Method for producing cell population containing CAR-expressing immune cells

[0001] The present disclosure relates to a cell population containing Chimeric Antigen Receptor (CAR)-expressing immune cells and a method of producing the same.

[0002] Treatment with Chimeric Antigen Receptor (CAR)-T cells, which are cytotoxic T cells (CTLs) whose T cell receptor (TCR) is genetically modified so that the CTLs directly and selectively recognize tumor cells to exert antitumor effects, has been developed as one of immunotherapies for cancer patients in recent years (Non-Patent Document 1) and attracting much attention as an extremely promising therapy for intractable tumors. The CAR is a general term for proteins that have, on its N-terminal side, a protein specifically recognizing a tumor antigen, such as a single-chain antibody (scFv) prepared by modifying antibody variable regions to a single-chain amino acid sequence, and, on its C-terminal side, the T cell receptor ζ chain. CAR-expressing T cells recognize the tumor antigen at the extracellular domain, transmit the signal into the T cells through the following ζ chain, and become activated to exert their antitumor effects by releasing cell killing factors such as perforin and granzyme (Non-Patent Document 1).

[0003] Cancer treatments using CAR-T cells have already been approved and put into practical use in Japan, Europe and the United States for some tumors. In the area of blood tumors, a phase III clinical trial was conducted for CD19-positive B lymphocytic tumor, wherein a CD19-specific CAR was introduced into T cells collected in advance from patients with recurrent acute lymphocytic leukemia by gene transfer, and the cells were cultured, expanded and infused into the patients' bodies. Then, it was reported that molecular biological remission in bone marrow was obtained in all 5 patients who received the administration (Non-Patent Document 2). Based on this report, two drugs, Tisagen lecleucel (product name: Kymriah®) and Axicabtagene ciloleucel (product name: Yescarta®), have been approved for CD19-positive acute lymphocytic leukemia and lymphoma and put on the market in Europe and the United States. They have attracted a great deal of attention as a breakthrough treatment for intractable CD19-positive lymphocytic leukemia and lymphoma, which have been difficult to cure to date.

[0004] Most of the clinically applied CAR-T cell preparations have been produced by gene modification using γ-retrovirus. Cell preparations produced by virus-mediated gene modification are manufactured through extremely complicated processes including GMP grade virus production, residue testing of the final product for viruses, and production in accordance with Cartagena Approval of Type 1 Use in some countries.

[0005] For producing CAR-T cells, in addition to the conventional methods using viral vectors, gene modification techniques using non-viral vectors have also been used (Patent Documents 1 and 2). For example, focusing on a gene transfer technology that does not use γ-retrovirus but utilizes a transposon called piggyBac (hereinafter referred to as “piggyBac transposon-mediated method”), research and development of non-virally genetically modified CAR-T cell therapies are also being carried out. CAR-T cell production by the non-viral gene modification technology is a safe and simple method for CAR-T cell production because no virus is used for gene transfer. The ACE method, a culturing method for non-virally genetically modified CAR-T cells that has been developed by one of the inventors Nakazawa et al. (Patent Document 2), is a pioneer method for non-viral gene modification and has overcome the issues of the production methods using viral vectors.

• [0006] Patent document 1: JP2017-22121A
• [0007] Patent document 2: WO2017/061615

• [0008] Non-Patent Document 1: Eshhar Z, Waks T, Gross G, Schindler D G., Specific activation and targeting of cytotoxic lymphocytes through chimeric single chains consisting of antibody-binding domains and the gamma or zeta subunits of the immunoglobulin and T-cell receptors. Proc Natl Acad Sci USA. 1993; 90:720-724.
• [0009] Non-Patent Document 2: Brentjens R J, Davila M L, Riviere I, Park J, Wang X, Cowell L G, Bartido S, Stefanski J, Taylor C, Olszewska M, Borquez-Ojeda O, Qu J, Wasielewska T, He Q, Bernal Y, Rijo I V, Hedvat C, Kobos R, Curran K, Steinherz P, Jurcic J, Rosenblat T, Maslak P, Frattini M, Sadelain M. CD19-targeted T cells rapidly induce molecular remissions in adults with chemotherapy-refractory acute lymphoblastic leukemia. Sci Transl Med. 2013; 5:177ra38.

[0010] Conventional methods for producing CAR-T cells can obtain CAR-T cells at a clinically available quality and number for target molecules of blood tumors such as CD19. It has been difficult, however, to obtain a sufficient number of cells for clinical use for target molecules of solid tumors. Also, attempts to secure the number of cells required for administration to patients by long-term culture or forced activation by co-stimulatory molecules can change the characteristics of T cells so that the T cells have less cytotoxic activity and are easily exhausted. Thus, it has been difficult to stably produce CAR-T cells of sufficient number and quality for clinical application.

[0011] The present inventors have diligently studied to solve the above problems. Then, the inventors have found that co-culturing CAR-introduced immune cells such as CAR-T cells with separately prepared target antigen-expressing cells that express the target antigen of the CAR not only improves gene transfer efficiency and cell proliferation rate but also enables stable culturing of immune cells that have high cytotoxic activity and are not easily exhausted.

[0012] That is, the present disclosure, in an aspect, provides a method of producing a cell population containing Chimeric Antigen Receptor (CAR) -expressing immune cells, comprising co-culturing CAR-expressing immune cells and cells expressing a target antigen of the CAR, wherein the CAR-expressing immune cells are cells into which a CAR gene has been introduced and the target antigen-expressing cells are normal blood cells that have been engineered to express the target antigen.

[0013] The present disclosure, in a further aspect, provides a cell population containing Chimeric Antigen Receptor (CAR)-expressing immune cells produced by the method as defined above.

[0014] The present disclosure, in a further aspect, provides a composition for treating cancer comprising the cell population as defined above.

[0015] According to the present invention, the production efficiency of CAR-expressing immune cells can be increased and CAR-T cells having high cytotoxic activity can be stably produced. In particular, the production efficiency of CAR-expressing immune cells for solid tumors can be dramatically improved, and thus CAR-T cell therapies can be applied to various cancer types.

[0024] Unless otherwise specified, the terms used in this disclosure have meanings commonly understood by those skilled in the art in the fields such as organic chemistry, medical science, pharmaceutical science, molecular biology, and microbiology. The followings are definitions of some terms used in this disclosure and these definitions supersede the common understandings in this disclosure.

[0025] In the present disclosure, when a number is accompanied by the term “about”, it is intended to include a range of ±10% of that value. For example, “about 20” shall include “18 to 22”. A range of numbers includes all numbers between the endpoints and the numbers at the endpoints. The term “about” used for a range applies to both ends of the range. Thus, for example, “about 20 to 30” shall include “18 to 33”.

[0026] In the present disclosure, sequence identity means the degree of sequence matching between polypeptides or polynucleotides, and it is determined by comparing two sequences optimally aligned (aligned such that the amino acid or nucleotide matching is maximized) over the region of the sequence to be compared. The number of sequence identity (%) is calculated by determining the same amino acids or nucleotides present in both sequences, determining the number of matching sites, dividing the number of matching sites by the total number of amino acids or nucleotides in the sequence region to be compared, and then multiplying the obtained value by 100. Examples of algorithms for obtaining the optimal alignment and sequence identity include various algorithms commonly available to those skilled in the art (e.g., BLAST algorithm, FASTA algorithm). The sequence identity can be determined, for example, by using a sequence analysis software such as BLAST or FASTA.

Chimeric Antigen Receptor

[0027] A chimeric antigen receptor (herein also referred to as CAR) is a protein having a structure containing a target-specific extracellular domain, a transmembrane domain, and an intracellular signal domain that works for the effector function of immune cells from the N-terminal side to the C-terminal side of the protein. A CAR gene is a gene encoding this receptor. Each domain will be described hereinafter.

(a) Extracellular Domain

[0028] The extracellular domain contains an antigen recognition site that exhibits target-specific binding. For example, the extracellular domain may contain a scFv fragment of a monoclonal antibody against the target (e.g., the fragment consisting of the amino acid sequence of SEQ ID NO: 1 or 2, or described in WO2017/061615, CN107164338A, WO2016/123143, WO2016/023253, or JP2018-198601A), or, when the target is a receptor, a ligand that binds to the receptor (e.g., a ligand consisting of the amino acid sequence of SEQ ID NO: 3, or described in WO2018/110374 or WO2018/052142). The monoclonal antibody as used herein can be, for example, a rodent (such as mouse, rat, or rabbit) antibody, a human antibody, or a humanized antibody. The humanized monoclonal antibody is an antibody prepared by making the structure of a monoclonal antibody of a non-human animal (e.g., mouse or rat) resemble to that of a human antibody, and includes a humanized chimeric antibody in which only the constant region of an antibody is replaced with that of a human antibody, and a humanized CDR-grafted antibody in which the constant region and the portions other than the Complementary Determination Regions (CDRs) in the variable region are replaced with those of a human antibody (P. T. Johons et al., Nature 321, 522, 1986). In order to enhance the antigen-binding activity of a humanized CDR-grafted antibody, improved techniques have already been developed and can be used to make humanized antibodies and they include, for example, selection of framework (FR) regions of a human antibody with high homology with those of a mouse antibody, production of a humanized antibody with high homology with a mouse antibody, and substitution of amino acids in the FR regions after transplant of mouse CDRs to a human antibody (see, for example, U.S. Pat. Nos. 5,585,089B, 5,693,761B, 5,693,762B, 6,180,370B, EP451216B, EP682040B, JP2828340B).

[0029] The scFv fragment has a structure in which a light chain variable region (VL) and a heavy chain variable region (VH) of an immunoglobulin are connected via a linker, and it retains the ability to bind to an antigen. As the linker, for example, a peptide linker can be used. A peptide linker is a linker being a peptide, in which amino acids are linearly connected. Examples of peptide linkers include linkers composed of glycine and/or serine (e.g., GGS or GS linker). Glycine and serine are small in size, preventing the linker from forming a higher-order structure. The length of the linker is not particularly limited to any specific length. For example, a linker having 5 to 25 amino acid residues can be used. The length of the linker is preferably 8 to 25, more preferably 15 to 20.

[0030] The target antigen can be an antigen that is significantly or markedly expressed in tumor cells as compared to non-tumor cells. Examples of target antigens include, for example, tumor-related or tumor-specific antigens, such as EPHB4, HER2, EPHA2, EPHB2, EGFR, GD2, Glypican-3, 5T4, 8H9, αvβ6 integrin, B cell maturation antigen (BCMA), B7-H3, B7-H6, CAIX, CA9, CD19, CD20, CD22, K light chain, CD30, CD33, CD38, CD44, CD44v6, CD44v7/8, CD70, CD116, CD123, CD138, CD171, CEA, CSPG4, EGFR, EGFRvIII, EGP2, EGP40, EPCAM, ERBB3, ERBB4, FAP, FAR, FBP, fetal AchR, folic acid receptor oa, GD3, HLA-AI MAGE A1, HLA-A2, IL11Ra, IL13Ra2, KDR, Lambda, Lewis Y, MCSP, mesothelin, MUC1, MUC4, MUC6, NCAM, NKG2D ligand, NY-ESO-1, PRAME, PSCA, PSC1, PSMA, ROR1, Sp17, SURVIVIN, TAG72, TEM1, TEM8, VEGF receptor 2, carcinoembryonic antigen, HMW-MAA, VEGF receptor, fibronectin, tenascin, or antigens present in the extracellular matrix such as carcinoembryonic antigen (CEA) in the necrotic regions of tumors, or proteins containing mutations identified by genomic analysis and/or differential expression studies of tumors.

[0031] When the target antigen is a receptor, a ligand for the receptor can be used as an antigen recognition site instead of scFv. For example, the extracellular domain of EFNB2 protein, which is a natural ligand for EPHB4 receptor, and GM-CSF, which is a ligand for GM-CSF receptor, as well as Adnectin for EGFR, IL-11 for IL11Ra, IL-13 for IL13Ra2, and FSH for FSHR, T1E for the ERBB2 family, CD27 for CD70, DNAM-1 for Nectin-2, NKG2D for MICA and MICB, and NKp30 for Gal3 can be used.

[0032] The production method of the present disclosure can obtain CAR-expressing immune cells in a sufficient number and quality not only for antigens expressed in blood cells but also for those not expressed in such cells, and it is particularly suitable for target antigens for solid tumors. Examples of such target antigens include EPHB4, HER2, EPHA2, EPHB2, EGFR, GD2, Glypican-3, 5T4, MUC1, MUC4, MUC6, NCAM, EGFR, EGFRvIII, ERBB3, ERBB4, NY-ESO-1, PSCA, PSC1, PSMA, VEGFR receptor 2, carcinoembryonic antigen, HMW-MAA, and VEGF receptor.

[0033] The extracellular domain may contain a leader sequence (signal peptide) that facilitates translocation of CAR to the cell surface. As the leader sequence, for example, the leader sequence of GM-CSF receptor can be used.

[0034] In an embodiment, the extracellular domain comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of any one of SEQ ID NOs: 1 to 3, preferably the amino acid sequence of SEQ ID NO: 1. In a further embodiment, the extracellular domain comprises or consists of the amino acid sequence of any one of SEQ ID NOs: 1 to 3, preferably the amino acid sequence of SEQ ID NO: 1.

(b) Transmembrane Domain

[0035] The transmembrane domain lies between the extracellular domain and the intracellular signal domain. As the transmembrane domain, a transmembrane domain of CD8, T cell receptor α or β chain, CD28, CD3E, CD45, CD4, CD5, CD8, CD9, CD16, CD22, CD33, CD37, CD64, CD80, CD86, CD134, CD137, CD154, GITR, or 4-1BB can be used. The transmembrane domain can also be an artificially constructed polypeptide. Preferably, the transmembrane domain is the transmembrane domain of CD28 (e.g., the domain consisting of the amino acid sequence of SEQ ID NO: 7 or 8).

[0036] In an embodiment, the transmembrane domain comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of SEQ ID NO: 7 or 8. In a further embodiment, the transmembrane domain comprises or consists of the amino acid sequence of SEQ ID NO: 7 or 8.

(c) Intracellular Signal Domain

[0037] The intracellular signal domain transmits a signal necessary for immune cells to exert its effector function. That is, the intracellular signal domain to be used is capable of transmitting a signal necessary for activating the immune cells when the extracellular domain binds to the target antigen. The intracellular signal domain comprises a domain for transmitting a signal mediated by TCR complex (referred to as “first domain” for convenience), and may further comprise a domain for transmitting a co-stimulatory signal (referred to as “second domain” for convenience). Examples of these domains include domains of CD2, CD4, CD5, CD28, CD134, 4-1BB (CD137), GITR, CD27, OX40, HVEM, CD3ζ, FcεRIγ, OX-40, and ICOS. The first domain is preferably the domain of CD3ζ or FcεRIγ, more preferably the domain of CD3ζ (e.g., the domain consisting of the amino acid sequence of SEQ ID NO: 9). The second domain is preferably the domain of CD28, 4-1BB (CD137), CD2, CD4, CD5, CD134, OX-40 or ICOS, and more preferably the domain of CD28 or 4-1BB. The first domain and the second domain may each be composed of a plurality of the same or different domains connected in tandem.

[0038] When the intracellular signal domain includes the first domain and the second domain, the first domain and the second domain may be connected in any way, but the second domain is preferably placed on the transmembrane domain side, since it is known that the co-stimulation was strongly transmitted in some cases when the CD3ζ was connected distally. The first domain and the second domain may be directly connected or may be connected by a linker. As the linker, for example, a peptide linker can be used. The peptide linker is a linker being a peptide, in which amino acids are linearly connected, and its structure and characteristics are described above. The linker that connects the first domain and the second domain may be a linker composed of glycine only. The length of the linker is not particularly limited to any specific length. For example, a linker having 2 to 15 amino acid residues can be used.

[0039] In an embodiment, the intracellular signal domain comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of SEQ ID NO: 9. In a further embodiment, the extracellular domain comprises or consists of the amino acid sequence of SEQ ID NO: 9.

(d) Other Elements

[0040] The extracellular domain and the transmembrane domain may be connected via a spacer domain. The spacer domain is used to promote the binding of the CAR to the target antigen. As the spacer domain, an Fc fragment of an antibody or a fragment or derivative thereof, a hinge region of an antibody or a fragment or derivative thereof, a CH2 region of an antibody, a CH3 region of an antibody, an artificial spacer sequence, or a combination thereof (e.g., the domain consisting of the amino acid sequence of any one of SEQ ID NOs: 4-6) can be used. For example, an Fc fragment of human IgG (e.g., human IgG1, human IgG4) can be used as the spacer domain. In addition, a part of the extracellular domain of CD28 and a part of the extracellular domain of CD8a can also be used as the spacer domain. A spacer domain can also be provided between the transmembrane domain and the intracellular signal domain.

[0041] In an embodiment, the spacer domain comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of any one of SEQ ID NOs: 4-6. In a further embodiment, the spacer domain comprises or consists of the amino acid sequence of any one of SEQ ID NOs: 4-6.

CAR Expression Vector

[0042] In the present disclosure, CAR-expressing immune cells are prepared by introducing a CAR gene into immune cells using a CAR expression vector. The CAR expression vector means a nucleic acid molecule capable of transporting a nucleic acid molecule encoding a CAR gene into immune cells. It can be DNA or RNA in any form and of any origin, and various types of vectors are available. The vector can be a viral vector or a non-viral vector. Examples of viral vectors include retrovirus vectors, lentivirus vectors, adenovirus vectors, adeno-associated virus vectors, herpesvirus vectors, and Sendai virus vectors. Among these, with a retrovirus vector, a lentivirus vector, and an adeno-associated virus vector, the gene of interest incorporated into the vector is integrated into the host chromosome and stable and long-term expression is expected. Each viral vector can be prepared according to conventional methods or by using commercially available kits for this purpose. Examples of non-viral vectors include plasmid vectors, liposome vectors, and positively charged liposome vectors (Felgner, P. L., Gadek, T. R., Holm, M. et al., Proc. Natl. Acad. Sci., 84: 7413-7417, 1987), YAC vectors, and BAC vectors.

[0043] The CAR expression vector comprises an expression unit for expressing a CAR gene, which usually comprises a promoter, a CAR gene, and a poly A addition signal. Examples of promoters that can be used in the CAR expression cassette include CMV-IE (cytomegalovirus early gene-derived promoter), SV40ori, retrovirus LTRSRα, EF1α, and β-actin promoter. Examples of poly A addition signal sequences include a poly A addition sequence of SV40, a poly A addition sequence of a bovine growth hormone gene, and a poly A addition sequence of globulin. The CAR gene is usually connected to the 3′end of the promoter directly or via another sequence so that the promoter regulates expression of the CAR gene, and the poly A addition signal sequence is placed downstream of the CAR gene. The CAR gene is transcribed into messenger RNA (mRNA) from such an expression unit, and the CAR is translated from the mRNA and presented on the cell surface.

[0044] The expression unit may comprise a gene for detection of gene expression (e.g., reporter gene, cell or tissue-specific gene, or selectable marker gene), an enhancer sequence for improving expression efficiency, a WRPE sequence, for example.

[0045] The gene for detection is used for determining success or failure and efficiency of introduction of the CAR expression vector, detecting expression or determining expression efficiency of the CAR gene, or selecting or sorting cells expressing the CAR gene. Examples of genes for detection include neo gene that confers resistance to neomycin, npt gene (Herrera Estrella, EMBO J. 2 (1983), 987-995) and nptII gene (Messing & Vierra, Gene 1 9:259-268 (1982)) that confer resistance to kanamycin or other antibiotics, hph gene that confers resistance to hygromycin (Blochinger and Diggl mann, Mol Cell Bio 4: 2929-2931), and dhfr gene that confers resistance to methotrexate (Bourouis et al., EMBO J.2 (7)) (examples of marker genes); luciferase gene (Giacomin, P1. Sci. 116(1996), 59-72; Scikantha, J. Bact. 178 (1996), 121), β-glucuronidase (GUS) gene, genes for fluorescent proteins such as GFP (Gerdes, FEBS Lett. 389 (1996), 44-47) or variants thereof (e.g., EGFP, d2EGFP) (examples of reporter genes); and epidermal growth factor receptor (EGFR) gene lacking the intracellular domain. The gene for detection may be connected to the CAR gene via, for example, a bicistronic control sequence (e.g., ribosome internal recognition sequence (IRES)) or a sequence encoding a self-cleaving peptide. Examples of self-cleaving peptides include 2A peptide derived from Thosea asigna virus (T2A). Different examples of self-cleaving peptides include picornavirus-derived 2A peptide (F2A), foot-and-mouth disease virus (FMDV)-derived 2A peptide (F2A), equine rhinitis A virus (ERAV)-derived 2A peptide (E2A), and porcine teschovirus (PTV-1)-derived 2A peptide (P2A), and rotavirus, insect virus, aft virus or tripanosoma virus-derived 2A peptide, but are not limited thereto.

Immune Cells

[0046] In the present disclosure, the CAR gene is introduced into immune cells. The immune cells in the present disclosure may be T cells (including CD4-positive CD8-negative T cells, CD4-negative CD8-positive T cells, αβ-T cells, γδ-T cells, and NKT cells), B cells, NK cells, monocytes, macrophages, dendritic cells or combinations thereof. The immune cells may be cells isolated from humans or may be cells differentiated from cells such as iPS cells, ES cells, or hematopoietic stem cells. Also, the immune cells may be either autologous cells or allogeneic cells. In the present disclosure, the term “autologous cells” means cells obtained from a subject to which a cell population produced by the method of the present disclosure is to be administered, or cells derived from such obtained cells. The term “allogeneic cells” means that the cells are not the “autologous cells”. Preferably, the immune cells are autologous cells. In an embodiment, the immune cells are lymphocytes (i.e., T cells, B cells, NK cells, or a combination thereof). In a further embodiment, the immune cells are T cells. CAR-expressing immune cells can be obtained by gene transfer into a cell population containing immune cells or progenitor cells thereof such as hematopoietic stem cells. For example, CAR-expressing immune cells may be obtained by differentiation of cells such as iPS cells, ES cells, or hematopoietic stem cells into which a CAR gene have been introduced, or may be obtained by differentiation of cells that have been transformed into iPS cells after a CAR gene have been introduced. In an embodiment, the CAR-expressing immune cells are prepared by introduction of a CAR gene into blood cells. In the present disclosure, the term “blood cell” or “blood cells” means a cell or cells constituting blood, and is used to mean a single cell or a cell population containing a plurality of cells, and in the sense of a cell population composed of one type of cells and also in the sense of a cell population containing multiple types of cells. Blood cells are preferably blood cells other than erythrocytes and platelets, and such blood cells include immune cells such as lymphocytes and monocytes. The blood cells may be cells isolated from humans or cells differentiated from cells such as iPS cells, ES cells, or hematopoietic stem cells, and may be either autologous cells or allogeneic cells, but preferably autologous cells. In a further embodiment, the CAR-expressing immune cells are prepared by introduction of a CAR gene into PBMCs. The PBMCs are preferably autologous PBMCs (i.e., PBMCs collected from a subject to which a cell population produced by the method of the present disclosure is to be administered). PBMCs can be prepared by conventional methods, for example, by referring to Saha S, Nakazawa Y, Huye L E, Doherty J E, Galvan D L, Rooney C M, Wilson M H. J Vis Exp. 2012 Nov. 5; (69): e4235. Unless otherwise specified, any cells herein described (e.g., T cells) are human cells.

Preparation of CAR-Expressing Immune Cells

[0047] The CAR gene expression vector prepared for gene transfer is introduced into immune cells by conventional methods. In the case of a viral vector, it is introduced into cells by viral infection. In the case of a non-viral vector such as a plasmid, conventional methods such as methods mediated by electroporation, liposome, or calcium phosphate can be used for introduction into cells, and the introduction is preferably carried out by electroporation.

[0048] In order to improve efficiency of integration into the host chromosome, it is preferable to carry out the gene transfer by a method mediated by transposon. The transposon-mediated method is one of non-viral gene transfer methods, and it can integrate a gene of interest into the host chromosome by utilizing the mechanism by which an enzyme acting on the genome (transposase) and its specific recognition sequence cause gene translocation in combination. The transposon-mediated method can be, for example, the piggyBac transposon-mediated method. The piggyBac transposon-mediated method utilizes a transposon isolated from an insect (Fraser M J et al., Insect Mol Biol. 1996 May; 5(2):141-51.; Wilson M H et al., Mol THER2007 January; 15(1):139-45.) and it enables highly efficient integration into mammalian chromosomes. The piggyBac transposon-mediated method is practically used for gene transfer already (see, for example, Nakazawa Y, et al., J Immunother 32:826-836, 2009; Nakazawa Y et al., J Immunother 6:3-10, 2013).

[0049] The transposon-mediated method is not limited to the one using piggyBac, and can use a transposon such as Sleeping Beauty (Ivics Z, Hackett P B, Plasterk R H, Izsvak Z (1997) Cell 91: 501-510.), Frog Prince (Miskey C, Izsvak Z, Plasterk R H, Ivics Z (2003) Nucleic Acids Res 31: 6873-6881.), Tol1 (Koga A, Inagaki H, Bessho Y, Hori H. Mol Gen Genet. 1995 Dec. 10; 249(4):400-5.; Koga A, Shimada A, Kuroki T, Hori H, Kusumi J, Kyono-Hamaguchi Y, Hamaguchi S. J Hum Genet. 2007; 52(7):628-35. Epub 2007 Jun. 7.), Tol2 (Koga A, Hori H, Sakaizumi M (2002) Mar Biotechnol 4: 6-11.; Johnson Hamlet M R, Yergeau D A, Kuliyev E, Takeda M, Taira M, Kawakami K, Mead P E (2006) Genesis 44: 438-445.; Choo B G, Kondrichin I, Parinov S, Emelyanov A, Go W, Toh W C, Korzh V (2006) BMC Dev Biol 6: 5.).

[0050] The process of gene transfer by the transposon-mediated method can be a conventional process. For example, the piggyBac transposon-mediated method can be carried out by preparing a vector carrying a gene encoding the piggyBac transposase (a transposase plasmid) and a vector having a structure in which a CAR gene expression unit is sandwiched between piggyBac reverse repeat sequences (a transposon plasmid) and introducing these vectors into target cells by any of various methods such as electroporation, nucleofection, lipofection, and calcium phosphate-mediated method.

Preparation of Target Antigen-Expressing Cells

[0051] In the present disclosure, in addition to the CAR-expressing immune cells, normal blood cells engineered to express a target antigen are used as target antigen-expressing cells. The target antigen-expressing cells are cells that have been engineered to express a part or all of a target antigen on the cell surface so that the CAR introduced into CAR-expressing immune cells can bind to the target antigen. The target antigen in the present disclosure means a target antigen recognized by a CAR, and may be a protein, a sugar chain, or a glycolipid expressed on the cell surface so that the CAR introduced into immune cells can bind to it. Examples of target antigens include, for example, tumor-related or tumor-specific antigens targeted by the aforementioned CAR, such as EPHA2, HER2, EPHB2, EPHB4, EGFR, GD2, Glypican-3, HER2, 5T4, 8H9, avP6 integrin, B cell maturation antigen (BCMA), B7-H3, B7-H6, CAIX, CA9, CD19, CD20, CD22, κ light chain, CD30, CD33, CD38, CD44, CD44v6, CD44v7/8, CD70, CD116, CD123, CD138, CD171, CEA, CSPG4, EGFR, EGFRvIII, EGP2, EGP40, EPCAM, ERBB3, ERBB4, ErbB3/4, FAP, FAR, FBP, fetal AchR, folic acid receptor α, GD2, GD3, HLA-AI MAGE A1, HLA-A2, IL11Ra, IL13Ra2, KDR, Lambda, Lewis Y, MCSP, mesothelin, MUC1, MUC4, MUC6, NCAM, NKG2D ligand, NY-ESO-1, PRAME, PSCA, PSC1, PSMA, ROR1, Sp17, SURVIVIN, TAG72, TEM1, TEM8, VEGF receptor 2, carcinoembryonic antigen, HMW-MAA, VEGF receptor, fibronectin, tenascin, or antigens present in the extracellular matrix such as carcinoembryonic antigen (CEA) in the necrotic regions of tumors, or proteins containing mutations identified by genomic analysis and/or differential expression studies of tumors.

[0052] In an embodiment, the target antigen comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of SEQ ID NO: 10, 11, or 16, preferably the amino acid sequence of SEQ ID NO: 10. In a further embodiment, the target antigen comprises or consists of the amino acid sequence of SEQ ID NO: 10, 11, or 16, preferably the amino acid sequence of SEQ ID NO: 10.

[0053] The target antigen-expressing cells can be prepared, to express the target antigen, by introducing a gene encoding the target antigen into cells using a vector having an expression unit for expressing the target antigen gene, as described for the CAR-expressing immune cells. Alternatively, the target antigen-expressing cells can also be prepared by preparing mRNA of the target antigen gene and introducing the mRNA directly into cells. In addition, the target antigen-expressing cells can be prepared, to express the target antigen, by introducing another gene that induces expression of the target antigen into cells instead of the gene encoding the target antigen, or treating cells with an agent that induces expression of the target antigen, such as a low molecular weight compound, growth factor, hormone or cytokine. For example, treatment with sialic acid or a histone deacetylase inhibitor can prepare target antigen-expressing cells that express GD2. In an embodiment, the target antigen-expressing cells are prepared by introducing a target antigen gene into cells, and thus, the target antigen-expressing cells comprise an exogenous target antigen gene.

[0054] The target antigen-expressing cells may be prepared by introducing a co-stimulatory molecule gene together with a target antigen gene into cells to express the target antigen and the co-stimulatory molecule on the cell surface. That is, in an embodiment, the target antigen-expressing cells comprise one or more genes for one or more exogenous co-stimulatory molecules. Examples of co-stimulatory molecules include CD40, CD80, 4-1BB ligand (4-1BBL), OX40, OX40L, CD52, CD54, CD70, CD58, CD86, CD95, CD252, CD275, and a ligand for the integrin family (e.g., CD49a to CD49h, CD51, CD103, CD41, CDlla to 11c, ITGA9 to 11, CD18, CD19, CD61, ITGB4 to 8). In an embodiment, the co-stimulatory molecule is at least one co-stimulatory molecule selected from CD40, CD80, 4-1BBL, OX40L, preferably CD80 and/or 4-1BBL, more preferably CD80 and 4-1BBL.

[0055] In an embodiment, the co-stimulatory molecule comprises or consists of an amino acid sequence having 90% or more sequence identity with the amino acid sequence of any one of SEQ ID NOs: 12 to 15. In a further embodiment, the co-stimulatory molecule comprises or consists of the amino acid sequence of any one of SEQ ID NOs: 12-15.

[0056] The co-stimulatory molecule gene can be introduced by gene transfer using an expression vector comprising the co-stimulatory molecule gene and the target antigen gene; or by gene transfer introducing an expression vector or mRNA of the co-stimulatory molecule and that of the target antigen simultaneously or separately, wherein the expression vector or mRNA of the co-stimulatory molecule is separate from that of the target antigen.

[0057] The cells to be processed to express the target antigen gene to prepare the target antigen-expressing cells are normal blood cells (that is, blood cells excluding cancerous cells or a cell line derived therefrom) and not particularly limited to, but can be, cells isolated from humans, cells differentiated from cells such as iPS cells, ES cells, or hematopoietic stem cells, and may be either autologous cells or allogeneic cells, but preferably autologous cells. The blood cells are preferably blood cells other than erythrocytes and platelets, and such blood cells include immune cells such as lymphocytes and monocytes. The target antigen-expressing cells can be immune cells such as lymphocytes to which a target antigen gene have been introduced, or cells in which expression of the target antigen has been induced by introduction of another gene or by treatment with an agent. The target antigen-expressing cells may also be cells obtained by introducing a target antigen gene or another gene that induces expression of the target antigen into progenitor cells such as iPS cells, ES cells, or hematopoietic stem cells, and then differentiating the cells. In a preferred embodiment, the target antigen-expressing cells are prepared from PBMCs, preferably by gene transfer into PBMCs. In an embodiment, the target antigen-expressing cells are prepared by introduction of a target antigen gene into PBMCs. When PBMCs are used, CAR-expressing immune cells with high proliferation efficiency and high quality can be obtained. In addition, when PBMCs are used, it is possible to efficiently produce CAR-expressing immune cells without introducing a co-stimulatory molecule gene. The PBMCs are preferably autologous PBMCs (i.e., PBMCs taken from a subject to which a cell population produced by the method of the present disclosure is to be administered). When the autologous PBMCs are used, it is not necessary to remove the target antigen-expressing cells to prepare cells to be administered to a patient. Further, the target antigen-expressing cells and the CAR-expressing immune cells are both preferably prepared from PBMCs of the same subject, and more preferably from autologous PBMCs.

[0058] In the gene transfer into target antigen-expressing cells, the gene expression may be either transient or constitutive. Since appropriate and transient stimulation of the CAR and the co-stimulatory molecule on the surface of CAR-expressing immune cells is sufficient, and for the purpose of obtaining a cell population with a high proportion of CAR-expressing immune cells in a relatively short period of time, the gene transfer is preferred to use a target antigen gene expression vector intended for transient gene expression.

[0059] In order to obtain a cell population with a high proportion of CAR-expressing immune cells, it is preferable that target antigen-expressing cells are treated to lose its proliferative ability before co-cultured with CAR-expressing immune cells. The treatment that causes loss of proliferative ability is typically irradiation of radiation or ultraviolet, but may be treatment with an agent. The radiation irradiation is performed, for example, by irradiating gamma ray with an intensity of 25 Gy to 50 Gy for 15 to 30 minutes. The ultraviolet irradiation is performed, for example, by setting the dose to 2 to 400 mJ/cm², preferably 6 to 200 mJ/cm². By such treatments, proliferation of CAR-expressing immune cells become dominant, and a sufficient number and quality of cells for clinical application can be obtained.

Co-Culture

[0060] By co-culturing CAR-expressing immune cells and target antigen-expressing cells, the CAR-expressing immune cells proliferate efficiently by antigen stimulation from the target antigen-expressing cells.

[0061] The CAR-expressing immune cells are preferably cells that have been cultured after introduction of the CAR gene for, for example, about 8 hours to 2 weeks, considering recovery of the cells and stable expression of the transgene. Since the CAR-expressing immune cells can be exhausted by long-term culture, the cells are used for co-culture more preferably within 8 hours to 1 week, 8 hours to 72 hours, or 24 hours to 72 hours after the CAR gene transfer. The target antigen-expressing cells should sufficiently express the target antigen by the start of co-culture after the process for expressing the target antigen, such as gene transfer into the cells or treatment of the cells with an agent. For example, it is preferable that the target antigen-expressing cells have undergone the process for expressing the target antigen 8 or more hours before the start of co-culture.

[0062] The method of the present disclosure may comprise preparing CAR-expressing immune cells and/or target antigen-expressing cells prior to the co-culture. For example, the method of the present disclosure may comprise introducing a CAR gene into immune cells and/or carrying out a process for expressing a target antigen of the CAR on normal blood cells. The method of the present disclosure may further comprise culturing CAR-expressing immune cells alone and/or target antigen-expressing cells alone.

[0063] The period of co-culture can be, but not limited to, 1 to 21 days, preferably 1 to 14 days.

[0064] The ratio of the cell number of CAR-expressing immune cells to target antigen-expressing cells at the start of co-culture (CAR-expressing immune. cells/target antigen-expressing cells) is not particularly limited to, but can be for example, 0.05 to 20, preferably 0.1 to 10, more preferably 0.5 to 5, wherein the ratio is shown with the total number of cells to which a process for expressing a CAR or a target antigen is carried out. The cell density during co-culture can be, for example, 1×10⁶ cells/mL to 100×10⁶ cells/mL, when it is shown as the number of cells in the culture medium.

[0065] The medium used for co-culture or for preparation of CAR-expressing immune cells and/or target antigen-expressing cells is not particularly limited to, but can be, a medium used for conventional cell culture such as RPMI1640, MEM, X-VIVIO, IMDM, DMEM, DC medium, or OptiMEM. The medium may be a medium to which serum (such as human serum or fetal bovine serum) is added according to conventional methods, or may be a serum-free medium. It is preferable to use a serum-free medium because it is highly safe for clinical application and the difference in culture efficiency between serum lots is unlikely to occur. Examples of serum-free media include TexMACS™ (Miltenyi Biotec), AIM V® (Thermo Fisher Scientific), and ALyS culture medium (Cell Science & Technology Institute, Inc.). When using serum, it is preferable to use autologous serum, that is, serum collected from an individual from which the CAR-expressing immune cell s are derived (more specifically, a patient to which the cell population obtained by the production method of the present disclosure is to be administered). The basal medium is a medium suitable for cell culture, and can be TexMACS™, AIM V@, or ALyS culture medium (Cell Science & Technology Institute, Inc.) as described above. Other culture conditions are not limited as long as they are suitable for cell survival and proliferation and conventional conditions can be adopted. For example, the cells may be cultured in a CO₂ incubator (CO₂ concentration: 5%) set at 37° C.

[0066] A T cell growth factor or activator may be added to the medium to aid cell survival and proliferation. Examples of T cell growth factors include IL-1, IL-2, IL-7, IL-15, and IL-21, and examples of activators include anti-CD3 antibodies and anti-CD28 antibodies. For example, IL-2, an anti-CD3 antibody, and an anti-CD28 antibody may be added to the medium during co-culture. These factors are not essential, and especially when target antigen-expressing cells prepared from PBMCs are used, clinically applicable CAR-expressing immune cells can be efficiently obtained in a short period of time without addition of anti-CD3 antibodies and/or anti-CD28 antibodies. When preparing CAR-expressing immune cells, IL-7 and/or IL-15 may also be added to the medium. For example, IL-7 and IL-15 can be added to the medium at 5 ng/ml to 10 ng/ml, respectively. The T cell growth factor or activator can be prepared according to conventional methods, and commercially available products can also be used. The T cell growth factor or activator may be of a non-human animal species, but is preferably of human origin (and may be a recombinant one).

[0067] By co-culturing CAR-expressing immune cells and target antigen-expressing cells, it is possible to obtain a cell population containing CAR-expressing immune cells in a sufficient number and quality for clinical use. In particular, even when the target antigen is not expressed in blood cells (for example, in the case of tumor-related antigens of solid tumors such as HER2 and EPHB4), co-culturing CAR-expressing immune cells and target antigen-expressing cells provides appropriate stimulation from the target antigen-expressing cells to the CAR-expressing immune cells, and produces a cell population containing a sufficient number of CAR-expressing immune cells that have high cytotoxic activity and are not easily exhausted. The method of the present disclosure can efficiently produce a cell population expected to be highly effective compared to conventional methods. For example, the cell population obtained by the production method of the present disclosure may have a proportion of CAR-expressing immune cells of 20%, 30%, or 40% or more, preferably 40% or more. In addition, the cell population obtained by the production method of the present disclosure has low expression of PD-1, which is an exhaustion marker, and for example, the ratio of PD-1-expressing cells in CAR-expressing immune cells may be less than 10%, preferably less than 5%, more preferably less than 1%. Also, in the cell population obtained by the production method of the present disclosure, the proportion of naive cells in the CAR-expressing immune cells can be 45%, 50%, 55%, or 60% or more, preferably 60% or more.

Use of Cell Population

[0068] The cell population containing CAR-expressing immune cells produced by the method of the present disclosure can be used for the treatment of cancer, particularly for the treatment of cancer expressing the target antigen of the CAR-expressing immune cells. The cancer may be a solid tumor or a blood tumor. Specific examples of cancers include various B-cell lymphomas (e.g., follicular malignant lymphoma, diffuse large B-cell malignant lymphoma, mantle cell lymphoma, MALT lymphoma, intravascular B-cell lymphoma, CD20-positive Hodgkin lymphoma), myeloproliferative neoplasm, myelodysplastic/myeloproliferative neoplasm (CMML, JMML, CML, MDS/MPN-UC), myelodysplastic syndrome, acute myeloid leukemia, neuroblastoma, brain tumor, Ewing sarcoma, osteosarcoma, retinoblastoma, small cell lung cancer, non-small cell lung cancer, melanoma, bone and soft tissue sarcoma, kidney cancer, pancreatic cancer, malignant mesothelioma, prostate cancer, breast cancer, endometrial cancer, cervical cancer, ovarian cancer, and colon cancer, but are not limited thereto. In a preferred embodiment, the cancer is a solid tumor. Examples of solid tumors include, for example, neuroblastoma, brain tumor, Ewing sarcoma, osteosarcoma, retinoblastoma, small cell lung cancer, non-small cell lung cancer, melanoma, ovarian cancer, rhabdomyosarcoma, bone and soft tissue sarcoma, kidney cancer, pancreatic cancer, malignant mesothelioma, prostate cancer, breast cancer, endometrial cancer, cervical cancer, ovarian cancer, and colon cancer.

[0069] The cell population of the present disclosure is administered in a therapeutically effective amount appropriately determined according to factors such as age, body weight, and symptoms of the subject. The subject of the present disclosure is usually a human, preferably a cancer patient. The cell population of the present disclosure can be administered, for example, from 1×10⁴ cells to 1×10¹⁰ cells at a time. The administration route is not particularly limited to, but can be for example, intravenous injection, intraarterial injection, intraportal injection, intradermal injection, subcutaneous injection, intramuscular injection, or intraperitoneal injection. The cell population of the present disclosure may be administered systemically or locally, and the local administration includes direct injection into a target tissue, organ, or part. The administration schedule is appropriately determined according to factors such as age, body weight, and symptoms of the subject, and may be a single administration or a continuous or periodic multiple administrations.

[0070] In addition to the cell population to be administered to the subject, the composition comprising the cell population of the present disclosure may comprise a component such as dimethylsulfoxide (DMSO) or serum albumin for the purpose of protecting cells, an antibiotic for the purpose of preventing contamination by bacteria, or any of various components for the purpose of activating, proliferating or inducing differentiation of cells (such as vitamins, cytokines, growth factors, steroids). The composition can be prepared by conventional methods.

[0071] An exemplary embodiment of the present invention is described below.

[1] A method of producing a cell population containing Chimeric Antigen Receptor (CAR)-expressing immune cells, comprising co-culturing CAR-expressing immune cells and cells expressing a target antigen of the CAR, wherein the CAR-expressing immune cells are cells into which a CAR gene has been introduced and the target antigen-expressing cells are normal blood cells that have been engineered to express the target antigen.
[2] The method according to item 1, wherein the immune cells are lymphocytes.
[3] The method according to item 1 or 2, wherein the immune cells are T cells.
[4] The method according to any one of items 1 to 3, wherein the target antigen is HER2 or EPHB4.
[5] The method according to any one of items 1 to 4, wherein the CAR-expressing immune cells are cells that have been prepared by gene transfer into peripheral blood mononuclear cells (PBMCs).
[6] The method according to any one of items 1 to 5, further comprising preparing the CAR-expressing immune cells.
[7] The method according to item 6, wherein the CAR-expressing immune cells are prepared by gene transfer into PBMCs.
[8] The method according to item 6 or 7, wherein the CAR-expressing immune cells are prepared by the piggyBac transposon-mediated method.
[9] The method according to any one of items 1 to 8, wherein the target antigen-expressing cells are cells into which the target antigen gene has been introduced.
[10] The method according to any one of items 1 to 9, wherein the target antigen-expressing cells are cells into which one or more genes of one or more co-stimulatory molecules have been introduced.
[11] The method according to any one of items 1 to 10, wherein the target antigen-expressing cells are cells that have been prepared from PBMCs.
[12] The method according to item 11, wherein the target antigen-expressing cells are cells that have been prepared by gene transfer into PBMCs.
[13] The method according to item 12, wherein the gene transfer includes transfer of a target antigen gene.
[14] The method according to any one of items 1 to 13, further comprising preparing the target antigen-expressing cells.
[15] The method according to item 14, wherein the target antigen-expressing cells are prepared from PBMCs.
[16] The method according to item 15, wherein the target antigen-expressing cells are prepared by gene transfer into PBMCs.
[17] The method according to item 16, wherein the gene transfer includes transfer of a target antigen gene.
[18] The method according to any of items 10 to 17, wherein the one or more co-stimulatory molecules are selected from CD40, CD80, 4-1BBL, and OX40L.
[19] A cell population containing Chimeric Antigen Receptor (CAR)-expressing immune cells produced by the method according to any one of items 1 to 18.
[20] A composition for treating cancer comprising the cell population according to item 19.
[21] The composition according to item 20, wherein the cancer is a solid tumor.
[22] A method for treating cancer, comprising administering the cell population according to item 19 to a subject.
[23] A method for treating cancer, comprising producing a cell population by the method according to any one of items 1 to 18, and administering the cell population thus obtained to a subject.
[24] The cell population according to item 19 for use in treating cancer.
[25] Use of the cell population according to item 19 for the manufacture of a medicament for use in the treatment of cancer.

[0072] Hereinafter, the present invention will be further described with reference, to the examples. The present invention, however, is not limited to these examples in any sense.

[0073] Peripheral blood mononuclear cells (PBMCs) were separated and collected from peripheral blood by specific gravity separation centrifugation. Then, to 15×10⁶ cells of the collected PBMCs, a vector to express EPHB4-CAR, which had an EPHB4 ligand (SEQ ID NO: 3) as an extracellular domain, and a spacer domain (SEQ ID NO: 6), a transmembrane domain (SEQ ID NO: 8), and an intracellular signal domain (SEQ ID NO: 9) (FIG. 1, (a)), and a transposase expression vector (FIG. 1, (c)) were introduced by gene transfer by electroporation to prepare EPHB4-CAR-expressing T cells. Also, to 5×10⁶ PBMCs, a vector to express EPHB4 (SEQ ID NO: 11), which was the target molecule of EPHB4-CAR, and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (a)) was introduced by electroporation to prepare EPHB4-expressing cells that transiently expressed EPHB4. The EPHB4-CAR-expressing T cells and EPHB4-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the EPHB4-expressing cells were irradiated with UV and 5×10⁶ UV-irradiated EPHB4-expressing cells were divided and mixed with the EPHB4-CAR-expressing T cells on the first and third days of culture. The cells were co-cultured with ALyS culture solution containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 12 days after the start of the culture.

[0074] In the same manner as in Example 1, PBMCs were collected and EPHB4-CAR-expressing T cells were prepared. Also, after UV irradiation to a part of the collected PBMCs, viral peptides (PepTivator CMV pp65, PepTivator AdV5 Hexon, PepTivator EBV EBNA-1, and PepTivator EBV BZLF1, Miltenyi Biotec) were added to the irradiated cells to prepare feeder cells. In addition, UV-irradiated Rh30 cells, which were cells of a cancer cell line expressing EPHB4, were prepared. Then, 10×10⁶ EPHB4-CAR-expressing T cells were mixed with 2×10⁶ feeder cells and 1×10⁶ Rh30 cells and these cells were co-cultured with ALyS culture solution containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) in the presence an anti-CD3 antibody and an anti-CD28 antibody, and collected 9 days after the start of the culture.

[0075] In the same manner as in Comparative Example 1, EPHB4-CAR-expressing T cells and UV-irradiated EPHB4-expressing Rh30 cells were prepared. Then, 10×10⁶ EPHB4-CAR-expressing T cells and 1×10⁶ Rh30 cells were mixed and co-cultured with ALyS culture solution containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) in the presence of an anti-CD3 antibody and an anti-CD28 antibody for 25 days, and the cells were collected after the culture.

[0076] In the same manner as in Comparative Example 1, EPHB4-CAR-expressing T cells were prepared. Then, 10×10⁶ EPHB4-CAR-expressing T cells were cultured with ALyS culture solution containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) in the presence of an anti-CD3 antibody and an anti-CD28 antibody for 25 days, and the cells were collected after the culture.

[0077] For the cells obtained in Example 1 and Comparative Examples 1 to 3, the total number of cells was counted and the proportion of EPHB4-CAR-expressing T cells was analyzed by flow cytometry. The results are shown in Table 1.

[0078]

TABLE 1
		Comparative	Comparative	Comparative
	Example 1	example 1	example 2	example 3
Culture	112	9	25	25
period (day)
Cell number	15	10	10	10
before culture
(×106)
Cell number	53	3.4	7.0	5.6
after culture
(×106)
EPHB4-CAR-	47.1	1.0	0	0
expressing T
cells (%)
EPHB4-CAR-	25.0	0.03	0	0
expressing T
cell number
(×106)

[0079] As shown in Table 1, it was possible to culture EPHB4-CAR T cells only under the condition of Example 1. These results demonstrated that the production method comprising co-culturing EPHB4-expressing cells engineered to express the target antigen EPHB4 by introduction of an EPHB4 gene and EPHB4-CAR-expressing T cells was extremely useful.

[0080] PBMCs were separated and collected in the same manner as in Example 1. To 10×10⁶ cells of the collected PBMCs, a vector to express HER2-CAR, which had an anti-HER2scFV (SEQ ID NO: 1) as an extracellular domain, and a spacer domain (SEQ ID NO: 4), a transmembrane domain (SEQ ID NO: 7), and an intracellular signal domain (SEQ ID NO: 9) (FIG. 1, (b)) and a transposase expression vector (FIG. 1, (c)) were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, to 20×10⁶ PBMCs, an expression vector to express HER2 (SEQ ID NO: 10), which was the target molecule of HER2-CAR, and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (b)) was introduced by electroporation to prepare HER2-expressing cells that transiently expressed HER2. The HER2-CAR-expressing T cells and HER2-expressing cells thus prepared were cultured separately for 3 days after the gene transfer, and then the HER2-expressing cells were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured with ALyS medium containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) as well as 2% artificial serum for 11 days in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of the culture.

[0081] PBMCs were separated and collected in the same manner as in Example 1. To 15×10⁶ cells of the collected PBMCs, a HER2-CAR expression vector (FIG. 1, (b)) and a transposase expression vector (FIG. 1, (c)) were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, after UV irradiation to 2×10⁶ PBMCs, viral peptides (PepTivator CMV pp65, PepTivator AdV5 Hexon, PepTivator EBV EBNA-1, and PepTivator EBV BZLF1, Miltenyi Biotec) were added to prepare feeder cells. Then, 15×10⁶ HER2-CAR-expressing T cells thus prepared were cultured for 7 days on a plate on which the target molecule of HER2-CAR, HER2 protein, was immobilized at 100 μg/mL, with ALyS medium containing IL-7 (10 ng/mL) and IL-15 (5 ng/mL) as well as 2% artificial serum, and then mixed with the feeder cells. The cells were co-cultured for another 7 days, and collected 14 days after the start of the culture.

[0082] For the cells obtained in Example 2 and Comparative Example 4, the total number of cells was counted, and the proportion of HER2-CAR-expressing T cells was analyzed by flow cytometry. The results are shown in Table 2.

[0083]

	TABLE 2
			Comparative
		Example 2	example 4
	Cell number before	10	15
	culture (×106)
	Cell number after	146	11
	culture (×106)
	HER2-CAR-	34.1	33.7
	expressing T cells (%)
	HER2-CAR-	49.8	3.7
	expressing T cell
	number (×106)

[0084] As shown in Table 2, it was possible to obtain a sufficient number of HER2-CAR-expressing T cells for clinical use in Example 2, although the number of HER2-CAR-expressing T cells prepared before the start of culture was smaller than that in Comparative Example 4. These results demonstrated that the production method comprising co-culturing HER2-expressing cells engineered to express the target antigen HER2 by introduction of an HER2 gene and HER2-CAR-expressing T cells was extremely useful.

[0085] PBMCs were separated and collected in the same manner as in Example 1. Then, to 20×10⁶ cells of the collected PBMCs, the HER2-CAR expression vector (FIG. 1, (b)) and the transposase expression vector (FIG. 1, (c)) as used in Example 2 were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, to 20×10⁶ PBMCs, an expression vector to express HER (SEQ ID NO: 10), which was the target molecule of HER2-CAR, (FIG. 2, (c)) was introduced by electroporation to prepare HER2-expressing cells that transiently expressed HER2 (SEQ ID NO: 10). The HER2-CAR-expressing T cells and HER2-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the HER2-expressing cells were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the presence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of the culture.

[0086] HER2-CAR-expressing T cells were prepared in the same manner as in Example 3. Also, to 20×10⁶ PBMCs, instead of the HER2 expression vector, a vector expressing EPHB4 (SEQ ID NO: 11) and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (a)) was introduced by electroporation to prepare EPHB4-expressing cells to be used as antigen-presenting cells. The HER2-CAR-expressing T cells and EPHB4-expressing cells thus prepared were co-cultured in the same manner as in Example 3, and the cells were collected 14 days after the start of the culture.

[0087] HER2-CAR-expressing T cells were prepared in the same manner as in Example 3. The HER2-CAR-expressing T cells thus prepared were co-cultured with 1×10⁶ U2OS cells, which were cells of a cancer cell line expressing HER2 and used as antigen-presenting cells instead of the HER2-expressing cells, in the same manner as in Example 3. The cells were collected 14 days after the start of the culture.

[0088] PBMCs were separated and collected in the same manner as in Example 1. Then, to 20×10⁶ cells of the collected PBMCs, the EPHB4-CAR expression vector (FIG. 1, (a)) and the transposase expression vector (FIG. 1, (c)) as used in Example 1 were introduced by electroporation to prepare EPHB4-CAR-expressing T cells. Also, to 20×10⁶ PBMCs, an expression vector to express EPHB4 (SEQ ID NO: 11), which was the target molecule of EPHB4-CAR, and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) was introduced by electroporation to prepare EPHB4-expressing cells that transiently express EPHB4. The EPHB4-CAR-expressing T cells and EPHB4-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the EPHB4-expressing cells were irradiated with UV and mixed with EPHB4-CAR-expressing T cells. The cells were co-cultured in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture.

[0089] EPHB4-CAR-expressing T cells were prepared in the same manner as in Example 4. To 20×10⁶ PBMCs, a vector to express CD19 (SEQ ID NO: 16) instead of EPHB4 and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (d)) was introduced by electroporation to prepare CD19-expressing cells to be used as antigen-presenting cells. The EPHB4-CAR-expressing T cells and CD19-expressing cells thus prepared were co-cultured in the same manner as in Example 4, and the cells were collected 14 days after the start of the culture.

[0090] For the cells obtained in Examples 3 and 4 and Comparative Examples 5 to 7, respectively, the total number of cells was counted, and the proportion of CAR-expressing T cells was analyzed by flow cytometry. The results are shown in Table 3.

[0091]

TABLE 3
				Total	CAR-T
			CAR-T	cell	cell
	CAR-T	Antigen	cells	number	number
	cells	presenting cells	(%)	(×106)	(×106)
Example 3	HER2	HER2-expressing	28.2	90	25.4
		PBMCs
Comparative	HER2	EPHB4, CD80, 4-	1.3	5.8	0.1
example 5		1BBL-expressing
		PBMCs
Comparative	HER2	U2OS	10.2	5.5	0.6
example 6		(expressing HER2)
Example 4	EPHB4	EPHB4, CD80, 4-	11.2	85.6	9.6
		1BBL-expressing
		PBMCs
Comparative	EPHB4	CD19, CD80, 4-	15.3	3	0.5
example 7		1BBL-expressing
		PBMCs

[0092] As shown in Table 3, it was not possible to produce a sufficient number of CAR-T cells by culture when cancer cells expressing the target molecule of HER2 were used as antigen-presenting cells (Comparative Example 6), and when antigen presenting cells expressed a target antigen that did not match the CAR of CAR-T cells (Comparative Examples 5 and 7). In contrast, it was possible to produce a sufficient number of CAR-T cells for clinical use when cells engineered to express the target antigen that matched the CAR of CAR-T cells were used as antigen-presenting cells (Examples 3 and 4).

[0093] In order to confirm the characteristics of the CAR-expressing immune cells produced by the production method of the present disclosure, CAR-expressing immune cells were produced as follows. First, peripheral blood mononuclear cells (PBMCs) were separated and collected from peripheral blood by specific gravity separation centrifugation. To 20×10⁶ cells of the collected PBMCs, the HER2-CAR expression vector (FIG. 1, (b)) and the transposase expression vector (FIG. 1, (c)) as used in Example 2 were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, in order to prepare target antigen-expressing cells, to 10×10⁶ PBMCs, an expression vector to express HER2 (SEQ ID NO: 10), which was the target molecule of HER2-CAR, and any one (FIG. 3, (a)) or two (FIG. 2, (b); FIG. 3, (b)) of CD80 (SEQ ID NO: 12), 4-1BBL (SEQ ID NO: 13), CD40 (SEQ ID NO: 14) and OX40 ligand (SEQ ID NO: 15) was introduced by electroporation to prepare HER2-expressing cells that transiently expressed HER2. The HER2-CAR-expressing T cells and HER2-expressing cells thus prepared were cultured for 1 day after the gene transfer. Then, the HER2-expressing cells were irradiated with UV, and 10×10⁶ HER2-expressing cells were mixed with 20×10⁶ HER2-CAR-expressing T cells. The cells were co-culture in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture. The number of cells obtained is shown in Table 4.

[0094]

TABLE 4
CAR-expressing	HER2-CAR-expressing T cells
immune cells	HER2			HER2
Target antigen-	CD80	HER2	HER2	CD40	HER2	HER2
expressing cells	4-1BBL	CD80	4-1BBL	OX40L	CD40	OX40L
Cell number	23.5	22.8	21.5	17	19.8	21.9
obtained (×107)

[0095] Regarding the HER2-CAR-expressing T cells thus obtained, the proportion of cells expressing any of a T cell marker, CD3; the introduced HER2-CAR; an exhaustion marker, PD-1; and markers for analysis of naive T cells or central memory T cells, CCR7 and CD45RA was analyzed by flow cytometry. The results are shown in FIGS. 4 and 5.

[0096] Also, a killing assay was performed using the obtained HER2-CAR-expressing T cells. First, U2OS cells, which were cells of a cancer cell line expressing HER2, were seeded on a plate for a real-time cell analyzer (xCELLigence, ACEA Bioscience, Inc.) at 1×10⁴ cells/well and allowed to attach the plate. Next, respective HER2-CAR-expressing T cells were seeded on the plate so that the ratio of HER2-CAR-expressing T cells to U2OS cells was 1: 2, and the cells were co-cultured for 72 hours to determine the ratio of injured U2OS cells with a real-time cell analyzer. After that, the HER2-CAR-expressing T cells co-cultured with the U2OS cells were added to U2OS cells prepared in another well, and the cells were co-cultured for another 72 hours. Then, the step of measuring cytotoxic activity was performed three times in total. The results are shown in FIGS. 6 and 7.

[0097] As shown with the results in FIGS. 4 and 5, the HER2-CAR-expressing T cells obtained by the production method of the present disclosure accounted for 20% or more of the total number of cells, indicating that HER2-CAR-expressing T cells were obtained at a high proportion. The proportion of cells expressing PD-1, which was an exhaustion marker of these T cells, was very small. Also, the proportion of naive T cells (CD45RA positive and CCR7 positive) and central memory T cells (CD45RA negative and CCR7 positive) in the HER2-CAR-expressing T cells was high and at least 45% or more in total.

[0098] Further, from the results of FIGS. 6 and 7, it was found that the HER2-CAR-expressing T cells of the present disclosure showed excellent cytotoxic activity against the HER2-expressing cancer cell line, and that the cells did not become exhausted in two consecutive measurements of killing activity and had sufficient cytotoxic activity even in the second killing activity measurement.

[0099] From these results, it was found that the production method of the present disclosure could efficiently produce a high-quality cell population containing a large number of cells having a low expression of the exhaustion marker and a phenotype of naive T cells or central memory T cells, and it was particularly effective in the production of CAR-introduced immune cells for solid tumors.

[0100] PBMCs were separated and collected from peripheral blood by specific gravity separation centrifugation. Then, to 20×10⁶ cells of the collected PBMCs, the HER2-CAR expression vector (FIG. 1, (b)) and the transposase expression vector (FIG. 1, (c)) as used in Example 2 were introduced by electroporation to prepare HER2-CAR-expressing T cell. Also, to 10×10⁶ PBMCs, an expression vector to express HER2 (SEQ ID NO: 10), which was the target molecule of HER2-CAR, and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (d)) was introduced by electroporation to prepare HER2-expressing cells that transiently expressed HER2. The HER2-CAR-expressing T cells and the HER2-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the HER2-expressing cells were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture.

[0101] PBMCs were separated and collected from peripheral blood by specific gravity separation centrifugation. Then, to 40×10⁶ PBMCs, an expression vector to express CD19-CAR, which had an anti-CD19scFV (SEQ ID NO: 2) as an extracellular domain, and a spacer domain (SEQ ID NO: 5), a transmembrane domain (SEQ ID NO: 7), and an intracellular signal domain (SEQ ID NO: 9) (FIG. 1, (d)) and a transposase expression vector (FIG. 1, (c)) were introduced by electroporation to prepare CD19-CAR-expressing T cells. Also, to 10×10⁶ PBMCs, an expression vector to express CD19 (SEQ ID NO: 16), which was the target molecule of CD19-CAR, and CD80 (SEQ ID NO: 12) and 4-1BBL (SEQ ID NO: 13) (FIG. 2, (d)) was introduced by electroporation to prepare CD19-expressing cells that transiently expressed CD19. The CD19-CAR-expressing T cells and the CD19-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the CD19-expressing cells were irradiated with UV and mixed with the CD19-CAR-expressing T cells. The cells were co-cultured in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture.

[0102] PBMCs were separated and collected from peripheral blood by specific gravity separation centrifugation. Then, 0.125×10⁶ PBMCs were stimulated with an anti-CD3 antibody and an anti-CD28 antibody, and subjected to gene transfer using a retroviral vector having the same HER2-CAR expression unit as in Example 2 (FIG. 3 (c)). The cells were cultured in the absence of IL-2, and collected 14 days after the start of the culture.

[0103] Killing assays were performed using the CAR-expressing T cells obtained in Example 5, Example 6, and Comparative Example 8. First, U2OS cells, which were cells of a cancer cell line expressing HER2, were seeded on a plate for a real-time cell analyzer (xCELLigence, ACEA Bioscience, Inc.) at 5000 cells/well, and allowed to attach the plate. Then, respective CAR-expressing T cells obtained in Example 5, Example 6, and Comparative Example 8 were seeded on the plate so that the ratio of the number of CAR-expressing T cells to U2OS cells was 4: 1. The cells were co-cultured for 100 hours and the proportion of injured U2OS cells was measured with a real-time cell analyzer. The results are shown in FIG. 8.

[0104] As shown with the results in FIG. 8, the HER2-CAR-expressing T cells of Example 5 injured 95% or more of the HER2-expressing U2OS cells 72 hours after the start of co-culture, whereas the cytotoxicity of the HER2-CAR-expressing T cells of Comparative Example 8 was about 65%. Also, in the CD19-CAR-expressing T cells of Example 6, non-specific cytotoxic reaction of about 30% to HER-expressing U2OS cells was observed. Therefore, it was considered that the CAR-dependent specific cytotoxic activity was weak in the CAR-T cells prepared in Comparative Example 8. From these results, it was considered that the HER2-CAR-expressing T cells obtained by the production method of the present disclosure had a strong CAR-specific cytotoxic activity.

[0105] PBMCs were separated and collected from a healthy subject. Then, to 20×10⁶ cells of the collected PBMCs, the HER2-CAR expression vector (FIG. 1, (b)) and the transposase expression vector (FIG. 1, (c)) as used in Example 2 were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, to 20×10⁶ PBMCs, an expression vector to express HER2 (SEQ ID NO: 10), which was the target molecule of HER2-CAR, (FIG. 2, (c)) was introduced by electroporation to prepare HER2-CAR-expressing T cells that transiently expressed HER2 (SEQ ID NO: 10). The HER2-CAR-expressing T cells and the HER2-expressing cells thus prepared were cultured separately for 1 day after the gene transfer, and then the HER2-expressing cells were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture.

[0106] In the same manner as in Example 7, to 10×10⁶ PBMCs, the HER2-CAR expression vector and the transposase expression vector were introduced by electroporation to prepare HER2-CAR-expressing T cells. Then, 3×10⁶ PBMCs collected from the same healthy subject were irradiated with UV and mixed with the HER2-CAR-expressing T cells thus prepared. The cells were co-cultured in the same manner as in Example 7, and collected 14 days after the start of culture.

[0107] For the cells obtained in Example 7 and Comparative Example 9, respectively, the total number of cells was counted and the proportion of CAR-expressing T cells was analyzed by flow cytometry. The results are shown in Table 5.

[0108]

TABLE 5
			Cell		CAR+
		Cell number	growth		cells
		(×106 cells)	rate	CAR+	(×106
	AP condition	day 0	day 14	(%)	(%)	cells)
Example 7	PBMCs with AP-	20	151.7	758.5	52.6	61.20
	tHER2.CD80.BBL
Com-	PBMCs alone	8	3.7	45.6	8.4	0.02
parative
example 9

[0109] As shown with the results in Table 5, it was not possible to produce a sufficient number of CAR-T cells by culture when the cells were simply co-cultured with PBMCs (Comparative Example 9). In contrast, the production method of the present invention was able to produce a sufficient number of CAR-T cells for clinical application (Example 7).

[0110] PBMC were separated and collected from a healthy subject. Then, to 17×10⁶ cells of the collected PBMCs, the HER2-CAR expression vector (FIG. 1, (b)) and the transposase expression vector (FIG. 1, (c)) as used in Example 2 were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, to 17×10⁶ PBMCs, an expression vector to express HER2 (SEQ ID NO: 10), which was the target molecule of HER2-CAR, (FIG. 2, (c)) was introduced by electroporation to prepare HER2-expressing cells that transiently expressed HER2 (SEQ ID NO: 10). The HER2-CAR-expressing T cells and the HER2-expressing cells thus prepared were separately cultured for 1 day after the gene transfer, and then the HER2-expressing cells were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the absence of IL-2, an anti-CD3 antibody and an anti-CD28 antibody, and collected 14 days after the start of culture.

[0111] In the same manner as in Example 8, to 17×10⁶ PBMCs, the HER2-CAR expression vector and the transposase expression vector were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, in the same manner except that 17×10⁶ K562 cells (not expressing HER2) were used instead of PBMCs, the HER2 expression vector was introduced into the cells to prepare HER2-expressing cells. The HER2-expressing cells thus prepared were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the same manner as in Example 8, and were collected 14 days after the start of culture.

[0112] In the same manner as in Example 8, to 17×10⁶ PBMCs, the HER2-CAR expression vector and the transposase expression vector were introduced by electroporation to prepare HER2-CAR-expressing T cells. Also, in the same manner except that 10×10⁶ Rh30 cells (expressing HER2) were used instead of PBMCs, the HER2 expression vector was introduced into the cells to prepare HER2-expressing cells. The HER2-expressing cells thus prepared were irradiated with UV and mixed with the HER2-CAR-expressing T cells. The cells were co-cultured in the same manner as in Example 8, and were collected 14 days after the start of culture.

[0113] For the cells obtained in Example 8 and Comparative Examples 10 and 11, respectively, the total number of cells was counted and the proportion of CAR-expressing T cell was analyzed by flow cytometry. The results are shown in Table 6.

[0114]

TABLE 6
						CD8+	PD-1-	Naïve
						cells/	expressing	cells*/	CAR+
		Cell number	Cell		CAR+	cells/	CAR+	cells	CD8+,
		(×106)	growth	CAR+	cells	CAR+ cells	cells	(×106	CAR+ cells
	AP condition	day 0	day 14	rate (%)	(%)	(%)	(%)	(%)	cells)	(×106 cells)
Example 8	PBMCs with AP-	17	170	997.1	62.3	58.7	0.7	62.8	106	62
	tHER2.CD80.BBL
Comparative	K562 with AP-	17	31	183.5	85.2	21.8	23.4	40.1	27	6
example 10	tHER2.CD80.BBL
Comparative	Rh30 with AP-	17	13	78.8	62.2	18.3	10.3	42.3	8	2
example 11	tHER2.CD80.BBL
*CD45RA-positive, CCR7-positive cells

[0115] As shown in Table 6, by using HER2-expressing cells prepared by subjecting PBMCs to express the target antigen HER2, 5 times or more cells were obtained as compared with the cells obtained by using K562 and Rh30 cells of the comparative examples. Therefore, it was found that the method of the present disclosure showed excellent cell productivity and enabled production of a sufficient number of cells necessary for clinical use. In particular, the proportion of CD8-positive cells was 58.7% when the cells prepared from PBMCs were used as HER2-expressing cells and it was more than twice as high as the proportion when K562 or Rh30 cells were used, and the number of CAR-positive, CD8-positive cells obtained was more than 10 times higher. It was found that CD8-positive CAR-T cells could be produced predominantly.

[0116] Further, in terms of quality, when cells prepared from PBMCs were used as HER2-expressing cells, the expression of PD-1 in CAR-positive cells was extremely low at 0.7% as compared with the expression when K562 or Rh30 cells were used, and the proportion of naive cells positive for CD45RA and CCR7 was also 62.8%, which was more than 1.5 times higher, indicating that the cells were young and not exhausted and high-quality CAR-T cells could be produced.

[0117] According to the present disclosure, the cell proliferation rate in the production of CAR-expressing immune cells can be increased, and CAR-T cells having high cytotoxic activity can be stably produced. In particular, the production efficiency of CAR-expressing immune cells for solid tumors can be dramatically improved, and thus CAR-T cell therapies can be applied to various cancer types.