Anti-DLL3 chimeric antigen receptor and uses thereof

Abstract

Provided herein are anti-DLL3 chimeric antigen receptors (CARs), DLL3 binding proteins, and the use of such CARs or DLL3 binding proteins in the treatment of DLL3-associated disorders (e.g., small cell lung cancer).

Description

[Technical Field]

[0001] The present invention relates to chimeric antigen receptors (CARs) that target DLL3 and binding proteins specific for DLL3. The present invention also relates to nucleic acid sequences encoding the CARs or binding proteins, modified immune cells that express the CARs, and their use to treat DLL3-associated disorders. [Background technology]

[0002] Advances in cellular immunotherapy offer a promising approach for the treatment of various tumors. One such treatment involves genetically engineering immune cells, particularly T cells, to express chimeric antigen receptors (CARs) on their cell surface. Chimeric antigen receptors are proteins that transfer the specificity of monoclonal antibodies (mAbs) to the effector functions of T cells in a conventional manner. When CARs are expressed in T cells, CAR-modified T cells (CAR-T or CAR-T cells) acquire several properties, such as antigen-specific recognition, antitumor reactivity, and proliferation, and can therefore act as "living drugs" to eradicate targeted tumor cells. In principle, any antigen (e.g., a cell surface molecule) can be targeted by these CAR-T cells. CAR-T cell therapy may circumvent tolerance to self-antigens and provide treatment independent of the patient's MHC status. Recent studies have demonstrated remarkable clinical responses in leukemia and lymphoma patients using T cells engineered to express chimeric antigen receptors targeting CD19.

[0003] CARs are expressed as transmembrane proteins containing an antigen-specific binding site, a transmembrane region, and a signaling cytoplasmic domain (e.g., CD3ζ chain). The antigen-specific binding site is usually a single-chain variable fragment (scFv) derived from a monoclonal antibody, consisting of a heavy chain and a light chain connected by a flexible linker. Recently, CAR constructs have incorporated additional cytoplasmic domains from costimulatory molecules such as CD28 or 4-1BB to enhance T cell survival in vivo. CARs have also undergone other genetic modifications, such as the addition of cytokine genes or genes to circumvent immunosuppressive mechanisms at tumor sites.

[0004] The DLL3 (Delta-like Ligand 3) protein has been found to be clinically associated with various proliferative disorders, including tumors exhibiting neuroendocrine characteristics, such as small cell lung cancer (SCLC). SCLC, which originates from neuroendocrine precursor cells, comprises approximately 15% of all lung cancers and has one of the lowest 5-year survival rates at 6% (Alvarado-Luna et al., 2016, Transl Lung Cancer Res 5:26-38; Siegel et al., 2017, CA Cancer J Clin 67:7-30). This is because it is highly aggressive, with approximately two-thirds of patients presenting with metastatic disease at the time of diagnosis, and is highly refractory to conventional treatments (e.g., platinum-based chemotherapy).

[0005] Improved therapeutic approaches for treating SCLC and other DLL3-expressing cancers are needed. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Alvarado-Luna et al.,2016,Transl Lung Cancer Res 5:26-38;Siegel et al.,2017,CA Cancer J Clin 67:7-30 Summary of the Invention

[0007] In one aspect, the present disclosure provides a chimeric antigen receptor (CAR) that targets DLL3 (anti-DLL3 CAR). The anti-DLL3 CAR comprises a DLL3-binding domain, which comprises or is derived from a single-domain antibody (sdAb) or a single-chain variable fragment (scFv).

[0008] In some embodiments, the sdAb comprises a polypeptide comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81 or a variant thereof comprising up to about three amino acid substitutions in CDR1, a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243 or a variant thereof comprising up to about three amino acid substitutions in CDR3.

[0009] In some embodiments, the sdAb comprises a polypeptide comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81, a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162, and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243, or a variant of the polypeptide comprising up to about three amino acid substitutions in CDR1, CDR2, and CDR3.

[0010] In some embodiments, the sdAb is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. The present invention also includes a polypeptide comprising any one of the following:

[0011] In some embodiments, the sdAb is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 The present invention also includes a polypeptide comprising any one of the following:

[0012] In some embodiments the sdAb is a camelid sdAb raised against human or rhesus DLL3.

[0013] In some embodiments, the sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274-354.

[0014] In some embodiments, the sdAb is humanized through CDR grafting.

[0015] In some embodiments, the humanized sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355-367.

[0016] In some embodiments, the scFv comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO: 498 or 504 or a variant thereof comprising up to about three amino acid substitutions in CDR1, CDR2 set forth in SEQ ID NO: 499 or 505 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and CDR3 set forth in SEQ ID NO: 500 or 506 or a variant thereof comprising up to about three amino acid substitutions in CDR3; and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO: 495 or 501 or a variant thereof comprising up to about three amino acid substitutions in CDR1, CDR2 set forth in SEQ ID NO: 496 or 502 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and CDR3 set forth in SEQ ID NO: 497 or 503 or a variant thereof comprising up to about three amino acid substitutions in CDR3.

[0017] In some embodiments, the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO: 498, CDR2 set forth in SEQ ID NO: 499, and CDR3 set forth in SEQ ID NO: 500, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO: 495, CDR2 set forth in SEQ ID NO: 496, and CDR3 set forth in SEQ ID NO: 497; or the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO: 504, CDR2 set forth in SEQ ID NO: 505, and CDR3 set forth in SEQ ID NO: 506, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO: 501, CDR2 set forth in SEQ ID NO: 502, and CDR3 set forth in SEQ ID NO: 503.

[0018] In some embodiments, the VH domain of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 508, and the VL domain of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 507; or the VH domain of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 510, and the VL domain of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 509.

[0019] In some embodiments, the scFvs are obtained from a synthetic human Fab phage library.

[0020] In some embodiments, the DLL3 is human or rhesus DLL3.

[0021] In some embodiments, the anti-DLL3 CAR comprises, from N- to C-terminus, a signal peptide, a DLL3-binding domain, a hinge domain, a transmembrane domain, and an intracellular signaling domain.

[0022] In some embodiments, the intracellular signaling domain is derived from CD3zeta, FcRgamma, FcRbeta, CD3gamma, CD3delta, CD3epsilon, CD5, CD22, CD79a, CD79b, or CD66d.

[0023] In some embodiments, the intracellular signaling domain further comprises an intracellular costimulatory sequence.

[0024] In some embodiments, the intracellular costimulatory sequence is derived from a costimulatory molecule selected from the group consisting of CD27, CD28, 4-1BB, OX40, CD40, PD-1, LFA-1, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3, TNFRSF9, TNFRSF4, TNFRSF8, CD40LG, ITGB2, KLRC2, TNFRSF18, TNFRSF14, HAVCR1, LGALS9, DAP10, DAP12, CD83, a ligand for CD83, and combinations thereof.

[0025] In some embodiments, the CAR comprises an amino acid sequence having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 476-484, 485-494, or 515-516.

[0026] In some embodiments, the DLL3 binding domain comprises two sdAbs linked to each other.

[0027] In some embodiments, each of the sdAbs independently comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:356 or SEQ ID NO:366.

[0028] In some embodiments, the CAR comprises an amino acid sequence having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 518-520.

[0029] In some embodiments, the CAR comprises the amino acid sequence of SEQ ID NO: 520.

[0030] In another aspect, the present disclosure provides a DLL3-binding protein comprising a single domain antibody (sdAb) portion that specifically binds to DLL3, wherein the sdAb portion comprises a polypeptide comprising: CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1-81 or a variant thereof comprising up to about three amino acid substitutions in CDR1; CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82-162 or a variant thereof comprising up to about three amino acid substitutions in CDR2; and CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163-243 or a variant thereof comprising up to about three amino acid substitutions in CDR3.

[0031] In some embodiments, the sdAb portion comprises a polypeptide comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81, a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162, and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243, or a variant of the polypeptide comprising up to about three amino acid substitutions in CDR1, CDR2, and CDR3.

[0032] In some embodiments, the sdAb portion comprises: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. The present invention also includes a polypeptide comprising any one of the following:

[0033] In some embodiments, the sdAb portion comprises: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 The present invention also includes a polypeptide comprising any one of the following:

[0034] In some embodiments the sdAb moiety is a camelid sdAb raised against human or rhesus DLL3.

[0035] In some embodiments, the sdAb portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274-354.

[0036] In some embodiments, the sdAb portion is humanized through CDR grafting.

[0037] In some embodiments, the humanized sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355-367.

[0038] In some embodiments, the DLL3 is human or rhesus DLL3.

[0039] In another aspect, the disclosure provides a DLL3 binding protein comprising a single chain variable fragment (scFv) portion that specifically binds to DLL3, wherein the scFv portion comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH domain of the scFv portion comprises a CDR1 set forth in SEQ ID NO: 498 or 504 or a variant thereof comprising up to about three amino acid substitutions in CDR1, a CDR2 set forth in SEQ ID NO: 499 or 505 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and a CDR3 set forth in SEQ ID NO: 500 or 506. and the VL domain of the scFv portion comprises CDR1 set forth in SEQ ID NO: 495 or 501 or a variant thereof comprising up to about three amino acid substitutions in CDR1, CDR2 set forth in SEQ ID NO: 496 or 502 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and CDR3 set forth in SEQ ID NO: 497 or 503 or a variant thereof comprising up to about three amino acid substitutions in CDR3.

[0040] In some embodiments, the scFv portion comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH domain of the scFv portion comprises CDR1 set forth in SEQ ID NO:498, CDR2 set forth in SEQ ID NO:499, and CDR3 set forth in SEQ ID NO:500, and the VL domain of the scFv portion comprises CDR1 set forth in SEQ ID NO:495, CDR2 set forth in SEQ ID NO:496, and CDR3 set forth in SEQ ID NO:497; or the VH domain of the scFv portion comprises CDR1 set forth in SEQ ID NO:504, CDR2 set forth in SEQ ID NO:505, and CDR3 set forth in SEQ ID NO:506, and the VL domain of the scFv portion comprises CDR1 set forth in SEQ ID NO:501, CDR2 set forth in SEQ ID NO:502, and CDR3 set forth in SEQ ID NO:503.

[0041] In some embodiments, the VH domain of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO:508, and the VL domain of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO:507; or the VH domain of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO:510, and the VL domain of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO:509.

[0042] In some embodiments, the scFv portion is obtained from a synthetic human Fab phage library.

[0043] In some embodiments, the DLL3 is human or rhesus DLL3.

[0044] In another aspect, the present disclosure provides an isolated nucleic acid molecule encoding an anti-DLL3 CAR or a DLL3 binding protein as described above.

[0045] In some embodiments, the isolated nucleic acid molecule comprises a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 368-448 that encodes a camelid single domain antibody (sdAb).

[0046] In some embodiments, the isolated nucleic acid molecule comprises a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 449-461 that encodes a humanized camelid sdAb.

[0047] In some embodiments, the isolated nucleic acid molecule comprises a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 511-514 that encodes the VL or VH domain of a human scFv.

[0048] In some embodiments, the nucleic acid molecule further comprises a polynucleotide sequence encoding a chimeric switch receptor (CSR) or a dominant negative receptor (DNR).

[0049] In some embodiments, the nucleic acid molecule further comprises a polynucleotide sequence encoding a PD-1 dominant negative receptor (PD-1 DNR), a PD-1 chimeric switch receptor (PD-1 CSR), or a TGF-β dominant negative receptor (TGF-β DNR).

[0050] In some embodiments, the PD-1 DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:523.

[0051] In some embodiments, the PD-1 CSR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:524.

[0052] In some embodiments, the TGF-β DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:529.

[0053] In some embodiments, the polynucleotide sequence encoding the PD-1 DNR, PD-1 CSR, or TGF-β DNR is linked to the polynucleotide sequence encoding the CAR via a polynucleotide sequence encoding a 2A self-cleaving peptide.

[0054] In some embodiments, the 2A self-cleaving peptide is a T2A peptide or a P2A peptide.

[0055] In some embodiments, the nucleic acid molecule comprises, in the 5' to 3' direction, a polynucleotide sequence encoding a CAR, a polynucleotide sequence encoding a 2A self-cleaving peptide, and a polynucleotide sequence encoding a PD-1 DNR, a PD-1 CSR, or a TGF-β DNR.

[0056] In some embodiments, the nucleic acid molecule encodes a peptide having at least about 95% sequence identity to SEQ ID NO: 521 or 522, or a nucleic acid molecule encoding a peptide having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 525-528.

[0057] In another aspect, the disclosure provides an expression vector comprising an isolated nucleic acid molecule as described above.

[0058] In another aspect, the present disclosure provides a modified immune cell comprising an isolated nucleic acid molecule as described above.

[0059] In some embodiments, the engineered immune cell is selected from the group consisting of a cytotoxic T cell, a helper T cell, a natural killer T cell, a gamma delta T cell, an NKT cell, and a nature killer cell.

[0060] In another aspect, the present disclosure provides modified immune cells that express an anti-DLL3 CAR as described above.

[0061] In some embodiments, the modified immune cells also express CSR or DNR.

[0062] In some embodiments, the CSR is a PD-1 CSR and the DNR is a PD-1 DNR or a TGF-β DNR.

[0063] In some embodiments, the PD-1 DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:523.

[0064] In some embodiments, the PD-1 CSR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:524.

[0065] In some embodiments, the TGF-β DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:529.

[0066] In some embodiments, the CAR and CSR, or the CAR and DNR, are co-expressed via a 2A self-cleaving peptide.

[0067] In some embodiments, the 2A self-cleaving peptide is a T2A peptide or a P2A peptide.

[0068] In some embodiments, the engineered immune cells express a CAR and a PD-1 DNR and are stimulated by cells that express DLL3 and PD-L1.

[0069] In some embodiments, the engineered immune cells express a CAR and a PD-1 CSR and are stimulated by cells that express DLL3 and PD-L1.

[0070] In some embodiments, the engineered immune cells express a CAR and a TGF-β DNR, and are stimulated by cells expressing DLL3 in the presence of TGF-β.

[0071] In some embodiments, the engineered immune cells are selected from the group consisting of cytotoxic T cells, helper T cells, natural killer T cells, γδ T cells, NKT cells, and natural killer cells.

[0072] In another aspect, the present disclosure provides a pharmaceutical composition comprising an anti-DLL3 CAR, an isolated DLL3 binding protein, an expression vector, or a modified immune cell as described above, and a physiologically acceptable excipient.

[0073] In another aspect, the present disclosure provides a method for treating a DLL3-associated disorder in a subject, the method comprising administering to the subject a therapeutically effective amount of modified immune cells as described above, or a therapeutically effective amount of a pharmaceutical composition as described above.

[0074] In another aspect, the present disclosure provides use of an anti-DLL3 CAR, an isolated DLL3 binding protein, an expression vector, or a modified immune cell as described above for the preparation of a medicament for treating a DLL3-associated disorder.

[0075] In another aspect, the present disclosure provides a medicament for use in treating a DLL3-associated disorder, the medicament comprising an anti-DLL3 CAR, a DLL3 binding protein, an expression vector, or a modified immune cell as described above.

[0076] In some embodiments, the DLL3-associated disorder is a cancer selected from the group consisting of lung cancer, melanoma, breast cancer, prostate cancer, colon cancer, renal cell carcinoma, ovarian cancer, neuroblastoma, rhabdomyosarcoma, leukemia, and lymphoma.

[0077] In some embodiments, the cancer expresses DLL3 and PD-L1.

[0078] In some embodiments, the cancer has a higher level of TGF-β expression compared to the corresponding normal tissue.

[0079] In some embodiments, the DLL3-associated disorder is small cell lung cancer. [The present invention 1001] A chimeric antigen receptor (CAR) comprising a DLL3-binding domain, wherein the DLL3-binding domain comprises or is derived from a single-domain antibody (sdAb) or a single-chain variable fragment (scFv). [The present invention 1002] 1001. A CAR of the present invention, wherein the sdAb comprises a polypeptide comprising: CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81 or a variant thereof comprising up to about three amino acid substitutions in the CDR1; CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162 or a variant thereof comprising up to about three amino acid substitutions in the CDR2; and CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243 or a variant thereof comprising up to about three amino acid substitutions in the CDR3. [The present invention 1003] The CAR of the present invention 1001 or 1002, wherein the sdAb comprises a polypeptide comprising CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81, CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162, and CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243, or a variant of the polypeptide comprising up to approximately three amino acid substitutions in the CDR1, the CDR2, and the CDR3. [The present invention 1004] the sdAb (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. A CAR of any one of 1001 to 1003, comprising a polypeptide comprising any one of the following: [The present invention 1005] the sdAb (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 A CAR of any one of 1001 to 1004, comprising a polypeptide comprising any one of the following: [The present invention 1006] The CAR of any of claims 1001 to 1005, wherein the sdAb is a camel sdAb raised against human or rhesus DLL3. [The present invention 1007] The CAR of any one of claims 1001 to 1006, wherein the sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274 to 354. [The present invention 1008] The CAR of any of claims 1001 to 1007, wherein the sdAb is humanized through CDR grafting. [The present invention 1009] The CAR of any one of claims 1001 to 1008, wherein the humanized sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355 to 367. [The present invention 1010] The CAR of any of the present inventions 1001 to 1009, wherein the scFv comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH of the scFv comprises CDR1 shown in SEQ ID NO: 498 or 504 or a variant thereof comprising up to about three amino acid substitutions in the CDR1, CDR2 shown in SEQ ID NO: 499 or 505 or a variant thereof comprising up to about three amino acid substitutions in the CDR2, and CDR3 shown in SEQ ID NO: 500 or 506 or a variant thereof comprising up to about three amino acid substitutions in the CDR3, and the VL of the scFv comprises CDR1 shown in SEQ ID NO: 495 or 501 or a variant thereof comprising up to about three amino acid substitutions in the CDR1, CDR2 shown in SEQ ID NO: 496 or 502 or a variant thereof comprising up to about three amino acid substitutions in the CDR2, and CDR3 shown in SEQ ID NO: 497 or 503 or a variant thereof comprising up to about three amino acid substitutions in the CDR3. [The present invention 1011] A CAR of any of the present inventions 1001 to 1010, wherein the VH of the scFv comprises CDR1 shown in SEQ ID NO: 498, CDR2 shown in SEQ ID NO: 499, and CDR3 shown in SEQ ID NO: 500, and the VL of the scFv comprises CDR1 shown in SEQ ID NO: 495, CDR2 shown in SEQ ID NO: 496, and CDR3 shown in SEQ ID NO: 497; or the VH of the scFv comprises CDR1 shown in SEQ ID NO: 504, CDR2 shown in SEQ ID NO: 505, and CDR3 shown in SEQ ID NO: 506, and the VL of the scFv comprises CDR1 shown in SEQ ID NO: 501, CDR2 shown in SEQ ID NO: 502, and CDR3 shown in SEQ ID NO: 503. [The present invention 1012] A CAR of any of the present inventions 1001 to 1011, wherein the VH of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence shown in SEQ ID NO: 508, and the VL of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence shown in SEQ ID NO: 507; or the VH of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence shown in SEQ ID NO: 510, and the VL of the scFv comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence shown in SEQ ID NO: 509. [The present invention 1013] The CAR of any of claims 1001 to 1012, wherein the scFv is obtained from a synthetic human Fab phage library. [The present invention 1014] The CAR of any of claims 1001 to 1013, wherein the DLL3 is human or rhesus DLL3. [The present invention 1015] The CAR of any of claims 1001 to 1014, comprising, from the N-terminus to the C-terminus, a signal peptide, the DLL3-binding domain, a hinge domain, a transmembrane domain, and an intracellular signaling domain. [The present invention 1016] The CAR of any one of claims 1001 to 1015, wherein the intracellular signaling domain is derived from CD3ζ, FcRγ, FcRβ, CD3γ, CD3δ, CD3ε, CD5, CD22, CD79a, CD79b, or CD66d. [The present invention 1017] The CAR of any one of claims 1001 to 1016, wherein the intracellular signaling domain further comprises an intracellular costimulatory sequence. [The present invention 1018] CAR of any of claims 1001 to 1017, wherein the intracellular costimulatory sequence is derived from a costimulatory molecule selected from the group consisting of CD27, CD28, 4-1BB, OX40, CD40, PD-1, LFA-1, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3, TNFRSF9, TNFRSF4, TNFRSF8, CD40LG, ITGB2, KLRC2, TNFRSF18, TNFRSF14, HAVCR1, LGALS9, DAP10, DAP12, CD83, a ligand for CD83, and combinations thereof. [The present invention 1019] A CAR of any one of SEQ ID NOs: 476 to 484, 485 to 494, or 515 to 516, comprising an amino acid sequence having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 476 to 484, 485 to 494, or 515 to 516. [The present invention 1020] The CAR of any of claims 1001 to 1019, wherein the DLL3-binding domain comprises two sdAbs linked to each other. [The present invention 1021] The CAR of any of claims 1001 to 1020, wherein each of the sdAbs independently comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO: 356 or SEQ ID NO: 366. [The present invention 1022] A CAR of any of the present inventions 1001 to 1021, comprising an amino acid sequence having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 518 to 520. [The present invention 1023] A CAR of any one of 1001 to 1022 of the present invention, comprising the amino acid sequence of SEQ ID NO: 520. [The present invention 1024] A DLL3-binding protein comprising a single domain antibody (sdAb) portion that specifically binds to DLL3, wherein the sdAb portion comprises a polypeptide comprising: a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81 or a variant thereof comprising up to about three amino acid substitutions in the CDR1; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162 or a variant thereof comprising up to about three amino acid substitutions in the CDR2; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243 or a variant thereof comprising up to about three amino acid substitutions in the CDR3. [The present invention 1025] 1024. A DLL3-binding protein of the present invention, wherein the sdAb portion comprises a polypeptide comprising CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1 to 81, CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82 to 162, and CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163 to 243, or a variant of the polypeptide comprising up to about three amino acid substitutions in the CDR1, the CDR2, and the CDR3. [The present invention 1026] the sdAb portion (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. DLL3-binding protein of the present invention 1024 or 1025, comprising a polypeptide comprising any one of: [The present invention 1027] the sdAb portion (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 DLL3-binding protein according to any one of claims 1024 to 1026, comprising a polypeptide comprising any one of the following: [The present invention 1028] DLL3-binding protein of any one of claims 1024 to 1027, wherein the sdAb portion is a camel sdAb raised against human or rhesus DLL3. [The present invention 1029] DLL3-binding protein of any one of claims 1024 to 1028, wherein the sdAb portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274 to 354. [The present invention 1030] DLL3-binding protein of any of claims 1024 to 1029, wherein the sdAb portion is humanized through CDR grafting. [The present invention 1031] DLL3-binding protein of any of claims 1024 to 1030, wherein said humanized sdAb comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355 to 367. [The present invention 1032] The DLL3-binding protein of any one of claims 1024 to 1031, wherein the DLL3 is human or rhesus DLL3. [The present invention 1033] 1. A DLL3 binding protein comprising a single chain variable fragment (scFv) portion that specifically binds to DLL3, wherein the scFv portion comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH of the scFv portion comprises a CDR1 set forth in SEQ ID NO: 498 or 504 or a variant thereof comprising up to about three amino acid substitutions in the CDR1, a CDR2 set forth in SEQ ID NO: 499 or 505 or a variant thereof comprising up to about three amino acid substitutions in the CDR2, and a CDR3 set forth in SEQ ID NO: 500 or 506 or A DLL3-binding protein comprising a CDR1 set forth in SEQ ID NO: 495 or 501 or a variant thereof comprising up to about three amino acid substitutions in the CDR1, a CDR2 set forth in SEQ ID NO: 496 or 502 or a variant thereof comprising up to about three amino acid substitutions in the CDR2, and a CDR3 set forth in SEQ ID NO: 497 or 503 or a variant thereof comprising up to about three amino acid substitutions in the CDR3. [The present invention 1034] A DLL3-binding protein of the present invention 1033, wherein the VH of the scFv portion comprises CDR1 set forth in SEQ ID NO: 498, CDR2 set forth in SEQ ID NO: 499, and CDR3 set forth in SEQ ID NO: 500, and the VL of the scFv portion comprises CDR1 set forth in SEQ ID NO: 495, CDR2 set forth in SEQ ID NO: 496, and CDR3 set forth in SEQ ID NO: 497; or the VH of the scFv portion comprises CDR1 set forth in SEQ ID NO: 504, CDR2 set forth in SEQ ID NO: 505, and CDR3 set forth in SEQ ID NO: 506, and the VL of the scFv portion comprises CDR1 set forth in SEQ ID NO: 501, CDR2 set forth in SEQ ID NO: 502, and CDR3 set forth in SEQ ID NO: 503. [This invention 1035] The DLL3 binding protein of the present invention 1033 or 1034, wherein the VH of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 508, and the VL of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 507; or the VH of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 510, and the VL of the scFv portion comprises an amino acid sequence having at least about 95% sequence identity to the amino acid sequence set forth in SEQ ID NO: 509. [The present invention 1036] DLL3-binding protein of any one of claims 1033 to 1035, wherein the scFv portion is obtained from a synthetic human Fab phage library. [This invention 1037] The DLL3-binding protein of any one of claims 1033 to 1036, wherein the DLL3 is human or rhesus DLL3. [The present invention 1038] An isolated nucleic acid molecule encoding a CAR of any one of the present inventions 1001 to 1023 or a DLL3-binding protein of any one of the present inventions 1024 to 1032 or 1033 to 1037. [This invention 1039] 1038. An isolated nucleic acid molecule of the present invention comprising a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 368 to 448, encoding a camelid single domain antibody (sdAb). [The present invention 1040] 1038 or 1039, an isolated nucleic acid molecule of the present invention, comprising a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 449 to 461, encoding a humanized camelid sdAb. [The present invention 1041] The isolated nucleic acid molecule of any one of claims 1038 to 1040, comprising a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 511 to 514, encoding the VL or VH domain of human scFv. [The present invention 1042] The isolated nucleic acid molecule of any of claims 1038 to 1041, further comprising a polynucleotide sequence encoding a chimeric switch receptor (CSR) or a dominant negative receptor (DNR). [This invention 1043] The isolated nucleic acid molecule of any one of claims 1038 to 1042, further comprising a polynucleotide sequence encoding a PD-1 dominant negative receptor (PD-1 DNR), a PD-1 chimeric switch receptor (PD-1 CSR), or a TGF-β dominant negative receptor (TGF-β DNR). [This invention 1044] The isolated nucleic acid molecule of any of claims 1038 to 1043, wherein the PD-1 DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO: 523; and the PD-1 CSR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO: 524. [This invention 1045] The isolated nucleic acid molecule of any one of claims 1038 to 1044, wherein the TGF-β DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:529. [The present invention 1046] The isolated nucleic acid molecule of any one of claims 1038 to 1045, wherein the polynucleotide sequence encoding the PD-1 DNR, the PD-1 CSR, or the TGF-β DNR is linked to the polynucleotide sequence encoding the CAR via a polynucleotide sequence encoding a 2A self-cleaving peptide. [This invention 1047] The isolated nucleic acid molecule of any one of claims 1038 to 1046, wherein the 2A self-cleaving peptide is a T2A peptide or a P2A peptide. [This invention 1048] The isolated nucleic acid molecule of any of claims 1038 to 1047, comprising, in the 5' to 3' direction, a polynucleotide sequence encoding the CAR, a polynucleotide sequence encoding the 2A self-cleaving peptide, and a polynucleotide sequence encoding the PD-1 DNR, the PD-1 CSR, or the TGF-β DNR. [This invention 1049] Any of the isolated nucleic acid molecules of the present invention 1038 to 1048, which encode a peptide having at least about 95% sequence identity to SEQ ID NO: 521 or 522, or encode a peptide having at least about 95% sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NOs: 525 to 528. [The present invention 1050] An expression vector comprising any one of the isolated nucleic acid molecules of the present inventions 1038 to 1049. [This invention 1051] A modified immune cell comprising the isolated nucleic acid molecule of any one of 1038 to 1049 of the present invention or the expression vector of 1050 of the present invention. [This invention 1052] The modified immune cell of the present invention 1051, selected from the group consisting of cytotoxic T cells, helper T cells, natural killer T cells, γδ T cells, NKT cells, and nature killer cells. [This invention 1053] A modified immune cell expressing any one of the CARs of the present invention 1001 to 1023. [This invention 1054] The modified immune cell of the present invention 1053, which also expresses CSR or DNR. [This invention 1055] The modified immune cell of the present invention 1053 or 1054, wherein the CSR is PD-1 CSR and the DNR is PD-1 DNR or TGF-β DNR. [The present invention 1056] The modified immune cell of any of claims 1053 to 1055, wherein the PD-1 DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO: 523; and the PD-1 CSR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO: 524. [This invention 1057] 1057. The modified immune cell of any of claims 1053 to 1056, wherein said TGF-β DNR comprises an amino acid sequence having at least about 95% sequence identity to SEQ ID NO:529. [This invention 1058] The modified immune cell of any of 1053 to 1057, wherein the CAR and the CSR, or the CAR and the DNR, are simultaneously expressed via a 2A self-cleaving peptide. [This invention 1059] The modified immune cell of any of claims 1053 to 1058, wherein the 2A self-cleaving peptide is a T2A peptide or a P2A peptide. [The present invention 1060] The modified immune cell of any of 1053 to 1059 of the present invention, which expresses the CAR and the PD-1 CSR. [The present invention 1061] The modified immune cell of any of claims 1053 to 1060, which expresses the CAR and the TGF-β DNR and is stimulated by a cell expressing DLL3 in the presence of TGF-β. [The present invention 1062] The modified immune cell of any of claims 1053 to 1061 of the present invention, which is selected from the group consisting of cytotoxic T cells, helper T cells, natural killer T cells, γδ T cells, NKT cells, and nature killer cells. [The present invention 1063] A pharmaceutical composition comprising a CAR of any one of claims 1001 to 1023 of the present invention, a DLL3-binding protein of any one of claims 1024 to 1032 of the present invention or claims 1033 to 1037 of the present invention, an expression vector of claim 1050 of the present invention, or a modified immune cell of any one of claims 1051 to 1062 of the present invention, and a physiologically acceptable excipient. [The present invention 1064] A method for treating a DLL3-related disorder in a subject, comprising administering to the subject a therapeutically effective amount of any of the modified immune cells of present inventions 1051 to 1062, or a therapeutically effective amount of the pharmaceutical composition of present invention 1063. [This invention 1065] 1064. The method of claim 1064, wherein said DLL3-related disorder is a cancer selected from the group consisting of lung cancer, melanoma, breast cancer, prostate cancer, colon cancer, renal cell carcinoma, ovarian cancer, neuroblastoma, rhabdomyosarcoma, leukemia, and lymphoma. [The present invention 1066] 1065. The method of claim 105, wherein said DLL3-related disorder is small cell lung cancer. [This invention 1067] The method of any one of claims 1064 to 1066, wherein the cancer expresses DLL3 and PD-L1. [The present invention 1068] The method of any of claims 1064 to 1067, wherein said cancer has a higher TGF-β expression level compared to corresponding normal tissue. [This invention 1069] Use of a CAR of any of claims 1001 to 1023, a DLL3-binding protein of any of claims 1024 to 1032 or claims 1033 to 1037, an expression vector of claim 1050, or a modified immune cell of any of claims 1051 to 1062, for the preparation of a medicament for treating a DLL3-associated disorder. [The present invention 1070] A drug for use in treating a DLL3-associated disorder, comprising a CAR of any of inventions 1001 to 1023, a DLL3-binding protein of any of inventions 1024 to 1032 or inventions 1033 to 1037, an expression vector of invention 1050, or a modified immune cell of any of inventions 1051 to 1062. [Brief explanation of the drawings]

[0080] [Figure 1] Figure 1 shows a schematic diagram of a VHH-based CAR construct. Sequences that can be used in the construct are listed in SEQ ID NOs: 462-472, 474 and 475. [Figure 2] Figure 2 shows the results of an in vitro cytotoxicity assay of T cells expressing exemplary monospecific CARs containing various camelid anti-DLL3 sdAbs against the small cell lung cancer cell line SHP-77 at an E:T ratio of 2:1 or 5:1. The results for the CARs are presented in order as shown in the legend on the right. [Figure 3] Figure 3 shows the results of cytokine release levels of T cells expressing exemplary monospecific CARs containing various camelid anti-DLL3 sdAbs after co-incubation with the DLL3-expressing tumor cell line SHP-77. IFN-γ and TNF-α release levels (E:T is 2:1 or 5:1) are shown in Figures 3A and 3B, respectively. In each figure, the results for the CARs are presented in order as shown in the legend on the right. [Figure 4] Figure 4 shows the fold expansion of T cells expressing exemplary monospecific CARs comprising various camelid anti-DLL3 sdAbs after long-term stimulation with the small cell lung cancer cell line SHP-77. [Figure 5]Figure 5 shows the in vivo antitumor efficacy results of CAR-T cells expressing a CAR bearing a camel anti-DLL3 sdAb in an SHP-77 tumor model, in which each mouse was injected with a dose of 1 million CAR-T cells. [Figure 6A] Figure 6 shows the results of in vitro cytotoxicity assays of T cells expressing exemplary monospecific CARs containing various humanized camelid anti-DLL3 sdAbs against the small cell lung cancer cell lines SHP-77 (Figure 6A, Figure 6B) and NCI-H82 (Figure 6C, Figure 6D). [Figure 6B] See legend to Figure 6A. [Figure 6C] See legend to Figure 6A. [Figure 6D] See legend to Figure 6A. [Figure 7] Figure 7 shows the results of cytokine release levels of T cells expressing exemplary monospecific CARs containing various humanized camelid anti-DLL3 sdAbs after stimulation with SHP-77. IFN-γ and TNF-α release levels (E:T is 3:1 or 10:1) are shown in Figures 7A and 7B, respectively. In each figure, the results for the CARs are presented in order as shown in the legend on the right. [Figure 8] FIG. 8 shows the fold expansion of T cells expressing exemplary monospecific CARs comprising various humanized camelid anti-DLL3 sdAbs after long-term stimulation with the small cell lung cancer cell line SHP-77. [Figure 9A] Figure 9 shows the in vivo antitumor efficacy results of CAR-T cells expressing a CAR bearing a humanized camelid anti-DLL3 sdAb in an SHP-77 tumor model. In this model, each mouse was injected with a dose of 200,000 CAR-T cells. The results of the nine groups are compared in Figure 9A. The results for each mouse in each group are shown in Figures 9B-9J, respectively. [Figure 9B] See legend to Figure 9A. [Figure 9C] See legend to Figure 9A. [Figure 9D] See legend to Figure 9A. [Figure 9E] See legend to Figure 9A. [Figure 9F] See legend to Figure 9A. [Figure 9G] See legend to Figure 9A. [Figure 9H] See legend to Figure 9A. [Figure 9I] See legend to Figure 9A. [Figure 9J] See legend to Figure 9A. [Figure 10A] Figure 10 shows a schematic diagram of a tandem CAR (Figure 10A) and an armed CAR construct (Figure 10B, Figure 10C). [Figure 10B] See legend to Figure 10A. [Figure 10C] See legend to Figure 10A. [Figure 11A] Figure 11 shows the comparison of the in vitro functional activity of tandem and monospecific CAR-T cells by short-term cytotoxicity (Figures 11A-E, 11V) and cytokine release (Figures 11F-K, 11W-X) and long-term stimulation assays (Figures 11L-U, 11Y-Z). [Figure 11B] See legend to Figure 11A. [Figure 11C] See legend to Figure 11A. [Figure 11D] See legend to Figure 11A. [Figure 11E] See legend to Figure 11A. [Figure 11F] See legend to Figure 11A. [Figure 11G] See legend to Figure 11A. [Figure 11H] See legend to Figure 11A. [Figure 11I] See legend to Figure 11A. [Figure 11J] See legend to Figure 11A. [Figure 11K] See legend to Figure 11A. [Figure 11L] See legend to Figure 11A. [Figure 11M] See legend to Figure 11A. [Figure 11N] See legend to Figure 11A. [Figure 11O]See legend to Figure 11A. [Figure 11P] See legend to Figure 11A. [Figure 11Q] See legend to Figure 11A. [Figure 11R] See legend to Figure 11A. [Figure 11S] See legend to Figure 11A. [Figure 11T] See legend to Figure 11A. [Figure 11U] See legend to Figure 11A. [Figure 11V] See legend to Figure 11A. [Figure 11W] See legend to Figure 11A. [Figure 11X] See legend to Figure 11A. [Figure 11Y] See legend to Figure 11A. [Figure 11Z] See legend to Figure 11A. [Figure 12A] Figure 12 shows the in vitro functional comparison of CAR-T cells and T3s armed with PD-1 DNR or PD-1 CSR targeting SHP-77 cells (Figures 12A and 12B) and SHP-77 / PD-L1 (Figures 12C and 12D), respectively. [Figure 12B] See legend to Figure 12A. [Figure 12C] See legend to Figure 12A. [Figure 12D] See legend to Figure 12A. [Figure 13A] Figure 13 shows that TGF-β-DNR enhances the in vitro and in vivo antitumor efficacy of DLL3 CAR-T cells. Figure 13A shows a schematic diagram of a CAR armed with TGF-β-DNR. Figure 13B shows the positive rates of CAR and TGF-β-DNR for each CAR-T cell. In vitro antitumor efficacy was evaluated in short-term stimulation assays (Figures 13C and 13D) and long-term stimulation assays (Figures 13E-G). Figure 13H shows in vivo antitumor efficacy. Figure 13I shows the pharmacokinetics of CAR-T cells in the peripheral blood of an SHP77 xenograft model after treatment. [Figure 13B] See legend to Figure 13A. [Figure 13C] See legend to Figure 13A. [Figure 13D] See legend to Figure 13A. [Figure 13E] See legend to Figure 13A. [Figure 13F] See legend to Figure 13A. [Figure 13G] See legend to Figure 13A. [Figure 13H] See legend to Figure 13A. [Figure 13I] See legend to Figure 13A. DETAILED DESCRIPTION OF THE INVENTION

[0081] Detailed Description Unless otherwise defined, scientific and technical terms used herein have the same meaning as commonly understood by those skilled in the art. Any methods, devices, and materials similar or equivalent to those described herein can be used in the practice of the present invention. The following definitions are provided to facilitate understanding of certain terms used frequently herein and are not intended to limit the scope of the present disclosure.

[0082] The articles "a" and "an" are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0083] The term "binding protein," as used herein, refers to a molecule or portion of a molecule that binds to a target molecule (e.g., DLL3). In some embodiments, the binding protein comprises an antibody. In some embodiments, the binding protein comprises an antigen-binding fragment of an antibody. In some embodiments, the binding protein may further comprise a low molecular weight component, such as a small molecule drug or toxin. The binding protein may also be an antibody or an antigen-binding fragment thereof. In some embodiments, the binding protein comprises the ligand-binding domain of a receptor. In some embodiments, the binding protein comprises the extracellular domain of a transmembrane receptor. The binding protein may also be the ligand-binding domain of a receptor or the extracellular domain of a transmembrane receptor. In some embodiments, the binding protein comprises a single-domain antibody (sdAb) or a single-chain variable fragment (scFv). In some embodiments, the binding protein may be an sdAb or an scFv. The DLL3-binding protein may be a DLL3-binding domain. In some embodiments, the DLL3-binding protein comprises an antibody or an antigen-binding fragment of an antibody that binds to DLL3. In some embodiments, the DLL3-binding protein may be an antibody or an antigen-binding fragment of an antibody. In some embodiments, the DLL3 binding protein comprises a single domain antibody (sdAb) or a single chain variable fragment (scFv) that binds to DLL3. In some embodiments, the DLL3 binding protein can be an sdAb or an scFv.

[0084] The term "antibody" generally refers to any immunoglobulin (Ig) molecule consisting of four polypeptide chains, two heavy (H) chains and two light (L) chains, or any functional fragment thereof, that retains the essential epitope-binding characteristics of an Ig molecule. In full-length antibodies, each heavy chain consists of a heavy chain variable region (abbreviated herein as HCVR or VH) and a heavy chain constant region. The heavy chain constant region consists of three domains, CH1, CH2, and CH3. Each light chain consists of a light chain variable region (abbreviated herein as LCVR or VL) and a light chain constant region. The light chain constant region consists of one domain, CL. The VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity-determining regions (CDRs), interspersed with more conserved regions, termed framework regions (FRs). Each VH and VL consists of three CDRs and four FRs arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The immunoglobulin molecule can be of any type (e.g., IgG, IgE, IgM, IgD, IgA, and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2), or subclass. In a broad sense, the term "antibody" also refers to scFvs or sdAbs that are not derived from immunoglobulin molecules having four polypeptide chains.

[0085] Antibody fragments are portions of antibodies, such as F(ab')2, Fab, Fv, scFv, sdAb, etc. Functional fragments of full-length antibodies retain the target specificity of the full-length antibody. Therefore, recombinant functional antibody fragments, such as scFv (single-chain variable fragment), have been used to develop therapeutics as an alternative to mAb-based therapeutics. scFv fragments (approximately 25 kDa) consist of two variable domains, VH and VL. In nature, the VH and VL domains tend to associate and dissociate non-covalently through hydrophobic interactions. However, stable fragments can be engineered to generate scFvs by linking the domains with a hydrophilic flexible linker.

[0086] As used herein, the term "single domain antibody" (sdAb) has its general meaning in the art and refers to a single heavy chain variable domain of an antibody type that can be found in camelid mammals and that naturally lacks light chains. Such single domain antibodies are characterized by a V H Single domain antibodies are also referred to as "H" or "nanobodies." The amino acid sequence and structure of single domain antibodies can be considered to consist of four framework regions (FR1, FR2, FR3, and FR4) and three complementarity determining regions (CDR1, CDR2, and CDR3). Thus, single domain antibodies can be defined as amino acid sequences with the general structure FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4, similar to the variable domains VH or VL. The use of sdAbs as single antigen-binding proteins or as antigen-binding domains in larger proteins or polypeptides offers several significant advantages over the use of conventional antibodies or antibody fragments (e.g., scFvs). The advantages of sdAbs include that only a single domain is required to bind antigen with high affinity and high selectivity; sdAbs are highly stable to denaturing agents or conditions, including heat, pH, and proteases; and sdAbs have access to targets and epitopes inaccessible to conventional antibodies. Typically, sdAbs are produced in camelids, such as llamas, but can also be made synthetically using techniques well known in the art.

[0087] As used herein, the term "humanized sdAb" refers to a humanized sdAb that is a naturally occurring V H It refers to an sdAb in which one or more amino acid residues in the amino acid sequence of the H sequence are replaced by one or more amino acid residues present at the corresponding positions in the VH domain of a normal four-chain antibody of human origin.This can be achieved by methods well known in the art.For example, the FR of the sdAb can be replaced by human variable FR.Therefore, the humanized sdAb has reduced antigenicity when administered to the human body.

[0088] As used herein, the term "heavy chain-only antibody" or "HCAb" refers to a functional antibody that contains a heavy chain but lacks the light chain typically found in four-chain antibodies. Camelids (such as camels, llamas, or alpacas) are known to produce HCAbs.

[0089] "DLL3," also known as "Delta-like ligand 3," is a transmembrane protein involved in the Notch signaling pathway. Initially identified in C. elegans and Drosophila and subsequently shown to be evolutionarily conserved across invertebrates and vertebrates, the Notch signaling pathway is involved in a range of fundamental biological processes, including normal embryonic development, adult tissue homeostasis, and stem cell maintenance. In Drosophila, Notch signaling is primarily mediated by one Notch receptor gene and two ligand genes, known as Serrate and Delta (Wharton et al., 1985; Rebay et al., 1991). In humans, four known Notch receptors and five DSL (Delta-Serrate LAG2) ligands—two homologs of Serrate, known as Jagged 1 and Jagged 2, and three homologs of Delta, termed Delta-like ligands or DLL1, DLL3, and DLL4—are found. In humans, the DLL3 gene is located on chromosome 19q13 and consists of eight exons spanning 9.5 kb. Alternative splicing within the last exon results in two protein isoforms, both of which share 100% overall identity throughout their extracellular and transmembrane domains, differing only in that the longer isoform has an extended cytoplasmic tail.

[0090] As used herein, the terms "specifically bind" or "specifically binding," or any synonym thereof, refer to the ability of a polypeptide, such as a single domain antibody (sdAb), to specifically recognize and detectably bind to a DLL3 molecule as assayed by standard in vitro assays. For example, binding, as used herein, is measured by the ability of an anti-DLL3 polypeptide of the invention to recognize a DLL3 molecule on the cell surface using well-described antigen-antibody binding assays, flow cytometry, and other assays known to those of skill in the art.

[0091] As used herein, the term "expression vector" refers to a nucleic acid construct or sequence produced recombinantly or synthetically using specific nucleic acid elements that enable the transcription and / or expression of another nucleic acid in a host cell. An expression vector can be part of a plasmid, virus, or nucleic acid fragment. In one example, an expression vector is a DNA vector, such as a plasmid, that contains at least one promoter sequence and at least one terminator sequence (e.g., a polyadenylation sequence), optionally an origin of replication (ori) sequence, and optionally a selection or selectable marker sequence. Optionally, the expression vector may further contain at least one nucleotide coding sequence of interest that encodes at least one polypeptide, wherein the at least one promoter sequence is operably linked to the at least one coding sequence. The term "expression" includes any step involved in the production of a polypeptide, including, but not limited to, transcription, post-transcriptional modification, translation, post-translational modification, and / or secretion.

[0092] The term "isolated" refers to material that is substantially or essentially free from components that normally accompany it in its natural state. The material can be a cell or a macromolecule such as a protein or nucleic acid. For example, "isolated nucleic acid," as used herein, refers to a polynucleotide that has been purified from sequences that flank it in its naturally occurring state, e.g., a DNA fragment that has been removed from sequences that normally flank the fragment. Alternatively, "isolated antibody" or "isolated polypeptide," etc., as used herein, refer to the in vitro isolation and / or purification of an antibody or polypeptide molecule from its natural cellular environment and association with other cellular components.

[0093] "Humanized" forms of non-human (e.g., camelid) antibodies are chimeric antibodies which contain minimal sequence derived from non-human immunoglobulin. In some embodiments, humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a hypervariable region (HVR) of the recipient are substituted by residues from an HVR of a non-human species (donor antibody) such as mouse, rat, rabbit, or non-human primate having the desired specificity, affinity, and / or capacity. In some cases, framework ("FR") residues of the human immunoglobulin are substituted by corresponding non-human residues. Furthermore, humanized antibodies may comprise residues which are not found in the recipient antibody or in the donor antibody. These modifications may be made to further refine antibody performance, e.g., binding affinity. Generally, a humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariable loops correspond to those of a non-human immunoglobulin sequence, and all or substantially all of the FR regions are identical to those of a human immunoglobulin sequence, although the FR regions may include one or more individual FR residue substitutions which improve antibody performance, e.g., binding affinity, isomerization, immunogenicity, etc. The number of these amino acid substitutions in the FRs will typically be no more than six in the H chain and no more than three in the L chain. The humanized antibody will also optionally comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. For further details, see, e.g., Jones et al., Nature 321:522-525 (1986); Riechmann et al., Nature 332:323-329 (1988); and Presta, Curr. Op. Struct. Biol. 2:593-596 (1992). Also see, e.g., Vaswani and Hamilton, Ann. Allergy, Asthma & Immunol. 1:105-115 (1998); Harris, Biochem. Soc. Transactions 23:1035-1038 (1995); Hurle and Gross, Curr. Op. Biotech. 5:428-433 (1994); and U.S. Patent Nos. 6,982,321 and 7,087,409.

[0094] With respect to peptide, polypeptide, or antibody sequences, "sequence identity" and "homology" are defined as the percentage of amino acid residues in a candidate sequence that are identical to the amino acid residues in a particular peptide or polypeptide sequence after aligning the sequences, introducing gaps as necessary, and achieving the maximum percent sequence identity without considering any conservative substitutions as part of the sequence identity. Alignment, intended to determine percent amino acid sequence identity, can be achieved in a variety of ways within the skill of the art, for example, using publicly available computer software such as BLAST, BLAST-2, ALIGN, or MEGALIGN™ (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared.

[0095] Dissociation constant (K D or K d ) is used as an index of the affinity of an antibody for an antigen. For example, analysis can be easily performed by the Scatchard method using antibodies labeled with various markers, and by using the OTC measurement kit BiacoreX (manufactured by Amersham Biosciences) or a similar kit in accordance with the user manual and experimental procedures provided with the kit. K that can be derived using these methods D Values ​​are expressed in M ​​(molar) units.

[0096] As used herein, "chimeric switch receptor (CSR)" refers to a receptor engineered to reverse the outcome of an immune cell's (e.g., CAR T cell) original signaling pathway to confer a desired activity on the cell, e.g., the ability to overcome an immunosuppressive tumor microenvironment and to enhance in vivo persistence. In some embodiments, the CSR can utilize inhibitory molecules expressed by cancer cells to further stimulate the CAR T cell. In a non-limiting example, a CAR T cell can be engineered to express a CSR consisting of the extracellular ligand-binding domain of the human inhibitory receptor, programmed cell death protein 1 (PD-1), fused to the transmembrane and cytoplasmic costimulatory signaling domains of CD28. When the CAR T cell is administered to a subject with a cancer that expresses DLL3 and programmed cell death ligand 1 (PD-L1), the expressed CAR can bind to DLL3, and the expressed switch receptor can bind to PD-L1. The properties of the PD-1 / CD28 chimeric switch receptor fusion protein block normal PD1 / PD-L1-mediated T cell suppression and instead promote signaling through the CD28 domain, leading to CAR T cell stimulation. Thus, swapping the transmembrane and intracellular domains of PD-1 with those of CD28 converts PD-L1 into a costimulatory ligand for CAR T cells. This induces enhanced toxicity against cancer cells expressing PD-L1. In other embodiments, CSR can also be used to inhibit the effect of CAR T cells on unintended target cells.

[0097] As used herein, a "dominant negative receptor (DNR)" refers to a receptor that can bind to its ligand but does not induce a signal transduction cascade inside the cell. DNRs typically have an intact ligand-binding domain but lack the intracellular enzymatic domain. They can be a mutant form of the full-length receptor or a truncated form of the receptor. After CAR T cell immunotherapy, some cancers, particularly solid cancers, may upregulate inhibitory ligands that bind to inhibitory receptors on CAR T cells. This adaptive resistance impairs the efficacy of chimeric CAR T cell therapy. Some cancers, particularly solid cancers, are known to secrete transforming growth factor-β (TGF-β), which creates an immunosuppressive environment. TGF-β is known to induce or promote metastasis and potently suppress the immune system. Therefore, in some embodiments, the inventors improve the anti-tumor performance of the CAR T cells disclosed herein by using a truncated version of the TGF-β receptor TGF-βRII as a TGF-β DNR. In some embodiments, the CAR and TGF-β DNR are simultaneously expressed on the surface of T cells by using a 2A self-cleaving peptide. In some embodiments, the CAR and TGF-β DNR are separately expressed on the surface of T cells by using two expression vectors. The inventors have found that when a TGF-β DNR is introduced into the anti-DLL3 CAR T cells disclosed herein, it can enhance the cytotoxicity of the CAR T cells against some DLL3-positive cancer cells, such as SCLC cells. Similarly, in some embodiments, the inventors use a truncated version of the PD-1 receptor as a PD-1 DNR to improve the anti-tumor performance of the CAR T cells disclosed herein.

[0098] As used herein, "treatment" or "treating" includes any beneficial or desired effect on the symptoms or pathology of a disease or condition, and may further include a minimal reduction in one or more measurable markers of the disease or condition being treated, e.g., cancer, autoimmune disease, immune disorder, etc. Treatment may optionally include a delay in the progression of the disease or condition. "Treatment" does not necessarily indicate a complete eradication or cure of the disease or condition or its associated symptoms.

[0099] Some embodiments of the present invention relate to DLL3 binding proteins that have binding specificity for human or rhesus monkey DLL3 protein.

[0100] In some embodiments, the DLL3 binding protein comprises a single domain antibody ("sdAb") portion that specifically binds to DLL3, and the sdAb portion comprises a polypeptide comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1-81 or a variant thereof comprising up to about three amino acid substitutions in CDR1, a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82-162 or a variant thereof comprising up to about three amino acid substitutions in CDR2, and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163-243 or a variant thereof comprising up to about three amino acid substitutions in CDR3.

[0101] In some embodiments, the sdAb comprises a polypeptide comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1-81, a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82-162, and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163-243, or a variant of the polypeptide comprising up to about three amino acid substitutions in the CDR regions. In some embodiments, the anti-DLL3 antibody is or comprises a single domain antibody (sdAb) produced from a camel after immunization with human or rhesus DLL3 protein. In some embodiments, the sdAb comprises a set of CDRs (i.e., a combination of CDR1, CDR2, and CDR3) as listed in each column of Table 1.

[0102] In some embodiments, the sdAb is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. The present invention also includes a polypeptide comprising any one of the following:

[0103] In some embodiments, the sdAb is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 The present invention also includes a polypeptide comprising any one of the following:

[0104] In some embodiments, the sdAb comprises an amino acid sequence having at least about 95% (e.g., about 96%, about 97%, about 98%, about 99% or about 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274-354. In some embodiments, the sdAb comprises the amino acid sequence of any one of SEQ ID NOs: 274-354. In other embodiments, the sdAb is humanized and comprises an amino acid sequence having at least about 95% (e.g., about 96%, about 97%, about 98%, about 99% or about 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355-367. In some embodiments, the sdAb comprises the amino acid sequence of any one of SEQ ID NOs: 355-367. Humanized antibodies can be produced using a variety of techniques known in the art, including, but not limited to, CDR grafting (see, e.g., U.S. Pat. Nos. 5,225,539, 5,530,101, and 5,585,089), veneering or resurfacing (see, e.g., European Patent Nos. 592,106 and 519,596), and chain shuffling (see, e.g., U.S. Pat. No. 5,565,332). Generally, during humanization, CDR residues of a recipient antibody (e.g., a human antibody) are replaced with CDR residues from a donor antibody (e.g., a rodent antibody) to retain antigen-binding specificity while minimizing in vivo immunogenicity. Often, framework residues within the framework regions are replaced with the corresponding residues from the donor antibody, resulting in altered, e.g., improved, antigen binding. These framework substitutions, e.g., conservative substitutions, are identified by methods well known in the art, such as modeling the interactions of CDR and framework residues to identify framework residues important for antigen binding and sequence comparison to identify unusual framework residues at particular positions (see, e.g., Queen et al., U.S. Pat. No. 5,585,089; and Riechmann et al., 1988, Nature, 332:323).

[0105] In some cases, an sdAb can be fused to a human IgG hinge fragment and Fc fragment to form a heavy chain antibody (HCAb). In some cases, an sdAb can be fused to another sdAb or scFv specific for an antigen other than DLL3 to form a bispecific antibody. In some cases, an sdAb can be fused to two or more sdAbs or scFvs specific for antigens other than DLL3 to form a multispecific antibody. In other cases, an sdAb can be chemically modified to carry a drug molecule. Thus, an anti-DLL3 sdAb can be used in vivo to target drug molecules to DLL3-expressing cells.

[0106] In some embodiments, the DLL3 binding protein is or comprises a single-chain variable fragment (scFv) that specifically binds to DLL3. In some cases, scFvs are isolated from a synthetic human Fab or scFv phage library through multiple rounds of phage panning, each round of panning including the process of binding, removal of nonspecific phage, and elution and amplification of bound phage in preparation for the next round. In some embodiments, the DLL3 binding protein comprises an scFv portion that specifically binds to DLL3, wherein the scFv comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO:498 or 504, CDR2 set forth in SEQ ID NO:499 or 505, and CDR3 set forth in SEQ ID NO:500 or 506, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO:495 or 501, CDR2 set forth in SEQ ID NO:496 or 502, and CDR3 set forth in SEQ ID NO:497 or 503. In some embodiments, the DLL3 binding protein comprises an scFv portion that specifically binds to DLL3, wherein the scFv comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO:498, CDR2 set forth in SEQ ID NO:499, and CDR3 set forth in SEQ ID NO:500, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO:495, CDR2 set forth in SEQ ID NO:496, and CDR3 set forth in SEQ ID NO:497; or wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO:504, CDR2 set forth in SEQ ID NO:505, and CDR3 set forth in SEQ ID NO:506, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO:501, CDR2 set forth in SEQ ID NO:502, and CDR3 set forth in SEQ ID NO:503.

[0107] In some cases, an scFv can be fused to another sdAb or scFv specific for an antigen other than DLL3 to form a bispecific antibody. In some cases, an scFv can be fused to two or more sdAbs or scFvs specific for antigens other than DLL3 to form a multispecific antibody. In other cases, an scFv can be chemically modified to carry a drug molecule. Thus, an anti-DLL3 scFv can be used in vivo to target drug molecules to DLL3-expressing cells.

[0108] Some embodiments of the present invention relate to a CAR or CAR-T cell that comprises a DLL3 binding domain (an anti-DLL3 CAR or an anti-DLL3 CAR-T cell).

[0109] The CAR of the present invention comprises an extracellular domain, a transmembrane domain, and an intracellular domain. In some embodiments, the CAR further comprises an N-terminal signal peptide and a hinge region between the extracellular domain and the transmembrane domain. The extracellular domain comprises a target-specific binding factor (also referred to as an antigen recognition domain or antigen binding domain). The intracellular domain or otherwise cytoplasmic domain often comprises one or more costimulatory signaling domains and a CD3 zeta chain portion. The costimulatory signaling domain refers to the portion of the CAR that comprises the intracellular domain of a costimulatory molecule.

[0110] Antigen recognition or targeting by a CAR molecule most commonly involves the use of an antibody or antibody fragment. According to the present invention, the antigen-binding domain is an antibody or antibody fragment that specifically binds to DLL3. Preferably, the antigen-binding domain of the CAR of the present invention is an anti-DLL3 scFv or sdAb as described above.

[0111] The transmembrane domain may be derived from either natural or synthetic sources. If the source is natural, the domain may be derived from any membrane-bound or transmembrane protein. A transmembrane region of particular use in the present invention may be derived from (i.e., may comprise at least the transmembrane region of) the alpha, beta, or zeta chain of the T cell receptor, the CD8 α chain, for example.

[0112] The intracellular signaling domain of the CAR of the present invention is involved in activating at least one of the normal effector functions of immune cells. The term "effector function" refers to a specialized function of a cell. For example, the effector function of a T cell can be cytolytic activity or helper activity, including cytokine secretion. Thus, the term "intracellular domain" refers to the portion of a protein that transmits an effector function signal and directs the cell to carry out a specialized function. Typically, the entire cytoplasmic domain can be utilized, although in many cases, it is not necessary to use the entire chain. To the extent that a truncated portion of the cytoplasmic domain is used, such a truncated portion can be used in place of the intact chain, so long as it transmits the effector function signal. Thus, the term intracellular domain is meant to include any truncated portion of the cytoplasmic domain sufficient to transmit the effector function signal. Preferred examples of cytoplasmic domains intended for use in the CAR of the present invention include the cytoplasmic sequences of a T cell receptor (TCR) and a co-receptor that act in conjunction to initiate signal transduction after antigen receptor engagement, as well as any derivatives or variants of these sequences and any synthetic sequences having the same functional capabilities. In some embodiments, the intracellular signaling domain is derived from CD3zeta, FcRgamma, FcRbeta, CD3gamma, CD3delta, CD3epsilon, CD5, CD22, CD79a, CD79b, or CD66d.

[0113] In many cases, the signal generated by the TCR alone is insufficient for full activation of T cells. Therefore, secondary or costimulatory signals are used. Therefore, it can be stated that T cell activation is mediated by two different classes of cytoplasmic signaling sequences: those that initiate antigen-dependent primary activation through the TCR (primary cytoplasmic signaling sequences) and those that act in an antigen-independent manner to provide secondary or costimulatory signals (secondary cytoplasmic signaling sequences). A costimulatory signaling sequence refers to the portion of a CAR that contains the intracellular domain of a costimulatory molecule. A costimulatory molecule is a cell surface molecule other than an antigen receptor or its ligand that is required for an efficient response of lymphocytes to antigens. Examples of such molecules include CD27, CD28, 4-1BB, OX40, CD40, PD-1, LFA-1, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3, TNFRSF9, TNFRSF4, TNFRSF8, CD40LG, ITGB2, KLRC2, TNFRSF18, TNFRSF14, HAVCR1, LGALS9, DAP10, DAP12, CD83, ligands for CD83, and combinations thereof.

[0114] The hinge region between the extracellular and transmembrane domains of a CAR generally refers to any oligo- or polypeptide that functions to link the transmembrane domain to the extracellular domain within the polypeptide chain. The hinge region can be up to 300 amino acids, preferably 2-100 amino acids, and most preferably 2-10 amino acids.

[0115] In addition to the antigen-binding domain, transmembrane domain, cytoplasmic domain, and hinge region, the CAR of the present invention may also contain a signal peptide sequence linked to the N-terminus of the CAR. Signal peptide sequences are present at the N-terminus of many secretory proteins and membrane proteins and are typically 15 to 30 amino acids in length. Since many of the above protein molecules have signal peptide sequences, these signal peptides can be used as signal peptides for the CAR of the present invention.

[0116] In some embodiments, the CAR comprises a DLL3 binding domain, which comprises or is derived from a single domain antibody (sdAb) or a single chain variable fragment (scFv).

[0117] In some embodiments, the CAR comprises a DLL3-binding domain, wherein the DLL3-binding domain comprises or is derived from a single domain antibody (sdAb), wherein the sdAb comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1-81 or a variant thereof comprising up to about three amino acid substitutions in CDR1; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82-162 or a variant thereof comprising up to about three amino acid substitutions in CDR2; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163-243 or a variant thereof comprising up to about three amino acid substitutions in CDR3. In some embodiments, the CAR comprises a DLL3-binding domain, wherein the DLL3-binding domain comprises or is derived from a single domain antibody (sdAb), wherein the sdAb comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 1-81; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 82-162; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 163-243.

[0118] In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 87 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168 or a variant thereof comprising up to about three amino acid substitutions; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 102 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183 or a variant thereof comprising up to about three amino acid substitutions; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 105 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186 or a variant thereof comprising up to about three amino acid substitutions; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 108 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189 or a variant thereof comprising up to about three amino acid substitutions; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 115 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196 or a variant thereof comprising up to about three amino acid substitutions; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 120 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201 or a variant thereof comprising up to about three amino acid substitutions; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 88 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169 or a variant thereof comprising up to about three amino acid substitutions; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 89 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170 or a variant thereof comprising up to about three amino acid substitutions; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9 or a variant thereof comprising up to about three amino acid substitutions; CDR2 comprising the amino acid sequence of SEQ ID NO: 90 or a variant thereof comprising up to about three amino acid substitutions; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 or a variant thereof comprising up to about three amino acid substitutions. The present invention also includes an sdAb comprising any one of the following:

[0119] In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain is: (1) CDR1 comprising the amino acid sequence of SEQ ID NO: 6; CDR2 comprising the amino acid sequence of SEQ ID NO: 87; and CDR3 comprising the amino acid sequence of SEQ ID NO: 168; (2) CDR1 comprising the amino acid sequence of SEQ ID NO: 21; CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and CDR3 comprising the amino acid sequence of SEQ ID NO: 183; (3) CDR1 comprising the amino acid sequence of SEQ ID NO: 24; CDR2 comprising the amino acid sequence of SEQ ID NO: 105; and CDR3 comprising the amino acid sequence of SEQ ID NO: 186; (4) CDR1 comprising the amino acid sequence of SEQ ID NO: 27; CDR2 comprising the amino acid sequence of SEQ ID NO: 108; and CDR3 comprising the amino acid sequence of SEQ ID NO: 189; (5) CDR1 comprising the amino acid sequence of SEQ ID NO: 34; CDR2 comprising the amino acid sequence of SEQ ID NO: 115; and CDR3 comprising the amino acid sequence of SEQ ID NO: 196; (6) CDR1 comprising the amino acid sequence of SEQ ID NO: 39; CDR2 comprising the amino acid sequence of SEQ ID NO: 120; and CDR3 comprising the amino acid sequence of SEQ ID NO: 201; (7) CDR1 comprising the amino acid sequence of SEQ ID NO: 7; CDR2 comprising the amino acid sequence of SEQ ID NO: 88; and CDR3 comprising the amino acid sequence of SEQ ID NO: 169; (8) CDR1 comprising the amino acid sequence of SEQ ID NO: 8; CDR2 comprising the amino acid sequence of SEQ ID NO: 89; and CDR3 comprising the amino acid sequence of SEQ ID NO: 170; or (9) CDR1 comprising the amino acid sequence of SEQ ID NO: 9; CDR2 comprising the amino acid sequence of SEQ ID NO: 90; and CDR3 comprising the amino acid sequence of SEQ ID NO: 171 The present invention also includes an sdAb comprising any one of the following:

[0120] In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain comprises a camelid sdAb, wherein the sdAb comprises an amino acid sequence having at least about 95% (e.g., 96%, 97%, 98%, 99% or 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 274-354. In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain comprises a camelid sdAb comprising the amino acid sequence of any one of SEQ ID NOs: 274-354. In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain comprises a humanized sdAb, wherein the sdAb comprises an amino acid sequence having at least about 95% (e.g., 96%, 97%, 98%, 99% or 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 355-367. In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain comprises a humanized sdAb comprising the amino acid sequence of any one of SEQ ID NOs: 355-367.

[0121] In some embodiments, the CAR comprises a DLL3 binding domain, wherein the DLL3 binding domain comprises or is derived from a single chain variable fragment (scFv), wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO:498, CDR2 set forth in SEQ ID NO:499, and CDR3 set forth in SEQ ID NO:500, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO:495, CDR2 set forth in SEQ ID NO:496, and CDR3 set forth in SEQ ID NO:497; or wherein the VH domain of the scFv comprises CDR1 set forth in SEQ ID NO:504, CDR2 set forth in SEQ ID NO:505, and CDR3 set forth in SEQ ID NO:506, and the VL domain of the scFv comprises CDR1 set forth in SEQ ID NO:501, CDR2 set forth in SEQ ID NO:502, and CDR3 set forth in SEQ ID NO:503. In some embodiments, the VH domain of the scFv comprises the amino acid sequence set forth in SEQ ID NO: 508, and the VL domain of the scFv comprises the amino acid sequence set forth in SEQ ID NO: 507; or the VH domain of the scFv comprises the amino acid sequence set forth in SEQ ID NO: 510, and the VL domain of the scFv comprises the amino acid sequence set forth in SEQ ID NO: 509.

[0122] In some embodiments, a CAR of the invention comprises a camelid sdAb provided herein as a DLL3-binding domain and comprises an amino acid sequence having at least about 95% (e.g., 96%, 97%, 98%, 99% or 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 476-484. In some embodiments, a CAR of the invention comprises a camelid sdAb provided herein as a DLL3-binding domain and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 476-484. In some embodiments, a CAR of the invention comprises a humanized sdAb provided herein as a DLL3-binding domain and comprises an amino acid sequence having at least about 95% (e.g., 96%, 97%, 98%, 99% or 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 485-494. In other embodiments, a CAR of the invention comprises a humanized sdAb provided herein as a DLL3-binding domain and comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 485-494.

[0123] In some embodiments, a CAR of the invention comprises a human scFv provided herein as a DLL3-binding domain and comprises an amino acid sequence having at least about 95% (e.g., 96%, 97%, 98%, 99% or 100%) sequence identity to the amino acid sequence of any one of SEQ ID NOs: 515-516. In some embodiments, a CAR of the invention comprises a human scFv provided herein as a DLL3-binding domain and has an amino acid sequence selected from the group consisting of SEQ ID NOs: 515-516.

[0124] In some embodiments, a CAR of the invention comprises, from N- to C-terminus, a signal peptide, a DLL3-binding domain, a hinge region, a transmembrane domain, and a cytoplasmic signaling domain. In a specific embodiment, a CAR of the invention comprises, from N- to C-terminus, a CD8α signal peptide as set forth in SEQ ID NO:465, a DLL3-binding domain, a CD8α hinge domain as set forth in SEQ ID NO:466, a CD8α transmembrane domain as set forth in SEQ ID NO:467, a CD137 cytoplasmic domain as set forth in SEQ ID NO:468, a CD28 cytoplasmic domain as set forth in SEQ ID NO:469, and a CD3ζ cytoplasmic domain as set forth in SEQ ID NO:470.

[0125] Some aspects of the invention relate to isolated nucleic acid molecules encoding an sdAb, scFv, or CAR of the invention. In some embodiments, the nucleic acid molecule encodes a camelid sdAb and comprises a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 368-448. In some embodiments, the nucleic acid molecule encodes a humanized sdAb and comprises a polynucleotide sequence selected from the group consisting of SEQ ID NOs: 449-461. In some embodiments, the nucleic acid molecule encodes the VH and VL domains of an scFv, wherein the sequence encoding the VH domain comprises the polynucleotide sequence of SEQ ID NO: 512 or 514, and the sequence encoding the VL domain comprises the polynucleotide sequence of SEQ ID NO: 511 or 513.

[0126] Some aspects of the present application relate to modified immune cells comprising any one of the CARs provided above, any one of the isolated nucleic acids described above, or any one of the vectors described above. In some embodiments, the modified immune cells are cytotoxic T cells, helper T cells, natural killer T cells, γδ T cells, NKT cells, and nature killer cells. In some embodiments, the cells comprise an expression vector carrying an isolated nucleic acid molecule of the present invention. Genetically modifying cells with an expression vector to express a polypeptide encoded by a portion of a nucleic acid molecule is a genetic technique well known in the art.

[0127] Some aspects of the present invention relate to the use of the DLL3-binding proteins, anti-DLL3 CARs, nucleic acid molecules, or CAR-T cells of the present invention. In some embodiments, the CAR-T cells of the present invention are formulated as a pharmaceutical composition with a physiologically acceptable excipient. As used herein, "physiologically acceptable excipient" includes, but is not limited to, any adjuvant, carrier, diluent, preservative, dispersing agent, suspending agent, stabilizer, isotonic agent, solvent, surfactant, or emulsifier acceptable for use in humans or veterinary medicine. In some embodiments, the CAR-T cells of the present invention or a pharmaceutical composition comprising the same are used to treat a DLL3-associated disorder in a subject. Accordingly, provided are methods for treating a DLL3-associated disorder, comprising administering a therapeutically effective amount of the CAR-T cells or pharmaceutical composition of the present invention to a subject suffering from a DLL3-associated disorder. The "therapeutically effective amount" of an antibody, CAR-T cell, or pharmaceutical composition may vary depending on factors such as the condition, age, sex, and weight of the subject (e.g., patient). The term "therapeutically effective amount" can include an amount that is effective to "treat" a subject. When a therapeutic amount is specified, the exact amount contemplated for administration in a particular embodiment can be determined by a physician in consideration of the subject's condition. In some embodiments, the DLL3-associated disorder is a cancer that expresses DLL3 as a cell surface protein, such as melanoma, breast cancer, prostate cancer, colon cancer, renal cell carcinoma, ovarian cancer, neuroblastoma, rhabdomyosarcoma, leukemia, and lymphoma. Preferably, the DLL3-associated disorder is lung cancer, particularly small cell lung cancer (SCLC). [Example]

[0128] The examples described herein are not intended to represent all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperatures, etc.), but some experimental error and deviation should be accounted for. Unless otherwise indicated, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric pressure.

[0129] Example 1. Animal immunization and antibody library construction In this example, it was demonstrated that immunized camels exhibited good immune responses to human or rhesus DLL3 proteins, and that the acquired immune library exhibited excellent quality.

[0130] animal immunity Immunogens containing the extracellular domain of human DLL3 protein (aa 27-466) with an N-terminal FLAG tag (AdipoGen, AG-40B-0151) or / and DLL3 expression plasmid or DLL3-expressing cells (CHO-K1 / DLL3 or / and CHO-K1 / EGF4) were mixed with adjuvant or PBS and injected into camels. Camels were typically immunized two to four times at weekly to biweekly intervals. After multiple immunizations, the immune response to the target antigen, DLL3, was assessed by serum titration using both enzyme-linked immunosorbent assay (ELISA) and flow cytometry assays.

[0131] Phage display library construction Total RNA was extracted from lymphocytes of immunized camels using TRIZOL® reagent according to the manufacturer's protocol. cDNA was synthesized from the RNA template using the PRIMESCRIPT™ First-Strand cDNA Synthesis Kit with oligo(dT)20 primers according to the manufacturer's protocol. H For the construction of the H phage library, V was isolated from camel cDNA. H H was amplified.

[0132] Example 2. Preparation of anti-DLL3 antibodies The anti-DLL3 antibodies provided herein include single domain antibodies (sdAbs) generated from immune camels or human Fabs isolated from a synthetic human Fab library.

[0133] phage display Phage display libraries were constructed using sdAbs obtained by immunization (immunogens containing the extracellular domain of human DLL3 protein (aa 27-466) with an N-terminal FLAG tag (AdipoGen, AG-40B-0151) or / and DLL3 expression plasmids or DLL3-expressing cells (CHO-K1 / DLL3 or / and CHO-K1 / EGF4)). A separate human Fab phage display library was synthesized. Both phage libraries were rescued and stored after filter sterilization at 4°C for further use. Binding phages were isolated using protein-based and cell-based panning with the two phage libraries. At least one round of panning was performed using both libraries until the percentage of DLL3-specific phage clones reached 30% for both the protein-based and cell-based panning approaches. The output phages from each round were evaluated for the number of total output clones, the percentage of DLL3-positive clones by ELISA, and the sequence diversity of the DLL3-specific clones. Based on these results, the best panning output was selected for high-throughput screening.

[0134] High-throughput screening The selected output phage was used to infect exponentially growing E. coli cells. Double-stranded DNA of the output phage was extracted. For high-throughput screening, the sdAb / Fab insert was excised from the phagemid vector and inserted into an antibody fragment expression vector. The resulting plasmid was used to transform exponentially growing E. coli cells, which were then plated and grown overnight at 37°C. Several thousand colonies were individually picked and grown in 96-deep-well plates containing 1 mL of 2xYT medium. Expression of the antibody fragment was induced by adding 1 mM IPTG.

[0135] The sdAb / Fab proteins in the supernatants were analyzed for their ability to bind to DLL3 ECD protein by ELISA and for their ability to bind to the DLL3-expressing SHP-77 cell line (American Type Culture Collection (ATCC)® CRL-2195™) and CHO-K1 / human DLL3 (in-house) by FACS. All binders were sequenced. Redundant sequences were removed. A total of 81 camelid sdAb and 2 human Fab binders were obtained that bound to both human and rhesus DLL3 protein and cell lines. All these binders have unique amino acid sequences.

[0136] Some of these unique binders were further characterized by surface plasmon resonance (SPR) on a BIAcore T200 instrument (GE Healthcare). The experiment was performed as follows: crude sdAb / Fab proteins were captured on a sensor chip via their affinity tags. A high concentration (100 nM) of human DLL3 was flowed over the sensor chip surface and allowed to bind to the antibody fragments for 300 seconds, after which running buffer was injected to allow the formed complexes to dissociate. The on-rate (ka) and off-rate (kd) were estimated based on a single association and dissociation curve and used to calculate the equilibrium dissociation constant (K D ) was estimated. The binding affinities of some of these unique binders are shown in Table 7.

[0137] The CDR sequences of the anti-DLL3 camelid sdAb are listed in Table 1, and the CDR sequences of the anti-DLL3 human scFv are listed in Table 2.

[0138] Table 1. CDR sequences of anti-DLL3 camel sdAb TIFF0007748933000001.tif118151TIFF0007748933000002.tif242151TIFF0007748933000003.tif243151TIFF0007748933000004.tif208151

[0139] Table 2: CDR sequences of anti-DLL3 human scFv TIFF0007748933000005.tif51151

[0140] The amino acid sequences of the anti-DLL3 sdAbs are listed in Table 3. The CDRs of the sdAbs are underlined. The nucleic acid sequences encoding the anti-DLL3 sdAbs are shown in SEQ ID NOs: 368-448.

[0141] Table 3. Amino acid sequences of anti-DLL3 camel sdAbs TIFF0007748933000006.tif190150TIFF0007748933000007.tif245150TIFF0007748933000008.tif245150TIFF00077489330 00009.tif241150TIFF0007748933000010.tif245150TIFF0007748933000011.tif246150TIFF0007748933000012.tif102150

[0142] The amino acid sequences of the VH and VL domains of anti-DLL3 human scFv are listed in Table 4. The nucleic acid sequences encoding the VH or VL domain of anti-DLL3 human scFv are shown in SEQ ID NOs: 511 to 514.

[0143] Table 4: Amino acid sequence of anti-DLL3 human scFv TIFF0007748933000013.tif95147

[0144] Example 3. Generation of monospecific camel CARs The amino acid sequences of the anti-DLL3 camelid sdAb fragments are presented in Table 3 above, and the nucleic acid sequences of the anti-DLL3 camelid sdAb fragments are presented in SEQ ID NOS: 368-448. CAR constructs (SEQ ID NOS: 476-484) were generated using the sdAb fragments in Table 3 and additional sequences. A reference CAR construct (CAR3) was also generated using the human anti-DLL3 scFv, CAR3 scFv (SEQ ID NOS: 473). The full-length CAR contains, from N- to C-terminus, a CD8α signal peptide (SEQ ID NOS: 465), the DLL3-binding domain sdAb presented in Table 3, a CD8α hinge domain (SEQ ID NOS: 466), a CD8α transmembrane domain (SEQ ID NOS: 467), a CD137 intracellular domain (SEQ ID NOS: 468) or a CD28 intracellular domain (SEQ ID NOS: 469), and a CD3ζ intracellular domain (SEQ ID NOS: 470). A schematic diagram of the CAR construct is shown in Figure 1. The nucleic acid encoding the CAR fragment was then cloned into a lentiviral vector, using the human EF1α promoter for expression to generate a full-length CAR construct in a single coding frame. The resulting CAR backbone vector was designated "PLLV-hEF1α-DLL3."

[0145] Example 4. Generation of camel anti-DLL3 CAR-T cells Preparation of lentivirus A lentiviral packaging plasmid mixture containing pCMV-ΔR-8.47 and pMD2.G (Addgene, catalog no. 12259) was premixed with the PLLV-hEF1α-DLL3 vector at a pre-optimized ratio (1:1:1:2) in the presence of polyethyleneimine before addition to HEK293 cells. After overnight incubation, the supernatant was collected. The virus-containing supernatant was filtered through a 0.45 μm PES filter and ultracentrifuged to concentrate the lentivirus. The viral pellet was rinsed with pre-chilled DPBS. The virus was appropriately aliquoted and immediately stored at -80°C. Viral titers were determined by measuring transduction efficiency in the supT1 cell line via flow cytometry assay.

[0146] T lymphocyte collection and transduction Leukocytes were collected from healthy donors by apheresis. Peripheral blood mononuclear cells (PBMCs) were isolated using Ficoll-Paque™ PLUS medium according to the manufacturer's protocol. Human T cells were purified from PBMCs using a pan T cell isolation kit (Miltenyi, catalog number 130-096-535) according to the manufacturer's protocol. Purified T cells were then preactivated for 48 hours using a human T cell activation / expansion kit (Miltenyi, catalog number 130-091-441) according to the manufacturer's protocol, and anti-CD3 / CD28 MACSiBead particles were added at a bead-to-cell ratio of 1:2. Preactivated T cells were transduced with lentiviral stock in the presence of 7 μg / mL polybrene. The transduced cells were then transferred to a cell culture incubator to allow transgene expression under appropriate conditions.

[0147] Example 5. Evaluation of the in vitro activity of camel anti-DLL3 CAR-T cells In vitro cytotoxicity assay Six days after transduction, transduced T cells were harvested and co-incubated with the DLL3-expressing tumor cell line SHP-77 at effector (CAR-T) to target cell ratios of 2:1 and 5:1 for 20 hours. In all assays, CAR3 CAR-T cells were used as a reference to compare assay variability and / or act as a control. Untransduced T cells (UnT) were used as a negative control.

[0148] The cytotoxicity of the transduced T cells was determined by lactate dehydrogenase (LDH) assay. The results show that CAR3 CAR-T and some anti-DLL3 CAR-T exhibit potent antitumor activity against SHP-77 cells in vitro, while UnT has no targeted cell-killing effect (Figure 2).

[0149] IFN-γ and TNF-α release detection In addition, supernatants from in vitro cytotoxicity assays were collected to assess CAR-induced cytokine release, such as interferon gamma (IFN-γ) and TNF-α release. As shown in Figures 3A and 3B, CAR3 CAR-Ts and some anti-DLL3 CAR-Ts stimulated by SHP-77 produced IFN-γ and TNF-α, whereas UnTs produced little or no IFN-γ or TNF-α. For protocols for detecting IFN-γ and TNF-α release, please refer to CISBIO's human TNF-α kit and IFN-γ kit.

[0150] CAR-T expansion by long-term stimulation assay Day 0, 1 x 10 5 SHP-77 cells were plated in 24-well plates to establish a monolayer. On day 1, transduced T cells were counted and 2 × 10 5 Individual Survival Car + T cells were plated on top of SHP-77 cells in fresh medium in the absence of cytokines. On day 3, fresh 1 x 10 5 A monolayer of SHP-77 cells was plated on top of the CAR-T cells. On day 4, viable CAR-T cells were counted for each well. On the same day, 2 × 10 5 CARs from expanded wells (with at least this amount of cells) + T cells were replated and a new monolayer was established as on day 1. The process was repeated 3–4 times for stimulation. The fold expansion after each stimulation was calculated as [day 4 viable CARs]. + T cells] / 2×10 5 The cumulative expansion was calculated as [(fold expansion) × (fold expansion + 1)] to normalize for cells discarded with each new stimulation.

[0151] After three stimulations, the fold expansion of different CAR-T constructs was calculated. As shown in Figure 4, most CAR-T constructs expanded more than CAR3 CAR-T after three stimulations with SHP-77 tumor cells.

[0152] Example 6. Evaluation of in vivo efficacy of camelid CARs by CAR-T cell-mediated tumor growth inhibition The antitumor activity of camelid CAR was evaluated in the SHP-77 tumor model. SHP-77 cells were implanted subcutaneously into NOD / SCID mice and randomized into seven groups (four mice per group, day 0). Group 1: vehicle (PBS only); Group 2: UnT (negative control); Group 3: CAR3; Group 4: CAS64380; Group 5: CAS64511; Group 6: CAS63931; Group 7: CAS63997. When tumors were palpable (100 mm 3 ), treatment with CAR-T cells, UnT cells, or vehicle (PBS only) was initiated, and their tumor volumes reached approximately 3000 mm 3 Mice were euthanized when tumor volume reached 1 × 10. Tumor volume was measured twice weekly. CAR-T cells were administered at a dose of 1 × 10. 6 CAR-positive T cells / mouse were administered intravenously. After tumor cell implantation, mice and tumors were monitored for approximately 21 days.

[0153] As shown in Figure 5, all selected camelid CARs exhibited antitumor activity in this animal tumor model.

[0154] Example 7. Humanization of camel sdAb Selected camelid sdAbs (SEQ ID NOS: 279, 294, 297, 312) were humanized using CDR-grafting techniques (see, e.g., U.S. Pat. No. 5,225,539). Briefly, camelid sdAb sequences were compared with those available in the Research Collaboratory for Structural Bioinformatics (RCSB) Protein Data Bank. Homology models of each camelid sdAb were generated based on the closest VH structure. From the model structures, residues located near the CDRs or buried in the interior of the molecule (i.e., with less than 15% of the side-chain solvent accessible surface area) were identified.

[0155] Each camelid sdAb sequence was then BLAST searched against the NCBI human germline V gene database to identify the human VH germline sequence (i.e., human acceptor) with the highest identity to the sdAb (see, e.g., Foote and Winter, J. Mol. Biol. 224:487-499 (1992); Morea V. et al., Methods 20:267-279 (2000); Chothia C. et al., J. Mol. Biol. 186:651-663 (1985)). In the CDR-grafting approach, the CDRs of the human acceptor were replaced with those of the camelid sdAb, generating a straight-graft sequence. Straight-grafted antibodies typically lose binding activity, which must be restored by replacing framework residues critical for antibody activity with non-human residues. Amino acid residues located near the CDRs or buried inside the molecule are usually important for the activity and structure of the antibody and therefore needed to be potential backmutation sites. A series of humanized variants were designed using this method. The CDR amino acid sequences of the humanized variants are shown in Table 5. The full-length amino acid sequences of the humanized variants are shown in Table 6. The CDRs are underlined.

[0156] Table 5. CDR sequences of anti-DLL3 humanized sdAbs TIFF0007748933000014.tif124151

[0157] Table 6. Amino acid sequences of anti-DLL3 humanized sdAbs TIFF0007748933000015.tif234147

[0158] The camel and humanized sdAb sequences were fused with human IgG1 hinge and Fc to generate chimeric and humanized HCAb sequences. DNA encoding these HCAbs was synthesized and inserted into the pTT5 vector. HEK293 cells were transfected with the HCAb expression plasmids. Crude HCAb proteins secreted into the culture medium were subjected to SPR affinity measurements as follows: the capture antibody, anti-human Fc pAb (GE Healthcare), was immobilized on a Biacore™ CM5 chip using EDC-activated amine coupling chemistry to approximately 6,000 RU. The HCAb of interest was captured on the sensor chip surface for 300 seconds. Human DLL3 (AdipoGen, AG-40B-0151) was flowed over the sensor chip surface at a series of increasing concentrations. The association and dissociation phases were monitored. Captured antibody and antigen were removed between cycles using 10 mM glycine-HCl, pH 2.0 buffer, confirming a new binding surface for the antigen. The resulting sensorgrams were globally fitted using a 1:1 binding model to determine on- and off-rates (ka and kd, respectively) and affinity (K D ) was calculated.

[0159] The binding affinity of some humanized sdAbs was measured and compared to that of the original camelid sdAb (Table 7). The majority of the humanized antibodies retained the binding affinity of the camelid sdAb. This example demonstrated the success of humanizing sdAbs using our standard protocol. The majority of sdAbs retained their binding affinity after humanization.

[0160] The scFvs had comparable K D values ​​(AS56788 and AS56704 in Table 7).

[0161] Table 7. Monovalent binding affinities of camelid and humanized antibodies and scFvs TIFF0007748933000016.tif126133

[0162] Example 8. Generation of monospecific humanized CARs The amino acid sequences of the anti-DLL3 humanized sdAbs are presented in Table 6 above, and the nucleic acid sequences of the anti-DLL3 humanized sdAbs are listed in SEQ ID NOs: 449-461. Full CAR constructs (SEQ ID NOs: 485-494) were generated using the humanized sdAbs and additional sequences in Table 6. The full-length CARs comprise, from N- to C-terminus, a CD8α signal peptide (SEQ ID NO: 465), the DLL3 binding domain (humanized sdAb) presented in Table 6, a CD8α hinge domain (SEQ ID NO: 466), a CD8α transmembrane domain (SEQ ID NO: 467), a CD137 intracellular domain (SEQ ID NO: 468) or a CD28 intracellular domain (SEQ ID NO: 469), and a CD3ζ cytoplasmic domain (SEQ ID NO: 470). A schematic diagram of the CAR construct is shown in Figure 1. The nucleic acids encoding the CAR fragments were then cloned into a lentiviral vector, generating full-length CAR constructs in a single coding frame using the human EF1α promoter for expression. The resulting CAR backbone vector was named "PLLV-hEF1α-DLL3."

[0163] Example 9. Evaluation of in vitro activity of humanized anti-DLL3 CAR-T cells Similar to the procedures described in Example 4, the efficacy of the humanized CAR was evaluated via CAR-T cell-mediated killing of tumor cells, cytokine release, and long-term stimulation assays.

[0164] In vitro cytotoxicity assay The results are shown in Figures 6A-6D. Our humanized CAR-T demonstrated superior antitumor efficacy in vitro.

[0165] IFN-γ release assay In addition, supernatants from in vitro cytotoxicity assays were collected to assess CAR-induced cytokine release, such as interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). As shown in Figures 7A and 7B, CAR3 CAR-Ts and some anti-DLL3 CAR-Ts were stimulated by SHP-77 to produce IFN-γ and TNF-α, whereas UnTs produced little to no IFN-γ or TNF-α.

[0166] CART expansion proliferation by long-term stimulation assay Day 0, 1 x 10 5 SHP-77 cells were plated in 24-well plates to establish a monolayer. On day 1, CAR-T cells were counted and 2 × 10 5 Individual Survival Car + T cells were plated on top of SHP-77 cells in fresh medium in the absence of cytokines. On day 3, fresh 1 x 10 5 A monolayer of NCI-H82 cells was plated on top of the CAR-T cells. On day 4, viable CAR-T cells were counted for each well. On the same day, 2 × 10 5 CARs from expanded wells (with at least this amount of cells) + T cells were replated and a new monolayer was established as on day 1. The process was repeated 3–4 times for stimulation. The fold expansion after each stimulation was calculated as [day 4 viable CARs]. + T cells] / 2×10 5 The cumulative expansion was calculated as [(expansion fold) × (expansion fold + 1)] to normalize for cells discarded with each new stimulation.

[0167] After three stimulations, the fold expansion of different CAR-T constructs was calculated. As shown in Figure 8, most CAR-T constructs expanded more than CAR3 CAR-T after three stimulations with SHP-77 tumor cells.

[0168] Example 10. Evaluation of in vivo efficacy of humanized CARs by CAR-T cell-mediated tumor growth inhibition The antitumor activity of humanized CARs was evaluated in the SHP-77 tumor model. SHP-77 cells were implanted subcutaneously into NOD / SCID mice and randomized into 9 groups: vehicle (PBS only), UnT (negative control), CAR3, CAS64380, CAS64380VH5, CAS64511, CAS64511VH5, CAS63997, and CAS63997VH5 (4 mice per group, day 0). When tumors were palpable (100 mm 3), treatment with CAR-T cells, UnT cells, or vehicle (PBS only) was initiated, and their tumor volumes reached approximately 3000 mm 3 Mice were euthanized when tumor volume reached 0.2 × 10. Tumor volume was measured twice weekly. CAR-T cells were administered at 0.2 × 10. 6 CAR-positive T cells / mouse were administered intravenously. After tumor cell implantation, mice and tumors were monitored for approximately 21 days.

[0169] As shown in Figures 9A-9J, compared to the benchmark CAR3, CAS64380VH5 and CAS63997VH5 exhibited superior antitumor activity in this animal model.

[0170] The antitumor activity of these humanized CARs was not found to correlate with their in vitro cell killing efficacy.

[0171] Some of the amino acid and nucleic acid sequences described herein are listed below. Camel sdAb nucleic acid sequence SEQ ID NO: 368 (Camel sdAb AS63930 nucleic acid sequence) TIFF0007748933000017.tif36147 SEQ ID NO: 369 (Camel sdAb AS63932 nucleic acid sequence) TIFF0007748933000018.tif36146 SEQ ID NO: 370 (Camel sdAb AS63951 nucleic acid sequence) TIFF0007748933000019.tif36146 SEQ ID NO: 371 (Camel sdAb AS63984 nucleic acid sequence) TIFF0007748933000020.tif36146 SEQ ID NO: 372 (Camel sdAb AS63987 nucleic acid sequence) TIFF0007748933000021.tif36146 SEQ ID NO: 373 (Camel sdAb AS63997 nucleic acid sequence) TIFF0007748933000022.tif36146 SEQ ID NO: 374 (Camel sdAb AS64047 nucleic acid sequence) TIFF0007748933000023.tif36146 SEQ ID NO: 375 (Camel sdAb AS64052 nucleic acid sequence) TIFF0007748933000024.tif36146 SEQ ID NO: 376 (Camel sdAb AS64062 nucleic acid sequence) TIFF0007748933000025.tif36146 SEQ ID NO: 377 (Camel sdAb AS64072 nucleic acid sequence) TIFF0007748933000026.tif36147 SEQ ID NO: 378 (Camel sdAb AS64097 nucleic acid sequence) TIFF0007748933000027.tif36146 SEQ ID NO: 379 (Camel sdAb AS64114 nucleic acid sequence) TIFF0007748933000028.tif36146 SEQ ID NO: 380 (Camel sdAb AS64123 nucleic acid sequence) TIFF0007748933000029.tif36146 SEQ ID NO: 381 (Camel sdAb AS64130 nucleic acid sequence) TIFF0007748933000030.tif36147 SEQ ID NO: 382 (Camel sdAb AS64137 nucleic acid sequence) TIFF0007748933000031.tif36147 SEQ ID NO: 383 (Camel sdAb AS64142 nucleic acid sequence) TIFF0007748933000032.tif36146 SEQ ID NO: 384 (Camel sdAb AS64154 nucleic acid sequence) TIFF0007748933000033.tif36146 SEQ ID NO: 385 (Camel sdAb AS64160 nucleic acid sequence) TIFF0007748933000034.tif36146 SEQ ID NO: 386 (Camel sdAb AS64228 nucleic acid sequence) TIFF0007748933000035.tif37146 SEQ ID NO: 387 (Camel sdAb AS64300 nucleic acid sequence) TIFF0007748933000036.tif36147 SEQ ID NO: 388 (Camel sdAb AS64380 nucleic acid sequence) TIFF0007748933000037.tif36147 SEQ ID NO: 389 (Camel sdAb AS64395 nucleic acid sequence) TIFF0007748933000038.tif36146 SEQ ID NO: 390 (Camel sdAb AS64443 nucleic acid sequence) TIFF0007748933000039.tif36146 SEQ ID NO: 391 (Camel sdAb AS64511 nucleic acid sequence) TIFF0007748933000040.tif36146 SEQ ID NO: 392 (Camel sdAb AS64536 nucleic acid sequence) TIFF0007748933000041.tif36146 SEQ ID NO: 393 (Camel sdAb AS64597 nucleic acid sequence) TIFF0007748933000042.tif36146 SEQ ID NO: 394 (Camel sdAb AS64617 nucleic acid sequence) TIFF0007748933000043.tif36146 SEQ ID NO: 395 (Camel sdAb AS64634 nucleic acid sequence) TIFF0007748933000044.tif36146 SEQ ID NO: 396 (Camel sdAb AS69498 nucleic acid sequence) TIFF0007748933000045.tif36146 SEQ ID NO: 397 (Camel sdAb AS69500 ​​nucleic acid sequence) TIFF0007748933000046.tif36147 SEQ ID NO: 398 (Camel sdAb AS69527 nucleic acid sequence) TIFF0007748933000047.tif36146 SEQ ID NO: 399 (Camel sdAb AS68280 nucleic acid sequence) TIFF0007748933000048.tif36146 SEQ ID NO: 400 (Camel sdAb AS68355 nucleic acid sequence) TIFF0007748933000049.tif36147 SEQ ID NO: 401 (Camel sdAb AS69443 nucleic acid sequence) TIFF0007748933000050.tif36147 SEQ ID NO: 402 (Camel sdAb AS75376 nucleic acid sequence) TIFF0007748933000051.tif36146 SEQ ID NO: 403 (Camel sdAb AS75387 nucleic acid sequence) TIFF0007748933000052.tif37147 SEQ ID NO: 404 (Camel sdAb AS75695 nucleic acid sequence) TIFF0007748933000053.tif36146 SEQ ID NO: 405 (Camel sdAb AS76169 nucleic acid sequence) TIFF0007748933000054.tif36146 SEQ ID NO: 406 (Camel sdAb AS63931 nucleic acid sequence) TIFF0007748933000055.tif36147 SEQ ID NO: 407 (Camel sdAb AS63937 nucleic acid sequence) TIFF0007748933000056.tif36146 SEQ ID NO: 408 (Camel sdAb AS63948 nucleic acid sequence) TIFF0007748933000057.tif36146 SEQ ID NO: 409 (Camel sdAb AS63956 nucleic acid sequence) TIFF0007748933000058.tif36147 SEQ ID NO: 410 (Camel sdAb AS63965 nucleic acid sequence) TIFF0007748933000059.tif36146 SEQ ID NO: 411 (Camel sdAb AS63993 nucleic acid sequence) TIFF0007748933000060.tif36146 SEQ ID NO: 412 (Camel sdAb AS63999 nucleic acid sequence) TIFF0007748933000061.tif36146 SEQ ID NO: 413 (Camel sdAb AS64006 nucleic acid sequence) TIFF0007748933000062.tif36146 SEQ ID NO: 414 (Camel sdAb AS64057 nucleic acid sequence) TIFF0007748933000063.tif36147 SEQ ID NO: 415 (Camel sdAb AS64060 nucleic acid sequence) TIFF0007748933000064.tif36146 SEQ ID NO: 416 (Camel sdAb AS64071 nucleic acid sequence) TIFF0007748933000065.tif36146 SEQ ID NO: 417 (Camel sdAb AS64093 nucleic acid sequence) TIFF0007748933000066.tif36146 SEQ ID NO: 418 (Camel sdAb AS64118 nucleic acid sequence) TIFF0007748933000067.tif36146 SEQ ID NO: 419 (Camel sdAb AS64120 nucleic acid sequence) TIFF0007748933000068.tif42146 SEQ ID NO: 420 (Camel sdAb AS64124 nucleic acid sequence) TIFF0007748933000069.tif36146 SEQ ID NO: 421 (Camel sdAb AS64135 nucleic acid sequence) TIFF0007748933000070.tif36147 SEQ ID NO: 422 (Camel sdAb AS64163 nucleic acid sequence) TIFF0007748933000071.tif36146 SEQ ID NO: 423 (Camel sdAb AS64182 nucleic acid sequence) TIFF0007748933000072.tif36146 SEQ ID NO: 424 (Camel sdAb AS64183 nucleic acid sequence) TIFF0007748933000073.tif36146 SEQ ID NO: 425 (Camel sdAb AS64207 nucleic acid sequence) TIFF0007748933000074.tif36146 SEQ ID NO: 426 (Camel sdAb AS64276 nucleic acid sequence) TIFF0007748933000075.tif36146 SEQ ID NO: 427 (Camel sdAb AS64336 nucleic acid sequence) TIFF0007748933000076.tif36146 SEQ ID NO: 428 (Camel sdAb AS64346 nucleic acid sequence) TIFF0007748933000077.tif36146 SEQ ID NO: 429 (Camel sdAb AS64420 nucleic acid sequence) TIFF0007748933000078.tif36146 SEQ ID NO: 430 (Camel sdAb AS64473 nucleic acid sequence) TIFF0007748933000079.tif36146 SEQ ID NO: 431 (Camel sdAb AS64475 nucleic acid sequence) TIFF0007748933000080.tif36146 SEQ ID NO: 432 (Camel sdAb AS64513 nucleic acid sequence) TIFF0007748933000081.tif36146 SEQ ID NO: 433 (Camel sdAb AS64562 nucleic acid sequence) TIFF0007748933000082.tif36146 SEQ ID NO: 434 (Camel sdAb AS64583 nucleic acid sequence) TIFF0007748933000083.tif36146 SEQ ID NO: 435 (Camel sdAb AS64594 nucleic acid sequence) TIFF0007748933000084.tif36146 SEQ ID NO: 436 (Camel sdAb AS64605 nucleic acid sequence) TIFF0007748933000085.tif36146 SEQ ID NO: 437 (Camel sdAb AS64606 nucleic acid sequence) TIFF0007748933000086.tif36146 SEQ ID NO: 438 (Camel sdAb AS68121 nucleic acid sequence) TIFF0007748933000087.tif36147 SEQ ID NO: 439 (Camel sdAb AS68170 nucleic acid sequence) TIFF0007748933000088.tif36147 SEQ ID NO: 440 (Camel sdAb AS63964 nucleic acid sequence) TIFF0007748933000089.tif36146 SEQ ID NO: 441 (Camel sdAb AS64116 nucleic acid sequence) TIFF0007748933000090.tif36146 SEQ ID NO: 442 (Camel sdAb AS68270 nucleic acid sequence) TIFF0007748933000091.tif36147 SEQ ID NO: 443 (Camel sdAb AS68320 nucleic acid sequence) TIFF0007748933000092.tif36147 SEQ ID NO: 444 (Camel sdAb AS68351 nucleic acid sequence) TIFF0007748933000093.tif36147 SEQ ID NO: 445 (Camel sdAb AS75378 nucleic acid sequence) TIFF0007748933000094.tif36146 SEQ ID NO: 446 (Camel sdAb AS75383 nucleic acid sequence) TIFF0007748933000095.tif36147 SEQ ID NO: 447 (Camel sdAb AS75751 nucleic acid sequence) TIFF0007748933000096.tif36146 SEQ ID NO: 448 (Camel sdAb AS76422 nucleic acid sequence) TIFF0007748933000097.tif36146

[0172] Humanized camel sdAb nucleic acid sequence SEQ ID NO: 449 (humanized sdAb AS64380VH4 nucleic acid sequence) TIFF0007748933000098.tif36146 SEQ ID NO: 450 (humanized sdAb AS64380VH5 nucleic acid sequence) TIFF0007748933000099.tif36146 SEQ ID NO: 451 (humanized sdAb AS64380VH6 nucleic acid sequence) TIFF0007748933000100.tif36146 SEQ ID NO: 452 (humanized sdAb AS64380VH7 nucleic acid sequence) TIFF0007748933000101.tif36146 SEQ ID NO: 453 (humanized sdAb AS64511VH4 nucleic acid sequence) TIFF0007748933000102.tif36147 SEQ ID NO: 454 (humanized sdAb AS64511VH5 nucleic acid sequence) TIFF0007748933000103.tif36147 SEQ ID NO: 455 (humanized sdAb AS64511VH6 nucleic acid sequence) TIFF0007748933000104.tif36147 SEQ ID NO: 456 (humanized sdAb AS63931VH4 nucleic acid sequence) TIFF0007748933000105.tif36146 SEQ ID NO: 457 (humanized sdAb AS63931VH5 nucleic acid sequence) TIFF0007748933000106.tif36146 SEQ ID NO: 458 (humanized sdAb AS63931VH6 nucleic acid sequence) TIFF0007748933000107.tif36146 SEQ ID NO: 459 (humanized sdAb AS63997VH4 nucleic acid sequence) TIFF0007748933000108.tif36147 SEQ ID NO: 460 (humanized sdAb AS63997VH5 nucleic acid sequence) TIFF0007748933000109.tif36147 SEQ ID NO: 461 (humanized sdAb AS63997VH6 nucleic acid sequence) TIFF0007748933000110.tif36147 SEQ ID NO: 462 (linker amino acid sequence) TIFF0007748933000111.tif3128 SEQ ID NO: 463 (linker amino acid sequence) TIFF0007748933000112.tif3128 SEQ ID NO: 464 (linker amino acid sequence) TIFF0007748933000113.tif3128 SEQ ID NO: 465 (CD8α signal peptide amino acid sequence) TIFF0007748933000114.tif3128 SEQ ID NO: 466 (CD8α hinge amino acid sequence) TIFF0007748933000115.tif9146 SEQ ID NO: 467 (CD8α transmembrane domain amino acid sequence) TIFF0007748933000116.tif3128 SEQ ID NO: 468 (4-1BB intracellular domain amino acid sequence) TIFF0007748933000117.tif4128 SEQ ID NO: 469 (CD28 intracellular domain amino acid sequence) TIFF0007748933000118.tif4128 SEQ ID NO: 470 (CD3ζ intracellular domain amino acid sequence) TIFF0007748933000119.tif9147 SEQ ID NO: 471 (F2A element amino acid sequence) TIFF0007748933000120.tif4128 SEQ ID NO: 472 (P2A element amino acid sequence) TIFF0007748933000121.tif4128 SEQ ID NO: 473 (CAR3 anti-DLL3 scFv amino acid sequence) TIFF0007748933000122.tif26147 SEQ ID NO: 474 (CD28 transmembrane domain amino acid sequence) TIFF0007748933000123.tif3128 SEQ ID NO: 475 (CD28 hinge) TIFF0007748933000124.tif3128

[0173] Camel anti-DLL3 CAR sequence SEQ ID NO: 476 (CAS63997) TIFF0007748933000125.tif37145 Sequence number 477 (CAS64380) TIFF0007748933000126.tif37146 Sequence number 478 (CAS64511) TIFF0007748933000127.tif37147 Sequence number 479 (CAS64617) TIFF0007748933000128.tif35147 Sequence number 480 (CAS69443) TIFF0007748933000129.tif37147 Sequence number 481 (CAS63931) TIFF0007748933000130.tif37145 Sequence number 482 (CAS64047) TIFF0007748933000131.tif37147 Sequence number 483 (CAS64052) TIFF0007748933000132.tif37146 Sequence number 484 (CAS64062) TIFF0007748933000133.tif37147

[0174] Humanized anti-DLL3 CAR sequence SEQ ID NO: 485 (CAS64380VH4) TIFF0007748933000134.tif37145 Sequence number 486 (CAS64380VH5) TIFF0007748933000135.tif37145 Sequence number 487 (CAS64380VH6) TIFF0007748933000136.tif37146 Sequence number 488 (CAS64380VH7) TIFF0007748933000137.tif37146 Sequence number 489 (CAS64511VH4) TIFF0007748933000138.tif37146 SEQ ID NO: 490 (CAS64511VH5) TIFF0007748933000139.tif37147 Sequence number 491 (CAS64511VH6) TIFF0007748933000140.tif37146 SEQ ID NO: 492 (CAS63997VH4) TIFF0007748933000141.tif37146 Sequence number 493 (CAS63997VH5) TIFF0007748933000142.tif37146 Sequence number 494 (CAS63997VH6) TIFF0007748933000143.tif37146

[0175] Anti-DLL3 human scFv VL and VH domain nucleic acid sequences SEQ ID NO: 511 (nucleic acid sequence of the VL domain of anti-DLL3 human scFv AS56704) TIFF0007748933000144.tif31146 SEQ ID NO: 512 (nucleic acid sequence of the VH domain of anti-DLL3 human scFv AS56704) TIFF0007748933000145.tif36146 SEQ ID NO: 513 (nucleic acid sequence of the VL domain of anti-DLL3 human scFv AS56788) TIFF0007748933000146.tif31146 SEQ ID NO: 514 (nucleic acid sequence of the VH domain of anti-DLL3 human scFv AS56788) TIFF0007748933000147.tif36146

[0176] Human anti-DLL3 scFv CAR sequence SEQ ID NO: 515 (CAS56704) TIFF0007748933000148.tif48147 Sequence number 516 (CAS56788) TIFF0007748933000149.tif48147

[0177] Anti-DLL3 Benchmark CAR SEQ ID NO: 517 (1H2.1 amino acid sequence) TIFF0007748933000150.tif42146

[0178] Example 11. Evaluation of the in vitro activity of humanized anti-DLL3 tandem CAR-T cells To improve the anti-tumor efficacy of CAR-T, we constructed three tandem CARs (T1, T2, and T3). The amino acid sequences of the tandem CARs are shown in SEQ ID NOs: 518-520. The amino acid sequences of anti-DLL3 humanized sdAb fragments are shown in SEQ ID NOs: 356 (AS64380VH5) and 366 (AS63997VH5). A reference CAR construct was also generated using the anti-DLL3 CAR, 1H2.1 (SEQ ID NO: 517; see, e.g., WO 2019200007). The full-length CAR comprises, from N- to C-terminus, a CD8α signal peptide (SEQ ID NO: 465), a DLL3-binding domain sdAb represented by SEQ ID NO: 356 (AS64380VH5) and SEQ ID NO: 366 (AS63997VH5), a CD8α hinge domain (SEQ ID NO: 466), a CD8α transmembrane domain (SEQ ID NO: 467), a CD137 intracellular domain (SEQ ID NO: 468) or a CD28 intracellular domain (SEQ ID NO: 469), and a CD3ζ intracellular domain (SEQ ID NO: 470). A schematic diagram of the CAR construct is shown in Figure 10A. For T1, both sdAb1 and sdAb2 were AS64380VH5. For T2, both sdAb1 and sdAb2 were AS63997VH5. For T3, sdAb1 and sdAb2 were AS63997VH5 and AS64380VH5, respectively. The nucleic acid encoding the CAR fragment was then cloned into a lentiviral vector, using the human EF1α promoter for expression to generate a full-length CAR construct in a single coding frame.

[0179] SEQ ID NO: 518 (T1 amino acid sequence) TIFF0007748933000151.tif48147 SEQ ID NO: 519 (T2 amino acid sequence) TIFF0007748933000152.tif48146 SEQ ID NO: 520 (T3 amino acid sequence) TIFF0007748933000153.tif48146

[0180] In vitro cytotoxicity assay Nine days after transduction, transduced T cells were harvested and co-incubated with DLL3-expressing tumor cell lines (SHP-77, which expresses high DLL3; NCI-H82, which expresses moderate DLL3; and NCI-H2171, which expresses low DLL3) and DLL3-negative cell lines (NCI-H460 and HEK293) at effector (CAR-T) to target cell ratios of 0.5:1 and 2:1 for 22 hours. In all assays, CAR3 CAR-T cells were used as a reference to compare assay variability and / or act as a control. Untransduced T cells (UnT) were used as a negative control.

[0181] The cytotoxicity of the transduced T cells was determined by lactate dehydrogenase (LDH) assay. The results show that CAR3 CAR-T and some anti-DLL3 tandem CAR-T exhibited potent antitumor activity against SHP-77 cells in vitro, while UnT had no targeted cell-killing effect (Figures 11A-C), and DLL3-negative expressing cells (NCI-H460 and HEK293) did not induce cytotoxicity (Figures 11D-E). In addition to CAR3, we also compared the in vitro cytotoxicity of T3 and 1H2.1 against SHP-77 cells. The results show that T3 had comparable or less potent cell-killing activity in short-term stimulation (Figure 11V).

[0182] IFN-γ and TNF-α release detection In addition, supernatants from in vitro cytotoxicity assays were collected to assess CAR-induced cytokine release, such as interferon gamma (IFN-γ) and TNF-α release. As shown in Figure 11F-K, CAR3 CAR-Ts and some anti-DLL3 tandem CAR-Ts produced IFN-γ and TNF-α when stimulated by DLL3-expressing cell lines, whereas UnTs produced little or no IFN-γ or TNF-α. DLL3-negative expressing cell lines did not reduce the specific release of IFN-γ and TNF-α (data not shown). For protocols for detecting IFN-γ and TNF-α release, please refer to CISBIO's Human TNF-α Kit and IFN-γ Kit.

[0183] Compared with 1H2.1, T3 released more IFN-γ and TNF-α (after 22 h of co-incubation) (FIGS. 11W-X).

[0184] Tandem CAR-T cytotoxicity and expansion by long-term stimulation assay We evaluated DLL3 CAR-T cells by repeated antigen stimulation assays. Upon repeated stimulation with SCLC and control cell lines, tandem CAR-T cells T3 exhibited more potent cytotoxicity against SCLC cells, particularly SHP-77 and NCI-H82 cells (Figures 11L-P). In addition to cytotoxic activity, tandem CAR-T cells T3 also exhibited higher proliferation potential than other CAR-T cells, particularly upon stimulation with SHP-77 and NCI-H82 cells (Figures 11Q-U).

[0185] In addition to CAR3, we also compared the in vitro cytotoxicity of T3 and 1H2.1 against SHP-77 cells. The results show that T3 had superior cytotoxicity and expanded proliferation in long-term stimulation (Figures 11Y-Z).

[0186] Repeated stimulation was performed as follows. Round 1: CAR-T cells and 3 × 10 5 Target cells (e.g., SHP-77) were added to a 24-well plate at a 1:5 effector-to-target cell ratio and co-incubated for 3 days in a carbon dioxide incubator at 37°C and 5% CO. For cytokine detection, 200 μL of cell culture supernatant was pipetted to collect the co-incubated cells, and the %CD3 and CAR positivity rates were evaluated by flow cytometry. Round 2: Based on the CAR-T positivity rate of the collected cells in Round 1, the collected cells were continued to be co-incubated with the same volume of fresh target cells (SHP-77) at an effector-to-target cell ratio of 1:2 for another 3 days. For cytokine detection, 200 μL of cell culture supernatant was pipetted, and the co-incubated cells were collected, and the %CD3 and CAR positivity rates were evaluated by flow cytometry; Round 3 and subsequent rounds were conducted in a similar manner to Round 2, based on the CAR-T positivity rate of each preceding round.

[0187] Example 12. Evaluation of the in vitro activity of humanized anti-DLL3 CAR-T cells armed with PD-1 DNR or CSR To improve the durability of CAR-T, we constructed DLL3 CARs armed with a PD-1 dominant-negative receptor (PD-1DNR) or a PD-1 chimeric switch receptor (PD-1CSR). The amino acid sequences of the two CARs are presented in SEQ ID NOs: 521-522. The PD-1DNR and PD-1CSR sequences were linked to the C-terminus of T3 via P2A. The amino acid sequences of PD-1DNR and PD-1CSR are presented in SEQ ID NOs: 523-524. A schematic diagram of the CAR construct is shown in Figure 10B.

[0188] SEQ ID NO: 521 (T3-PD-1DNR amino acid sequence) TIFF0007748933000154.tif75146 SEQ ID NO: 522 (T3-PD-1CSR amino acid sequence) TIFF0007748933000155.tif70146 SEQ ID NO: 523 (PD-1DNR amino acid sequence) TIFF0007748933000156.tif26146 SEQ ID NO: 524 (PD-1CSR amino acid sequence) TIFF0007748933000157.tif20146

[0189] We evaluated DLL3 CAR-T cells armed with PD-1DNR or PD-1CSR in a repeated antigen stimulation assay. When repeatedly stimulated with SHP-77 cells, the armed CAR-T cells did not exhibit enhanced cytotoxicity or improved expansion capacity compared with standard CAR-T cells (Figures 12A-B). When repeatedly stimulated with SHP-77 / PD-L1 cells (overexpressing human PD-L1 in SHP-77 cells), CAR-T cells armed with PD-1CSR exhibited superior cytotoxicity and expansion capacity (Figures 12C-D).

[0190] Example 13. TGF-β-DNR enhances the antitumor efficacy of DLL3 CAR-T cells Construction of TGF-β-DNR-armed DLL3 CAR-T cells To improve the antitumor performance of DLL3 CAR-T cells within the tumor microenvironment, we incorporated a TGF-β-DNR sequence into the DLL3 CAR, as shown in Figure 13A. TGF-β-DNR is a truncated version of TGFBRII, consisting of the extracellular and transmembrane domains of TGFBRII. Constructs T3-P2A-TGF-β-DNR and T3-T2A-TGF-β-DNR contain a T3-BBZ sequence at the N-terminus, a P2A or T2A peptide as shown, and a TGF-β-DNR sequence at the C-terminus. Constructs TGF-β-DNR-P2A-T3 and TGF-β-DNR-T2A-T3 contain a TGF-β-DNR sequence at the N-terminus, a P2A or T2A peptide as shown, and a T3-BBZ sequence at the C-terminus. The detailed sequences of the TGF-β-DNR and armed DLL3 CAR are provided in SEQ ID NOs: 525-529.

[0191] SEQ ID NO: 525 (T3-P2A-TGF-β-DNR amino acid sequence) TIFF0007748933000158.tif70146 SEQ ID NO: 526 (TGF-β-DNR-P2A-T3 amino acid sequence) TIFF0007748933000159.tif70147 SEQ ID NO: 527 (T3-T2A-TGF-β-DNR amino acid sequence) TIFF0007748933000160.tif70147 SEQ ID NO: 528 (TGF-β-DNR-T2A-T3 amino acid sequence) TIFF0007748933000161.tif70147 SEQ ID NO: 529 (TGF-β-DNR amino acid sequence) TIFF0007748933000162.tif20146

[0192] All constructs were packaged into lentiviruses based on a second-generation lentivirus system. Primary T cells isolated from PBMCs of healthy donors were then transduced with the lentiviruses. Four days after transduction, the sdAb and TGF-β-DNR positivity rates were detected by FACS (Figure 13B). The results showed that the sdAb positivity rates of T3-P2A-TGF-β-DNR, T3-T2A-TGF-β-DNR, TGF-β-DNR-P2A-T3, and TGF-β-DNR-T2A-T3 CAR-T cells were comparable. However, the positivity rates of TGF-β-DNR were higher for the constructs T3-P2A-TGF-β-DNR and T3-T2A-TGF-β-DNR than for TGF-β-DNR-P2A-T3 and TGF-β-DNR-T2A-T3. These results indicated that the expression of TGF-β-DNR was higher when conjugated to the C-terminus of CAR.

[0193] In vitro cytotoxicity assay The cytotoxicity of these CAR-T cells was then assessed by LDH or IFN-γ release assays. Five days after transduction, CAR-T cells were regulated by untransduced T cells (UnT) to the same sdAb positivity rate. Next, CAR-T cells or UnT cells were co-incubated with SHP77 cells in the presence of 5 ng / mL TGF-β for 48 hours, and LDH and IFN-γ release were measured (Figure 13C-D). The results showed that CAR-T cells armed with TGF-β-DNR induced more specific lysis of target cells than unarmed CAR-T cells. Therefore, CAR-T cells armed with TGF-β-DNR showed a higher IFN-γ release capacity upon antigen activation. Consistent with the TGF-β-DNR expression levels of different CAR-T cells, T3-P2A-TGF-β-DNR and T3-T2A-TGF-β-DNR secreted higher levels of IFN-γ than TGF-β-DNR-P2A-T3 and TGF-β-DNR-T2A-T3 CAR-T cells. Collectively, these results demonstrated that TGF-β-DNR can enhance the cytotoxicity of DLL3 CAR-T cells against DLL3-positive SCLC cells.

[0194] Long-term stimulation assay To determine whether TGF-β-DNR could counteract the inhibitory effects of TGF-β on CAR-T cells, we performed a long-term stimulation assay. Specifically, T3-P2A-TGF-β-DNR and T3 CAR-T cells were repeatedly loaded with SHP77 cells every 3 days in the presence or absence of 5 ng / mL TGF-β. At the end of each stimulation, the percentage of T cells among total viable cells was analyzed by FACS, and CAR-T cell expansion was calculated. As shown in Figures 13E and 13F, the persistence and expansion of T3 CAR-T cells was inhibited by TGF-β. In contrast, the persistence and expansion of T3-P2A-TGF-β-DNR were fully maintained even in the presence of TGF-β. After two rounds of stimulation with SHP77 cells, T cell exhaustion markers were analyzed by FACS. As shown in Figure 13G, treatment with TGF-β upregulated the expression of exhaustion markers in T3 cells but not in T3-P2A-TGF-β-DNR CAR-T cells. Collectively, these results demonstrated that TGF-β-DNR protects DLL3 CAR-T cells from TGF-β inhibition. Because TGF-β expression levels are typically elevated in the microenvironment of solid tumors, our results suggest that the addition of TGF-β-DNR improves the antitumor efficacy of DLL3 CAR-T cells in solid tumors.

[0195] In vivo antitumor efficacy studies To further explore whether TGF-β-DNR could enhance the antitumor efficacy of DLL3 CAR-T cells in vivo, T3-T2A-TGF-β-DNR CAR-T cells or parental CAR-T cells were evaluated in a xenograft model. 7 SHP77 cells were subcutaneously implanted into NCG mice. After 7–10 days, tumor volumes reached 100–200 mm. 3 When it reaches 2.5 × 10 5CAR-T cells were intravenously injected into mice. Tumor volume was then measured twice weekly, and the percentage of CAR-T in peripheral blood was measured weekly. As shown in Figure 13H, at suboptimal doses, T3-T2A-TGF-β-DNR CAR-T cells were able to potently suppress tumor growth, whereas parental T3 CAR-T cells were unable to do so. As shown in Figure 13I, the percentage of T3-T2A-TGF-β-DNR CAR-T in peripheral blood leukocytes was higher than that of T3. Collectively, these results indicate that TGF-β-DNR can enhance the antitumor efficacy of DLL3 CAR-T cells in vivo.

Claims

1. Engineered immune cells expressing chimeric antigen receptors (CARs) and dominant negative receptors (DNRs): wherein the CAR specifically binds to DLL3, and the CAR (a) a first single domain antibody (sdAb) portion comprising: a CDR1 comprising the amino acid sequence of SEQ ID NO:6; a CDR2 comprising the amino acid sequence of SEQ ID NO:87; and a CDR3 comprising the amino acid sequence of SEQ ID NO:168; and (b) a second single domain antibody (sdAb) portion comprising: a CDR1 comprising the amino acid sequence of SEQ ID NO: 21; a CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and a CDR3 comprising the amino acid sequence of SEQ ID NO:

183. Including, wherein the DNR is a TGF-β DNR having the amino acid sequence of SEQ ID NO:

529.

2. the first sdAb portion comprises the amino acid sequence of SEQ ID NO: 366, and the second sdAb portion comprises the amino acid sequence of SEQ ID NO: 356; The modified immune cell of claim 1 .

3. 3. The modified immune cell of claim 1 or 2, wherein the CAR comprises, from N- to C-terminus, a signal peptide, a DLL3-binding domain, a hinge domain, a transmembrane domain, and an intracellular signaling domain, wherein the DLL3-binding domain comprises the first sdAb portion and the second sdAb portion.

4. 4. The modified immune cell of claim 3, wherein the intracellular signaling domain is an intracellular signaling domain of CD3ζ, FcRγ, FcRβ, CD3γ, CD3δ, CD3ε, CD5, CD22, CD79a, CD79b, or CD66d.

5. 5. The modified immune cell of claim 3 or 4, wherein the intracellular signaling domain further comprises an intracellular costimulatory sequence.

6. 6. The modified immune cell of claim 5, wherein the intracellular costimulatory sequence is a costimulatory molecule selected from the group consisting of CD27, CD28, 4-1BB, OX40, CD40, PD-1, LFA-1, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3, TNFRSF9, TNFRSF4, TNFRSF8, CD40LG, ITGB2, KLRC2, TNFRSF18, TNFRSF14, HAVCR1, LGALS9, DAP10, DAP12, CD83, a ligand for CD83, and combinations thereof.

7. Nucleic acid molecules encoding chimeric antigen receptors (CARs) and dominant negative receptors (DNRs): wherein the CAR specifically binds to DLL3, and the CAR (a) a first single domain antibody (sdAb) portion comprising: a CDR1 comprising the amino acid sequence of SEQ ID NO:6; a CDR2 comprising the amino acid sequence of SEQ ID NO:87; and a CDR3 comprising the amino acid sequence of SEQ ID NO:168; and (b) a second single domain antibody (sdAb) portion comprising: a CDR1 comprising the amino acid sequence of SEQ ID NO: 21; a CDR2 comprising the amino acid sequence of SEQ ID NO: 102; and a CDR3 comprising the amino acid sequence of SEQ ID NO:

183. Including, wherein the DNR is a TGF-β DNR having the amino acid sequence of SEQ ID NO:

529.

8. 8. The nucleic acid molecule of claim 7, wherein the first sdAb portion comprises the amino acid sequence of SEQ ID NO: 366 and the second sdAb portion comprises the amino acid sequence of SEQ ID NO:

356.

9. The nucleic acid molecule of claim 7 or 8, further comprising a polynucleotide sequence encoding a 2A self-cleaving peptide located between the CAR and the TGF-β DNR.

10. The nucleic acid molecule of claim 9, wherein the 2A self-cleaving peptide is a T2A peptide or a P2A peptide.

11. The nucleic acid molecule according to any one of claims 7 to 10, which encodes a peptide having at least 95% sequence identity to the amino acid sequence of SEQ ID NOs: 525 to 528.

12. The nucleic acid molecule of any one of claims 7 to 11, which encodes a peptide having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:

527.

13. An expression vector comprising the nucleic acid molecule of any one of claims 7 to 12.

14. A cell comprising the nucleic acid molecule of any one of claims 7 to 12 or the expression vector of claim 13.

15. 15. The modified immune cell of any one of claims 1 to 6, or the cell of claim 14, wherein the modified immune cell or the cell is selected from the group consisting of a cytotoxic T cell, a helper T cell, a natural killer T cell, and a γδ T cell.

16. A pharmaceutical composition comprising the modified immune cells of any one of claims 1 to 6 and a physiologically acceptable excipient.

17. 19. A medicament for treating cancer in a subject, comprising a therapeutically effective amount of the modified immune cells of any one of claims 1 to 6, or a therapeutically effective amount of the pharmaceutical composition of claim 16, wherein the cancer is selected from the group consisting of lung cancer, melanoma, breast cancer, prostate cancer, colon cancer, renal cell carcinoma, ovarian cancer, neuroblastoma, rhabdomyosarcoma, leukemia, and lymphoma.

18. The method of claim 17, wherein the cancer is small cell lung cancer.

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