IMMU-31. QUANTITATIVE EVALUATION OF ROUTES OF ADMINISTRATION OF IMMUNOTHERAPEUTIC T CELLS TO ORTHOTOPIC GLIOMA

Abstract SIGNIFICANCE Adoptive T cell therapy (ACT) has emerged as the most effective treatment against advanced malignant melanoma, eliciting remarkable objective clinical responses in up to 75% of patients with refractory metastatic disease, including within the central nervous system. Immunologic surrogate endpoints correlating with treatment outcome have been identified in these patients, with clinical responses being dependent on the migration of transferred T cells to sites of tumor growth. OBJECTIVE We investigated the biodistribution of intravenously or intraventricularly administered T cells in a murine model of glioblastoma at whole body, organ, and cellular levels. METHODS gp100-specific T cells were isolated from the spleens of pmel DsRed transgenic C57BL/6 mice and injected intravenously or intraventricularly, after in vitro expansion and activation, in murine KR158B-Luc-gp100 glioma-bearing mice. To determine transferred T cell spatial distribution, the brain, lymph nodes, heart, lungs, spleen, liver, and kidneys of mice were processed for 3D imaging using light-sheet and multiphoton imaging. ACT T cell quantification in various organs was performed ex vivo using flow cytometry, 2D optical imaging (IVIS), and magnetic particle imaging (MPI) after ferucarbotran nanoparticle transfection of T cells. T cell biodistribution was also assessed in vivo using MPI. RESULTS Following T cell intravenous injection, the spleen, liver, and lungs accounted for more than 90% of transferred T cells; the proportion of DsRed T cells in the brains was found to be very low, hovering below 1%. In contrast, most ACT T cells persisted in the tumor-bearing brains following intraventricular injections. ACT T cells mostly concentrated at the periphery of tumor masses and in proximity to blood vessels. CONCLUSIONS The success of ACT immunotherapy for brain tumors requires optimization of delivery route, dosing regimen, and enhancement of tumor-specific lymphocyte trafficking and effector functions to achieve maximal penetration and persistence at sites of invasive tumor growth.

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Dendritic cells transduced by multiply deleted HIV-1 vectors exhibit normal phenotypes and functions and elicit an HIV-specific cytotoxic T-lymphocyte response in vitro

Blood ◽

10.1182/blood.v96.4.1327 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1327-1333 ◽

Cited By ~ 105

Author(s):

Andreas Gruber ◽

June Kan-Mitchell ◽

Kelli L. Kuhen ◽

Tetsu Mukai ◽

Flossie Wong-Staal

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Ex Vivo ◽

T Cell Response ◽

Adoptive T Cell Therapy ◽

Cytotoxic T Cell ◽

T Cell Therapy ◽

Hiv 1

Abstract Dendritic cells (DCs) genetically modified to continually express and present antigens may be potent physiologic adjuvants for induction of prophylactic or therapeutic immunity. We have previously shown that an env and nef deleted HIV-1 vector (HIV-1ΔEN) pseudotyped with VSV-G transduced monocyte-derived macrophages as well as CD34+ precursors of DCs. Here we extended these findings with HIV-1ΔEN to highly differentiated human DCs derived in culture from circulating monocytes (DCs). In addition, a new vector derived from HIV-1ΔEN but further deleted in its remaining accessory genes vif, vpr, and vpu(HIV-1ΔEN V3) was also tested. Both vectors efficiently transduced DCs. Transduction of DCs did not significantly alter their viability or their immunophenotype when compared with untransduced DCs. Furthermore, the phagocytic potential of immature DCs, as well as their ability to differentiate into mature DCs capable of stimulating T-cell proliferation, was not affected. Finally, DCs transduced by the HIV-1ΔEN vector were able to elicit a primary antiviral cytotoxic T-cell response in autologous CD8 T cells. These results suggest that HIV-1–based vectors expressing viral antigens may be useful for in vivo active immunization as well as ex vivo priming of cytotoxic T cells for adoptive T-cell therapy.

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Dendritic cells transduced by multiply deleted HIV-1 vectors exhibit normal phenotypes and functions and elicit an HIV-specific cytotoxic T-lymphocyte response in vitro

Blood ◽

10.1182/blood.v96.4.1327.h8001327_1327_1333 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1327-1333 ◽

Cited By ~ 1

Author(s):

Andreas Gruber ◽

June Kan-Mitchell ◽

Kelli L. Kuhen ◽

Tetsu Mukai ◽

Flossie Wong-Staal

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Ex Vivo ◽

T Cell Response ◽

Adoptive T Cell Therapy ◽

Cytotoxic T Cell ◽

T Cell Therapy ◽

Hiv 1

Dendritic cells (DCs) genetically modified to continually express and present antigens may be potent physiologic adjuvants for induction of prophylactic or therapeutic immunity. We have previously shown that an env and nef deleted HIV-1 vector (HIV-1ΔEN) pseudotyped with VSV-G transduced monocyte-derived macrophages as well as CD34+ precursors of DCs. Here we extended these findings with HIV-1ΔEN to highly differentiated human DCs derived in culture from circulating monocytes (DCs). In addition, a new vector derived from HIV-1ΔEN but further deleted in its remaining accessory genes vif, vpr, and vpu(HIV-1ΔEN V3) was also tested. Both vectors efficiently transduced DCs. Transduction of DCs did not significantly alter their viability or their immunophenotype when compared with untransduced DCs. Furthermore, the phagocytic potential of immature DCs, as well as their ability to differentiate into mature DCs capable of stimulating T-cell proliferation, was not affected. Finally, DCs transduced by the HIV-1ΔEN vector were able to elicit a primary antiviral cytotoxic T-cell response in autologous CD8 T cells. These results suggest that HIV-1–based vectors expressing viral antigens may be useful for in vivo active immunization as well as ex vivo priming of cytotoxic T cells for adoptive T-cell therapy.

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Melanoma reactive TCR-modified T cells generated without activation retain a less differentiated phenotype and mediate a superior in vivo response

Scientific Reports ◽

10.1038/s41598-021-92808-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Siao-Yi Wang ◽

Tamson V. Moore ◽

Annika V. Dalheim ◽

Gina M. Scurti ◽

Michael I. Nishimura

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Viral Vectors ◽

Cell Activation ◽

Adoptive T Cell Therapy ◽

In Vitro Assays ◽

T Cell Therapy

AbstractAdoptive T cell therapy with T cell receptor (TCR)-modified T cells has shown promise in treating metastatic melanoma and other malignancies. However, studies are needed to improve the efficacy and durability of responses of TCR-modified T cells. Standard protocols for generating TCR-modified T cells involve activating T cells through CD3 stimulation to allow for the efficient transfer of tumor-reactive receptors with viral vectors. T cell activation results in terminal differentiation and shortening of telomeres, which are likely suboptimal for therapy. In these studies, we demonstrate efficient T cell transduction with the melanoma-reactive TIL1383I TCR through culturing with interleukin 7 (IL-7) in the absence of CD3 activation. The TIL1383I TCR-modified T cells generated following IL-7 culture were enriched with naïve (TN) and memory stem cell populations (TSCM) while maintaining longer telomere lengths. Furthermore, we demonstrated melanoma-reactivity of TIL1383I TCR-modified cells generated following IL-7 culture using in vitro assays and a superior response in an in vivo melanoma model. These results suggest that utilizing IL-7 to generate TCR-modified T cells in the absence of activation is a feasible strategy to improve adoptive T cell therapies for melanoma and other malignancies.

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Melanoma-reactive TCR-modified T Cells Generated in the Absence of Activation Retain a Less-differentiated Phenotype and Have Increased Therapeutic Potential.

10.21203/rs.3.rs-238261/v1 ◽

2021 ◽

Author(s):

Siao-Yi Wang ◽

Tamson V. Moore ◽

Annika V. Dalheim ◽

Gina M. Scurti ◽

Michael I. Nishimura

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Viral Vectors ◽

Cell Activation ◽

Therapeutic Potential ◽

Adoptive T Cell Therapy ◽

T Cell Therapy

Abstract Adoptive T cell therapy with T cell receptor (TCR)-modified T cells has shown promise in treating metastatic melanoma and other malignancies. However, studies are needed to improve the efficacy and durability of responses of TCR-modified T cells. Standard protocols for generating TCR-modified T cells involve activating T cells through CD3 stimulation to allow for the efficient transfer of tumor-reactive receptors with viral vectors. T cell activation results in terminal differentiation and shortening of telomeres, which are likely suboptimal for therapy. In these studies, we demonstrate efficient T cell transduction with the melanoma-reactive TIL1383I TCR through culturing with interleukin 7 (IL-7) in the absence of CD3 activation. The TIL1383I TCR-modified T cells generated following IL-7 culture were enriched with naïve (TN) and memory stem cell populations (TSCM) while maintaining longer telomere lengths. Furthermore, we demonstrated melanoma-reactivity of TIL1383I TCR-modified cells generated following IL-7 culture using in vitro assays and a superior response in an in vivo melanoma model. These results suggest that utilizing IL-7 to generate TCR-modified T cells in the absence of activation is a feasible strategy to improve adoptive T cell therapies for melanoma and other malignancies.

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An inducible caspase 9 safety switch for T-cell therapy

Blood ◽

10.1182/blood-2004-11-4564 ◽

2005 ◽

Vol 105 (11) ◽

pp. 4247-4254 ◽

Cited By ~ 395

Author(s):

Karin C. Straathof ◽

Martin A. Pulè ◽

Patricia Yotnda ◽

Gianpietro Dotti ◽

Elio F. Vanin ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cell Therapy ◽

Adoptive T Cell Therapy ◽

Antigen Specificity ◽

Caspase 9 ◽

T Cell Therapy ◽

Human T Cell

Abstract The efficacy of adoptive T-cell therapy as treatment for malignancies may be enhanced by genetic modification of infused cells. However, oncogenic events due to vector/transgene integration, and toxicities due to the infused cells themselves, have tempered enthusiasm. A safe and efficient means of removing aberrant cells in vivo would ameliorate these concerns. We describe a “safety switch” that can be stably and efficiently expressed in human T cells without impairing phenotype, function, or antigen specificity. This reagent is based on a modified human caspase 9 fused to a human FK506 binding protein (FKBP) to allow conditional dimerization using a small molecule pharmaceutical. A single 10-nM dose of synthetic dimerizer drug induces apoptosis in 99% of transduced cells selected for high transgene expression in vitro and in vivo. This system has several advantages over currently available suicide genes. First, it consists of human gene products with low potential immunogenicity. Second, administration of dimerizer drug has no effects other than the selective elimination of transduced T cells. Third, inducible caspase 9 maintains function in T cells overexpressing antiapoptotic molecules. These characteristics favor incorporation of inducible caspase 9 as a safety feature in human T-cell therapies.

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EXTH-42. QUANTITATIVE BIODISTRIBUTION OF ADOPTIVELY TRANSFERRED T CELLS IN BRAIN TUMOR-BEARING MICE

Neuro-Oncology ◽

10.1093/neuonc/noz175.374 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi91-vi91

Author(s):

Lan Hoang-Minh ◽

Fernanda Pohl-Guimarães ◽

Angelie Rivera-Rodriguez ◽

Seth Currlin ◽

Kevin Otto ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Tumor Growth ◽

The Body ◽

Confocal Imaging ◽

Adoptive T Cell Therapy ◽

Whole Body ◽

Light Sheet Microscopy ◽

Tumor Bearing ◽

Clinical Responses

Abstract SIGNIFICANCE Adoptive T cell therapy (ACT) has emerged as the most effective treatment strategy against advanced malignant melanoma, eliciting remarkable objective clinical responses in up to 75% of patients with refractory metastatic disease, including those with lesions within the central nervous system. Importantly, immunologic surrogate endpoints that correlate with treatment outcome have been identified in these patients, with clinical responses being dependent on the migration of transferred T cells to sites of tumor growth. OBJECTIVE We investigated the biodistribution of exogenously administered T cells in a murine model of glioblastoma at whole body, organ, and cellular levels. METHODS T cells were isolated from the spleens of DsRed transgenic C57BL/6 mice and injected intravenously, after in vitro expansion and activation, in murine KR158B glioma-bearing mice. To determine transferred T cell spatial distribution, brains, lymph nodes, hearts, lungs, spleens, livers, kidneys and stomachs were isolated for active clearing, immunostaining, and 3D imaging using light sheet microscopy, or processed for fluorescent immunohistochemistry and confocal imaging. Transferred T cell quantification in various organs was performed using flow cytometry, 2D optical imaging (IVIS), and magnetic particle imaging (MPI) after ferucarbotran nanoparticle labeling. T cell distribution was also assessed in vivo using IVIS and MPI. RESULTS The spleen, liver, and lungs accounted for more than 90% of transferred T cells in the body. The proportion of DsRed T cells in tumor-bearing brains was found to be very low, hovering below 1% (and representing ~15% of total tumor-infiltrating lymphocytes). Transferred T cells mostly concentrated at the periphery of the tumor mass and in proximity to blood vessels. CONCLUSIONS The success of ACT immunotherapy for brain tumors likely requires optimization of delivery route, dosing regimen, and modification of tumor-specific lymphocyte trafficking and effector functions in order to achieve maximal penetration and persistence at sites of invasive tumor growth.

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Ex Vivo AKT Inhibition Promotes the Generation of Potent CD19CAR T Cells for Adoptive Immunotherapy

Blood ◽

10.1182/blood.v126.23.3086.3086 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3086-3086

Author(s):

Ryan Urak ◽

ChingLam Wong ◽

Wen-Chung Chang ◽

Elizabeth E. Budde ◽

Christine Brown ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Antitumor Activity ◽

Ex Vivo ◽

Akt Inhibitor ◽

T Cell Therapy ◽

Car T Cells ◽

Car T

Abstract Insufficient persistence and effector function of Chimeric Antigen Receptor (CAR) re-directed T cells in vivo has been a challenge for adoptive T cell therapy. Generation of long-lived potent CAR T cells is an increasing demand in the field. AKT activation triggered by convergent extracellular signals evokes a transcription program that enhances effector functions. However, sustained AKT activation severely impairs T cell memory and protective immunity because AKT drives differentiation of effectors, therefore diminishing T cell potential to survive and differentiate into memory cells. We now investigate whether inhibition of AKT signaling during ex vivo expansion can prevent terminal differentiation of CD19- chimeric antigen receptor (CD19 CAR) engineered T cells and increase the number of memory CD19 CAR T cells, which would enhance the antitumor activity following adoptive therapy. CD8+ T cells from healthy donors were isolated, activated with CD3/CD28 beads, and then transduced with a lentiviral vector encoding a second-generation CD19CAR containing a CD28 co-stimulatory domain and two mutations (L235E; N297Q) within the CH2 region on the IgG4-Fc spacers which enhances potency and persistence by blocking Fc receptor binding. In addition, the lentiviral construct also expresses a truncated human epidermal growth factor receptor (huEGFRt) which allows us to use as a selectable marker and a mechanism to ablate the CAR T cells if necessary. IL-2 (50U/mL) and AKT inhibitor (1uM/mL) were supplemented every other day. Transduced CD19CAR T cells without AKT inhibitor treatment were used as controls. The engineered CD19CAR T cells were expanded in vitro for 21 days before in vitro and in vivo analyses. We found that AKT inhibitor did not compromise the CD19CAR T cell proliferation and survival in vitro. There was a comparable CD19CAR T cell expansion after culturing in the presence or absence AKT inhibitor. Functionally, AKT inhibitor did not dampen the effector function of CD19CAR T cells as indicated by equivalent levels of interferon gamma production and CD107a expression upon CD19 antigen stimulation. Memory-like phenotype such as CD62L and CD28 expression on CAR T cells is associated with better antitumor activity in vivo. We therefore characterized the CD19CAR T cells after ex vivo expansion. We found that 40% of AKT-inhibited CD19CAR T cells expressed CD62L and co-expressed CD28. More importantly, no exhaustion markers such as KRLG and PD-1 were induced on the AKT inhibitor treated cells. In contrast, only 10% of control untreated CD19CAR T cells expressed CD62L and they were CD28 negative, indicating that AKT-inhibited CD19CAR T cells with higher levels of CD62L and CD28 expression may have superior anti-tumor activity following adoptive transfer. To test the potency of the AKT inhibitor treated CAR T cells, 0.5x106 CD19+ acute lymphoid leukemic cells (SupB15) engineered to express firefly luciferase were inoculated intravenously into NOD/Scid IL-2RgammaCnull (NSG) mice. Five days post tumor engraftment, 2x106 CD8+ CD19CAR T cells were intravenously injected into tumor bearing mice. Control mice received either no T cells, non-transduced T cells (Mock), or CD19CAR T cells that were not treated with AKT inhibitor during in vitro expansion. Tumor signals post T cell infusion were monitored by biophotonic imaging. Compared to the untreated CD19CAR T cells, which exhibited lower and transient anti-tumor activity, AKT inhibitor treated CD19CAR T cells completely eradicated the CD19+ tumor in all mice (Figure 1) 21 days post CD19CAR T cell infusion. In conclusion, our results demonstrate that inhibition of AKT signaling during the ex vivo priming and expansion gives rise to a CD19CAR T cell population that possesses superior antitumor activity. These findings suggest that ex vivo therapeutic modulation of AKT might be a strategy to augment antitumor immunity for adoptive CAR T cell therapy, which could easily be transitioned into the clinic with the availability of pharmaceutical grade AKT inhibitor. Disclosures Forman: Amgen: Consultancy; Mustang: Research Funding.

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Exceptionally Potent Cytotherapy Using T Cells Armed with Novel Tetravalent Recombinant Bispecific Antibodies Specific for GD2 and HER2

Blood ◽

10.1182/blood-2018-99-120210 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4536-4536

Author(s):

Jeong A Park ◽

Hong Xu ◽

Brian Santich ◽

Nai-Kong V. Cheung

Keyword(s):

T Cells ◽

T Cell ◽

Chimeric Antigen Receptor ◽

Interleukin 2 ◽

Antigen Receptor ◽

Adoptive T Cell Therapy ◽

Bispecific Antibodies ◽

T Cell Therapy

Abstract Introduction: T-cell based therapies have emerged as one of the major breakthroughs in anticancer treatment: Immune checkpoint inhibitors, chimeric antigen receptor gene-modified T-cells (CAR-T-cells), and T-cell engaging bispecific antibodies (BsAb) are leading the advances. In the era of personalized medicine, T-cells offer alternative strategies to overcome resistance to chemotherapy or small molecules. Yet, hurdles for such therapy can be crippling, such as inability of T cells to infiltrate "cold tumors", cytokine release syndrome following T cell-based therapies, neurologic toxicity, and on-target off-tumor effects. To address these hurdles, polyclonal T-cells armed with GD2xCD3 or HER2xCD3 BsAb for cytotherapy hold promise. Ganglioside GD2 and HER2 are tumor associated surface antigens expressed in a broad spectrum of aggressive malignancies, while being restricted in normal tissues. Phase I trials of T-cells armed with a chemical conjugate of hu3F8 x mouse OKT3 (NCT02173093) or trastuzumab x mouse OKT3 (NCT00027807) demonstrated the safety of 160 x 106/kg/injection x 8 doses (or 1.28 x 109/cycle) with suggestion of clinical benefit. Here, we report the safety and efficacy of adoptive T-cell therapy armed with the recombinant forms of these BsAb for the treatment of GD2(+) and/or HER2(+) tumors in preclinical models. Methods: Recombinant anti-GD2 BsAb and anti-HER2 BsAb were made using the IgG(L)-scFv platform (Can Immunol Res, 3:266, 2015, Oncoimmunology, PMID:28405494). T-cells from normal volunteer donors were isolated, activated and expanded by CD3/CD28 beads in the presence of 100 IU/mL of interleukin 2 (IL-2). Between day 7 and day 14, activated T cells (ATCs) were harvested and armed for 20 minutes at room temperature with -GD2-BsAb or HER2-BsAb. After washing, armed ATCs were tested for cell surface density of BsAb and antibody dependent T cell mediated cytotoxicity (ADTC) in vitro. In vivo anti-tumor potencies of armed T cells were tested against GD2(+) or HER2(+) cell lines or patient derived xenografts (PDXs) in BALB-Rag2-/-IL-2R-γϲ-KO (DKO) mice. Results: GD2-BsAb of the IgG(L)-scFv form showed superior potency over other bispecific platforms in vitro and in vivo. GD2-BsAb or HER2-BsAb armed ATCs showed potent antigen-specific cytotoxicity against GD2 or HER2 positive tumors such as neuroblastoma, melanoma and osteosarcoma in vitro over a range of antibody dose (5 to 500 ng/106 cells). Optimal arming per T cell required 25,000 to 45,000 idiotype(+) molecules. There was no evidence of activation induced cell death when confronted by antigen or tumor target. In vivo GD2-BsAb or HER2-BsAb armed ATCs could ablate neuroblastoma, malignant melanoma, and osteosarcoma tumors over a range of cell doses (10x106, 20x106 and 40x106 per injection, one to three times a week for 2 to 4 weeks) with a range of BsAb doses (5 ng to 500 ng/million of T-cells) without significant toxicities in DKO mice. By immunohistochemistry, the frequency of tumor infiltrating CD3(+) T-cells strongly correlated with tumor response. Conclusions: Using the IgG(L)-scFv format, GD2-BsAb or HER2-BsAb armed ATCs could provide a potent and economical cytotherapy platform against GD2(+) or HER2(+) tumors without the complexity of gene modification (as in chimeric antigen receptor modified T cells). At such low arming doses, where BsAb is T cell bound, where ADTC is not induced, and T cell expansion is not required for anti-tumor effect, clinical toxicity is expected to be low. Disclosures Cheung: Ymabs: Patents & Royalties.

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627 The DLL3-targeted half-life extended bispecific T cell engager (HLE BiTE®) immune-oncology therapy AMG 757 has potent antitumor activity in neuroendocrine cancer

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-sitc2020.0627 ◽

2020 ◽

Vol 8 (Suppl 3) ◽

pp. A663-A663

Author(s):

Keegan Cooke ◽

Juan Estrada ◽

Jinghui Zhan ◽

Jonathan Werner ◽

Fei Lee ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Tumor Growth ◽

Mouse Models ◽

T Cell Activation ◽

Phase 1 ◽

Phase 1 Study ◽

Human T Cells

BackgroundNeuroendocrine tumors (NET), including small cell lung cancer (SCLC), have poor prognosis and limited therapeutic options. AMG 757 is an HLE BiTE® immune therapy designed to redirect T cell cytotoxicity to NET cells by binding to Delta-like ligand 3 (DLL3) expressed on the tumor cell surface and CD3 on T cells.MethodsWe evaluated activity of AMG 757 in NET cells in vitro and in mouse models of neuroendocrine cancer in vivo. In vitro, co-cultures of NET cells and human T cells were treated with AMG 757 in a concentration range and T cell activation, cytokine production, and tumor cell killing were assessed. In vivo, AMG 757 antitumor efficacy was evaluated in xenograft NET and in orthotopic models designed to mimic primary and metastatic SCLC lesions. NSG mice bearing established NET were administered human T cells and then treated once weekly with AMG 757 or control HLE BiTE molecule; tumor growth inhibition was assessed. Pharmacodynamic effects of AMG 757 in tumors were also evaluated in SCLC models following a single administration of human T cells and AMG 757 or control HLE BiTE molecule.ResultsAMG 757 induced T cell activation, cytokine production, and potent T cell redirected killing of DLL3-expressing SCLC, neuroendocrine prostate cancer, and other DLL3-expressing NET cell lines in vitro. AMG 757-mediated redirected lysis was specific for DLL3-expressing cells. In patient-derived xenograft and orthotopic models of SCLC, single-dose AMG 757 effectively engaged human T cells administered systemically, leading to a significant increase in the number of human CD4+ and CD8+ T cells in primary and metastatic tumor lesions. Weekly administration of AMG 757 induced significant tumor growth inhibition of SCLC (figure 1) and other NET, including complete regression of established tumors and clearance of metastatic lesions. These findings warranted evaluation of AMG 757 (NCT03319940); the phase 1 study includes dose exploration (monotherapy and in combination with pembrolizumab) and dose expansion (monotherapy) in patients with SCLC (figure 2). A study of AMG 757 in patients with neuroendocrine prostate cancer is under development based on emerging data from the ongoing phase 1 study.Abstract 627 Figure 1AMG 757 Significantly reduced tumor growth in orthotopic SCLC mouse modelsAbstract 627 Figure 2AMG 757 Phase 1 study designConclusionsAMG 757 engages and activates T cells to kill DLL3-expressing SCLC and other NET cells in vitro and induces significant antitumor activity against established xenograft tumors in mouse models. These preclinical data support evaluation of AMG 757 in clinical studies of patients with NET.Ethics ApprovalAll in vivo work was conducted under IACUC-approved protocol #2009-00046.

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98 ATA3271: an armored, next-generation off-the-shelf, allogeneic, mesothelin-CAR T cell therapy for solid tumors

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-sitc2020.0098 ◽

2020 ◽

Vol 8 (Suppl 3) ◽

pp. A109-A109

Author(s):

Jiangyue Liu ◽

Xianhui Chen ◽

Jason Karlen ◽

Alfonso Brito ◽

Tiffany Jheng ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Next Generation ◽

Phase 3 ◽

T Cell Therapy ◽

Cell Therapies ◽

Car T Cells ◽

Car T

BackgroundMesothelin (MSLN) is a glycosylphosphatidylinositol (GPI)-anchored membrane protein with high expression levels in an array of malignancies including mesothelioma, ovaria, non-small cell lung cancer, and pancreatic cancers and is an attractive target antigen for immune-based therapies. Early clinical evaluation of autologous MSLN-targeted chimeric antigen receptor (CAR)-T cell therapies for malignant pleural mesothelioma has shown promising acceptable safety1 and have recently evolved with incorporation of next-generation CAR co-stimulatory domains and armoring with intrinsic checkpoint inhibition via expression of a PD-1 dominant negative receptor (PD1DNR).2 Despite the promise that MSLN CAR-T therapies hold, manufacturing and commercial challenges using an autologous approach may prove difficult for widespread application. EBV T cells represent a unique, non-gene edited approach toward an off-the-shelf, allogeneic T cell platform. EBV-specific T cells are currently being evaluated in phase 3 trials [NCT03394365] and, to-date, have demonstrated a favorable safety profile including limited risks for GvHD and cytokine release syndrome.3 4 Clinical proof-of-principle studies for CAR transduced allogeneic EBV T cell therapies have also been associated with acceptable safety and durable response in association with CD19 targeting.5 Here we describe the first preclinical evaluation of ATA3271, a next-generation allogeneic CAR EBV T cell therapy targeting MSLN and incorporating PD1DNR, designed for the treatment of solid tumor indications.MethodsWe generated allogeneic MSLN CAR+ EBV T cells (ATA3271) using retroviral transduction of EBV T cells. ATA3271 includes a novel 1XX CAR signaling domain, previously associated with improved signaling and decreased CAR-mediated exhaustion. It is also armored with PD1DNR to provide intrinsic checkpoint blockade and is designed to retain functional persistence.ResultsIn this study, we characterized ATA3271 both in vitro and in vivo. ATA3271 show stable and proportional CAR and PD1DNR expression. Functional studies show potent antitumor activity of ATA3271 against MSLN-expressing cell lines, including PD-L1-high expressors. In an orthotopic mouse model of pleural mesothelioma, ATA3271 demonstrates potent antitumor activity and significant survival benefit (100% survival exceeding 50 days vs. 25 day median for control), without evident toxicities. ATA3271 maintains persistence and retains central memory phenotype in vivo through end-of-study. Additionally, ATA3271 retains endogenous EBV TCR function and reduced allotoxicity in the context of HLA mismatched targets. ConclusionsOverall, ATA3271 shows potent anti-tumor activity without evidence of allotoxicity, both in vitro and in vivo, suggesting that allogeneic MSLN-CAR-engineered EBV T cells are a promising approach for the treatment of MSLN-positive cancers and warrant further clinical investigation.ReferencesAdusumilli PS, Zauderer MG, Rusch VW, et al. Abstract CT036: A phase I clinical trial of malignant pleural disease treated with regionally delivered autologous mesothelin-targeted CAR T cells: Safety and efficacy. Cancer Research 2019;79:CT036-CT036.Kiesgen S, Linot C, Quach HT, et al. Abstract LB-378: Regional delivery of clinical-grade mesothelin-targeted CAR T cells with cell-intrinsic PD-1 checkpoint blockade: Translation to a phase I trial. Cancer Research 2020;80:LB-378-LB-378.Prockop S, Doubrovina E, Suser S, et al. Off-the-shelf EBV-specific T cell immunotherapy for rituximab-refractory EBV-associated lymphoma following transplantation. J Clin Invest 2020;130:733–747.Prockop S, Hiremath M, Ye W, et al. A Multicenter, Open Label, Phase 3 Study of Tabelecleucel for Solid Organ Transplant Subjects with Epstein-Barr Virus-Driven Post-Transplant Lymphoproliferative Disease (EBV+PTLD) after Failure of Rituximab or Rituximab and Chemotherapy. Blood 2019; 134: 5326–5326.Curran KJ, Sauter CS, Kernan NA, et al. Durable remission following ‘Off-the-Shelf’ chimeric antigen receptor (CAR) T-Cells in patients with relapse/refractory (R/R) B-Cell malignancies. Biology of Blood and Marrow Transplantation 2020;26:S89.

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