BACKGROUND

[001] Tumor-specific T cell based immunotherapies, including therapies employing engineered T cells, have been investigated for anti-tumor treatment.

[002] CD 19 CAR-T cell therapy is effective in many patients with B-ALL and lymphoma. However, relapse due to antigen loss variants escaping CD19-directed CAR- T therapy can occur in up to 20-30% of patient. CD22 CAR-T cell therapy has been proposed as one alternative strategy to overcome relapse from CD 19 antigen loss, as demonstrated by achievement of clinical responses in patients with CD 19-negative B- ALL. However, CD22 expression density can vary particularly in mixed lineage leukemia (MLL) and its expression was reported to diminish after CD22 -targeted therapy.

SUMMARY

[003] Described herein are methods for treating B cell malignancies, including B-ALL and lymphoma, using T cells expressing a chimeric antigen receptor (CAR) targeted to B cell activating factor receptor (BAFF-R) and CD19. In some cases, a single CAR targets both BAFF-R and CD19. In the case of a single CAR targeting both BAFF-R and CD19 the extracellular targeting portion can have a tandem format in which an scFv to one of the targets precedes the other scFv or a loop format in which an scFv to one of the two targets is disposed between the VL and VH domains of a scFv to the other target. In any of these formats, the CAR includes: a transmembrane domain (e.g., a CD8

transmembrane domain), a co-stimulatory domain (e.g., a 4- IBB co-stimulatory domain) and a CD3 zeta signaling domain. The CAR can also include a spacer sequence between, for example, the scFv domain(s) and the transmembrane domain, between the transmembrane domain and the co-stimulatory domain, and/or between the co stimulatory domain and the CD3 zeta signaling domain.

[004] Described herein is a nucleic acid molecule comprising a nucleotide sequence encoding a chimeric antigen receptor targeted to both BAFF-R and CD 19, wherein the chimeric antigen receptor comprises, from amino to carboxy terminus: a targeting domain for targeting BAFF-R and CD 19; a spacer domain; a transmembrane domain; a costimulatory domain; and a CD3z signaling domain.

[005] In various embodiments: (1) the targeting domain comprises, from amino to carboxy terminus: a) a scFv targeted to BAFF-R and a scFv targeted to CD 19; or b) a scFv targeted to CD 19 and a scFv targeted to BAFF-R; (2) the targeting domain comprises, from amino to carboxy terminus: a) a VL domain of a CD 19 scFv; a scFv targeted to BAFF-R; and a VH of the CD 19 scFv; or b) a VH domain of a CD 19 scFv; a scFv targeted to BAFF-R; and a VL of the CD19 scFv; and (3) the targeting domain comprises, from amino to carboxy terminus: a) a VL domain of a BAFF-R scFv; a scFv targeted to CD19; and a VH of the BAFF-R scFv; or b) a VH domain of a BAFF-R scFv; a scFv targeted to CD 19; and a VL of the BAFF-R scFv.

[006] Also described herein is a nucleic acid molecule comprising a nucleotide sequence encoding a chimeric antigen receptor targeted to both BAFF-R and a chimeric antigen receptor targeted to CD 19, wherein the chimeric antigen receptor targeted to BAFF-R comprises, from amino to carboxy terminus: a BAFF-R scFv; a spacer domain; a transmembrane domain; a costimulatory domain; and a CD3z signaling domain; and the chimeric antigen receptor targeted to CD 19 comprises, from amino to carboxy terminus: a CD 19 scFv; a spacer domain; a transmembrane domain; a costimulatory domain; and a CD3z signaling domain.

[007] In various embodiments: the costimulatory domain is selected from the group consisting of: a CD28 costimulatory domain or a variant thereof having 1-5 amino acid modifications, a 4- IBB costimulatory domain or a variant thereof having 1-5 amino acid modifications and an 0X40 costimulatory domain or a variant thereof having 1-5 amino acid modifications; the transmembrane domain is selected from: a CD4 transmembrane domain or variant thereof having 1-5 amino acid modifications, a CD8 transmembrane domain or variant thereof having 1-5 amino acid modifications, a CD28 transmembrane domain or a variant thereof having 1-5 amino acid modifications, and a Oϋ3z transmembrane domain or a variant thereof having 1-5 amino acid modifications; a costimulatory domain; and Oϋ3z signaling domain of a variant thereof having 1-5 amino acid modifications; and the spacer domain is selected from the group consisting of: IgG4 hinge (S P), IgG4 hinge, IgG4 hinge (S228P)+linker, CD28 hinge, CD8 hinge-48aa,

CD 8 hmge-45aa, IgG4(HL-CH3), IgG4(L235E,N297Q), IgG4(S228P, L235E,N297Q), and IgG4(CH3), and a variant of each of IgG4 hinge (S P), IgG4 hinge, IgG4 hinge (S228P)+linker, CD28 hinge, CD 8 hmge-48aa, CD 8 hmge-45aa, IgG4(HL-CH3), IgG4(L235E,N297Q), IgG4(S228P, L235E,N297Q), and IgG4(CH3) thereof having 1-5 amino acid modifications.

[008] In various embodiments: (1) the BAFF-R scFv includes a light chain variable region and a heavy chain variable region, wherein the light chain variable region includes: CDR LI (SEQ ID NO: 1), CDR L2 (SEQ ID NO:2) and CDR L3 (SEQ ID NO:3); and the heavy chain variable region includes: CDR HI (SEQ ID NO:4), CDR H2 (SEQ ID NO: 5), and CDR H3 (SEQ ID NO: 6); (2) the BAFF-R scFv includes a light chain variable region and a heavy chain variable region, wherein the light chain variable region includes: CDR LI (SEQ ID NO:7), CDR L2 (SEQ ID NO: 8) and CDR L3 (SEQ ID NO:9); and the heavy chain variable region includes: CDR HI (SEQ ID NO: 10), CDR H2 (SEQ ID NO: 11), and CDR H3 (SEQ ID NO: 12); (3) the BAFF-R scFv includes: a heavy chain variable domain selected from: Chi90 HC, Hu90 HC-1, Hu90 HC-2, Hu90 HC-3, Chi55 HC, Hu55 HC-1, Hu55 HC-2, and Hu55 HC-3 and a light chain variable domain selected from: Chi90 LC, Hu90 LC-1, Hu90 LC-2, Hu90 LC-3, Chi55 LC, Hu55 LC-1, Hu55 LC-2, and Hu55 LC-3; (4) the BAFF-R scFv includes a light chain variable domain having an amino acid sequence selected from SEQ ID NOs: 17-20 and 25-28; (5) the BAFF-R scFv includes a heavy chain variable domain having an amino acid sequence selected from SEQ ID NOs: 13-16 and 21-24; (6) the CD19 scFv comprises a VL comprising the amino acid sequence

DIQMTQTTSSLSASLGDRVTISCRASQDISKYLNWYQQKPDGTVKLLIYHTSRLH S GVP SRF S GS GS GTD Y S LTI SNLEQEDI AT YF C QQGNTLP YTF GGGTKLEIT (SEQ ID NO: 30) and a VH comprising the amino acid sequence EVK

LQESGPGLVAPSQSLSVTCTVSGVSLPDYG

V S WIRQPPRKGLEWLGVIW GSETT Y YNS ALKSRLTIIKDN SKS Q VFLKMN SLQTD DTAIYY C AKHYYY GG SYAMDYWGQGTSVTVSS (SEQ ID NO: 31).

[009] Also described herein is a vector comprising one or more of the nucleic acid molecules described above. In various embodiments the vector is a lentiviral vector.

Also described is a population of human T cells transduced by a vector described herein.

[0010] Also described is a method of treating cancer in a subject in need thereof comprising administering to a subject a therapeutically effective amount of a composition comprising a population of human T cells as described herein. In various embodiments of the method: the cancer is lymphoma, leukemia or myeloma; the lymphoma is mantle cell lymphoma, follicular lymphoma, diffuse large B-cell lymphoma, marginal zone lymphoma or Burkitt’s lymphoma; the leukemia is acute lymphoblastic leukemia, chronic lymphocytic leukemia or hairy cell leukemia; the myeloma is multiple myeloma; the population of T cells are autologous or allogeneic to the patient; and the population of human T cells comprise cells comprise CD4+ cell and CD8+ cells.

[0011] In some embodiments, the BAFF-R scFv includes a light chain variable region and a heavy chain variable region, wherein the light chain variable region includes CDR LI as set forth in SEQ ID NO: 7, a CDR L2 as set forth in SEQ ID NO: 8 and a CDR L3 as set forth in SEQ ID NO: 9; and the heavy chain variable region includes a CDR HI as set forth in SEQ ID NO: 10, a CDR H2 as set forth in SEQ ID NO: 11 , and a CDR H3 as set forth in SEQ ID NO: 12. In embodiments, the antibody is a humanized antibody.

[0012] In some embodiments, the BAFF-R scFv includes: CDR LI of SEQ ID NO: 1 or 7, CDR L2 of SEQ ID NO:2 or 8, CDR L3 of SEQ ID NO: 3 or 9, CDR HI of SEQ ID NO: 4 or 10, CDR H2 of SEQ ID NO: 5 or 11, and CDR H3 of SEQ ID NO: 7 or 13.

[0013] In some embodiments, the portion of the BAFF-R scFv includes: the light chain variable domain of monoclonal antibody H90 and the heavy chain variable domain of monoclonal antibody H90 or the light chain variable domain of monoclonal antibody H55 and the heavy chain variable domain of monoclonal antibody H55. The heavy and light chain variable domains can be joined by a linker of, 5-100, 10-50 or 10-20 amino acids (e g., GGGGSGGGGSGGGGS).

[0014] In some embodiments, the BAFF-R scFv includes: a) a humanized variant of the light chain variable domain of monoclonal antibody H90 and a humanized variant of the heavy chain variable domain of monoclonal antibody H90; or b) a humanized variant of the light chain variable domain of monoclonal antibody H55 and a humanized variant of the heavy chain variable domain of monoclonal antibody H55. The heavy and light chain variable domains can be joined by a linker of 10-20 amino acids (e.g.,

GGGGSGGGGSGGGGS). In some cases, the humanized variant of the H90 light chain variable domain is selected from: Hu90 LC-1, Hu90 LC-2 and Hu90 LC-3 and the humanized variant of the H90 heavy chain variable domain is selected from: Hu90 HC-1, Hu90 HC-2 and Hu90 HC-3. In some cases, the humanized variant of the H55 light chain variable domain is selected from: Hu55 LC-1, Hu55 LC-2 and Hu55 LC-3 and the humanized variant of the H55 heavy chain variable domain is selected from: Hu55 HC-1, Hu55 HC-2 and Hu90 HC-3.

[0015] In embodiments, the BAFF-R scFv light chain variable region includes a serine at a position corresponding to Rabat position 7. In embodiments, the light chain variable region includes a proline at a position corresponding to Rabat position 8. In

embodiments, the light chain variable region includes a valine at a position corresponding to Rabat position 15. In embodiments, the light chain variable region includes a threonine at a position corresponding to Rabat position 22. In embodiments, the light chain variable region includes a glutamine at a position corresponding to Rabat position 24. In embodiments, the light chain variable region includes a glycine at a position corresponding to Rabat position 41. In embodiments, the light chain variable region includes a lysine at a position corresponding to Rabat position 42. In embodiments, the light chain variable region includes an alanine at a position corresponding to Rabat position 43. In embodiments, the light chain variable region includes a proline at a position corresponding to Rabat position 44. In embodiments, the light chain variable region includes a threonine at a position corresponding to Kabat position 56. In embodiments, the light chain variable region includes a threonine at a position corresponding to Kabat position 72. In embodiments, the light chain variable region includes a phenylalanine at a position corresponding to Kabat position 73. In

embodiments, the light chain variable region includes a glutamine at a position corresponding to Kabat position 79. In embodiments, the light chain variable region includes a valine at a position corresponding to Kabat position 104.

[0016] In embodiments, the BAFF-R scFv the light chain variable region includes a serine at a position corresponding to Kabat position 7, a proline at a position

corresponding to Kabat position 8, a valine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 22, a glutamine or a serine at a position corresponding to Kabat position 24, a glycine at a position corresponding to Kabat position 41, a lysine at a position corresponding to Kabat position 42, an alanine or a threonine at a position corresponding to Kabat position 43, a proline at a position corresponding to Kabat position 44, a threonine at a position corresponding to Kabat position 56, a threonine at a position corresponding to Kabat position 72, a phenylalanine or a lysine at a position corresponding to Kabat position 73, a glutamine at a position corresponding to Kabat position 79 or a valine at a position corresponding to Kabat position 104.

[0017] In embodiments, the BAFF-R scFv the light chain variable region includes a binding framework region residue that is a serine at a position corresponding to Kabat position 7, a proline at a position corresponding to Kabat position 8, a valine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 22, a glutamine or a serine at a position corresponding to Kabat position 24, a glycine at a position corresponding to Kabat position 41, a lysine at a position corresponding to Kabat position 42, an alanine or a threonine at a position corresponding to Kabat position 43, a proline at a position corresponding to Kabat position 44, a threonine at a position corresponding to Kabat position 56, a threonine at a position corresponding to Kabat position 72, a phenylalanine or a lysine at a position corresponding to Kabat position 73, a glutamine at a position corresponding to Kabat position 79 or a valine at a position corresponding to Kabat position 104.

[0018] In embodiments, the BAFF-R scFv the heavy chain variable region includes a threonine or an alanine at a position corresponding to Kabat position 10. In

embodiments, the heavy chain variable region includes a lysine at a position

corresponding to Kabat position 11. In embodiments, the heavy chain variable region includes a valine at a position corresponding to Kabat position 12. In embodiments, the heavy chain variable region includes a threonine at a position corresponding to Kabat position 15. In embodiments, the heavy chain variable region includes a threonine at a position corresponding to Kabat position 19. In embodiments, the heavy chain variable region includes a threonine at a position corresponding to Kabat position 23. In embodiments, the heavy chain variable region includes a proline at a position

corresponding to Kabat position 41. In embodiments, the heavy chain variable region includes an alanine at a position corresponding to Kabat position 44. In embodiments, the heavy chain variable region includes a proline or a threonine at a position

corresponding to Kabat position 61. In embodiments, the heavy chain variable region includes an arginine at a position corresponding to Kabat position 66. In embodiments, the heavy chain variable region includes a threonine at a position corresponding to Kabat position 70. In embodiments, the heavy chain variable region includes a lysine at a position corresponding to Kabat position 75. In embodiments, the heavy chain variable region includes a valine at a position corresponding to Kabat position 79. In

embodiments, the heavy chain variable region includes a threonine at a position corresponding to Kabat position 81. In embodiments, the heavy chain variable region includes a methionine at a position corresponding to Kabat position 82. In embodiments, the heavy chain variable region includes an asparagine at a position corresponding to Kabat position 82B. In embodiments, the heavy chain variable region includes a methionine at a position corresponding to Kabat position 82C. In embodiments, the heavy chain variable region includes a proline at a position corresponding to Kabat position 84. In embodiments, the heavy chain variable region includes a valine at a position corresponding to Kabat position 85. In embodiments, the heavy chain variable region includes a lysine at a position corresponding to Kabat position 108. In

embodiments, the heavy chain variable region includes a valine at a position

corresponding to Kabat position 109.

[0019] In embodiments, the BAFF-R scFv heavy chain variable region includes a threonine or an alanine at a position corresponding to Kabat position 10, a lysine at a position corresponding to Kabat position 11, a valine at a position corresponding to Kabat position 12, a threonine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 19, a threonine at a position corresponding to Kabat position 23, a proline at a position corresponding to Kabat position 41, an alanine at a position corresponding to Kabat position 44, a proline, a serine or a threonine at a position corresponding to Kabat position 61, an arginine at a position corresponding to Kabat position 66, a threonine at a position corresponding to Kabat position 70, a lysine at a position corresponding to Kabat position 75, a valine at a position corresponding to Kabat position 79, a threonine or a lysine at a position corresponding to Kabat position 81, a methionine at a position corresponding to Kabat position 82, an asparagine at a position corresponding to Kabat position 82B, a methionine at a position corresponding to Kabat position 82C, a proline at a position corresponding to Kabat position 84, a valine at a position corresponding to Kabat position 85, a lysine at a position corresponding to Kabat position 108 or a valine at a position corresponding to Kabat position 109.

[0020] In embodiments, the BAFF-R scFv heavy chain variable region includes a binding framework region residue that is a threonine or an alanine at a position corresponding to Kabat position 10, a lysine at a position corresponding to Kabat position 11, a valine at a position corresponding to Kabat position 12, a threonine at a position corresponding to Kabat position 15, a threonine at a position corresponding to Kabat position 19, a threonine at a position corresponding to Kabat position 23, a proline at a position corresponding to Kabat position 41, an alanine at a position corresponding to Kabat position 44, a proline, a serine or a threonine at a position corresponding to Kabat position 61, an arginine at a position corresponding to Kabat position 66, a threonine at a position corresponding to Kabat position 70, a lysine at a position corresponding to Kabat position 75, a valine at a position corresponding to Kabat position 79, a threonine or a lysine at a position corresponding to Kabat position 81, a methionine at a position corresponding to Kabat position 82, an asparagine at a position corresponding to Kabat position 82B, a methionine at a position corresponding to Kabat position 82C, a proline at a position corresponding to Kabat position 84, a valine at a position corresponding to Kabat position 85, a lysine at a position corresponding to Kabat position 108 or a valine at a position corresponding to Kabat position 109.

DESCRIPTION OF DRAWINGS

[0021] FIGURE 1 depicts schematic drawings of two example of tandem constructs and one example of a loop construct for BAFF-R/CD19 dual CARs. Also shown is an example of bicistronic construct in which a single cell expresses two CARs, one targeted to BAFF-R and one targeted to CD 19.

[0022] FIGURE 2 depicts the amino acid sequence of an immature 1250 dual CAR, including signal sequence (SEQ ID NO: 58). The mature CAR (SEQ ID NO: 59) includes, from amino to carboxy terminus: a BAFF-R scFv, a linker, a CD 19 scFv (derived from FMC63), an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4- IBB cytoplasmic domain, a GGG linker, and a CD3 signaling domain.

[0023] FIGURE 3 depicts the amino acid sequence of an immature 1296 dual CAR, including signal sequence (SEQ ID NO:60). The mature CAR (SEQ ID NO:61) includes, from amino to carboxy terminus: a CD19 scFv (derived from FMC63), a linker, a BAFF- R scFv, an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4- IBB cytoplasmic domain, a GGG linker, and a CD3 signaling domain.

[0024] FIGURE 4 depicts the amino acid sequence of an immature 1316 dual CAR, including signal sequence (SEQ ID NO:62). The mature CAR (SEQ ID NO:63) includes, from amino to carboxy terminus: a CD19 VL (derived from FMC63), a GGGS linker, a BAFF-R scFv, a CD 19 VH (derived from FMC63), an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4 IBB cytoplasmic domain, a GGG linker, and a CD3 signaling domain. [0025] FIGURE 5 depicts the amino acid sequence of: (A) an immature CD 19 CAR, including signal sequence (SEQ ID NO: 64) and B an immature BAFF-R CAR including a signal sequence (SEQ ID NO:66). The mature CD19 CAR (SEQ ID NO:65) includes, from amino to carboxy terminus: a CD 19 scFv (derived from FMC63), an IgG4

(SmP/L235E,N297Q) spacer domain, a CD28 transmembrane domain, a CD28(GG) cytoplasmic domain, a GGG linker, and a CD3 signaling domain. The mature BAFF-R CAR (SEQ ID NO: 67) includes, from amino to carboxy terminus: a BAFF-R scFv, an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4-1BB cytoplasmic domain, a GGG linker, and a CD3 signaling domain.

[0026] FIGURE 6 is a schematic drawing of an example of a vector for expressing a BAFF-R/CD19 dual CAR. BAFF-R and CD19 scFv elements can be varied to express the different arrangement of dual CARs. Truncated EGFR (EGFRt) is expressed as a selection marker.

[0027] FIGURE 7 depicts the results of a study of dual CAR expression. T cells (Jurkat) were transduced with each CAR construct or an empty vector (mock). Cells were stained with Protein L- or EGFR-APC conjugated antibodies. Protein L targets the variable light chain of the scFv, and truncated EGFR is co-expressed by the CAR vector. Constructs that were able to properly express dual CARs were further examined. Dual CAR 1296 and dual CAR 1316 expressed intact CAR and EGFRt selection marker, whereas dual CAR 1250 failed to express intact CAR.

[0028] FIGURE 8 depicts the result of a FACS assay assessing 1250 dual CAR T-cell degranulation following incubation with target cells. Targets cells are either BAFF-R single positive, CD19 single positive, or BAFF-R and CD19 double negative. Control BAFF-R single CAR and non-transduced T cells (non-CAR) were used as controls. The 1250 dual CAR failed to elicit response against BAFF-R-positive L cells suggesting BAFF-R-targeting scFv is not properly expressed.

[0029] FIGURE 9 depicts the results of analysis related to development of cells lines used to develop a model for studying BAFF-R/CD19 dual CAR. FACS histograms of Nalm-6 knockout lines used for dual CAR model development. Nalm-6 B-ALL tumor line was gene edited with CRISPR to knockout BAFF-R (left) or CD19 (right). Surface protein expression was confirmed by FACS staining with commercial BAFF-R and CD 19 antibodies. Nalm-6 wildtype (WT) was used as controls.

[0030] FIGURE 10A-10B depicts the results of an analysis of the CTL function of BAFF-R/CD19 dual CAR. Graphs show calculated specific lysis are plotted from a cytotoxic T lymphocyte assay against Nalm-6 ALL tumor lines. Target cell line Nalm-6 (WT, CD19 knockout, or BAFF-R knockout variants) were labeled with chromium-51 and incubated with effector CAR T cells. CARs included BAFF-R/CD19 dual -targeting CARs: A). 1296 and 1250 or B). 1296 and 1316; controls in both panels include single targeting CARs: BAFF-R CAR and CD 19 CAR and non-transduced T cells (non-CAR, allogeneic control). All T cells were derived from a single healthy donor in each panel. Chromium released by target cells due to effector T cell function was measured by a gamma counter and calculated as a percentage of maximum possible release. Experiment was conducted in triplicate and analyzed by a Student’s t-test; A. ** P<0.001 compared between dual CARs; and B). ** P0.001 c/w non-CAR control. 1250 dual CAR CTL data suggests potential BAFF-R targeting deficiency.

[0031] FIGURE 11A-11B depicts the activity of BAFF-R/CD19 Dual CAR in BAFF-R- plus CD19-deficiant mixed B-ALL tumor. A) Bioluminescence images of NSG mice following IV tumor challenge on day 0 with a mixture of 1 x 10 ⁵ RFP-negative, luciferase-expressing Nalm-6-CD19KO plus 2.5 x 10 ⁵ RFP-positive, luciferase- expressing Nalm-6-BAFF-RKO tumor cells. Groups of 5 tumor-bearing mice each were then randomly assigned to treatment with either 2.5 x 10 ⁶ CD4 T _N CAR-T + lO ⁶ CD8 T _N 1296 or 1316 dual CAR T cells/mouse IV on day 10, as a single infusion. Non- transduced CD4/CD8 T cells from the same donor were used as allogeneic controls (non- CAR). B) Kaplan-Meier plots of overall survival are shown. Log-rank test compare experimental groups as shown. 1316 treatment conferred significant prolonged survival compared to 1296 treatment.

[0032] FIGURE 12 depicts the activity of 1316 BAFF-R/CD19 Dual CAR against knock-out tumors. FACS plots of BAFF-R CAR T cell functional potency as measured by a CD 107a degranulation assay. CD4 or CD8 BAFF-R CAR T cells were coincubated with either CD19 BAFF-R ⁺ Nalm-6 or CD19 ⁺ BAFF-R Nalm-6 lines. Single targeting CD19 or BAFF-R CAR T cells were used as controls.

[0033] FIGURE 13A-13B depicts the activity of TN/MEM 1316 BAFF-R/CD19 Dual CAR in mixed B-ALL tumor. A) Bioluminescence images of NSG mice following IV tumor challenge on day 0 with a mixture of 1 x 10 ⁵ RFP-negative, luciferase-expressing Nalm-6-CD19KO plus 1 x 10 ⁵ RFP-positive, luciferase-expressing Nalm-6-BAFF-RKO tumor cells. Groups of 5 tumor-bearing mice each were then randomly assigned to treatment with 1316 dual CAR T cells/mouse IV on day 9, as a single infusion of either low dose (2.8 x 10 ⁶ TN/MEM), high dose (5.6 x 10 ⁶ TN/MEM), which yielded 1 x 10 ⁶ and 2 x 10 ⁶ BAFF-R CAR T cells, respectively.2.5 or 5 x 10 ⁶ non-transduced TN/MEM cells from the same donor were used as allogeneic controls (non-CAR). B) Kaplan-Meier plots of overall survival are shown. Log-rank test compare experimental groups as shown. No significant difference in survival between the two dosing were observed.

DETAILED DESCRIPTION

[0034] The BAFF-R/CD19 dual CAR and BAFF-R/CD19 bicistromc CAR can employ any of a variety of BAFF-R scFv and CD19 scFv and, in the case of BAFF-R/CD19 dual CAR in which a first scFv is located between the variable domains of a second scFv, any of a variety of VL and VH can be used.

[0035] FIGURE 1 depicts schematic drawings of two example of tandem construct, one in which the BAFF-R scFv is amino terminal to the CD 19 scFv and one in which the CD19 scFv is amino terminal to the BAFF-R scFv. Also depicted is one example of a loop construct for BAFF-R/CD29 dual CARs. In this example a BAFF-R is located between the CD 19 VL (amino terminal to the scFv) and the CD 19 VH domain (carboxy terminal to the scFv). Also shown is an example of bicistronic construct in which a single cell expresses two CARs, one targeted to BAFF-R and one targeted to CD 19.

BAFF-R scFv Sequences [0036] The BAFF-R scFv sequences used in BAFF-R/CD19 dual CAR can be derived from two monoclonal antibodies, Clone 90 and Clone 55 described in greater detail in US PCT/US2017/036181. For example, the VL can include the C90 CDR sequences or the C55 CDR sequences described below.

[0037] C90 CDR LI : ESVDNYGISF (SEQ ID NO: 1)

[0038] C90 CDR L2: AAS (SEQ ID NO:2)

[0039] C90 CDR L3: QQSKEVPWT (SEQ ID NO:3)

[0040] C90 CDR HI : GDSITSGY (SEQ ID NO:4)

[0041] C90 CDR H2: ISYSGST (SEQ ID NO: 5)

[0042] C90 CDR H3: ASPNYPF Y AMD Y (SEQ ID NO: 6)

[0043] C55 CDR LI : QDISNY (SEQ ID NO:7)

[0044] C55 CDR L2: YTS (SEQ ID NO: 8)

[0045] C55 CDR L3: FSELPWT (SEQ ID NO:9)

[0046] C55 CDR HI : GFSLSTSGMG (SEQ ID NO: 10)

[0047] C55 CDR H2: IWWDDDK (SEQ ID NO: 11)

[0048] C55 CDR H3: ARSFGYGLDY (SEQ ID NO: 12)

[0049] Among the suitable heavy chain variable domains (VH) for use in the BAFF-R scFv of a dual CAR are the following heavy chain variable domains derived from monoclonal antibody Clone 90 (Described in greater detail in PCT/US2017/036181. Of these, Hu90 HC-1, HC-2 and HC-3 are humanized.

[0050] Chi90 HC:

MYRMQLLSCIALSLALVTNSEVQLQESGPSLVKPSQTLSLTCSVTGDSITSGYWN WIRKFPGNKLEYMGYISYSGSTYYNPSLKSRISITRDTSKNQYYLQLNSVTPEDTA TYYCASPNYPFYAMDYWGQGTSVTVSSDI (SEQ ID NO: 13)

[0051] Hu90 HC-1 :

MDPKGSLSWRILLFLSLAFELSYGQVQLQESGPGLVKPSQTLSLTCTVSGDSITSG YWNWIRQHPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQFSLKLSSVTA ADTAVYYCASPNYPFYAMDYWGQGTLVTVSS (SEQ ID NO: 14)

[0052] Hu90 HC-2:

MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSQTLSLTCTVSGDSITSG YWNWIRQHPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQYSLKLSSVTA ADTAVYYCASPNYPFYAMDYWGQGTLVTVSS (SEQ ID NO: 15)

[0053] Hu90 HC-3:

MDPKGSLSWRILLFLSLAFELSYGEVQLQESGPGLVKPSETLSLTCSVSGDSITSG YWNWIRQPPGKGLEYIGYISYSGSTYYNPSLKSRVTISRDTSKNQYSLRLSSVTAA DTALYY CASPNYPF YAMD YWGQGTRVTV S S (SEQ ID NO: 16)

[0054] Among the suitable light chain variable domains (VL) for use in the BAFF-R scFv of a dual CAR are the following heavy chain variable domains derived from monoclonal antibody Clone 90 (Described in greater detail in PCT/US2017/036181. Of these, Hu90 LC-1, LC-2 and LC-3 are humanized.

[0055] Chi90 LC:

MYRMQLLSCIALSLALVTNSDIVLTQSPASLAVSLGQRATISCRASESVDNYGISF MNWF Q QKPGQPPKLLI Y A ASN Q GS GVP ARF S GS GS GTDF S LNIHPMEEDD T AMY FCQQSKEVPWTFGGGTKLEIKTMEIKR (SEQ ID NO: 17)

[0056] HuC90 LC-1 :

METDTLLLWVLLLWVPGSTGEIVLTQSPATLSLSPGERATLSCRASESVDNYGISF LNWFQQKPGQ APRLLIY AASNRATGIP ARFS GS GS GTDFTLTIS SLEPEDF AVYY C QQSKEVPWTFGGGTKVEIKRTV (SEQ ID NO: 18) [0057] Hu90 LC-2:

METDTLLLWVLLLWVPGSTGDIVLTQSPATLSLSPGERATLSCRASESVDNYGIS FMNWF Q QKP GQ APRLLI Y A ASNRAT GIP ARF S GS GS GTDF TLTIS S LEPEDF A V Y Y CQQ SKEVPWTF GGGTKVEIKRT V (SEQ ID NO: 19)

[0058] HuC90 LC-3:

METDTLLLWVLLLWVPGSTGDIVMTQSPSSLSASVGDRVTITCRASESVDNYGIS FMNWFQQKPGKAPKLLIYAASNLGSGVPSRFSGSGSGTDFTLTISSLQPEDFATY Y CQQSKEVPWTFGQGTKVEIKRTV (SEQ ID NO:20)

[0059] Also among the suitable heavy chain variable domains (VH) for use in the BAFF IN scFv of a dual CAR are the following heavy chain variable domains derived from monoclonal antibody Clone 55 (described in greater detail in PCT/US2017/036181). Of these, Hu55 HC-1, HC-2 and HC-3 are humanized.

[0060] Chi 55 HC:

MYRMQLLSCIALSLALVTNSQVTLKESGPGILKPSQTLSLTCSFSGFSLSTSGMGV GWIRQPSGKGLEWLAHIWWDDDKYYN S SLKSHLTISKDTSRN QVFLKITS VDTA DTATYYCARSFGYGLDYWGQGTTLTVSSAS (SEQ ID NO: 21)

[0061] Hu55 HC-1 :

MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFSGFSLSTS GMGVGWIRQPPGKALEWLAHIWWDDDKYYNPSLKSRLTITKDTSKNQWLTMT NMDPVDT ATYY C ARSF GY GLD YWGQGTL VT V S S (SEQ ID NO: 22)

[0062] Hu55 HC-2:

MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPTLVKPTQTLTLTCTFSGFSLSTS GMGVGWIRQPPGKALEWLAHIWWDDDKYYNSSLKSRLTITKDTSKNQWLTMT NMDPVDT ATYY C ARSF GY GLD YWGQGTL VTV S S (SEQ ID NO: 23)

[0063] Hu55 HC-3:

MDPKGSLSWRILLFLSLAFELSYGQVTLKESGPALVKPTQTLTLTCTFSGFSLSTS GMGVGWIRQPPGKALEWLAHIWWDDDKYYNTSLKSRLTITKDTSKNQWLKM TNMDPVDTATYY C ARSF GY GLD YWGQGTL VTV S S (SEQ ID NO: 24) [0064] Also among the suitable light chain variable domains (VL) for use in the BAFF-R scFv of a dual CAR are the following heavy chain variable domains derived from monoclonal antibody Clone 90 (described in greater detail in PCT/US2017/036181). Of these, Hu55 LC-1, LC-2 and HC-3 are humanized.

[0065] Chi 55 LC:

MYRMQLLSCIALSLALVTNSDIQMTQTTSSLSASLGDRVTISCSASQDISNYLNW YQQKPDGTVKLLIYYTSSLHSGVPSRFSGSGSGTDYSLTISSLEPEDIATYYCHQFS ELP WTF GGGTKLEIKRT (SEQ ID NO: 25)

[0066] Hu55 LC-1 :

METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQASQDISNYLN WYQQKPGKAPKLLIYYTSSLHTGVPSRFSGSGSGTDYTFTISSLQPEDIATYYCHQ FSELPWTF GGGTKVEIKRTV (SEQ ID NO: 26)

[0067] Hu55 LC-2:

METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCSASQDISNYLNW YQQKPGKAPKLLIYYTS SLHTGVPSRFSGSGS GTD YTLTIS SLQPEDIATYY CHQF SELPWTF GGGTKVEIKRTV (SEQ ID NO: 27)

[0068] Hu55 LC-3:

METDTLLLWVLLLWVPGSTGDIQMTQSPSSLSASVGDRVTITCQASQDISNYLN WYQQKPGKTPKLLIYYTS SLHTGVPSRFSGS GSGTD YTLTIS SLQPEDIATYY CHQ FSELPWTF GGGTKVEIKRTV (SEQ ID NO: 28)

[0069] The VH and VL domains of the BAFF-R scFv can be modified. Thus, each of Hu90 LC-1, Hu90 LC-2, Hu90 LC-3, Hu90 HC-1, Hu90 HC-2 and Hu90 HC-3, Hu55 LC-1, Hu55 LC-2, Hu55 LC-3, Hu55 HC-1, Hu55 HC-2 and Hu90 HC-3 in a scFv can include 1, 2, 3, 4 or 5 single amino acid substitutions. In some cases, the substitutions are confined to the framework regions (FRs) rather than the CDRs. In some cases, the substitutions are conservative substitutions.

[0070] The position of CDRs and FRs may be defined by the Rabat numbering system (Rabat et al, Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, U.S. Government Printing Office (1991)). Likewise, the positions occupied by individual residues within the light or the heavy chain of an antibody may be defined by the Kabat numbering system. Therefore, the location of residues required for binding within a humanized light chain and a humanized heavy chain of a humanized antibody may be defined by the position of the residue according to the Kabat numbering system as is well known in the art. As described above, a humanized antibody may be an antibody having CDRs from a donor antibody (e.g. mouse) and variable region framework (FR) from a human antibody. The framework regions (FRs) are said to hold the CDRs in place in a humanized antibody. Proceeding from the amino-terminus, these regions are designated FR LI, FR L2, FR L3, and FR L4 for the light chain and FR HI, FR H2, FR H3, and FR H4, for the heavy chain, respectively.

CD 19 scFv Sequences

[0071] A variety of scFv targeting CD19 can be used in BAFF-R/CD19 dual CAR.

[0072] FMC63 scFv: IPDIQMTQTTSSLSASLGDRVTISCRASQDISKYLNWYQQ KPDGTVKLLI YHTSRLHSGV P SRF S GS GS GTD YSLTISNLEQEDIAT YF C Q Q GNTLP YTF GGGTKLEIT GS TS GS GKPGS GEGS TKGEVKLQE S GP GL V A PSQSLSVTCT VSGVSLPDYG V S WIRQPPRKGLEWLGVIWGSETTYYNS AL KSRLTIIKDN SKSQVFLKMN SLQTDDTAIYYCAKHYYYGGSYAMDYWGQG TSVTVSS (SEQ ID NO: 29).

[0073] FMC63 VL: DIQMTQTTSSLSASLGDRVTISCRASQDISKYLNWYQQ KPDGTVKLLIYHTSRLHS GVPSRFSGS GSGTD Y SLTISNLEQEDIATYF C QQGNTLPYTF GGGTKLEIT (SEQ ID NO: 30).

[0074] FMC63 VH: EVK LQESGPGLVAPSQSLSVTCTVSGVSLPDYG

VS WIRQPPRKGLEWLGVIWGSETTYYNS ALKSRLTIIKDN SKS QVFLKMN SLQTDDTAIYYCAKHYYYGGSYAMDYWGQGTSVTVSS (SEQ ID NO: 31).

[0075] Additional scFv that bind CD19 are described in US 2016/0152723 and in WO 2016/033570 Spacer Region

[0076] The dual CAR and bicistronic CAR described herein can include a spacer located between the targeting domain (e.g., the scFv) and the transmembrane domain. A variety of different spacers can be used. Some of them include at least portion of a human Fc region, for example a hinge portion of a human Fc region or a CH3 domain or variants thereof. Table 1 below provides various spacers that can be used in the CARs described herein.

Table 1: Examples of Spacers

[0077] Some spacer regions include all or part of an immunoglobulin (e.g., IgGl, IgG2, IgG3, IgG4) hinge region, i.e., the sequence that falls between the CHI and CH2 domains of an immunoglobulin, e.g., an IgG4 Fc hinge or a CD8 hinge. Some spacer regions include an immunoglobulin CH3 domain or both a CH3 domain and a CH2 domain. The immunoglobulin derived sequences can include one or more amino acid modifications, for example, 1, 2, 3, 4 or 5 substitutions, e.g., substitutions that reduce off-target binding.

[0078] The hinge/linker region can also comprise a IgG4 hinge region having the sequence ESKYGPPCPSCP (SEQ ID NO:34) or ESKYGPPCPPCP (SEQ ID NO:33).

[0079] The hinge/linger region can also comprise the sequence ESKYGPPCPPCP (SEQ ID NO:33) followed by the linker sequence GGGSSGGGSG (SEQ ID NO:32) followed by IgG4 CH3 sequence

GQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTT PPVLDSDGSFFLYSRLTVDKSRWQEGNYFSCSVMHEALHNHYTQKSLSLSLGK

(SEQ ID NO:41). Thus, the entire linker/spacer region can comprise the sequence:

ESKY GPPCPPCPGGGS S GGGS GGQPREPQ VYTLPPS QEEMTKN Q V SLT CLVKGF Y PSDI AVEWESN GQPENNYKTTPP VLD SDGSFFLY SRLTVDKSRW QEGNVF S C S V MHEALHNHYTQKSLSLSLGK (SEQ ID NO: J. In some cases, the spacer has 1,2, 3, 4, or 5 single amino acid changes (e.g., conservative changes) compared to SEQ ID NO: _ .

In some cases, the IgG4 Fc hinge/linker region that is mutated at two positions (L235E; N297Q) in a manner that reduces binding by Fc receptors (FcRs).

Transmembrane Domain

[0080] A variety of transmembrane domains can be used in the dual CAR and biscistonic CAR described herein. Table 2 includes examples of suitable transmembrane domains. Where a spacer region is present, the transmembrane domain is located carboxy terminal to the spacer region.

Table 2: Examples of Transmembrane Domains

Costimulatory and CD3zeta Domain

[0081] The costimulatory domain can be any domain that is suitable for use with a Oϋ3z signaling domain. In some cases, the costimulatory domain is a CD28 costimulatory domain that includes a sequence that is at least 90%, at least 95%, at least 98% identical to or identical to: RSKRSRGGHSD YMNMTPRRPGPTRKHY QP Y APPRDF AA YRS (SEQ ID NO: 52; LL to GG amino acid change double underlined). In some cases, the CD28 co-signaling domain has 1, 2, 3, 4 of 5 amino acid changes (preferably

conservative and preferably not in the underlined GG sequence) compared to SEQ ID NO:23. In some cases the co-signaling domain is a 4-1BB co-signaling domain that includes a sequence that is at least 90%, at least 95%, at least 98% identical to or identical to: KRGRKKLLYIFKQPFMRPVQTTQEEDGCSCRFPEEEEGGCEL (SEQ ID NO:54). In some cases, the 4-1BB co-signaling domain has 1, 2, 3, 4 or 5 amino acid changes (preferably conservative) compared to SEQ ID NO:24. [0082] The costimulatory domain(s) are located between the transmembrane domain and the Oϋ3z signaling domain. Table 3 includes examples of suitable costimulatory domains together with the sequence of the Oϋ3z signaling domain.

Table 3:€ϋ3z Domain and Examples of Costimulatory Domains

[0083] In various embodiments: the costimulatory domain is selected from the group consisting of: a costimulatory domain depicted in Table 3 or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications, a CD28 costimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications, a 4-1BB costimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications and an 0X40 costimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid

modifications. In certain embodiments, a 4-1BB costimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications in present. In some

embodiments there are two costimulatory domains, for example a CD28 co-stimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications (e.g., substitutions) and a 4-1BB co-stimulatory domain or a variant thereof having 1-5 (e.g., 1 or 2) amino acid modifications (e.g., substitutions). In various embodiments the 1-5 (e.g., 1 or 2) amino acid modification are substitutions. The costimulatory domain is amino terminal to the Oϋ3z signaling domain and in some cases a short linker consisting of 2 - 10, e.g., 3 amino acids (e.g., GGG) is positioned between the costimulatory domain and the Oϋ3z signaling domain.

CD3C Signaling Domain

[0084] The Oϋ3z Signaling domain can be any domain that is suitable for use with a Oϋ3z signaling domain. In some cases, the Oϋ3z signaling domain includes a sequence that is at least 90%, at least 95%, at least 98% identical to or identical to:

RVKF SRS AD AP A YQQ GQN QLYNELNLGRREE YD VLDKRRGRDPEMGGKPRRK NPQEGLYNELQKDKMAEAYSEIGMKGERRRGKGHDGLYQGLSTATKDTYDAL HMQALPPR (SEQ ID NO: 51). In some cases, the Oϋ3z signaling has 1 , 2, 3, 4 of 5 amino acid changes (preferably conservative) compared to SEQ ID NO: 51.

Truncated EGFR

[0085] The Oϋ3z signaling domain can be followed by a ribosomal skip sequence (e.g., LEGGGEGRGSLLTCGDVEENPGPR; SEQ ID NO: 56) and a truncated EGFR having a sequence that is at least 90%, at least 95%, at least 98% identical to or identical to: LVTSLLLCELPHPAFLLIPRKVCNGIGIGEFKDSLSINATNIKHFKNCTSISGDLHIL PVAFRGDSFTHTPPLDPQELDILKTVKEITGFLLIQAWPENRTDLHAFENLEIIRGR TKQHGQFSLAWSLNITSLGLRSLKEISDGD VIIS GNKNLCY ANTINWKKLFGTSG QKTKIISNRGEN S CKAT GQ V CHALCSPEGC W GPEPRDC V S CRNV SRGREC VDKC NLLEGEPREFVENSECIQCHPECLPQAMNITCTGRGPDNCIQCAHYIDGPHCVKT CP AGVMGENNTL VWKY AD AGHV CHLCHPNCTYGCTGPGLEGCPTN GPKIP SI A TGMV GALLLLLWALGIGLFM (SEQ ID NO: 57). In some cases, the truncated EGFR has 1 , 2, 3, 4 of 5 amino acid changes (preferably conservative) compared to SEQ ID NO:57.

[0086] An amino acid modification refers to an amino acid substitution, insertion, and/or deletion in a protein or peptide sequence. An“amino acid substitution” or "substitution" refers to replacement of an amino acid at a particular position in a parent peptide or protein sequence with another amino acid. A substitution can be made to change an amino acid in the resulting protein in a non-conservative manner (i.e., by changing the codon from an amino acid belonging to a grouping of amino acids having a particular size or characteristic to an amino acid belonging to another grouping) or in a conservative manner (i.e., by changing the codon from an amino acid belonging to a grouping of amino acids having a particular size or characteristic to an amino acid belonging to the same grouping). Such a conservative change generally leads to less change in the structure and function of the resulting protein. The following are examples of various groupings of amino acids: 1) Amino acids with nonpolar R groups: Alanine, Valine, Leucine, Isoleucine, Proline, Phenylalanine, Tryptophan, Methionine; 2) Amino acids with uncharged polar R groups: Glycine, Serine, Threonine, Cysteine, Tyrosine, Asparagine, Glutamine; 3) Amino acids with charged polar R groups (negatively charged at pH 6.0): Aspartic acid, Glutamic acid; 4) Basic amino acids (positively charged at pH 6.0): Lysine, Arginine, Histidine (at pH 6.0). Another grouping may be those amino acids with phenyl groups: Phenylalanine, Tryptophan, and Tyrosine.

[0087] The CAR can include a sequence that is at least 90%, at least 95%, at least 98% identical to or identical to the mature amino acid sequence depicted in FIG 9 (SEQ ID Nos: 29-40), either including or excluding the GMCSFRa signal sequence and either including or excluding the T2A ribosomal skip sequence and the truncated EGFRt).

[0088] In some cases, the CAR can be produced using a vector in which the CAR open reading frame is followed by a T2A ribosome skip sequence and a truncated EGFR (EGFRt), which lacks the cytoplasmic signaling tail. In this arrangement, co-expression of EGFRt provides an inert, non-immunogenic surface marker that allows for accurate measurement of gene modified cells, and enables positive selection of gene-modified cells, as well as efficient cell tracking of the therapeutic T cells in vivo following adoptive transfer. Efficiently controlling proliferation to avoid cytokine storm and off- target toxicity is an important hurdle for the success of T cell immunotherapy. The EGFRt incorporated in the CAR lentiviral vector can act as suicide gene to ablate the CAR+ T cells in cases of treatment-related toxicity.

[0089] The CAR described herein can be produced by any means known in the art, though preferably it is produced using recombinant DNA techniques. Nucleic acids encoding the several regions of the chimeric receptor can be prepared and assembled into a complete coding sequence by standard techniques of molecular cloning known in the art (genomic library screening, overlapping PCR, primer-assisted ligation, site-directed mutagenesis, etc.) as is convenient. The resulting coding region is preferably inserted into an expression vector and used to transform a suitable expression host cell line, preferably a T lymphocyte cell line, and most preferably an autologous T lymphocyte cell line.

[0090] Various T cell subsets isolated from the patient can be transduced with a vector for CAR expression. Central memory T cells are one useful T cell subset. Central memory T cell can be isolated from peripheral blood mononuclear cells (PBMC) by selecting for CD45RO+/CD62L+ cells, using, for example, the CliniMACS® device to immunomagnetically select cells expressing the desired receptors. The cells enriched for central memory T cells can be activated with anti-CD3/CD28, transduced with, for example, a lentiviral vector that directs the expression of the CAR as well as a non- immunogenic surface marker for in vivo detection, ablation, and potential ex vivo selection. The activated/genetically modified central memory T cells can be expanded in vitro with IL-2/IL-15 and then cryopreserved.

Example 1 : Preparation of T Cell Populations for Expression of Dual CAR

[0091] The following T cell populations can be prepared for expression of BAFF-CD19 dual CAR: CD4+ naive T cells (CD4+ T _N ), CD8+ naive T cells (CD8+ T _N ), CD8+ central memory T cells (CD8+ TCM), CD8+ memory stem cells (CD8+ MSC) and Pan T cells (Pan T). Briefly, 5 mL of a blood sample are added to 5 mL histopaque-1077 (Sigma Aldrich). The mixture is centrifuged for 20 min at 2500 RPM (room temperature (RT), no brake). The middle peripheral blood mononuclear cell (PBMC) layer is collected, washed with 50 mL PBS (Corning), centrifuged for 5 min at 1500 RPM (RT). The collected cells are combined withlO mL RBC lysis buffer (Qiagen) and incubated for 7 min. The cells are then washed with PBS and centrifuged for 5 min (1500 RPM, RT).

[0092] Various T cell populations can be prepared using the following kits available from StemCell Technologies, Inc. using the manufacturer’s instructions: EasySep™ Human Naive CD4+ T Cell Enrichment Kit (CD4+ TN), EasySep™ Human Naive CD8+ T Cell Enrichment Kit (CD8+ TN), and EasySep™ Human T Cell Enrichment Kit (Pan T). CD8+ TCM can be prepared by isolating CD8+ T cells using the EasySep™ Human CD8+ T Cell Enrichment Kit from StemCell Technologies, Inc. using the manufacturer’s instructions and then stained with: CD8-PerCP-Cy5.5, CD45 RO-APC, and CD62L-PE. The stained cells are then sorted to isolate CD8+/CD45+/CD62L+ triple positive cells. CD8+ memory stem cells (CD8+ MSC) can be generated from CD8+ TN using the culture conditions shown in Table 4. The other T cell populations can be cultured as indicated in Table 4.

Example 2: Sequence of BAEF-R/CD19 Dual CAR

[0093] A variety of BAFF-R/CD19 dual CAR were prepared. The 1250 dual CAR (SEQ ID NO:59) includes, from amino to carboxy terminus: a BAFF-R scFv, a linker, a CD19 scFv (derived from FMC63), an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4 IBB cytoplasmic domain, a GGG linker, and a CD3 zeta signaling domain. (FIGURE 2). The 1296 dual CAR (SEQ ID NO:61) includes, from amino to carboxy terminus: a CD19 scFv (derived from FMC63), a linker, a BAFF-R scFv, an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 41BB cytoplasmic domain, a GGG linker, and a CD3 zeta signaling domain (FIGURE 3). The 1316 dual CAR (SEQ ID NO:63) includes, from amino to carboxy terminus: a CD19 VL (derived from FMC63), a GGGS linker, a BAFF-R scFv, a CD19 VH (derived from FMC63), an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4 IBB cytoplasmic domain, a GGG linker, and a CD3 zeta signaling domain. [0094] A biscitronic CAR expresses a BAFF-R CAR and a CD 19 CAR using the lentiviral vector. The two CAR are expressed in the same T cell. The mature CD 19 CAR (SEQ ID NO:65) can include, from amino to carboxy terminus: a CD19 scFv (derived from FMC63), an IgG4 (SmP/L235E,N297Q) spacer domain, a CD28 transmembrane domain, a CD28(GG) cytoplasmic domain, a GGG linker, and a CD3 signaling domain. The mature BAFF-R CAR (SEQ ID NO:67) can include, from amino to carboxy terminus: a BAFF-R scFv, an IgG4 (SmP/L235E,N297Q) spacer domain, a CD4 transmembrane domain, a 4- IBB cytoplasmic domain, a GGG linker, and a CD3 signaling domain.

Example 2: Preparation of Lentiviral Vectors Expressing BAFF-R/CD19 Dual CAR

[0095] FIGURE 5 is a schematic diagram of the lentiviral vector used to express 1250 dual CAR. The 1296 dual CAR, and the 1316 dual CAR were produced using similar lentiviral vectors (with replacement of the svFv portion).

Example 3: Preparation of CAR Expressing Cells

[0096] Cells were activated in preparation for transduction with lenitviral vectors expressing a dual CAR by combining the cells with CD3/CD28 human T-cell activation beads (Thermo Fisher) at a 1 : 1 bead to cell ratio and incubating overnight (humidified,

5% CO2, 37 °C). After incubation, the cells were counted and distributed 1 x 10 ⁶ cell/well in a 48-well plate. Cells were infected at an MOI of 1. In each case the total culture media was supplemented to 250 pL, centrifuged for 30 min (800 g, RT). Cells are incubated overnight (humidified, 5% CO2, 37 °C) and then cultured for 10 days in the media indicated in Table 1. Cultures of CD4+ TN, CD8+ TN, CD8+ TCM, and Pan T cells included CD3/CD28 beads at a 1 : 1 cell to bead ratio. The culture of CD8+ T MSC did not include CD3/CD28 beads. Expression of the CAR was assessed by the percentage of GFP positive cells using flow cytometry.

[0097] Example 4: Expression of CAR

[0098] T cells (Jurkat) were transduced with each CAR construct or an empty vector. To assess expression of the CAR, cells were stained with Protein L- or EGFR-APC conjugated antibodies. Protein L targets the variable light chain of the scFv, and truncated EGFR is co-expressed by the CAR vector. Constructs that were able to properly express dual CARs were further examined. As can be seen in FIGURE 7, Dual CAR 1296 and dual CAR 1316 expressed intact CAR and EGFRt selection marker, whereas dual CAR 1250 failed to express intact CAR.

[0099] Example 5: In Vitro Cell Killing by BAFF-R Targeted CAR T Cells

[00100] An in vitro assay using various T cell populations expressing 1296 Dual CAR, 1316 Dual CAR, CD 19 CAR or BAFF-R CAR cells. Target cell line Nalm-6 (WT, CD 19 knockout, or BAFF-R knockout variants) were labeled with chromium-31 and incubated with effector CAR T cells. CARs included BAFF-R/CD19 dual-targeting CARs: 1296 and 1316; single-targeting CARs: BAFF-R CAR and CD19 CAR. Non- transduced T cells (non-CAR) were used as an allogeneic control. All T cells were derived from a single healthy donor. Chromium released by target cells due to effector T cell function was measured by a gamma counter and calculated as a percentage of maximum possible release. As can be seen in FIGURE 8, 1250 dual CAR failed to elicit response against BAFF-R-positive L cells suggesting BAFF-R-targeting scFv is not properly expressed.

[00101] Example 6: BAFF-R- and CD 19-deficient Murine Model

[00102] Nalm-6 B-ALL tumor line was gene edited with CRISPR to knockout

BAFF-R or CD19. Surface protein expression was confirmed by FACS staining with commercial BAFF-R and CD19 antibodies. Nalm-6 wild-type (WT) was used as controls. As shown in FIGURE 9, FACS analysis confirms the knockout.

[00103] Example 7: CTL Function of Dual CAR T Cells

[00104] In this study, the results of which are shown in FIGURE 10, target cell lines Nalm-6, WT, CD19 knockout, or BAFF-R knockout variants, were labeled with chromium-51 and incubated with effector CAR T cells. CARs included BAFF-R/CD19 dual-targeting CARs. The 1250 dual CAR CTL data suggests potential BAFF-R targeting deficiency. [00105] Example 8: Activity of BAFF-R/CD19 Dual CAR in BAFF-R-positive CD 19-negative mixed B-AFF tumor

[00106] FIGURE 11A-11B shows the results of a study examining the impact of 1316 Dual CAR and 1296NSG mice following IV tumor challenge on day 0 with a mixture of 1 x 10 ⁵ RFP-negative, luciferase-expressing Nalm-6-CD19KO plus 2.5 x 10 ⁵ RFP-positive, luciferase-expressing Nalm-6-BAFF-RKO tumor cells. Groups of 5 tumor bearing mice each were then randomly assigned to treatment with either 2.5 x 10 ⁶ CD4 TN CAR-T + 10 ⁶ CD8 TN 1296 or 1316 dual CAR T cells/mouse IV on day 10, as a single infusion. Non-transduced CD4/CD8 T cells from the same donor were used as allogeneic controls (non-CAR). As can be seen, 1316 treatment conferred significant prolonged survival compared to 1296 treatment.

[00107] Example 9: Degranulation of 1316 BAFF-R/CD19 Dual CAR against knock-out tumors

[00108] A CD 107a degranulation was used to assess Dual CAR 1316 potency against knockout tumors. CD4 or CD8 BAFF-R CAR T cells were incubated with either CD19 BAFF-R ⁺ Nalm-6 or CD! 9 BAFF-R- Nalm-6 lines. Single targeting CD 19 or BAFF-R CAR T cells were used as controls.

[00109] Example 10: Activity of TN/MEM 1316 BAFF-R/CD19 Dual CAR in mixed B-AFF tumor

[00110] NSG mice were challenged on day 0 with a mixture of 1 x 105 RFP- negative, luciferase-expressing Nalm-6-CD19KO plus 1 x 105 RFP-positive, luciferase- expressing Nalm-6-BAFF-RKO tumor cells. Groups of 5 tumor-bearing mice each were then randomly assigned to treatment with 1316 dual CAR T cells/mouse IV on day 9, as a single infusion of either low dose (2.8 x 106 TN/MEM), high dose (5.6 x 106 TN/MEM), which yielded 1 x 106 and 2 x 106 BAFF-R CAR T cells, respectively.2.5 or 5 x 106 non-transduced TN/MEM cells from the same donor were used as allogeneic controls (non-CAR). 1316 Dual CAR conferred significant prolonger survival. No significant difference in survival between the two dosing were observed.