG. 2  shows the amino acid sequence of SEQ ID NO: 2, which is TR3. The TRAIL domains of TR3 are TRAIL 91-281 , TRAIL 108-281 , and TRAIL 108-281 . The dark grey shading identifies TRAIL 91-281 . The light grey shading identifies TRAIL 108-281 . The N-terminal seven amino acids are not critical for the killing capacity of the TRAIL trimer. In other embodiments of this disclosure, these two amino acids may be substituted with any other natural or non-natural amino acid, or deleted entirely. The two amino acids at the end of each TRAIL domain are also not critical. In other embodiments of this disclosure, these two amino acids may be substituted with any other natural or non-natural amino acid, or deleted entirely. 
         FIG. 3  shows a schematic representation of the TRAIL forms used in this study including a commercially available TRAIL (rTRAIL, aa 114-281) and TR3. A first TRAIL domain (domain I, aa 91-281) has been joined with two shorter TRAIL domain (domain I′, aa 108-281) to result in TR3. The striped boxes represent the native TRAIL sequence used to connect the subunits where the sequence length is slightly smaller in domains I′ (aa 108-113) compared to domain I (aa 91-113). 
         FIG. 4  shows a restriction map of plasmid pTR3. 
         FIG. 5  shows the confirmation of the single chain character of the fusion to the TR3 drug platform in comparison to the conventional rTRAIL configuration. The single chain character of the fusion proteins are verified by Western blot analysis. Under reducing conditions, commercially available recombinant TRAIL (rTRAIL, aa 114-281) exhibits a molecular weight of 18 kDa and TR3 has a molecular weight of approximately 61 kDa, consistent with the calculated size. Insertion of single chain antibody fragments HN1, P4 and SS into TR3 increases the molecular weight of each targeted therapeutic as expected. 
         FIG. 6  shows that cells overexpressing mesothelin tether all scFv-containing TR3 variants to cell surface. Mature human mesothelin is inserted into the membrane of Jurkat cells via a glycosylphosphatidyl (GPI) anchor. Anti-mesothelin immunostaining confirms expression of human mesothelin on Jurkat-Meso cells using flow cytometry. Jurkat-Meso cells are treated with SS-TR3, P4-TR3, or HN1-TR3. Anti-TRAIL immunostaining confirms tethering of SS-TR3, P4-TR3, and HN1-TR3 to human mesothelin on Jurkat-Meso cells using flow cytometry. 
         FIG. 7A-B  shows that the TR3 variants SS-TR3, P4-TR3 and HN1-TR3 induce apoptosis in a mesothelin-expressing cancer model. Mesothelin-deficient Jurkat wild-type cells ( FIG. 7A ) and mesothelin-expressing Jurkat-Meso cells ( FIG. 7B ) are treated in vitro with increasing equimolar concentrations of TR3 (red) and the targeted variants SS-TR3 (green), P4-TR3 (blue) and HN1-TR3 (black). In the absence of mesothelin expression, all drugs are equally potent in cell viability assays. When mesothelin is present on the surface of the cancer cells, SS-TR3 is the most potent reagent, followed by P4-TR3 and HN1-TR3 (similar activity profiles), and TR3 is the least effective at inducing apoptosis. 
         FIG. 8  shows that TR3 drug platforms engage in extrinsic death pathway via death receptor binding. Jurkat wild-type (WT) cells are treated with a constant amount of TR3, and the targeted variants SS-TR3, P4-TR3, and HN1-TR3 (70% specific cell death) in the presence of anti-TRAIL mAb, a blocker of death receptor engagement. Cells treated with DMSO are used as a control. 
         FIG. 9  shows that TR3 drug platforms engage in caspase-dependent apoptosis. Jurkat wild-type (WT) cells are treated with a constant amount of TR3, and the targeted variants SS-TR3, P4-TR3, and HN1-TR3 (70% specific cell death) in the presence of Z-VAD-FMK, a pan-caspase inhibitor to block the extrinsic death pathway. Cells treated with DMSO are used as a control. 
         FIG. 10A-G  shows the phenotypic characterization that reveals the differential cell death mechanisms between SS-TR3 and the humanized variants P4-TR3 and HN1-TR3. A mesothelin-expressing Jurkat-Meso cell pool (˜5% mesothelin-positive cells) is treated with vehicle ( FIG. 10C ), TR3 ( FIG. 10E ), SS-TR3 ( FIG. 10B ), HN1-TR3 ( FIG. 10D ) and P4-TR3 ( FIG. 10F ) for several days before the mesothelin-expression cell ratio is determined by FACS analysis. SS-TR3 treatment leads to a significant accumulation of the cancer cells whereas P4-TR3 and HN1-TR3 treatment eliminates their cancer targets directly, while treatment with non-targeted TR3 alone does not change this ratio as expected. Representative schematics of TR3 variants are shown beside their corresponding panels. As a negative control, wild type Jurkat cells show absence of mesothelin expression ( FIG. 10A ). In comparison, the amount of mesothelin-positive cells is statistically higher in SS-TR3-treated Jurkat-Meso cells compared to cells treated with P4-TR3 and HN1-TR3 ( FIG. 10G ). 
         FIG. 11A-B  shows treatment of adherent human ovarian cancer cells with TR3, P4-TR3, HN1-TR3 and SS-TR3. Endogenous cell-surface mesothelin expression in the ovarian cancer cell line OVCAR3 is confirmed by immunostaining with an anti-mesothelin antibody, detected by flow cytometry ( FIG. 11A ). OVCAR3 cells are treated with increasing concentrations of TR3, P4-TR3, HN1-TR3 or SS-TR3. After 24 hours, cell viability of drug-treated cells is determined using the CellTiter-Glo kit (Promega) ( FIG. 11B ). 
         FIG. 12A-B  shows treatment of adherent human pancreatic cancer cells with TR3, P4-TR3, HN1-TR3 and SS-TR3. Endogenous cell-surface mesothelin expression in the pancreatic cancer cell line BxPC-3 is confirmed by immunostaining with an anti-mesothelin antibody, detected by flow cytometry ( FIG. 12A ). BxPC-3 cells are treated with increasing concentrations of TR3, P4-TR3, HN1-TR3 or SS-TR3. After 24 hours, cell viability of drug-treated cells is determined using the CellTiter-Glo kit (Promega) ( FIG. 12B ). 
         FIG. 13A-B  shows treatment of adherent human pancreatic cancer cells AsPC-1 with TR3, P4-TR3, HN1-TR3 and SS-TR3. Endogenous cell-surface mesothelin expression in the pancreatic cancer cell line AsPC-1 is confirmed by immunostaining with an anti-mesothelin antibody, detected by flow cytometry ( FIG. 13A ). AsPC-1 cells are treated with increasing concentrations of TR-3, P4-TR3, HN1-TR3 or SS-TR3. After 24 hours, cell viability of drug-treated cells is determined using the CellTiter-Glo kit (Promega) ( FIG. 13B ). 
         FIG. 14  shows a coculture of mesothelin-positive AsPC-1 with Jurkat bystander cells in the presence of non-targeted and targeted-TR3. TRAIL resistant, mesothelin-positive AsPC-1 pancreatic cancer cells are decorated with increasing concentrations of TR3, P4-TR3 and HN1-TR3 and SS-TR3 by incubating the cells with the TR3 constructs for 2 hours. TR3 constructs are removed by washing and decorated AsPC-1 cells are cocultured with WT Jurkat bystander cells for 24 hours. Cells are harvested and analyzed for viability. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides constructs that preferentially induce apoptosis in transformed and tumor cells. Constructs of the present disclosure comprise (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer comprising three consecutive extracellular TRAIL domains fused together in a head-to-tail configuration, (b) an epitope binding agent, and (c) optionally one or more additional components, wherein the epitope binding agent competitively inhibits binding of P4-TR3 or HN1-TR3 to cell surface human mesothelin. Advantageously, epitope binding agents disclosed herein target a TRAIL trimer to mesothelin-positive cells in a manner that results in death of the cell to which the construct is bound (i.e., a cis-acting phenotype), as well as bystander cell death (i.e., a trans-acting phenotype). 
     I. Constructs Comprising a Trail Trimer and an Epitope Binding Agent 
     The present disclosure provides a construct comprising a TNF-related apoptosis-inducing ligand (TRAIL) trimer and an epitope binding agent that competitively inhibits binding of scFv-P4 (SEQ ID NO: 6) or scFv-HN1 (SEQ ID NO: 7) to cell surface human mesothelin. The epitope binding agent is attached to the TRAIL trimer in manner that preserves the ability of the epitope binding agent to bind its cognate ligand and the killing capacity of the TRAIL trimer. In one embodiment, the epitope binding agent can be directly or indirectly attached to the C-terminus of the TRAIL trimer. In another embodiment, the epitope binding agent can be directly or indirectly attached to the N-terminus of the TRAIL trimer. 
     (a) TRAIL Trimer 
     The term “TRAIL trimer” refers to a polypeptide comprising three extracellular TRAIL domains arranged in a head-to-tail configuration that substantially retains the killing capacity of TRAIL. 
     Endogenous human TRAIL is initially synthesized as a Type-II transmembrane protein with its carboxyl (C)-terminus facing the extracellular milieu. It is subsequently cleaved at amino acid position V114 and is then released from the cell surface. The minimal human TRAIL domain, however, is amino acids 122-281 of human TRAIL. See, for example, Siegemund et al.  MABS  2016, 8(5): 879-891, which is hereby incorporated by reference in its entirety. As used herein, the term “extracellular TRAIL domain” refers to a polypeptide comprising amino acids 122-281 of human TRAIL (i.e., TRAIL 122-281 ), or a polypeptide comprising an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281  that substantially retains the killing capacity of TRAIL 122-281 . The amino acid sequence of human TRAIL is SEQ ID NO: 1. A skilled artisan will be able to determine if an amino acid sequence has at least 80% sequence identity using methods well known in the art. 
     A TRAIL trimer of the present disclosure may be a homotrimer (i.e., each domain is the same) or a heterotrimer (i.e., at least two of the domains are unique). In some embodiments, each the extracellular TRAIL domain is independently selected from the group consisting of (a) TRAIL 114-281 , (b) TRAIL 113-281 , (c) TRAIL 112-281 , (d) TRAIL 111-281 , (e) TRAIL 110-281 , (f) TRAIL 109-281 , (g) TRAIL 108-281 , (h) TRAIL 107-281 , (i) TRAIL 106-281 , (j) TRAIL 105-281 , (k) TRAIL 104-281 , (l) TRAIL 103-281 , (m) TRAIL 102-281 , (n) TRAIL 101-281 , (o) TRAIL 100-281 , (p) TRAIL 99-281 , (q) TRAIL 98-281 , (r) TRAIL 97-281 , (s) TRAIL 96-281 , (t) TRAIL 95-281 , (u) TRAIL 94-281 , (v) TRAIL 93-281 , (w) TRAIL 92-281 , (x) TRAIL 91-281 , (y) TRAIL 115-281 , (z) TRAIL 116-281 , (aa) TRAIL 117-281 , (bb) TRAIL 118-281 , (cc) TRAIL 119-281 , (dd) TRAIL 120-281 , (ee) TRAIL 121-281 , (ff) TRAIL 122-281 , and (gg) an amino acid sequence that has at least 80% sequence identity to the peptide of (a) to (ff). In other embodiments, each the extracellular TRAIL domain is independently selected from the group consisting of (a) TRAIL 114-281 , (b) TRAIL 108-281 , (c) TRAIL 95-281 , (d) TRAIL 91-281 , (e) TRAIL 122-281 , or (f) an amino acid sequence that has at least 80% sequence identity to the peptide of (a) to (e). 
     The term “head-to-tail configuration” means that each extracellular TRAIL domain is arranged N-terminally to C-terminally. Stated another way, a TRAIL trimer comprises a first extracellular TRAIL domain, a second extracellular TRAIL domain, and a third extracellular TRAIL domain, wherein the C-terminus of the first extracellular TRAIL domain is attached to N-terminus of the second extracellular TRAIL domain, and the C-terminus of the second extracellular TRAIL domain is attached to N-terminus of the third extracellular TRAIL domain. Each extracellular TRAIL domain may be directly or indirectly attached to the next. The type of linkage (i.e., direct or indirect) may depend, in part, upon the size of the extracellular TRAIL domain, as there needs to enough flexibility between each extracellular TRAIL domain to allow the domains to interact with each other. 
     When indirectly attached, one or more amino acids (natural or non-natural) may be between each domain. For example, 1, 2, 3, 4, or 5 amino acids (natural or non-natural) may be between each domain. In another example, 6, 7, 8, 9, or 10 amino acids (natural or non-natural) may be between each domain. In another example, 10 or more amino acids (natural or non-natural) may be between each domain. In certain embodiments, an amino acid linker may encode one or tags or cleavage sites (see below) that indirectly link the first and second extracellular TRAIL domain and/or the second and third extracellular TRAIL domain. Alternatively, or in addition, other peptide and non-peptide linkers may also be used to link one or more domains. 
     The term “substantially retains the killing capacity of TRAIL”, as used herein, means a TRAIL trimer retains at least 80%, preferably at least 85%, more preferably at least 90%, even more preferably at least 95% of the killing capacity of TR3 (SEQ ID NO: 2) as assessed using a cell viability assay, for example as described in Su et al,  Oncotarget,  2016; 7(21):31534-31549, which is incorporated herein by reference. 
     Based on the disclosure above, a skilled artisan will appreciate that a TRAIL timer may also be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein each peptide comprises TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may also be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein each peptide comprises TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide, the second peptide and the third peptide each have an amino acid sequence comprising (a) TRAIL 91-281 , (b) an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , (c) TRAIL 114-281 , or (d) an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide comprises an amino acid sequence of TRAIL 91-281  or an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , the second peptide comprises TRAIL 114-281  or amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and third peptide comprises TRAIL 114-281  or an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may also be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , the second peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide comprises an amino acid sequence of TRAIL 91-281  or an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , the second peptide comprises TRAIL 108-281  or amino acid sequence that has at least 80% sequence identity to TRAIL 108-281 , and third peptide comprises TRAIL 108-281  or an amino acid sequence that has at least 80% sequence identity to TRAIL 108-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. In certain embodiments, the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain, and in each instance the peptides are attached by an amino acid linker that is 1 to 50 amino acids in length, 1 to 30 amino acids in length, or 1 to 5 amino acids in length 1 to 10 amino acids in length, or 1 to 5 amino acids in length. 
     In another embodiment, a TRAIL timer may be described as a fusion protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , the second peptide is TRAIL 109-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 108-281 , and the third peptide is TRAIL 108-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 108-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain; and wherein the fusion protein substantially retains the killing capacity of TRAIL. 
     In an exemplary embodiment, a TRAIL trimer is TR3 (SEQ ID NO: 2). In another exemplary embodiment, a TRAIL trimer is a protein that (a) has at least 80% sequence identity to SEQ ID NO: 2, and (b) substantially retains the killing capacity of TRAIL. In another exemplary embodiment, a TRAIL trimer is a protein that (a) has at least 85% sequence identity to SEQ ID NO: 2, and (b) substantially retains the killing capacity of TRAIL. In another exemplary embodiment, a TRAIL trimer is a protein that (a) has at least 90% sequence identity to SEQ ID NO: 2, and (b) substantially retains the killing capacity of TRAIL. In another exemplary embodiment, a TRAIL trimer is a protein that (a) has at least 95% sequence identity to SEQ ID NO: 2, and (b) substantially retains the killing capacity of TRAIL. 
     (b) Epitope Binding Agent 
     The term “epitope-binding agent,” as used herein, is used in the broadest sense and encompasses oligonucleic acids, polypeptides, and proteins that specifically bind to an antigen. The domain(s) of an epitope-binding agent that is involved in binding the antigen is referred to, herein, as a “variable region” or “variable domain”. Non-limiting examples of epitope-binding agents include antibodies, antibody mimetics, and aptamers. In some embodiments, an epitope-binding agent is an antibody. In other embodiments, an epitope-binding agent is an antibody mimetic. In other embodiments, an epitope-binding agent is an aptamer. 
     Epitope-binding agents disclosed herein can be described or specified in terms of the epitope(s) that they recognize or bind. The portion of a target polypeptide that specifically interacts with the variable domain of an epitope-binding agent is an “epitope.” The term “affinity” refers to a measure of the strength of the binding of an individual epitope with an epitope-binding agent&#39;s variable domain. Methods for determining affinity are known in the art. 
     Epitope binding agents of the present disclosure bind to cell surface human mesothelin with an affinity constant or affinity of interaction (KD) between about 0.1 pM to about 10 μM, preferably about 0.1 pM to about 1 μM, more preferably about 0.1 pM to about 100 nM. Human mesothelin can comprise any number of epitopes, depending on processing, conformational state, and location. Furthermore, it should be noted that an “epitope” on human mesothelin can be a linear epitope or a conformational epitope, and in both instances can include non-polypeptide elements, e.g., an epitope can include a carbohydrate or lipid side chain. As used herein, cell surface human mesothelin refers to a 40 kDa protein that is physiologically or recombinantly expressed and attached at the cell surface by a GPI anchor. The amino acid sequence of the 40 kDa protein, also referred to as membrane-bound, mature mesothelin, is provided in SEQ ID NO: 4. Non-limiting examples of suitable cell types include epithelial cells, mesothelial cells, and tumor cells. Non-limiting examples of suitable tumor cell types include mesothelioma cells, pancreatic tumor cells, ovarian tumor cells, stomach tumor cells, lung tumor cells and endometrial tumor cells. Additional non-limiting examples of tumor cells include tumor cells from a cancer selected from the group consisting of mesothelioma, papillary serous ovarian adenocarcinoma, clear cell ovarian carcinoma, mixed Mullerian ovarian carcinoma, endometroid mucinous ovarian carcinoma, pancreatic adenocarcinoma, ductal pancreatic adenocarcinoma, uterine serous carcinoma, lung adenocarcinoma, extrahepatic bile duct carcinoma, gastric adenocarcinoma, esophageal adenocarcinoma, colorectal adenocarcinoma and breast adenocarcinoma. Cell types that do not physiologically express mesothelin can also be used to recombinantly express human mesothelin. For example, the Examples detail recombinant expression of human mesothelin in Jurkat cells. Other cell line and cell types are also contemplated. In other embodiments, an epitope-binding agent of the present disclosure binds to an epitope on soluble mesothelin. As used herein, “soluble mesothelin” refers to fragment of mature mesothelin that results from cleavage of mesothelin from the cell&#39;s surface. Soluble mesothelin may be obtained from cell culture supernatant or soluble mesothelin in a body fluid sample, such as, for example, a blood, ascites, or serum sample. The epitope(s) to which epitope-binding agents of this disclosure bind may or may not be unique to cell surface human mesothelin. 
     An epitope binding agent of the present disclosure also competitively inhibits binding of the scFv-P4 (SEQ ID NO: 6) or the scFv-HN1 (SEQ ID NO: 7) to cell surface human mesothelin. As used herein, “scFv-P4” and “P4” are used interchangeably. Similarly, “scFv-HN1” and “HN1” are also used interchangeably. An epitope binding agent is said to competitively inhibit binding of scFv-P4 or scFv-HN1 to cell surface human mesothelin if the epitope binding agent binds to cell surface human mesothelin to the extent that it reduces binding of scFv-P4 or scFv-HN1 by at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%. Competitive inhibition can be determined by any method known in the art, including but not limited to any antibody-antigen binding assay, for example, radioimmunoassay (RIA), ELISA, Western blot, immunoprecipitation, and competitive inhibition assays. A non-limiting example of a suitable assay is also described in Garg et al,  BMC Cancer.  2014; 14:35. 
     An epitope-binding agent need not bind the exact same epitope as scFv-P4 to competitively inhibit binding of scFv-P4 to cell surface human mesothelin. Similarly, an epitope-binding agent need not bind the exact same epitope as scFv-HN1 to competitively inhibit binding of scFv-HN1 to cell surface human mesothelin. In some embodiments, an epitope-binding agent binds to the same epitope as scFv-P4 or to a cross-reactive epitope of scFv-P4. In other embodiments, an epitope-binding agent binds to the same epitope as scFv-HN1 or a cross-reactive epitope of scFv-HN1. A cross-reactive epitope generally contains many of the same complementary structural features as the inducing epitope, and in some cases, can actually fit better than the original. For example, certain antibodies have some degree of cross-reactivity, in that they bind related, but non-identical epitopes, e.g., epitopes with at least about 85%, at least about 90%, or at least about 95% identity (as calculated using methods known in the art) to a reference epitope. 
     In preferred embodiments, an epitope-binding agent is an antibody. The term “antibody,” as used herein, is used in the broadest sense and encompasses various antibody and antibody-like structures, including but not limited to full-length monoclonal, polyclonal, and multispecific (e.g., bispecific, trispecific, etc.) antibodies, as well as heavy chain antibodies and antibody fragments provided they exhibit the desired antigen-binding activity. The domain(s) of an antibody that is involved in binding an antigen is referred to as a “variable region” or “variable domain,” and is described in further detail below. A single variable domain may be sufficient to confer antigen-binding specificity. Preferably, but not necessarily, antibodies useful in the discovery are produced recombinantly. Antibodies may or may not be glycosylated, though glycosylated antibodies may be preferred. An “isolated” antibody is one which has been separated from a component of its natural environment. In some embodiments, an antibody is purified to greater than 95% or 99% purity as determined by methods known in the art. 
     In addition to antibodies described herein, it may be possible to design an antibody mimetic or an aptamer using methods known in the art that functions substantially the same as an antibody of the invention. An “antibody mimetic” refers to a polypeptide or a protein that can specifically bind to an antigen but is not structurally related to an antibody. Antibody mimetics have a mass of about 3 kDa to about 20 kDa. Non-limiting examples of antibody mimetics are affibody molecules, affilins, affimers, affitins, alphabodies, anticalins, avimers, knottins, DARPins, and monobodies. Aptamers interact with and bind to their targets through structural recognition, a process similar to that of an antigen-antibody reaction. Aptamers have a lower molecular weight than antibodies, typically about 8-25 kDa. 
     The terms “full length antibody” and “intact antibody” may be used interchangeably, and refer to an antibody having a structure substantially similar to a native antibody structure or having heavy chains that contain an Fc region as defined herein. The basic structural unit of a native antibody comprises a tetramer. Each tetramer is composed of two identical pairs of polypeptide chains, each pair having one “light” chain (about 25 kDa) and one “heavy” chain (about 50-70 kDa). Light chains are classified as gamma, mu, alpha, and lambda. Heavy chains are classified as gamma, mu, alpha, delta, or epsilon, and define the antibody&#39;s isotype as IgG, IgM, IgA, IgD and IgE, respectively. The amino-terminal portion of each light and heavy chain includes a variable region of about 100 to 110 or more amino acid sequences primarily responsible for antigen recognition (VL and VH, respectively). The carboxy-terminal portion of each chain defines a constant region primarily responsible for effector function. Within light and heavy chains, the variable and constant regions are joined by a “J” region of about 12 or more amino acid sequences, with the heavy chain also including a “D” region of about 10 more amino acid sequences. Intact antibodies are properly cross-linked via disulfide bonds, as is known in the art. 
     The variable domains of the heavy chain and light chain of an antibody generally have similar structures, with each domain comprising four conserved framework regions (FRs) and three hypervariable regions (HVRs). (See, e.g., Kindt et al.  Kuby Immunology,  6 th  ed., W.H. Freeman and Co., page 91 (2007).) A single VH or VL domain may be sufficient to confer antigen-binding specificity. Furthermore, antibodies that bind a particular antigen may be isolated using a VH or VL domain from an antibody that binds the antigen to screen a library of complementary VL or VH domains, respectively. See, e.g., Portolano et al.,  J. Immunol.  150:880-887 (1993); Clarkson et al.,  Nature  352:624-628 (1991). 
     “Framework region” or “FR” refers to variable domain residues other than hypervariable region (HVR) residues. The FR of a variable domain generally consists of four FR domains: FR1, FR2, FR3, and FR4. Accordingly, the HVR and FR sequences generally appear in the following sequence: FR1-HVR1-FR2-HVR2-FR3-HVR3-FR4. The FR domains of a heavy chain and a light chain may differ, as is known in the art. 
     The term “hypervariable region” or “HVR” as used herein refers to each of the regions of a variable domain which are hypervariable in sequence (also commonly referred to as “complementarity determining regions” or “CDR”) and/or form structurally defined loops (“hypervariable loops”) and/or contain the antigen-contacting residues (“antigen contacts”). Generally, antibodies comprise six HVRs: three in the VH (H1, H2, H3), and three in the VL (L1, L2, L3). As used herein, “an HVR derived from a variable region” refers to an HVR that has no more than two amino acid substitutions, as compared to the corresponding HVR from the original variable region. Exemplary HVRs herein include: (a) hypervariable loops occurring at amino acid residues 26-32 (L1), 50-52 (L2), 91-96 (L3), 26-32 (H1), 53-55 (H2), and 96-101 (H3) (Chothia and Lesk,  J. Mol. Biol.  196:901-917 (1987)); (b) CDRs occurring at amino acid residues 24-34 (L1), 50-56 (L2), 89-97 (L3), 31-35b (H1), 50-65 (H2), and 95-102 (H3) (Kabat et al.,  Sequences of Proteins of Immunological Interest,  5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)); (c) antigen contacts occurring at amino acid residues 27c-36 (L1), 46-55 (L2), 89-96 (L3), 30-35b (H1), 47-58 (H2), and 93-101 (H3) (MacCallum et al.  J. Mol. Biol.  262: 732-745 (1996)); and (d) combinations of (a), (b), and/or (c), as defined below for various antibodies of this disclosure. Unless otherwise indicated, HVR residues and other residues in the variable domain (e.g., FR residues) are numbered herein according to Kabat et al., supra. 
     The term “Fc region” herein is used to define a C-terminal region of an immunoglobulin heavy chain that contains at least a portion of the constant region. The term includes native sequence Fc regions and variant Fc regions. In one embodiment, a human IgG heavy chain Fc region extends from Cys226, or from Pro230, to the carboxyl-terminus of the heavy chain. However, the C-terminal lysine (Lys447) of the Fc region may or may not be present. Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, also called the EU index, as described in Kabat et al.,  Sequences of Proteins of Immunological Interest,  5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md., 1991. 
     A “variant Fc region” comprises an amino acid sequence that can differ from that of a native Fc region by virtue of one or more amino acid substitution(s) and/or by virtue of a modified glycosylation pattern, as compared to a native Fc region or to the Fc region of a parent polypeptide. In an example, a variant Fc region can have from about one to about ten amino acid substitutions, or from about one to about five amino acid substitutions in a native sequence Fc region or in the Fc region of the parent polypeptide. The variant Fc region herein may possess at least about 80% homology, at least about 90% homology, or at least about 95% homology with a native sequence Fc region and/or with an Fc region of a parent polypeptide. 
     An “antibody fragment” refers to a molecule other than an intact antibody that comprises a portion of an intact antibody that binds the antigen to which the intact antibody binds. Non-limiting examples of antibody fragments include but are not limited to Fv, Fab, Fab′, Fab′-SH, F(ab′) 2 ; single-chain forms of antibodies and higher order variants thereof; single-domain antibodies, and multispecific antibodies formed from antibody fragments. 
     Single-chain forms of antibodies, and their higher order forms, may include, but are not limited to, single-domain antibodies, single chain variant fragments (scFvs), divalent scFvs (di-scFvs), trivalent scFvs (tri-scFvs), tetravalent scFvs (tetra-scFvs), diabodies, and triabodies and tetrabodies. ScFv&#39;s are comprised of heavy and light chain variable regions connected by a linker. In most instances, but not all, the linker may be a peptide. A linker peptide is preferably from about 5 to 30 amino acids in length, or from about 10 to 25 amino acids in length. Typically, the linker allows for stabilization of the variable domains without interfering with the proper folding and creation of an active binding site. In preferred embodiments, a linker peptide is rich in glycine, as well as serine or threonine. ScFvs can be used to facilitate phage display or can be used for flow cytometry, immunohistochemistry, or as targeting domains. Methods of making and using scFvs are known in the art. ScFvs may also be conjugated to a human constant domain (e.g. a heavy constant domain is derived from an IgG domain, such as IgG1, IgG2, IgG3, or IgG4, or a heavy chain constant domain derived from IgA, IgM, or IgE). Diabodies, triabodies, and tetrabodies and higher order variants are typically created by varying the length of the linker peptide from zero to several amino acids. Alternatively, it is also well known in the art that multivalent binding antibody variants can be generated using self-assembling units linked to the variable domain. 
     A “single-domain antibody” refers to an antibody fragment consisting of a single, monomeric variable antibody domain. 
     Multispecific antibodies include bi-specific antibodies, tri-specific, or antibodies of four or more specificities. Multispecific antibodies may be created by combining the heavy and light chains of one antibody with the heavy and light chains of one or more other antibodies. These chains can be covalently linked. 
     “Monoclonal antibody” refers to an antibody that is derived from a single copy or clone, including e.g., any eukaryotic, prokaryotic, or phage clone. “Monoclonal antibody” is not limited to antibodies produced through hybridoma technology. Monoclonal antibodies can be produced using hybridoma techniques well known in the art, as well as recombinant technologies, phage display technologies, synthetic technologies or combinations of such technologies and other technologies readily known in the art. Furthermore, the monoclonal antibody may be labeled with a detectable label, immobilized on a solid phase and/or conjugated with a heterologous compound (e.g., an enzyme or toxin) according to methods known in the art. 
     A “heavy chain antibody” refers to an antibody that consists of two heavy chains. A heavy chain antibody may be an IgG-like antibody from camels, llamas, alpacas, sharks, etc., or an IgNAR from a cartiliaginous fish. 
     A “humanized antibody” refers to a non-human antibody that has been modified to reduce the risk of the non-human antibody eliciting an immune response in humans following administration but retains similar binding specificity and affinity as the starting non-human antibody. A humanized antibody binds to the same or similar epitope as the non-human antibody. The term “humanized antibody” includes an antibody that is composed partially or fully of amino acid sequences derived from a human antibody germline by altering the sequence of an antibody having non-human hypervariable regions (“HVR”). The simplest such alteration may consist simply of substituting the constant region of a human antibody for the murine constant region, thus resulting in a human/murine chimera which may have sufficiently low immunogenicity to be acceptable for pharmaceutical use. Preferably, the variable region of the antibody is also humanized by techniques that are by now well known in the art. For example, the framework regions of a variable region can be substituted by the corresponding human framework regions, while retaining one, several, or all six non-human HVRs. Some framework residues can be substituted with corresponding residues from a non-human VL domain or VH domain (e.g., the non-human antibody from which the HVR residues are derived), e.g., to restore or improve specificity or affinity of the humanized antibody. Substantially human framework regions have at least about 75% homology with a known human framework sequence (i.e. at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% sequence identity). HVRs may also be randomly mutated such that binding activity and affinity for the antigen is maintained or enhanced in the context of fully human germline framework regions or framework regions that are substantially human. As mentioned above, it is sufficient for use in the methods of this discovery to employ an antibody fragment. Further, as used herein, the term “humanized antibody” refers to an antibody comprising a substantially human framework region, at least one HVR from a nonhuman antibody, and in which any constant region present is substantially human. Substantially human constant regions have at least about 90% with a known human constant sequence (i.e. about 90%, about 95%, or about 99% sequence identity). Hence, all parts of a humanized antibody, except possibly the HVRs, are substantially identical to corresponding pairs of one or more germline human immunoglobulin sequences. 
     If desired, the design of humanized immunoglobulins may be carried out as follows, or using similar methods familiar to those with skill in the art (for example, see Almagro, et al.  Front. Biosci.  2008, 13(5):1619-33). A murine antibody variable region is aligned to the most similar human germline sequences (e.g. by using BLAST or similar algorithm). The CDR residues from the murine antibody sequence are grafted into the similar human “acceptor” germline. Subsequently, one or more positions near the CDRs or within the framework (e.g., Vernier positions) may be reverted to the original murine amino acid in order to achieve a humanized antibody with similar binding affinity to the original murine antibody. Typically, several versions of humanized antibodies with different reversion mutations are generated and empirically tested for activity. The humanized antibody variant with properties most similar to the parent murine antibody and the fewest murine framework reversions is selected as the final humanized antibody candidate. 
     In an exemplary embodiment, an epitope binding agent of the present disclosure is an antibody that (a) competitively inhibits binding of scFv-P4, and (b) comprises a VL that has one or more HVRs derived from SEQ ID NO: 8 or a VH that has one or more HVRs derived from SEQ ID NO: 9. The HVR derived from SEQ ID NO: 8 may be L1, L2, L3, or any combination thereof. In certain embodiments, the VL may comprise an L1 of SEQ ID NO: 10, an L2 of SEQ ID NO: 11, an L3 of SEQ ID NO: 12, or any combination thereof (e.g. antibodies 1-7 in Table A). The HVR derived from SEQ ID NO: 9 may be H1, H2, H3, or any combination thereof. In certain embodiments, the VH may comprise an H1 of SEQ ID NO: 13, an H2 of SEQ ID NO: 14, an H3 of SEQ ID NO: 15, or any combination thereof (e.g. antibodies 8-14 in Table A). The antibody comprising one or more HVRs derived from SEQ ID NO: 9 may further comprise a light chain variable region (VL) comprising one or more HVRs derived from SEQ ID NO: 8. The HVR may be L1, L2, L3, or any combination thereof. In a preferred embodiment, the VL may comprise an L1 of SEQ ID NO: 10, an L2 of SEQ ID NO: 11, an L3 of SEQ ID NO: 12, or any combination thereof (e.g. antibodies 15-63 in Table A). In various embodiments above, the antibody may be a humanized antibody, or the antibody may have a VL with 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% identity to SEQ ID NO: 8 and/or a VH with 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% identity to SEQ ID NO: 9. In each of the above embodiments, the antibody may optionally comprise one or more constant regions, or a portion of a constant region, that is substantially human (i.e. at least 90%, 95%, or 99% sequence identity with a known human framework sequence). In each of the above embodiments, the antibody may be multivalent (e.g., recognize a second target in addition to mesothelin.) The present disclosure also encompasses the corresponding nucleic acid sequences of SEQ ID NO: 8, 9, 10, 11, 12, 13, 14, and 15, which can readily be determined by one of skill in the art, and may be incorporated into a vector or other large DNA molecule, such as a chromosome, in order to express an antibody of the disclosure. 
     In another exemplary embodiment, an epitope binding agent of the present disclosure is an antibody that (a) competitively inhibits binding of scFv-HN1, and (b) comprises a VL that has one or more HVRs derived from SEQ ID NO: 16 or a VH that has one or more HVRs derived from SEQ ID NO: 17. The HVR derived from SEQ ID NO: 16 may be L1, L2, L3, or any combination thereof. In certain embodiments, the VL may comprise an L1 of SEQ ID NO: 18, an L2 of the amino acid sequence KAS, an L3 of SEQ ID NO: 19, or any combination thereof (e.g. antibodies 64-70 in Table A). The HVR derived from SEQ ID NO: 17 may be H1, H2, H3, or any combination thereof. In certain embodiments, the VH may comprise an H1 of SEQ ID NO: 20, an H2 of SEQ ID NO: 21, an H3 of SEQ ID NO: 22, or any combination thereof (e.g. antibodies 71-77 in Table A). The antibody comprising one or more HVRs derived from SEQ ID NO: 17 may further comprise a light chain variable region (VL) comprising one or more HVRs derived from SEQ ID NO: 16. The HVR may be L1, L2, L3, or any combination thereof. In a preferred embodiment, the VL may comprise an L1 of SEQ ID NO: 18, an L2 of the amino acid sequence KAS, an L3 of SEQ ID NO: 19, or any combination thereof (e.g. antibodies 78-126 in Table A). In various embodiments above, the antibody may be a humanized antibody, or the antibody may have a VL with 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100% identity to SEQ ID NO: 16 and/or a VH with 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100% identity to SEQ ID NO: 17. In each of the above embodiments, the epitope binding agent may optionally comprise one or more constant regions, or a portion of a constant region, that is substantially human (i.e. at least 90%, 95%, or 99% sequence identity with a known human framework sequence). In each of the above embodiments, the antibody may be multivalent (e.g., recognize a second target in addition to mesothelin.) The present disclosure also encompasses the corresponding nucleic acid sequences of SEQ ID NO: 16, 17, 18, 19, 20, 21, 22, and 23, which can readily be determined by one of skill in the art, and may be incorporated into a vector or other large DNA molecule, such as a chromosome, in order to express an antibody of the disclosure. 
     In another exemplary embodiment, an epitope binding agent of the present disclosure is the scFv-P4 (SEQ ID NO: 6). In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 80% sequence identity to SEQ ID NO: 6, and (b) competitively inhibits binding of scFv-P4. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 85% sequence identity to SEQ ID NO: 6, and (b) competitively inhibits binding of scFv-P4. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 90% sequence identity to SEQ ID NO: 6, and (b) competitively inhibits binding of scFv-P4. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 95% sequence identity to SEQ ID NO: 6, and (b) competitively inhibits binding of scFv-P4. 
     In another exemplary embodiment, an epitope binding agent of the present disclosure is the scFv-HN1 (SEQ ID NO: 7). In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 80% sequence identity to SEQ ID NO: 7, and (b) competitively inhibits binding of scFv-HN1. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 85% sequence identity to SEQ ID NO: 7, and (b) competitively inhibits binding of scFv-HN1. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 90% sequence identity to SEQ ID NO: 7, and (b) competitively inhibits binding of scFv-HN1. In another exemplary embodiment, an epitope binding agent of the present disclosure is a polypeptide that (a) has at least 95% sequence identity to SEQ ID NO: 7, and (b) competitively inhibits binding of scFv-HN1. 
     
       
         
           
               
             
               
                 TABLE A 
               
             
            
               
                   
               
               
                 Exemplary Antibodies 
               
            
           
           
               
               
               
            
               
                   
                 Light Chain HVR 
                 Heavy Chain HVR 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Antibody 
                 L1 
                 L2 
                 L3 
                 H1 
                 H2 
                 H3 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 
                 SEQ ID NO: 10 
                   
                   
                   
                   
                   
               
               
                 2 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
               
               
                 3 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
               
               
                 4 
                   
                 SEQ ID NO: 11 
               
               
                 5 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
               
               
                 6 
                   
                   
                 SEQ ID NO: 12 
               
               
                 7 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
               
               
                 8 
                   
                   
                   
                 SEQ ID NO: 13 
               
               
                 9 
                   
                   
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 10 
                   
                   
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 11 
                   
                   
                   
                   
                 SEQ ID NO: 14 
               
               
                 12 
                   
                   
                   
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 13 
                   
                   
                   
                   
                   
                 SEQ ID NO: 15 
               
               
                 14 
                   
                   
                   
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 15 
                 SEQ ID NO: 10 
                   
                   
                 SEQ ID NO: 13 
               
               
                 16 
                 SEQ ID NO: 10 
                   
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 17 
                 SEQ ID NO: 10 
                   
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 18 
                 SEQ ID NO: 10 
                   
                   
                   
                 SEQ ID NO: 14 
               
               
                 19 
                 SEQ ID NO: 10 
                   
                   
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 20 
                 SEQ ID NO: 10 
                   
                   
                   
                   
                 SEQ ID NO: 15 
               
               
                 21 
                 SEQ ID NO: 10 
                   
                   
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 22 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
               
               
                 23 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 24 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 25 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                   
                 SEQ ID NO: 14 
               
               
                 26 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 27 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                   
                   
                 SEQ ID NO: 15 
               
               
                 28 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 29 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
               
               
                 30 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 31 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 32 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
               
               
                 33 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 34 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 35 
                 SEQ ID NO: 10 
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                   
                 SEQ ID NO: 15 
               
               
                 36 
                   
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
               
               
                 37 
                   
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 38 
                   
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 39 
                   
                 SEQ ID NO: 11 
                   
                   
                 SEQ ID NO: 14 
               
               
                 40 
                   
                 SEQ ID NO: 11 
                   
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 41 
                   
                 SEQ ID NO: 11 
                   
                   
                   
                 SEQ ID NO: 15 
               
               
                 42 
                   
                 SEQ ID NO: 11 
                   
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 43 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
               
               
                 44 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 45 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 46 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
               
               
                 47 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 48 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                   
                   
                 SEQ ID NO: 15 
               
               
                 49 
                   
                 SEQ ID NO: 11 
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 50 
                   
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
               
               
                 51 
                   
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 52 
                   
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 53 
                   
                   
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
               
               
                 54 
                   
                   
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 55 
                   
                   
                 SEQ ID NO: 12 
                   
                   
                 SEQ ID NO: 15 
               
               
                 56 
                   
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 57 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
               
               
                 58 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
               
               
                 59 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 60 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
               
               
                 61 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                   
                 SEQ ID NO: 14 
                 SEQ ID NO: 15 
               
               
                 62 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                   
                   
                 SEQ ID NO: 15 
               
               
                 63 
                 SEQ ID NO: 10 
                   
                 SEQ ID NO: 12 
                 SEQ ID NO: 13 
                   
                 SEQ ID NO: 15 
               
               
                 64 
                 SEQ ID NO: 18 
               
               
                 65 
                 SEQ ID NO: 18 
                 KAS 
               
               
                 66 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
               
               
                 67 
                   
                 KAS 
               
               
                 68 
                   
                 KAS 
                 SEQ ID NO: 19 
               
               
                 69 
                   
                   
                 SEQ ID NO: 19 
               
               
                 70 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
               
               
                 71 
                   
                   
                   
                 SEQ ID NO: 102 
               
               
                 72 
                   
                   
                   
                 SEQ ID NO: 102 
                 SEQ ID NO: 21 
               
               
                 73 
                   
                   
                   
                 SEQ ID NO: 102 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 74 
                   
                   
                   
                   
                 SEQ ID NO: 21 
               
               
                 75 
                   
                   
                   
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 76 
                   
                   
                   
                   
                   
                 SEQ ID NO: 22 
               
               
                 77 
                   
                   
                   
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 78 
                 SEQ ID NO: 18 
                   
                   
                 SEQ ID NO: 20 
               
               
                 79 
                 SEQ ID NO: 18 
                   
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 80 
                 SEQ ID NO: 18 
                   
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 81 
                 SEQ ID NO: 18 
                   
                   
                   
                 SEQ ID NO: 21 
               
               
                 82 
                 SEQ ID NO: 18 
                   
                   
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 83 
                 SEQ ID NO: 18 
                   
                   
                   
                   
                 SEQ ID NO: 22 
               
               
                 84 
                 SEQ ID NO: 18 
                   
                   
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 85 
                 SEQ ID NO: 18 
                 KAS 
                   
                 SEQ ID NO: 20 
               
               
                 86 
                 SEQ ID NO: 18 
                 KAS 
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 87 
                 SEQ ID NO: 18 
                 KAS 
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 88 
                 SEQ ID NO: 18 
                 KAS 
                   
                   
                 SEQ ID NO: 21 
               
               
                 89 
                 SEQ ID NO: 18 
                 KAS 
                   
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 90 
                 SEQ ID NO: 18 
                 KAS 
                   
                   
                   
                 SEQ ID NO: 22 
               
               
                 91 
                 SEQ ID NO: 18 
                 KAS 
                   
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 92 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
               
               
                 93 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 94 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 95 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
               
               
                 96 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 97 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 98 
                 SEQ ID NO: 18 
                 KAS 
                 SEQ ID NO: 19 
                   
                   
                 SEQ ID NO: 22 
               
               
                 99 
                   
                 KAS 
                   
                 SEQ ID NO: 20 
               
               
                 100 
                   
                 KAS 
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 101 
                   
                 KAS 
                   
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 102 
                   
                 KAS 
                   
                   
                 SEQ ID NO: 21 
               
               
                 103 
                   
                 KAS 
                   
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 104 
                   
                 KAS 
                   
                   
                   
                 SEQ ID NO: 22 
               
               
                 105 
                   
                 KAS 
                   
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 106 
                   
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
               
               
                 107 
                   
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 108 
                   
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 109 
                   
                 KAS 
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
               
               
                 110 
                   
                 KAS 
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 111 
                   
                 KAS 
                 SEQ ID NO: 19 
                   
                   
                 SEQ ID NO: 22 
               
               
                 112 
                   
                 KAS 
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 113 
                   
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
               
               
                 114 
                   
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 115 
                   
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 116 
                   
                   
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
               
               
                 117 
                   
                   
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 118 
                   
                   
                 SEQ ID NO: 19 
                   
                   
                 SEQ ID NO: 22 
               
               
                 119 
                   
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                 120 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
               
               
                 121 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
               
               
                 122 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 123 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
               
               
                 124 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                   
                 SEQ ID NO: 21 
                 SEQ ID NO: 22 
               
               
                 125 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                   
                   
                 SEQ ID NO: 22 
               
               
                 126 
                 SEQ ID NO: 18 
                   
                 SEQ ID NO: 19 
                 SEQ ID NO: 20 
                   
                 SEQ ID NO: 22 
               
               
                   
               
            
           
         
       
     
     (c) Spacer 
     As used herein, the term “spacer” refers to a flexible linker that is positioned between an epitope binding agent and a TRAIL trimer. Prior research in this field indicated that it was necessary to include a large molecular spacer (˜40 kDa) between an anti-mesothelin scFv and TR3 to allow the membrane-tethered TRAIL trimer to bend over and engage receptors on the same cell in a productive fashion (i.e., a cis-acting cell death phenotype). See Tatzel et al., “Membrane-proximal TRAIL species are incapable of inducing short circuit apoptosis signaling: Implications for drug development and basic cytokine biology,”  Scientific Reports,  2016, 6: 22661. In the absence of the spacer, mesothelin-positive targets were unexpectedly protected from cell death and were actively enriched following exposure to a spacer-deficient SS-TR3 construct. 
     In contrast, constructs of the present disclosure do not require a large molecular spacer between the epitope binding agent and the TRAIL trimer to achieve cis-killing of mesothelin positive cells. Without wishing to be bound by theory, it is believed that the epitopes on cell surface human mesothelin that are recognized by the epitope binding agents disclosed herein favorably contribute to the spatial requirements needed for a functional interaction between the TRAIL trimer and DR5 (or other death receptors) at the plasma membrane. Although a spacer is not necessary for constructs disclosed herein to achieve cis-killing, inclusion of a spacer may be desired to further improve cis-killing and/or improve trans-killing. 
     In some embodiments, a construct comprises a TNF-related apoptosis-inducing ligand (TRAIL) trimer and an epitope binding agent that competitively inhibits binding of scFv-P4 (SEQ ID NO: 6) or scFv-HN1 (SEQ ID NO: 7) to cell surface human mesothelin, wherein the construct does not comprise a spacer. 
     In other embodiments, a construct comprises (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer; (b) a spacer; and (c) an epitope binding agent that competitively inhibits binding of scFv-P4 (SEQ ID NO: 6) or scFv-HN1 (SEQ ID NO: 7) to cell surface human mesothelin; wherein the spacer is directly attached to the TRAIL trimer at one end and the epitope binding agent on the other end. In certain embodiments, the spacer is less than about 200 amino acids in length, preferably less than about 100 amino acids in length, more preferably less than preferably less than about 50 amino acids in length, even more preferably less than preferably less than about 25 amino acids in length. In certain embodiments, the spacer is more than about 200 amino acids or less in length. For example, a spacer domain may comprise one or more protein domains from human DAF (SCR1) and CR1 (SCRs 15-17), or any other suitable spacer known in the art. See, for example, U.S. Pat. No. 8,461,311. Generally, an amino acid sequence is selected such that the spacer is flexible. In exemplary embodiments, the spacer comprises one or more glycosylation sites. 
     (d) Optional Construct Components 
     Constructs of the present disclosure may further comprise a signal peptide, one or more cleavage sites, and/or one or more epitope tags. 
     In some embodiments, a construct of the disclosure may further comprise an N-terminal signal peptide. Addition of a signal peptide may be advantageous when secretion of the construct is desired for purification purposes. Suitable signal peptides are known in the art. 
     In some embodiments, a construct of the disclosure may further comprise one or more cleavage sites. For example, a cleavage site may be between the epitope binding agent and the TRAIL trimer. Alternatively, or in addition, a cleavage site may be between one or more of the extracellular TRAIL domains. In embodiments where the construct comprises a signal peptide, a cleavage site may also be between the signal peptide and the epitope binding agent or the TRAIL trimer, whichever is proximal to the signal peptide. Cleavage sites recognized by various proteases are well known in the art. 
     In some embodiments, a construct of the disclosure may further comprise one or more tags. A tag may be attached at various positions within the construct including but not limited to the N-terminus, the C-terminus, between the epitope binding agent and the TRAIL trimer, between one or more of the extracellular TRAIL domains of the TRAIL trimer, or to a side chain of any amino acid in the construct provided construct substantially retains the killing capacity of the TRAIL trimer and the ability of the epitope binding agent to competitively inhibit binding of scFv-P4 or scFv-HN1 to cell surface human mesothelin. Non-limiting examples of suitable tags include radioisotopes, fluorophores, chromophores, protein tags, and peptide tags. Techniques for incorporating these tags into a polypeptide are well known in the art. 
     (e) Exemplary Embodiments 
     As disclosed herein, a construct of the present disclosure comprises (a) a TNF-related apoptosis-inducing ligand (TRAIL) trimer comprising three extracellular TRAIL domains fused together in a head-to-tail configuration that substantially retains the killing capacity of TRAIL; and (b) an epitope binding agent, wherein the epitope binding agent competitively inhibits binding of scFv-P4 or scFv-HN1 to cell surface human mesothelin. 
     In an exemplary embodiment, the epitope binding agent is an antibody that has a heavy chain variable region comprising SEQ ID NO: 13, SEQ ID NO: 14, and/or SEQ ID NO: 15; and/or a light chain variable region comprising SEQ ID NO: 10, SEQ ID NO: 11, and/or SEQ ID NO: 12; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain; and wherein the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that has a heavy chain variable region comprising SEQ ID NO: 13, SEQ ID NO: 14, and/or SEQ ID NO: 15; and/or a light chain variable region comprising SEQ ID NO: 10, SEQ ID NO: 11, and/or SEQ ID NO: 12; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that a heavy chain variable region comprising SEQ ID NO: 20, SEQ ID NO: 21, and/or SEQ ID NO: 22; and/or a light chain variable region comprising SEQ ID NO: 18, the amino acid sequence KAS, and/or SEQ ID NO: 19; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 122-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 122-281 , and the C-terminus of the first peptide is indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is indirectly attached to N-terminus of the third domain; and wherein the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that a heavy chain variable region comprising SEQ ID NO: 20, SEQ ID NO: 21 and/or SEQ ID NO: 22; and/or a light chain variable region comprising SEQ ID NO: 18, the amino acid sequence KAS, and/or SEQ ID NO: 19]; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that has a heavy chain variable region comprising SEQ ID NO: 13, SEQ ID NO: 14, and/or SEQ ID NO: 15; and/or a light chain variable region comprising SEQ ID NO: 10, SEQ ID NO: 11, and/or SEQ ID NO: 12; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , and each of the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that a heavy chain variable region comprising SEQ ID NO: 20, SEQ ID NO: 21 and/or SEQ ID NO: 22; and/or a light chain variable region comprising SEQ ID NO: 18, the amino acid sequence KAS, and/or SEQ ID NO: 19; and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , and each of the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is scFv-HN1 and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is scFv-P4 and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein each of the first peptide, the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is scFv-HN1 and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , and each of the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is scFv-P4 and the TRAIL trimer is a protein comprising a first peptide, a second peptide and third peptide; wherein the first peptide is TRAIL 91-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 91-281 , and each of the second peptide, and the third peptide is TRAIL 114-281  or a peptide that has an amino acid sequence that has at least 80% sequence identity to TRAIL 114-281 , and the C-terminus of the first peptide is directly or indirectly attached to N-terminus of the second peptide, and the C-terminus of the second peptide is directly or indirectly attached to N-terminus of the third domain. When indirectly attached, the first peptide is attached to the second peptide by an amino acid linker that is 1 to 50 amino acids in length, and the second peptide is attached to the third peptide by an amino acid linker that is 1 to 50 amino acids in length. 
     In another exemplary embodiment, the epitope binding agent is an antibody that has a heavy chain variable region comprising SEQ ID NO: 13, SEQ ID NO: 14, and/or SEQ ID NO: 15; and/or a light chain variable region comprising SEQ ID NO: 10, SEQ ID NO: 11, and/or SEQ ID NO: 12; and the TRAIL trimer is TR3. 
     In another exemplary embodiment, the epitope binding agent is an antibody that a heavy chain variable region comprising SEQ ID NO: 20, SEQ ID NO: 21, and/or SEQ ID NO: 22; and/or a light chain variable region comprising SEQ ID NO: 18, the amino acid sequence KAS, and/or SEQ ID NO: 19; and the TRAIL trimer is TR3. 
     In each of the above exemplary embodiments, the epitope binding agent is either N-terminal or C-terminal to the TRAIL trimer; and the epitope binding agent is either directly attached to the TRAIL trimer or attached by a spacer that consists of no more than 100 amino acids (or a non-amino acid spacer that is equivalent in terms of size and flexibility). 
     In another exemplary embodiment, the construct is P4-TR3 (SEQ ID NO: 26). 
     In another exemplary embodiment, the construct is HN1-TR3 (SEQ ID NO: 25). 
     II. Nucleic Acids Encoding Constructs 
     Another aspect of the present disclosure provides nucleic acids encoding any of the constructs described above in Section I. The nucleic acid can be RNA or DNA. In one embodiment, the nucleic acid encoding the construct is mRNA. The m RNA can be 5′ capped and/or 3′ polyadenylated. In another embodiment, the nucleic acid encoding the construct is DNA. The DNA can be present in a vector (see below). 
     In some embodiments, DNA encoding the construct can be operably linked to at least one promoter control sequence. In some iterations, the DNA coding sequence can be operably linked to a promoter control sequence for expression in a eukaryotic cell of interest. The promoter control sequence can be constitutive or regulated. Suitable constitutive promoter control sequences include, but are not limited to, cytomegalovirus immediate early promoter (CMV), simian virus (SV40) promoter, human elongation factor-1 alpha (EF-1 alpha) promoter, adenovirus major late promoter, Rous sarcoma virus (RSV) promoter, mouse mammary tumor virus (MMTV) promoter, phosphoglycerate kinase (PGK) promoter, elongation factor (EDI)-alpha promoter, ubiquitin promoters, actin promoters, tubulin promoters, immunoglobulin promoters, fragments thereof, or combinations of any of the foregoing. Examples of suitable regulated promoter control sequences include without limit those regulated by heat shock, metals, steroids, antibiotics, or alcohol. Non-limiting examples of tissue-specific promoters include B29 promoter, CD14 promoter, CD43 promoter, CD45 promoter, CD68 promoter, desmin promoter, elastase-1 promoter, endoglin promoter, fibronectin promoter, Flt-1 promoter, GFAP promoter, GPIIb promoter, ICAM-2 promoter, INF-β promoter, Mb promoter, Nphsl promoter, OG-2 promoter, SP-B promoter, SYN1 promoter, and WASP promoter. The promoter sequence can be wild type or it can be modified for more efficient or efficacious expression. The promoter sequence can be wild type or it can be modified for more efficient or efficacious expression. 
     In certain embodiments, the sequence encoding the construct can be operably linked to a promoter sequence that is recognized by a phage RNA polymerase for in vitro mRNA synthesis. For example, the promoter sequence can be a T7, T3, or SP6 promoter sequence or a variation of a T7, T3, or SP6 promoter sequence. 
     In alternate embodiments, the sequence encoding the construct can be operably linked to a promoter sequence for in vivo expression of the construct in bacterial or eukaryotic cells. In such embodiments, the expressed protein can be purified for use in the methods detailed below in Sections III and IV. Suitable bacterial promoters include, without limit, T7 promoters, lac operon promoters, trp promoters, variations thereof, and combinations thereof. An exemplary bacterial promoter is tac which is a hybrid of trp and lac promoters. Non-limiting examples of suitable eukaryotic promoters are listed above. 
     In additional aspects, the DNA encoding the construct can be linked to a polyadenylation signal (e.g., SV40 polyA signal, bovine growth hormone (BGH) polyA signal, etc.) and/or at least one transcriptional termination sequence. Additionally, the sequence encoding the construct also can be linked to a sequence encoding at least one nuclear localization signal or at least one cell-penetrating domain. 
     In various embodiments, the DNA sequence encoding the construct can be present in a vector. Suitable vectors include plasmid vectors, phagemids, cosmids, artificial/mini-chromosomes, transposons, and viral vectors. In one embodiment, the DNA encoding the construct is present in a plasmid vector. Non-limiting examples of suitable plasmid vectors include pUC, pBR322, pET, pBluescript, and variants thereof. In another embodiment, the DNA encoding the construct is present in a viral vector. Non-limiting examples of suitable plasmid vectors include lentiviral vectors, adeno-associated viral vectors, adenovirus vectors, alphavirus vectors, herpesvirus vectors, and vaccinia virus vectors. In such embodiments, the expressed viral vector can be purified for use in the methods detailed below in Sections III and IV. In an exemplary embodiment, a DNA sequence encoding a construct of Section I is present in an Ad5 vector or a modified Ad5 vector. In another exemplary embodiment, a DNA sequence encoding a construct of Section I is present in Ad5pK7. The vector can comprise additional expression control sequences (e.g., enhancer sequences, Kozak sequences, polyadenylation sequences, transcriptional termination sequences, etc.), selectable marker sequences (e.g., antibiotic resistance genes), origins of replication, and the like. Additional information can be found in “Current Protocols in Molecular Biology” Ausubel et al., John Wiley &amp; Sons, New York, 2003 or “Molecular Cloning: A Laboratory Manual” Sambrook &amp; Russell, Cold Spring Harbor Press, Cold Spring Harbor, N.Y., 3rd edition, 2001. 
     In some embodiments, the expression vector comprising the DNA sequence encoding the construct is operably linked to at least one transcriptional control sequence for expression of the construct in a cell of interest. For example, DNA encoding the construct can be operably linked to a promoter sequence that is recognized by RNA polymerase III (Pol III). Examples of suitable Pol III promoters include, but are not limited to, mammalian U6, U3, H1, and 7SL RNA promoters. 
     III. Methods of Treatment 
     Another aspect of the present disclosure provides methods of treatment that comprise administering to a subject in need thereof a therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I. As used herein, the terms “treat,” “treating,” or “treatment” refer to both therapeutic treatment and prophylactic or preventative measures, wherein the object is to prevent or slow down (lessen) an undesired physiological change or disease/disorder as compared to an untreated subject with a similar disease, condition or disorder. Beneficial or desired clinical results include, but are not limited to, alleviation of symptoms, diminishment of extent of disease, stabilized (i.e., not worsening) state of disease, a delay or slowing of disease progression, amelioration or palliation of the disease state, and remission (whether partial or total), whether detectable or undetectable. “Treatment” can also mean prolonging survival as compared to expected survival if not receiving treatment. 
     Subjects in need of treatment include those already with a disease, a condition, or a disorder associated with increased cell-surface expression of mesothelin, as well as those prone to have the disease, condition or disorder or those in which the disease, condition or disorder is to be prevented. Preferred subjects are mammals, more preferably humans, and include both adult and pediatric subjects. Non-limiting examples of diseases, conditions, or disorders associated with increased expression of cell-surface mesothelin include liver fibrosis, lung fibrosis, acute kidney injury, chronic kidney disease, and cancer (i.e., a malignant tumor). 
     When a subject in need of treatment is a subject diagnosed with cancer, the subject may have active disease or may be in remission (complete or partial). When a subject with cancer has active disease, treatment may reduce the size of the tumor, slow or inhibit growth of the tumor, slow or inhibit metastasis, or any combination thereof. For subjects in partial remission, treatment may reduce the size of the tumor, slow or inhibit growth of the tumor, slow or inhibit metastasis, or any combination thereof. When a subject is in complete remission, treatment may prevent a cancer from re-growing (i.e. disease progression). In subjects with active disease or in remission, treatment may also prolong survival as compared to an untreated patient. 
     As used herein, the term “cancer” includes solid tumors, non-solid tumors, and circulating tumor cells. Solid tumors are formed by an abnormal growth of cells other than blood, bone marrow or lymphatic cells, and include tumors that are not vascularized, or not yet substantially vascularized, as well as vascularized tumors. Non-limiting examples of solid tumors include sarcomas and carcinomas. Different types of solid tumors are named for the type of cells that form them. Non-limiting examples of malignant solid tumors associated with overexpression of mesothelin include ovarian cancer, pancreatic cancer, lung cancer, esophageal cancer, gastric cancer, colon cancer, kidney cancer, liver cancer, synovial sarcoma, triple-negative breast cancer, cervical cancer, or mesothelioma. Non-solid tumors usually originate from blood-forming tissues. Non-limiting examples of malignant non-solid tumors associated with overexpression of mesothelin include leukemia, lymphoma and multiple myeloma. Circulating tumor cells are cancer cells that detach from a primary tumor and travel through the bloodstream or lymphatic system to other parts of the body. Methods for detecting circulating tumor cells. 
     In one embodiment, treating a subject in need thereof by administering to the subject a therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may increase survival of the subject as compared to expected survival if the subject did not receive treatment. Survival may be increased at least about 5%. For example, survival may be increase at least about 5%, at least about 10%, at least about 15%, or at least about 20%. In another example, survival may be increased by at least about 25%, at least about 30%, at least about 35%, or at least about 40%. In still another example, survival may be increased by at least about 50%, at least about 100%, at least about 150%, at least about 200%, or more. In subjects diagnosed with cancer, survival may refer to overall survival or progression free survival (i.e., the length of time the subject is both alive and free from any significant increase in cancer). 
     In another embodiment, treating a subject in need thereof by administering to the subject therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may alleviate or ameliorate one or more signs or symptoms of a disease, a condition, or a disorder associated with increased expression of cell-surface mesothelin. In certain embodiments, the subject is diagnosed with cancer. Non-limiting examples symptoms associated with cancer that may be alleviated include, fatigue, unintended weight loss or gain, pain, fevers, frequent infections, and easy bleeding or bruising. 
     In another embodiment, treating a subject diagnosed with cancer by administering to the subject a therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may decrease tumor volume. For example, tumor volume may decrease by less than 25%, by about 25% to about 50%, or by about 50% to about 100%. In certain embodiments, treatment may result in no evidence of disease, i.e., all detectable tumor has disappeared in the subject. Response duration may vary depending upon the type of cancer and the severity of disease. In certain embodiments, the cancer is selected from ovarian cancer, cervical cancer, pancreatic cancer, mesothelioma or lung cancer. 
     In another embodiment, treating a subject diagnosed with cancer by administering to the subject a therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may decrease the number of circulating tumor cells. For example, the number of circulating tumor cells may decrease by less than 25%, by about 25% to about 50%, or by about 50% to about 100%. Method for detecting circulating tumor cells are known in the art. In certain embodiments, the cancer is selected from cervical cancer, pancreatic cancer, mesothelioma or lung cancer. 
     In another embodiment, administering to a subject diagnosed with cancer a therapeutically effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may decrease the risk of metastasis as compared to an untreated patient. The risk of metastasis may be decreased by at least about 5%. For example, the risk of metastasis may be decreased (as compared to an untreated patient) by at least about 5%, at least about 10%, at least about 15%, or at least about 20%. In another example, the risk of metastasis may be decreased (as compared to an untreated patient) by at least about 25%, at least about 30%, at least about 35%, or at least about 40%. In still another example, the risk of metastasis may be decreased (as compared to an untreated patient) by at least about 50%, at least about 75%, or at least about 90%, or more. In certain embodiments, the cancer is selected from ovarian cancer, cervical cancer, pancreatic cancer, mesothelioma or lung cancer. 
     For each of the above embodiments, suitable constructs are described in Section I or Section II. In an exemplary embodiment, the construct comprises scFv-HN1 (SEQ ID NO: 7) and TR3 (SEQ ID NO: 2). In another exemplary embodiment, the construct comprises scFv-P4 (SEQ ID NO: 6) and TR3 (SEQ ID NO: 2). 
     Constructs of the present disclosure may be used alone or in combination with one or more additional therapeutic agent known to effectively treat a disease, a condition, or a disorder associated with dysregulated expression of mesothelin. For example, when a subject is diagnosed with cancer, constructs of the present disclosure may be combined with standard-of-care cancer therapies. As used herein, “standard-of-care cancer therapies” refer to one or more treatments accepted by medical experts as a proper treatment for a certain type of disease and that is widely used by healthcare professionals. Standard-of-care cancer therapies for cancer include, but are not limited to, cytotoxic agents, cytostatic agents, chemotherapeutic agents, targeted anti-cancer agents, biological response modifiers, immunotherapeutic agents, cancer vaccines, anti-angiogenic agents, cytokines, hormone therapies, radiation therapy and anti-metastatic agents. 
     Administration of a construct of Section I, Section II, or a DNA or an RNA virus encoding a construct of Section I, or a composition comprising a construct of Section I, Section II, or a DNA or an RNA virus encoding a construct of Section I, is performed using standard effective techniques. Administration may occur orally, parenterally, by inhalation, rectally, intradermally, transdermally, or topically in dosage unit formulations containing conventional nontoxic pharmaceutically acceptable carriers, adjuvants, and vehicles as desired. The term parenteral as used herein includes subcutaneous, intravenous, intramuscular, intrathecal, or intrasternal injection, or infusion techniques. 
     Although the foregoing methods appear the most convenient and most appropriate and effective for administration, by suitable adaptation other effective techniques for administration may be employed provided proper formulation is utilized herein. For example, a person skilled in the art can use a nucleic acid of the invention encoding a construct of Section I instead of the protein material itself. 
     In addition, it may be desirable to employ controlled release formulations using biodegradable films and matrices, or osmotic mini-pumps, or delivery systems based on dextran beads, alginate, or collagen. 
     Pharmaceutical compositions for effective administration are deliberately designed to be appropriate for the selected mode of administration, and pharmaceutically acceptable excipients such as compatible dispersing agents, buffers, surfactants, preservatives, solubilizing agents, isotonicity agents, stabilizing agents and the like are used as appropriate. Remington&#39;s Pharmaceutical Sciences, Mack Publishing Co., Easton Pa., 16Ed ISBN: 0-912734-04-3, latest edition, incorporated herein by reference in its entirety, provides a compendium of formulation techniques as are generally known to practitioners. 
     The concentration of a construct or combination of constructs in formulations to be administered is an effective amount and ranges from as low as about 0.1% by weight to as much as about 15 or about 20% by weight and will be selected primarily based on fluid volumes, viscosities, and so forth, in accordance with the particular mode of administration selected if desired. A typical composition for injection to a living subject could be made up to contain 1 mL sterile buffered water of phosphate buffered saline and about 1-1000 mg of any one of or a combination of constructs of Section I or Section II disclosed herein. The formulation could be sterile filtered after making the formulation, or otherwise made microbiologically acceptable. A typical composition for intravenous infusion could have volumes between 1-250 mL of fluid, such as sterile Ringer&#39;s solution, and 1-100 mg per ml, or more in concentration of a construct of Section I or Section II. The construct of Section I or Section II disclosed herein can be frozen or lyophilized for storage and reconstituted in a suitable sterile carrier prior to use. Lyophilization and reconstitution may lead to varying degrees of activity loss of a construct of Section I or Section II. Dosages administered are effective dosages and may have to be adjusted to compensate. The pH of the formulations, generally pharmaceutical grade quality, will be selected to balance recombinant protein stability (chemical and physical) and comfort to the subject when administered. Generally, a pH between 4 and 8 is tolerated. Doses will vary from individual to individual based on size, weight, and other physiobiological characteristics of the individual receiving the successful administration. 
     Methods for administering a DNA or an RNA virus are well-known in the art. Although the exact dosage will be determined on a drug-by-drug basis, in most cases, some generalizations regarding the dosage can be made. In some embodiments, the recombinant a DNA or an RNA virus encoding a construct of Section I can be administered via injection to a subject at a dose of about 1×10 9  genome copies (GC) of the recombinant virus per kg of the subject to about 1×10 13  GC per kg, for example about 1×10 9  GC/kg to 1×10 10  GC/kg, about 1×10 9  GC/kg to 5×10 10  GC/kg, about 1×10 9  GC/kg to 1×10 11  GC/kg, about 1×10 9  GC/kg to 5×10 11  GC/kg, about 1×10 9  GC/kg to 1×10 12  GC/kg, about 1×10 9  GC/kg to 5×10 12  GC/kg, about 1×10 9  GC/kg to 1×10 13  GC/kg, about 5×10 9  GC/kg to 1×10 10  GC/kg, about 5×10 9  GC/kg to 5×10 10  GC/kg, about 5×10 9  GC/kg to 1×10 11  GC/kg, about 5×10 9  GC/kg to 5×10 11  GC/kg, about 5×10 9  GC/kg to 1×10 12  GC/kg, about 5×10 9  GC/kg to 5×10 12  GC/kg, about 5×10 9  GC/kg to 1×10 13  GC/kg, about 1×10 10  GC/kg to 5×10 10  GC/kg, about 1×10 10  GC/kg to 1×10 11  GC/kg, about 1×10 10  GC/kg to 5×10 11  GC/kg, about 5×10 10  GC/kg to 1×10 12  GC/kg, about 1×10 10  GC/kg to 5×10 12  GC/kg, about 1×10 10  GC/kg to 1×10 13  GC/kg, about 5×10 10  GC/kg to 1×10 11  GC/kg, about 5×10 10  GC/kg to 5×10 11  GC/kg, about 5×10 10  GC/kg to 1×10 12  GC/kg, about 5×10 10  GC/kg to 5×10 12  GC/kg, about 5×10 10  GC/kg to 1×10 13  GC/kg, about 1×10 11  GC/kg to 5×10 11  GC/kg, about 1×10 11  GC/kg to 1×10 12  GC/kg, about 1×10 11  GC/kg to 5×10 12  GC/kg, about 1×10 11  GC/kg to 1×10 13  GC/kg, about 5×10 11  GC/kg to 1×10 12  GC/kg, or about 5×10 11  GC/kg to 1×10 13  GC/kg. 
     Actual administration of the AAV vector encoding a gene product of interest, expression system, or component thereof can be accomplished by using any physical method that will transport the recombinant AAV vector into the target tissue of the subject. For example, the recombinant AAV vector can be injected into muscle, the bloodstream, and/or directly into the liver. Capsid proteins of the recombinant AAV vector may be modified so that the recombinant AAV vector is targeted to a particular target tissue of interest such as muscle or bone marrow. Pharmaceutical compositions can be prepared as injectable formulations or as topical formulations to be delivered to the muscles by transdermal transport. 
     For intramuscular injection, solutions in an adjuvant such as sesame or peanut oil or in aqueous propylene glycol can be employed, as well as sterile aqueous solutions. Such aqueous solutions can be buffered, if desired, and the liquid diluent first rendered isotonic with saline or glucose. Solutions of the AAV vector as a free acid (DNA contains acidic phosphate groups) or a pharmacologically acceptable salt can be prepared in water suitably mixed with a surfactant such as hydroxypropylcellulose. A dispersion of the AAV vector can also be prepared in glycerol, liquid polyethylene glycols and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms. 
     The AAV vector to be used can be utilized in liquid or freeze-dried form (in combination with one or more suitable preservatives and/or protective agents to protect the virus during the freeze-drying process). For gene therapy (e.g., of neurological disorders which may be ameliorated by a specific gene product) a therapeutically effective dose of the recombinant virus expressing the therapeutic protein is administered to a host in need of such treatment. The use of the recombinant virus disclosed herein in the manufacture of a medicament for inducing immunity in, or providing gene therapy to, a host is within the scope of the present application. In some embodiments, the AAV can be administered to a cell that is subsequently transplanted into the host, for example a hematopoietic stem cell, embryonic stem cell, induced pluripotent stem cell, or the like. 
     In instances where human dosages for the AAV vectors have been established for at least some condition, those same dosages, or dosages that are between about 0.1% and 500%, more preferably between about 25% and 250% of the established human dosage can be used. Where no human dosage is established, as will be the case for newly-discovered pharmaceutical compositions, a suitable human dosage can be inferred from ED 50  or ID 50  values, or other appropriate values derived from in vitro or in vivo studies, as qualified by toxicity studies and efficacy studies in animals. 
     The timing of administration of the treatment relative to the disease itself and duration of treatment will be determined by the circumstances surrounding the case. Duration of treatment could range from a single dose administered on a one-time basis to a life-long course of therapeutic treatments. In another embodiment of the present disclosure, a treatment regimen composed of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may include treatment of the subject once or multiple times. In another embodiment, treatment of the subject with a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, may occur multiple times until desired results are observed. It is appreciated that one skilled in the art would be able to select an appropriate number of treatments to achieve the desired response for purposes of the present disclosure. In another embodiment of the present disclosure, a subject may be treated with a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, multiple times at irregular intervals. In yet another embodiment, a subject may be treated with a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, multiple times at regular intervals. In still another embodiment, a subject may be treated with a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, multiple times at about at least 2-week or greater, at least 3-week or greater, at least 4-week or greater, at least 5-week or greater, at least 6-week or greater intervals. In another embodiment, a subject may be treated with a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I, multiple times at about at least 2-week or greater to at least 3-week or greater, at least 3-week or greater to at least 4-week or greater, at least 4-week or greater to at least 5-week or greater, at least 5-week or greater to at least 6-week or greater intervals. It is appreciated that one skilled in the art would be able to select an appropriate interval of treatment to achieve the desired response for purposes of the present disclosure. 
     The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples that follow represent techniques discovered by the inventors to function well in the practice of the invention. Those of skill in the art should, however, in light of the present disclosure, appreciate that changes may be made in the specific embodiments that are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention. Therefore, all matter set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. 
     IV. Methods for Using a Construct to Induce Apoptosis in a Cell 
     Another aspect of the present disclosure provides methods of inducing apoptosis in a cell. The method comprises contacting a cell with an effective amount of a construct of Section I or Section II, or a DNA or an RNA virus encoding a construct of Section I. Constructs of the present disclosure target a TRAIL trimer to mesothelin-positive cells in a manner that results in death of the cell to which the construct is bound (i.e., a cis-acting phenotype). In certain embodiment, constructs also result in bystander cell death (i.e., a trans-acting phenotype). 
     A variety of cells can be used in the method disclosed herein, provided the cell expresses cell surface human mesothelin and either DR4 (RefSeq NP_003835) or DR5 (NP_003833 or NP_671716). In general, the cell is a eukaryotic cell. In various aspects, the cell can be a human cell, a non-human mammalian cell, a non-mammalian vertebrate cell, an invertebrate cell, an insect cell, a plant cell, a yeast cell, or a single cell eukaryotic organism. In exemplary aspects, the cell is a human cell. The cell can be a primary cell or a cell line cell. The cell may be an adult cell, an embryonic cell, or a stem cell. The cell can be a normal cell, a diseased cell, or a cancerous cell. 
     In some embodiments, the cell can be a human cell line cell. Non-limiting examples of suitable cell lines include DU145 (metastatic cancer), SW490 (colon cancer), DLD-1 (colon cancer), KM20L2 (colon cancer), COLO 205 (colon cancer), HCC-2998, (colon cancer), HCT-1 16 (colon cancer), HCT-15 (colon cancer), HT29 (colon cancer), KM12 (colon cancer), SW-620 (colon cancer), SF-268 (CNS), SF-295 (CNS), SF-539 (CNS), SNB-19 (CNS), SNB-75 (CNS), U251 (CNS), CCRF-CEM (leukemia), HL-60 (TB) (leukemia), K-562 (leukemia), MOLT-4 (leukemia), RPMI-8226 (leukemia), SR (leukemia), A549 (non-small cell lung cancer), EKVX (non-small cell lung cancer), HOP-62 (non-small cell lung cancer), HOP-92 (non-small cell lung cancer), NCI-H226 (non-small cell lung cancer), NCI-H23 (non-small cell lung cancer), NCI-H322M (non-small cell lung cancer), NCI-H460 (non-small cell lung cancer), NCI-H522 (non-small cell lung cancer), LOX IMVI (melanoma), MALME-3M (melanoma), M14 (melanoma), MDA-MB-435 (melanoma), SK-MEL-2 (melanoma), SK-MEL-28 (melanoma), SK-MEL-5 U (melanoma), ACC-257 (melanoma), UACC-62 (melanoma), IGR-OV1 (ovarian), OVCAR-3 (ovarian), OVCAR-4 OVCAR-5 (ovarian), OVCAR-8 (ovarian), SK-OV-3 (ovarian), 786-0 (renal), A498 (renal), ACHN (renal), CAKI-1 (renal), RXF 393 (renal), SN12C (renal), TK-10 (renal), UO-31 (renal), PC-3 (prostate), DU-145 (prostate), MCF7 (breast), MDA-MB-231 (breast), MDA-MB-468 (breast), HS 578T (breast), BT-549 (breast), and T-47D (breast). 
     In other embodiments, the cell can be a primary human cell. For example, the cell can be diseased or cancerous cell obtained from a subject in need of treatment. The term “subject in need of treatment” is defined above in Section III. The cell can be in a purified form (partially or completely) or can be in a biological sample obtained from the subject (e.g., blood, plasma, lymphatic fluid, etc.). In an exemplary embodiment, the cell can be a circulating tumor cell. 
     Contacting a cell with an effective amount of a construct of Section I generally involves admixing the construct and the cell for a period of time sufficient to allow the epitope binding agent of the construct to bind mesothelin on the surface of the cell. This may occur in vitro or ex vivo. Contacting a cell with an effective amount of a construct of Section II generally involves transfecting a cell with a construct of Section II. Contacting a cell with an effective amount of a DNA or an RNA virus encoding a construct of Section I generally involves infecting a cell with an effective amount of viral particle. See, for example, Kuroki et al., PLoS ONE, 2017, 12(12): e0190125. This may occur in vitro or ex vivo. The term “effective amount”, as used herein, means an amount of a construct that leads to measurable effect, e.g., engagement of a cell death receptor, signaling through a cell death receptor, apoptosis, etc. The effective amount may be determined by using the methods described in further detail in the examples. 
     
       
         
           
               
               
               
             
               
                   
               
               
                 SEQ ID 
                   
                   
               
               
                 NO 
                 SEQUENCE 
                 DESCRIPTION 
               
               
                   
               
             
            
               
                  1 
                 MAMMEVQGGPSLGQTCVLIVIFTVLLQSLCVAVTYVYFTNELKQMQDKYSK 
                 Human TRAIL 
               
               
                   
                 SGIACFLKEDDSYWDPNDEESMNSPCWQVKWQLRQLVRKMILRTSEETIST 
                   
               
               
                   
                 VQEKQQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINS 
                   
               
               
                   
                 WESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDK 
                   
               
               
                   
                 QMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDR 
                   
               
               
                   
                 IFVSVTNEHLIDMDHEASFFGAFLVG 
                   
               
               
                   
               
               
                  2 
                 LPPRTPPMILRTSEETISTVQEKQQNISPLVRERGPQRVAAHITGTRGRSN 
                 TR3 
               
               
                   
                 TLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIY 
                   
               
               
                   
                 SQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAE 
                   
               
               
                   
                 YGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRSQNIS 
                   
               
               
                   
                 PLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSGHS 
                   
               
               
                   
                 FLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKY 
                   
               
               
                   
                 TSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEH 
                   
               
               
                   
                 LIDMDHEASFFGAFLVGRSQNISPLVRERGPQRVAAHITGTRGRSNTLSSP 
                   
               
               
                   
                 NSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYF 
                   
               
               
                   
                 RFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYS 
                   
               
               
                   
                 IYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRS 
                   
               
               
                   
               
               
                  3 
                 MGIQGGSVLFGLLLVLAVFCHSGHSLPPRTPPMILRTSEETISTVQEKQQN 
                 Signal peptide 
               
               
                   
                 ISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSG 
                 (SP) + TR3 
               
               
                   
                 HSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIY 
                   
               
               
                   
                 KYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTN 
                   
               
               
                   
                 EHLIDMDHEASFFGAFLVGRSQNISPLVRERGPQRVAAHITGTRGRSNTLS 
                   
               
               
                   
                 SPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQT 
                   
               
               
                   
                 YFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGL 
                   
               
               
                   
                 YSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRSQNISPLV 
                   
               
               
                   
                 RERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSGHSFLS 
                   
               
               
                   
                 NLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSY 
                   
               
               
                   
                 PDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLID 
                   
               
               
                   
                 MDHEASFFGAFLVGRS 
                   
               
               
                   
               
               
                  4 
                 EVEKTACPSGKKAPEIDESLIFYKKWELEACVDAALLATQMDRVNAIPFTY 
                 Mesothelin 
               
               
                   
                 EQLDVLKHKLDELYPQGYPESVIQHLGYLFLKMSPEDIRKWNVTSLETLKA 
                 (mature form) 
               
               
                   
                 LLEVNKGHEMSPQVATLIDRFVKGRGQLDKDTLDTLTAFYPGYLCSLSPEE 
                   
               
               
                   
                 LSSVPPSSIWAVRPQDLDTCDPRQLDVLYPKARLAFQNMNGSEYFVKIQSF 
                   
               
               
                   
                 LGGAPTEDLKALSQQNVSMDLATFMKLRTDAVLPLTVAEVQKLLGPHVEGL 
                   
               
               
                   
                 KAEERHRPVRDWILRQRQDDLDTLGLGLQGGIPNGYLVLDLSMQEALSGTP 
                   
               
               
                   
                 CLLGPGPVLTVLALLLASTLA 
                   
               
               
                   
               
               
                  5 
                 QVQLQQSGPELEKPGASVKISCKASGYSFTGYTMNWVKQSHGKSLEWIGLI 
                 SS 
               
               
                   
                 TPYNGASSYNQKFRGKATLTVDKSSSTAYMDLLSLTSEDSAVYFCARGGYD 
                   
               
               
                   
                 GRGFDYWGQGTTVTVSSGVGGSGGGGSGGGGSDIELTQSPAIMSASPGEKV 
                   
               
               
                   
                 TMTCSASSSVSYMHWYQQKSGTSPKRWIYDTSKLASGVPGRFSGSGSGNSY 
                   
               
               
                   
                 SLTISSVEAEDDATYYCQQWSGYPLTFGAGTKLEIKRA 
                   
               
               
                   
               
               
                  6 
                 QVQLQQSGPGLVTPSQTLSLTCAISGDSVSSNSATWNWIRQSPSRGLEWLG 
                 P4 
               
               
                   
                 RTYYRSKWYNDYAVSVKSRMSINPDTSKNQFSLQLNSVTPEDTAVYYCARG 
                   
               
               
                   
                 MMTYYYGMDVWGQGTTVTVSSGILGSGGGGSGGGGSGGGGSQPVLTQSSSL 
                   
               
               
                   
                 SASPGASASLTCTLRSGINVGPYRIYWYQQKPGSPPQYLLNYKSDSDKQQG 
                   
               
               
                   
                 SGVPSRFSGSKDASANAGVLLISGLRSEDEADYYCMIWHSSAAVFGGGTQL 
                   
               
               
                   
                 TVLS 
                   
               
               
                   
               
               
                  7 
                 QVQLVQSGAEVKRPGASVQVSCRASGYSINTYYMQWVRQAPGAGLEWMGVI 
                 HN1 
               
               
                   
                 NPSGVTSYAQKFQGRVTLTNDTSTNTVYMQLNSLTSADTAVYYCARWALWG 
                   
               
               
                   
                 DFGMDVWGKGTLVTVSSGGGGSGGGGSGGGGSDIQMTQSPSTLSASIGDRV 
                   
               
               
                   
                 TITCRASEGIYHWLAWYQQKPGKAPKLLIYKASSLASGAPSRFSGSGSGTD 
                   
               
               
                   
                 FTLTISSLQPDDFATYYCQQYSNYPLTFGGGTKLEIKRA 
                   
               
               
                   
               
               
                  8 
                 QPVLTQSSSLSASPGASASLTCTLRSGINVGPYRIYWYQQKPGSPPQYLLN 
                 VL P4 
               
               
                   
                 YKSDSDKQQGSGVPSRFSGSKDASANAGVLLISGLRSEDEADYYCMIWHSS 
                   
               
               
                   
                 AAVFGGGTQLTVLS 
                   
               
               
                   
               
               
                  9 
                 QVQLQQSGPGLVTPSQTLSLTCAISGDSVSSNSATWNWIRQSPSRGLEWLG 
                 VH P4 
               
               
                   
                 RTYYRSKWYNDYAVSVKSRMSINPDTSKNQFSLQLNSVTPEDTAVYYCARG 
                   
               
               
                   
                 MMTYYYGMDVWGQGTTVTVSSGILGS 
                   
               
               
                   
               
               
                 10 
                 TLRSGINVGPYRIYWYQQ 
                 P4 L1 
               
               
                   
               
               
                 11 
                 DKQQGSG 
                 P4 L2 
               
               
                   
               
               
                 12 
                 MIWHSSAAVFGGG 
                 P4 L3 
               
               
                   
               
               
                 13 
                 GDSVSSNSATW 
                 P4 H1 
               
               
                   
               
               
                 14 
                 RTYYRSKWYN 
                 P4 H2 
               
               
                   
               
               
                 15 
                 ARGMMTYYYGMDV 
                 P4 H3 
               
               
                   
               
               
                 16 
                 DIQMTQSPSTLSASIGDRVTITCRASEGIYHWLAWYQQKPGKAPKLLIYKA 
                 VL HN1 
               
               
                   
                 SSLASGAPSRFSGSGSGTDFTLTISSLQPDDFATYYCQQYSNYPLTFGGGT 
                   
               
               
                   
                 KLEIKRA 
                   
               
               
                   
               
               
                 17 
                 QVQLVQSGAEVKRPGASVQVSCRASGYSINTYYMQWVRQAPGAGLEWMGVI 
                 VH HN1 
               
               
                   
                 NPSGVTSYAQKFQGRVTLTNDTSTNTVYMQLNSLTSADTAVYYCARWALWG 
                   
               
               
                   
                 DFGMDVWGKGTLVTVSS 
                   
               
               
                   
               
               
                 18 
                 EGIYHW 
                 HN1 L1 
               
               
                   
               
               
                 19 
                 QQYSNYPLT 
                 HN1 L3 
               
               
                   
               
               
                 20 
                 GYSINTYY 
                 HN1 H1 
               
               
                   
               
               
                 21 
                 INPSGVT 
                 HN1 H2 
               
               
                   
               
               
                 22 
                 ARWALWGDFGMDV 
                 HN1 H3 
               
               
                   
               
               
                 23 
                 MGIQGGSVLFGLLLVLAVFCHSGHSLPPRTQVQLVQSGAEVKRPGASVQVS 
                 SP-HN1-TR3 
               
               
                   
                 CRASGYSINTYYMQWVRQAPGAGLEWMGVINPSGVTSYAQKFQGRVTLTND 
                   
               
               
                   
                 TSTNTVYMQLNSLTSADTAVYYCARWALWGDFGMDVWGKGTLVTVSSGGGG 
                   
               
               
                   
                 SGGGGSGGGGSDIQMTQSPSTLSASIGDRVTITCRASEGIYHWLAWYQKPG 
                   
               
               
                   
                 KAPKLLIYKASSLASGAPSRFSGSGSGTDFTLTISSLQPDDFATYYCQQYS 
                   
               
               
                   
                 NYPLTFGGGTKLEIKRARTPPMILRTSEETISTVQEKQQNISPLVRERGPQ 
                   
               
               
                   
                 RVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRN 
                   
               
               
                   
                 GELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILL 
                   
               
               
                   
                 MKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEAS 
                   
               
               
                   
                 FFGAFLVGRSQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALG 
                   
               
               
                   
                 RKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKEN 
                   
               
               
                   
                 TKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFEL 
                   
               
               
                   
                 KENDRIFVSVTNEHLIDMDHEASFFGAFLVGRSQNISPLVRERGPQRVAAH 
                   
               
               
                   
                 ITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVI 
                   
               
               
                   
                 HEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSAR 
                   
               
               
                   
                 NSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAF 
                   
               
               
                   
                 LVGRS 
                   
               
               
                   
               
               
                 24 
                 MGIQGGSVLFGLLLVLAVFCHSGHSLPPRTQVQLQQSGPGLVTPSQTLSLT 
                 SP-P4-TR3 
               
               
                   
                 CAISGDSVSSNSATWNWIRQSPSRGLEWLGRTYYRSKWYNDYAVSVKSRMS 
                   
               
               
                   
                 INPDTSKNQFSLQLNSVTPEDTAVYYCARGMMTYYYGMDVWGQGTTVTVSS 
                   
               
               
                   
                 GILGSGGGGSGGGGSGGGGSQPVLTQSSSLSASPGASASLTCTLRSGINVG 
                   
               
               
                   
                 PYRIYWYQQKPGSPPQYLLNYKSDSDKQQGSGVPSRFSGSKDASANAGVLL 
                   
               
               
                   
                 ISGLRSEDEADYYCMIWHSSAAVFGGGTQLTVLSRTPPMILRTSEETISTV 
                   
               
               
                   
                 QEKQQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSW 
                   
               
               
                   
                 ESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQ 
                   
               
               
                   
                 MVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRI 
                   
               
               
                   
                 FVSVTNEHLIDMDHEASFFGAFLVGRSQNISPLVRERGPQRVAAHITGTRG 
                   
               
               
                   
                 RSNTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFY 
                   
               
               
                   
                 YIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK 
                   
               
               
                   
                 DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRSQ 
                   
               
               
                   
                 NISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRS 
                   
               
               
                   
                 GHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYI 
                   
               
               
                   
                 YKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVT 
                   
               
               
                   
                 NEHLIDMDHEASFFGAFLVGRS 
                   
               
               
                   
               
               
                 25 
                 LPPRTQVQLVQSGAEVKRPGASVQVSCRASGYSINTYYMQWVRQAPGAGLE 
                 HN1-TR3 
               
               
                   
                 WMGVINPSGVTSYAQKFQGRVTLTNDTSTNTVYMQLNSLTSADTAVYYCAR 
                   
               
               
                   
                 WALWGDFGMDVWGKGTLVTVSSGGGGSGGGGSGGGGSDIQMTQSPSTLSAS 
                   
               
               
                   
                 IGDRVTITCRASEGIYHWLAWYQKPGKAPKLLIYKASSLASGAPSRFSGSG 
                   
               
               
                   
                 SGTDFTLTISSLQPDDFATYYCQQYSNYPLTFGGGTKLEIKRARTPPMILR 
                   
               
               
                   
                 TSEETISTVQEKQQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEK 
                   
               
               
                   
                 ALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI 
                   
               
               
                   
                 KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGI 
                   
               
               
                   
                 FELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRSQNISPLVRERGPQRV 
                   
               
               
                   
                 AAHITGTRGRSNTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGE 
                   
               
               
                   
                 LVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMK 
                   
               
               
                   
                 SARNSCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFF 
                   
               
               
                   
                 GAFLVGRSQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRK 
                   
               
               
                   
                 INSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTK 
                   
               
               
                   
                 NDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKE 
                   
               
               
                   
                 NDRIFVSVTNEHLIDMDHEASFFGAFLVGRS 
                   
               
               
                   
               
               
                 26 
                 LPPRTQVQLQQSGPGLVTPSQTLSLTCAISGDSVSSNSATWNWIRQSPSRG 
                 P4-TR3 
               
               
                   
                 LEWLGRTYYRSKWYNDYAVSVKSRMSINPDTSKNQFSLQLNSVTPEDTAVY 
                   
               
               
                   
                 YCARGMMTYYYGMDVWGQGTTVTVSSGILGSGGGGSGGGGSGGGGSQPVLT 
                   
               
               
                   
                 QSSSLSASPGASASLTCTLRSGINVGPYRIYWYQQKPGSPPQYLLNYKSDS 
                   
               
               
                   
                 DKQQGSGVPSRFSGSKDASANAGVLLISGLRSEDEADYYCMIWHSSAAVFG 
                   
               
               
                   
                 GGTQLTVLSRTPPMILRTSEETISTVQEKQQNISPLVRERGPQRVAAHITG 
                   
               
               
                   
                 TRGRSNTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEK 
                   
               
               
                   
                 GFYYIYSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSC 
                   
               
               
                   
                 WSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVG 
                   
               
               
                   
                 RSQNISPLVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWES 
                   
               
               
                   
                 SRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEIKENTKNDKQMV 
                   
               
               
                   
                 QYIYKYTSYPDPILLMKSARNSCWSKDAEYGLYSIYQGGIFELKENDRIFV 
                   
               
               
                   
                 SVTNEHLIDMDHEASFFGAFLVGRSQNISPLVRERGPQRVAAHITGTRGRS 
                   
               
               
                   
                 NTLSSPNSKNEKALGRKINSWESSRSGHSFLSNLHLRNGELVIHEKGFYYI 
                   
               
               
                   
                 YSQTYFRFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKDA 
                   
               
               
                   
                 EYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEASFFGAFLVGRS 
               
               
                   
               
            
           
         
       
     
     EXAMPLES 
     The following examples illustrate various iterations of the invention and are not intended to be limiting of the scope of any claim. 
     Example 1. Construction of a TRAIL Trimer Plasmid 
     Recombinant human TRAIL (aa 114-281, (SEQ ID NO: 1) was purchased from Enzo Life Sciences. The wild type, N-terminal ectodomain of human TRAIL (TR) described herein contains amino acids 91-281 (SEQ ID NO: 1) (domain I, compare  FIG. 3  including the striped box; the white box represents aa 114-281 of rTRAIL). A 594 bp DNA fragment amplified by PCR from a human U937 cDNA library (Spitzer, D., et al., J. Immunol. 2007, 179: 2600-2608) was inserted via BsiWI (5′) and HindIII (3′) into sT-DAF (Spitzer, D., et al., Mol. Immunol. 2004, 40: 5 911-919). This basic TRAIL plasmid, designated pTRBgI, contains an additional BgIII site immediately upstream of TRAIL&#39;s native stop codon for subsequent cloning purposes. It also contains a signal peptide to ensure secretion of the protein. Following linearization of pTRBgI with BgIII and HindIII, the slightly smaller PCR-derived domains I′ (5′ BamHI and 3′ HindIII), containing amino acids 108-281 of native TRAIL (SEQ ID NO: 1), were added stepwise resulting in pTR2 (intermediate) and pTR3, respectively ( FIG. 4 ). 
     Example 2. Construction of a TRAIL Trimer Plasmid Further Comprising an Epitope-Binding Agent 
     The non-targeted platform TR3 is easily accessible for further genetic modifications for targeted cancer therapy. Mesothelin targeting of TR3 can be achieved by insertion of a nucleotide sequence encoding an epitope-binding agent into the pTR3 plasmid. In this example, a nucleotide sequence of a single chain antibody fragment (scFv) was inserted into the pTR3 plasmid. To generate targeted constructs, the following cDNA sequences are custom-synthesized: 1) a 738 bp cDNA encoding for SS, an anti-mouse scFv that binds with high affinity to mesothelin (Chowdhury, et al.,  PNAS.  1998; 95(2):669-674); 2) a 795 bp fragment encoding for P4, an anti-human scFv that binds with high affinity to mesothelin (Bergan, et al., 2007 , Cancer Lett  255: 263-274); and 3) a 732 bp fragment encoding for HN1, an anti-human scFv that binds with high affinity to mesothelin (Ho, et al., 2011 , International Journal of Cancer.  128(9), 2020-2030). The 738 bp BsiWI scFv-SS fragment, the 795 bp BsiWI scFv-P4 fragment, or the 732 bp BsiWI scFv-HN1 fragment, is inserted into the BsiWI-linearized pTR3 plasmid to generate pSS-TR3 plasmid, pP4-TR3 plasmid, or pHN1-TR3 plasmid, respectively. 
     Example 3. Preparation and Confirmation of Constructs Described in Section I 
     The pTR3, pSS-TR3, pP4-TR3, and pHN1-TR3 plasmids are transiently expressed in HEK293T cells using Opti-Mem serum-free medium (Gibco) and TransIT-293 (Mirus, MIR2700) transfection reagent, as per the manufacturer&#39;s instructions. To obtain concentrated TR3 protein stocks from harvested cells, the supernatants are applied to centrifugal filter devices with a 10 kDa molecular cut-off (Centricon Plus-20, Millipore, Bedford, Md.). 
     The single chain character of the TR3 proteins is verified by Western blot analysis. Under reducing conditions, commercially available recombinant TRAIL (rTRAIL, aa 114-281) exhibits a molecular weight of 18 kDa and TR3 has a molecular weight of approximately 61 kDa, consistent with the calculated size. Insertion of single chain antibody fragments HN1, P4 and SS into TR3 increases the molecular weight of each targeted therapeutic as expected ( FIG. 5 ). 
     Example 4. Cells Overexpressing Mesothelin Tether all scFv-Containing Constructs to Cell Surface 
     Mature human mesothelin is inserted into the membrane of Jurkat cells via a glycosylphosphatidyl (GPI) anchor. Anti-mesothelin immunostaining confirms surface expression of human mesothelin on Jurkat-Meso cells using flow cytometry. To test the ability of scFv-containing TR3 variants to bind to cell surface human mesothelin, Jurkat-Meso cells are treated with SS-TR3, P4-TR3, or HN1-TR3. The staining pattern of anti-TRAIL immunostaining confirms the tethering of SS-TR3, P4-TR3, and HN1-TR3 to human mesothelin on Jurkat-Meso cells using flow cytometry ( FIG. 6 ). 
     Example 5. SS-TR3, P4-TR3 and HN1-TR3 Induce Apoptosis in a Mesothelin-Expressing Cancer Model 
     Mesothelin-deficient Jurkat wild-type cells and mesothelin-expressing Jurkat-Meso cells are treated in vitro with increasing equimolar concentrations of TR3 and the targeted variants SS-TR3, P4-TR3, and HN1-TR3. Cell viability of the treated cells was determined using the CellTiter-Glo kit (Promega) according to the manufacturer&#39;s instructions. Data are recorded with a luminescence plate reader (Molecular Devices, SpectraMAX-Gemini, SoftMax Version 5 software, Sunnyvale, Calif.). In the absence of mesothelin expression, all constructs are equally potent in cell viability assays ( FIG. 7A ). When mesothelin is present on the surface of the cancer cells, SS-TR3 is the most potent, followed by P4-TR3 and HN1-TR3 (similar activity profiles), and TR3 is the least effective at inducing apoptosis ( FIG. 7B ). 
     Example 6. The Delivery Moieties of the Targeted Biologics do not Interfere with TRAIL Death Receptor Recognition 
     Jurkat wild-type cells are treated with a constant amount of TR3, SS-TR3, P4-TR3, and HN1-TR3 (70% specific cell death) in the presence of anti-TRAIL mAb, a blocker of death receptor engagement. Cells treated with the vehicle DMSO are used as a control. Cell viability of the treated cells was determined using the CellTiter-Glo kit (Promega) according to the manufacturer&#39;s instructions. Data are recorded with a luminescence plate reader (Molecular Devices, SpectraMAX-Gemini, SoftMax Version 5 software, Sunnyvale, Calif.). The addition of anti-TRAIL mAb prevents cell specific death by all of the constructs ( FIG. 8 ), indicating that the TR3 domain has unrestricted access to the death receptors expressed on the Jurkat cells. 
     The downstream effector of the extrinsic pathway, intracellular caspases, is blocked by using the pan-caspase inhibitor, Z-VAD-FMK (Enzo). Jurkat wild-type cells are treated with a constant amount of TR3, SS-TR3, P4-TR3, and HN1-TR3 (70% specific cell death) in the presence of Z-VAD-FMK or DMSO as a control. Cell death is completely blocked with Z-VAD-FMK, confirming that the constructs engage the extrinsic death pathway ( FIG. 9 ). 
     Example 7. P4-TR3 and HN1-TR3 Induce Apoptosis Via a Direct “Cis” Mechanism in a Mesothelin-Expressing Cancer Model 
     Phenotypic characterization reveals the differential cell death mechanisms between SS-TR3 and the humanized variants P4-TR3 and HN1-TR3. SS-TR3 treatment results in a significant accumulation of cancer cells (from 5.01% to 17.7%, anti-mesothelin stain), in agreement with an established “trans” killing profile. In contrast, P4-TR3 and HN1-TR3 eliminate their cancer targets directly via a more desirable “cis” mechanism (from 5.01% to 0.92% and 0.75%, respectively) ( FIG. 10 ). 
     Example 8. Treatment of Adherent Human Cancer Cells Expressing Endogenous Mesothelin with TR-3, P4-TR3, HN1-TR3 and SS-TR3 
     Three human, adherent cancer cell lines express endogenous mesothelin: ovarian cancer cell line OVCAR3 ( FIG. 11A ), pancreatic cancer cell line BxPC-3 ( FIG. 12A ), and adenocarcinoma cell line AsPC-1 ( FIG. 13A ). Each adherent cancer cell line is treated with increasing concentrations of TR-3, P4-TR3, HN1-TR3 or SS-TR3. Cell viability of the treated cells was determined using the CellTiter-Glo kit (Promega) according to the manufacturer&#39;s instructions. Data are recorded with a luminescence plate reader (Molecular Devices, SpectraMAX-Gemini, SoftMax Version 5 software, Sunnyvale, Calif.). OVCAR3 cells treated with P4-TR3 and HN1-TR3 are readily eliminated whereas the SS-TR3 performs worse than TR3 ( FIG. 11B ). BxPC-3 cells demonstrated a similar profile ( FIG. 12B ). The data reveal the strong killing capacity of P4-TR3 and HN1-TR3, consistent with a proposed cis-killing phenotype. TR3 shows little killing capacity, while SS-TR3 is even less potent, consistent with an exclusive trans-killing phenotype. Some cancer cells are quite resistant to TRAIL therapy as seen with construct treatment of AsPC-1 cells ( FIG. 13B ); however, this observation indicates that AsPC-1 cells can be used to study the bystander killing properties of the constructs. 
     Example 9. Coculture of Mesothelin-Positive AsPC-1 with Jurkat Bystander Cells in the Presence of Section I Constructs 
     TRAIL resistant, mesothelin-positive AsPC-1 pancreatic cancer cells decorated with increasing concentrations of TR-3, P4-TR3 and HN1-TR3 and SS-TR3, washed in order to eliminate traces of the soluble constructs and are subsequently cocultured with WT Jurkat bystander cells for 24 hours. Cells are next analyzed for viability. SS-TR3-decorated AsPC-1 cells cultured in the presence of wild-type Jurkat cells leads to substantial cell death induction of the Jurkat bystander cells; however, P4-TR3- and HN1-TR3-decorated AsPC-1 cells have only a very limited ability to induce Jurkat bystander cell killing, similar to TR3 alone ( FIG. 14 ). These data confirm the inability of SS-TR3 to kill mesothelin-positive cancer cells directly via a cis mechanism but is very much capable of killing bystander Jurkat cells via a trans mechanism. P4-TR3 and HN1-TR3 nearly exclusively kill via a cis mechanism and are nearly incapable to induce bystander killing (no trans killing).