ICOS Is Widely Expressed in Cutaneous T-Cell Lymphoma and Its Targeting Promotes Potent Killing of Malignant Cells

Abstract Background: Advanced cutaneous T-cell lymphomas (CTCLs) remain an unmet medical need. Brentuximab vedotin (BV), an anti-CD30 antibody-drug conjugate (ADC) linked to monomethyl auristatin E (MMAE), do not deliver significant long-term improvements in patient outcomes. More recently, mogamulizumab and anti-KIR3DL2 provided encouraging results but new targeted therapies are needed. Inducible Co-Stimulator (ICOS), a T-cell costimulatory receptor involved in the development of CTCLs, arouses interest. Methods: We used immunohistochemistry to study ICOS expression in skin biopsies of 23 patients with early-stage mycosis fungoides (MF), 12 with transformed MF (TMF) and 17 with Sézary Syndrome (SS), at diagnosis or in relapse. Skin samples from 12 patients with B-cell lymphomas, 14 with CD30 + lymphoproliferative disease (LPD), 12 with primary cutaneous CD4+ small/medium T-cell lympho-proliferative disorder and 13 with angioimmunoblastic T-cell lymphoma (AITL) were used as controls. ICOS expression by circulating Sézary cells and regulatory T cells (Tregs) in patients with SS was evaluated using flow cytometry and compared to healthy donors (HD) lymphocytes. In 5 patients with SS, we also analyzed concomitant biopsies from involved nodes. Then, we investigated the efficacy of anti-ICOS ADCs generated by coupling murine anti-ICOS 314.8 monoclonal antibodies with MMAE and pyrrolobenzodiazepine (PBD), in comparison to BV. We used ICOS + CTCL cell lines (MyLa, MJ and HUT78), murine xenograft models with MyLa and ICOS + Patient Derived Xenografts (PDXs) from patients with SS and AITL. In order to identify the best anti-ICOS clone that we should develop for a clinical trial, we evaluated the affinity of the antibody on the receptor, the internalization capacity of the antibody using pHAb Reactive Dyes kit (Promega®), and the ability of the antibody to act as an ADC using a secondary conjugate (Mab-ZAP kit, Advanced Targeting Systems®). Results: ICOS was highly expressed by the cutaneous atypical lymphocytic infiltrates in respectively 61%, 75% and 88% of patients with early-stage MF, TMF and SS, such as in all the involved nodes. Double staining experiments which were performed in both skin and lymph node revealed that ICOS expression appears mainly restricted to neoplastic CD4 + T-cells, with rare ICOS +CD8 + T-cells in the tumor micro-environment. ICOS expression by circulating Sézary cells was strong: 69 ± 7.3% versus 38.8 ± 7.1% of non-tumoral CD4 + cells (p<0.009; CI95%: 8.7-51.6); and 31 ± 3.2% of CD4+ cells in HD (p<0.0001; CI95%: 20.3-46.3). Percentages of ICOS + Tregs were significantly higher in patients with SS than in HD. In CTCL cell lines, we observed a significant dose-dependent decrease in cell viability in the presence of anti-ICOS-MMAE (IC50 = 8.2ng/mL) and anti-ICOS-PBD (IC50 = 1.2ng/mL) ADCs. In a mouse xenograft model (MyLa), anti-ICOS-MMAE ADCs provided a longer overall survival (OS) than BV (HR=15.2; CI95%: 3.2-71.1; p<0.0006). Finally, in ICOS + PDXs, anti-ICOS-MMAE ADCs significantly improved OS, and reduced the number of tumor cells in the blood, spleen, and bone marrow. No evidence of ADC toxicity was observed in treated mice. Among 8 different anti-ICOS clones, clone 314.8 had the best affinity on MyLa and MJ cell lines. Clones 53.3, 293.1, 92.17, 88.2 and 279.1 also had good affinity to receptor, whereas clones 145.1 and 121.4 had poor affinity. Using the internalization pHAb reactive dyes kit, we found that clones 314.8, 53.3, 92.17, 88.2 internalized significantly better and faster than the other ones. In order to verify if there is a correlation between internalization capacity and ADC effect, clones 53.3, 92.17 and 145.1 were coupled to MMAE. While anti-ICOS-53.3 and anti-ICOS-92.17 ADCs had similar efficacy to anti-ICOS-314.8 ADCs on MyLa, anti-ICOS 145.1 ADCs resulted in significantly lower cell death. Finally, all clones showed good ability to act as ADCs with Mab-ZAP, excluding clones 279.1, 145.1 and 121.4. Discussion: ICOS is a promising therapeutic target because it is expressed both by tumor T-cells and regulatory T-cells. We report for the first time the strong and frequent expression of ICOS in CTCLs, as well as the preclinical efficacy of anti-ICOS ADCs on CTCL cell line and PDXs. These results could be extended to the spectrum of follicular variant peripheral T-cell lymphomas. Conclusion: Collectively, our findings provide the preliminary basis for a therapeutic trial Figure 1 Figure 1. Disclosures Lopez: Emergence Therapeutics: Current holder of individual stocks in a privately-held company. Bagot: Takeda: Membership on an entity's Board of Directors or advisory committees. Olive: ImCheck Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Emergence Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Alderaan Biotechnology: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees.

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Targeting BTN2A1 By a Unique Activating Mab Improves Vγ9Vδ2 T Cell Cytotoxicity Against Primary Acute Lymphoblastic Blasts

Blood ◽

10.1182/blood-2021-152577 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2302-2302

Author(s):

Anne-Charlotte Le Floch ◽

Caroline Imbert ◽

Aude De Gassart ◽

Florence Orlanducci ◽

Aude Le Roy ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Leukemic Cells ◽

Target Cells ◽

Advisory Committees ◽

Vγ9vδ2 T Cells ◽

Privately Held

Abstract Introduction Vγ9Vδ2 T cells are new promising cytotoxic effectors in hematological malignancies. In acute myeloid leukemia and in non-Hodgkin lymphomas, Vγ9Vδ2 T cells-based immunotherapy has shown encouraging results both in preclinical models and in early phase clinical trials. Acute lymphoblastic leukemia (ALL) includes very heterogeneous clinico-biological entities, for which recent immunotherapy approaches are currently being developed. Nevertheless, global prognosis of ALL patients still be poor with a 5 years-overall survival of less than 40% and therefore, treatments need to be improved. Very few data are currently available on susceptibility of ALL blasts to Vγ9Vδ2 T cell cytotoxic activity. Vγ9Vδ2 T cells are activated by phosphoantigens bound to BTN3A1 on target cells. BTN3A molecules are targeted at clinical level, with the ICT01 agonist monoclonal antibody (mAb), that is currently tested in a multicentric phase ½ study (EVICTION study). Biology of Vγ9Vδ2 T cells has recently undergone a new paradigm with the identification of BTN2A1 as the direct ligand for Vγ9 chain of γδ TCR. BTN2A1 is mandatory for Vγ9Vδ2 T cell activation but its precise role in modulating functions of Vγ9Vδ2 T cells remains unknown. Here, we show that allogenic and autologous Vγ9Vδ2 T cells exert cytolytic functions against ALL cell lines and primary ALL blasts, and we report that Vγ9Vδ2 T cell cytotoxic activity is enhanced after treatment with a unique agonist mAb targeting BTN2A1. Material and methods 5 ALL cell lines (697, RS4;11, NALM-6, HPB-ALL, SUP-T1) and PBMC from 11 adults ALL patients at diagnosis (B-ALL, T-ALL and Ph+ ALL) were tested in functional assays. We evaluated apoptosis of ALL cell lines and of primary ALL blasts after coculture with allogenic Vγ9Vδ2 T cells. ALL samples were also tested for their expansion capacities and a degranulation assay was performed at D14. We assessed in parallel relative quantification of the level expression of BTN2A1 (ICT0302 and 7.48 epitopes), and BTN3A (20.1 and 108.5 epitopes) on surface of ALL blasts. DAUDI-BTN2AKO+2A1 and HEK293-BTN2AKO+2A1 cells were used in binding assays, and modulation of TCR binding was assessed using recombinant tetramerized Vγ9Vδ2 TCR. Results We showed that Vγ9Vδ2 T cells exert spontaneous cytotoxicity against ALL cell lines and primary ALL blasts with a heterogeneous susceptibility depending on the target. We demonstrated that anti-BTN2A1 ICT0302 agonist mAb significantly enhanced Vγ9Vδ2 T cells mediated apoptosis in comparison to control condition, even for the less spontaneously susceptible cells. We confirmed these observations with degranulation of autologous Vγ9Vδ2 T cells expanded from 5 ALL patients at diagnosis that was increased after treatment with anti-BTN2A1 ICT0302 agonist mAb. BTN3A and BTN2A1 were detected on surface of ALL blasts, and BTN3A 108.5 was the most expressed epitope. Interestingly, we observed that anti-BTN2A1 ICT0302 strongly increased binding of a recombinant Vγ9Vδ2 TCR to target cells using with HEK293 and DAUDI cells. Discussion Our results highlighted that Vγ9Vδ2 T cells exert cytolytic functions against ALL cells, both in allogenic and autologous setting and demonstrated that BTN2A1 targeting with our unique agonist mAb could potentiate effector activities of Vγ9Vδ2 T cells against ALL blasts. These results indicate that the sensitization of leukemic cells can be induced by activation BTN3A as well as BTN2A1 mAbs. These data bring novel understanding on the biology of BTN2A1 on leukemic cells and our ability to enhance both binding and function. These findings could be of great interest for the design of innovative Vγ9Vδ2 T cells-based immunotherapy strategies for treating ALL that could be extended to other cancer types. Disclosures De Gassart: ImCheck Therapeutics: Current Employment, Current holder of individual stocks in a privately-held company. Vey: Amgen: Honoraria; BMS: Honoraria; BIOKINESIS: Consultancy, Research Funding; NOVARTIS: Consultancy, Honoraria, Research Funding; SERVIER: Consultancy; JAZZ PHARMACEUTICALS: Honoraria; JANSSEN: Consultancy. Cano: ImCheck Therapeutics: Current Employment, Current holder of individual stocks in a privately-held company. Olive: Emergence Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Alderaan Biotechnology: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; ImCheck Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Anti-BTN2A1 ICT0302 is a murine agonist monoclonal antibody targeting BTN2A1 whose aim is to increase Vgamma9Vdelta2 T cells functions.

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Chimerized Anti-ICOS 314.8 Monoclonal Antibodies Inhibit Tumor Cells and Regulatory T Cells in Patients with Sézary Syndrome

Blood ◽

10.1182/blood-2021-153345 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2260-2260

Author(s):

Florent Amatore ◽

Mathilde Barré ◽

Florence Orlanducci ◽

Marc Lopez ◽

Remy Castellano ◽

...

Keyword(s):

Board Of Directors ◽

Tumor Cells ◽

Cell Lines ◽

Target Cells ◽

Cd4 Cells ◽

Advisory Committees ◽

Significant Difference ◽

Negative Controls ◽

Sézary Cells ◽

Privately Held

Abstract Background: In a previous study, we reported the strong expression of Inducible T-cell costimulatory (ICOS) by Sézary cells, and presented the excellent preclinical efficacy results of anti-ICOS antibody drug conjugates (ADCs) in both Sézary syndrome (SS) and angioimmunoblastic T-cell lymphoma. Although exerting a potent direct action on the tumor cell, ADCs have the disadvantage of being associated with a cumulative toxicity, related to the conjugated drug. The development of antibody-dependent cell-mediated cytotoxicity/phagocytosis (ADCC/ADCP)-inducing anti-ICOS monoclonal antibodies (mAbs) is therefore of great importance to ensure long-term maintenance therapy. Methods: We first determined which anti-ICOS clone was the best candidate to induce an ADCC effect on ICOS + cell lines (MyLa, MJ and HUT78), using Mouse FcγRIII ADCC Bioassay (Promega®). The selected mAb was then chimerized and afucosylated (GlymaxX® technology, Evitria®). Secondly, we evaluated in vitro ADCC and ADCP effect of the chimeric anti-ICOS mAb against ICOS + CTCL cell lines, compared to both positive controls (mogamulizumab (moga) and alemtuzumab) and negative controls (IgG1 isotype control, and rituximab). To perform ADCC experiments, we co-incubated target cells with mAbs and allogenic NK lymphocytes from healthy volunteers (HV). Cellular apoptosis was measured by flow cytometry using the Caspase 3/7 assay (Promega®). For ADCP, monocytes were sorted from HV blood samples and treated with M-CSF. Target cells were labeled with PKH67 (Sigma-Aldrich®) and after co-incubation, CD14 +CD11b +PKH67 + monocytes were analyzed by flow cytometry. Finally, we verified the ADCC/ADCP potency of anti-ICOS mAbs on primary Sézary cells isolated from 16 moga-naïve SS patients, and 6 patients who had developed resistance to moga. We also questioned whether anti-ICOS mAbs were able to promote the autologous apoptosis of Sézary cells and T regulatory cells (Tregs) when directly incubated with peripheral blood mononuclear cells (PBMCs) from patients with SS. Results: Among 7 different anti-ICOS clones, 314.8, 92.17 and 293.1 clones had the higher ADCC activity against MyLa, MJ and HUT78. Of these 3 clones, 314.8 had the best affinity to the receptor, and the best ability to inhibit binding between ICOS receptor and a recombinant ICOS ligand protein. Anti-ICOS 314.8 mAb was then chosen to be chimerized and glyco-engineered. ICOS and CCR4 were strong and similarly expressed on MyLa and MJ. HUT78 had only mild expression of ICOS and CD52. Anti-ICOS mediated potent ADCC of cell lines (respectively 39.1±5% and 52.6±2.4% for MyLa and MJ cells), without significant difference when compared to mogamulizumab. In HUT78 cells, anti-ICOS induced a specific apoptosis of 35.7±5% versus 15.6±5.6% with alemtuzumab (p=0.02; CI95%: 4.1-36.1). Moreover, phagocytosis induced by anti-ICOS was significantly increased than that induced by negative controls. On MyLa cells, anti-ICOS had a greater phagocytosis activity than moga (59.4±5.2% vs 39.4±5.1%, p=0.031). Expression of ICOS by circulating tumor cells was found in all the 16 moga-naïve patients. The expression was strong, as 61±6% of tumor cells expressed ICOS vs 20±8% of non-tumoral CD4 + cells. CCR4 was more expressed than ICOS on both Sézary cells and non-tumoral CD4 + cells (91±6%, and 44±9% respectively). Anti-ICOS induced the apoptosis of 57.1±4.7% Sézary cells, compared to 16.9±2.2% with rituximab (p<0.01; CI95%:-53--27). The efficacy was better than with alemtuzumab, but there was no significant difference with moga. The ADCP effect induced by anti-ICOS did not differ with moga. Interestingly, anti-ICOS were effective in 6 moga-resistant patient, as they induced 38.9±5.9% of apoptosis, compared to 12.4±4.7% with moga (p<0.001). Ex vivo, anti-ICOS allowed 39.4±19.9% and 70.1±20.1% lysis of Sézary cells and Tregs respectively, with no difference with moga and alemtuzumab. However, the depletion of non-tumoral CD4 + and total PBMCs was significantly lower with anti-ICOS mAbs than with moga and alemtuzumab. Discussion: In a recent study, we showed that Treg cells of patients with SS have a high expression of ICOS. Here, we demonstrate that anti-ICOS mAbs induce Tregs depletion, which may improve immune profiles and emphasize Sézary cells killing. Our data suggest robust anti-tumor activity of anti-ICOS mAbs in SS, and xenograft experiments are underway to confirm these findings. Disclosures Lopez: Emergence Therapeutics: Current holder of individual stocks in a privately-held company. Bagot: Takeda: Membership on an entity's Board of Directors or advisory committees. Olive: Alderaan Biotechnology: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; ImCheck Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Emergence Therapeutics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees.

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Myeloid Derived Suppressor Cells (MDSCs) Regulate Tumor Growth, Immune Response and Regulatory T Cell (Treg) Development in the Multiple Myeloma Bone Marrow Microenvironment

Blood ◽

10.1182/blood.v120.21.565.565 ◽

2012 ◽

Vol 120 (21) ◽

pp. 565-565

Author(s):

Gullu Topal Gorgun ◽

Gregory Whitehill ◽

Jennifer Lindsey Anderson ◽

Teru Hideshima ◽

Jacob P. Laubach ◽

...

Keyword(s):

Bone Marrow ◽

T Cells ◽

T Cell ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Tumor Development ◽

Suppressor Cells ◽

Advisory Committees ◽

Healthy Donors

Abstract Abstract 565 Background: The interaction of myeloma (MM) cells with bone marrow accessory cells induces genomic, epigenomic and functional changes which promote tumor development, progression, cell adhesion mediated-drug resistance (CAM-DR), and immune suppression. As in other cancers, bidirectional interaction between MM cells and surrounding cells regulates tumor development on the one hand, while transforming the BM microenvironment into a tumor promoting and immune suppressive milieu on the other. Recent developments in targeted therapies have indicated that generation of the most effective therapeutic strategies requires not only targeting tumor or stroma cells, but also methods to overcome blockade of anti-tumor immune responses. In addition to lymphoid immune suppressor cells such as regulatory T cells (Tregs), distinct populations of myeloid cells such as myeloid derived suppressor cells (MDSCs) can effectively block anti-tumor immune responses, thereby representing an important obstacle for immunotherapy. While MDSCs are rare or absent in healthy individuals, increased numbers of MDSCs have been identified in tumor sites and peripheral circulation. Recent studies have in particular focused on MDSCs in the context of tumor promoting, immune suppressing, stroma in solid tumors. However, their presence and role in the tumor promoting, immune suppressive microenvironment in MM remains unclear. Methods: Here we assessed the presence, frequency, and functional characteristics of MDSCs in patients with newly diagnosed or relapsed MM compared to MM patients with response and healthy donors. We first identified a distinct MDSC population (CD11b+CD14−HLA-DR-/lowCD33+CD15+) with tumor promoting and immune suppressive activity in both PB and BM of MM patients. Moreover, we determined the immunomodulatory effects of lenalidomide and bortezomib on induction of MDSCs by MM cells, as well as on MDSC function. Results: MDSCs were significantly increased in both PB and BM of patients with active MM compared to healthy donors and MM in response (p<0.01). To determine whether the CD11b+CD14−HLA-DR-/lowCD33+CD15+ myeloid cell population represents functional MDSCs, we first assessed tumor promoting role of MDSCs in the MM microenvironment by culturing MM cell lines with MM patient bone marrow stroma cells (BMSC), with or without depletion of MDSCs. Importantly, BMSC-mediated MM growth decreased to baseline levels of MM cells alone when MDSCs were removed from the BMSC microenvironment. Moreover, MDSCs isolated from MM-BM using magnetic-Ab and/or FACS sorting cell separation, directly induced MM cell growth and survival, evidenced by 3H-thymidine incorporation and MTT assays. Since the interaction between tumor and stromal accessory cells is bidirectional, we next analysed the impact of MM cells on MDSC development. Importantly, MM cell lines cultured with PBMCs from healthy donors induced a 7 fold increase in MDSCs. We also examined the immune suppressive functions of MDSCs in cultures of autologous T cells with T cell stimulators, in the presence and absence of MDSCs from MM-PB or MM-BM. Freshly isolated MDSCs from both MM-PB and MM-BM induced significant inhibition of autologous T cell proliferation. Moreover, MDSC-associated immune inhibitory molecules arginase-1 (ARG-1) and reactive oxygen species (ROS), as well as inhibitory cytokines IL-6 and IL-10, were significantly increased in BM MDSCs, evidenced by intracellular flow cytometry analysis. In addition, MM BM MDSCs induced development of Treg from autologous naïve CD4+T cells. Finally, we analysed whether MDSCs impacted response to bortezomib and lenalidomide. Culture of MDSCs with MM cell lines, with or without bortezomib (5nM) and lenalidomide (1uM), demonstrated that less MM cell cytotoxicity in the presence of MDSCs. Conclusions: Our data show that MDSCs are increased in the MM microenvironment and mediate tumor growth and drug resistance, as well as immune suppression. Therefore targeting MDSCs represents a promising novel immune-based therapeutic strategy to both inhibit tumor cell growth and restore host immune function in MM. Disclosures: Raje: Onyx: Consultancy; Celgene: Consultancy; Millennium: Consultancy; Acetylon: Research Funding; Amgen: Research Funding; Eli-Lilly: Research Funding. Munshi:Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy. Richardson:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees.

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Patient-Derived Chimeric Antigen Receptor T-Cell Production Based on a Gammaretroviral Vector Platform Is Not Associated with Generation of CAR+ Leukemia Blasts

Blood ◽

10.1182/blood-2018-99-119413 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2204-2204

Author(s):

Concetta Quintarelli ◽

Iolanda Boffa ◽

Matilde Sinibaldi ◽

Domenico Orlando ◽

Marika Guercio ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Cell Lines ◽

Suicide Gene ◽

Leukemic Cells ◽

Advisory Committees ◽

Daudi Cell ◽

Car T Cells ◽

Car T

Abstract In view of the exciting results reported in patients with CD19+ malignancies given CAR T cells, it is expected that a continuously growing number of patients will be offered this treatment and, thus, will be exposed to gene-modified products. Since the techniques of gene manipulation are relatively new, some of the risks associated to CAR T therapy may be unpredictable. Recently, two patients who relapsed with CD19-, CAR-expressing leukemia were reported, this observation being interpretable in light of an inadvertent leukemic cell transduction with the second generation CAR.CD19 lentivirus during CAR T cell manufacturing (Lacey, ASH, 2016 128:281). Immunoglobulin heavy chain sequencing analysis of 17 additional infusion products also identified the leukemic clonotypes in six additional products (86%). In vitro and in vivo experiments proved that these CAR+ leukemic clones were not killed by CAR.CD19 T cells (Ruella, ASH, 2017 130:4463). Since lentiviruses proved to be superior for transduction of quiescent hematopietic stem cells due to their ability to infect non-dividing cells, we hypothesized that CAR-T cell manufacturing based on the genetic modification of T cells by gammaretroviral vector could theoretically represent a safe approach. Peripheral blood or bone marrow (BM)-derived mononuclear cells of patients with >40% of blasts at diagnosis (CD45dim+/CD34+/CD19+/CD22+/CD10+), were transduced with a retrovirus encoding for a second generation CAR.CD19.41bb.z in frame with a suicide gene (i.e., inducible caspase 9, iC9) employed in the academic Clinical Trial (NCT03373071) run at the Bambino Gesù Children's Hospital, Rome, Italy. Patient-derived CAR-T cells showed a phenotype not significantly different from that found on CAR-T cells generated by healthy-donors (data not shown). In particular, we demonstrated that both flow-cytofluorimetry and RealTime-quantitative PCR (with a sensitivity up to 10-5) failed to identify leukemic cells in the final CAR-T cell products generated from Bcp-ALL patients. To generate an in vitro model of CAR+ leukemic cells, we genetically modified CD19+ RAJI and DAUDI cell lines with the bicistronic retroviral vector carrying both second generation CAR.CD19 and the suicide gene iC9 (iC9.CAR-RAJI and iC9.CAR-DAUDI). We demonstrated the possibility of promptlyeliminating CAR+ leukemic cells, through exposure to 20nM of AP1903 of iC9.CAR-DAUDI and iC9.CAR-RAJI cells. Indeed, very early activation (6 hours) of the suicide gene iC9 resulted into a significant reduction in the percentage of CAR+ RAJI leukemic cells (Fig.A). The presence of iC9.CAR.CD19 molecule on leukemic cells precluded the detection of the CD19 antigen, whereas cells retain the expression of all other specific B-lineage markers. CD19 antigen started to be detectable 72 hours after AP1903 exposurewhen CAR negative leukemic cells become preponderant. To demonstrate that CD19 antigen was not down-regulated, but only masked by CAR molecule in iC9.CAR-RAJI and iC9.CAR-DAUDI cell lines, we measured CD19 mRNA, showing no significant modification with respect to wild-type (WT) RAJI and DAUDI cell lines. Moreover, iC9.CAR-RAJI and iC9.CAR-DAUDI cell lines were effectively eliminated by CAR.CD19 T cells (12.5±13.7% and 3.4±4.3% residualleukaemia, respectively) at the same extent of WT cell line (0% and 0.08±0.1%, residual leukaemia, respectively; p>0.05 Fig.B). To assess if patient-derived iC9.CAR.CD19 T cells were able to generate leukemia in vivo mouse model, NSG female mice were infused i.v. with 10x106 CAR-T cells and control NT-T cells. Mice were monitored for a total period of 250 days, by recurrent bleed. Simultaneously, another cohort of mice was infused with patient-derived BM cells (5x106) and monitored for the same time. Mice infused with Bcp-ALL BM cells developed leukemia-phenotype,with 82% of cells expressing hCD45dim and hCD19. By contrast, mice receiving patient-derived CAR-T cells showed a lowpercentage of CD45+ cells (0.1±0.01%), all CD3+. Despite the long period of observation, we did not detect any expansion of hCD19+ cells in this animal cohort. Taken together these data suggest that the use of a retroviral platform, associated with the presence of iC9 suicide gene, contributes to the genesis of a highly functional and safe CAR-T product, even when the production starts from a biological material characterized by high contamination of leukemic blasts. Disclosures Locatelli: Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria; bluebird bio: Consultancy; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees.

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Combinatorial Antigen Targeting Strategy for Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2020-141540 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 22-23

Author(s):

Pinar Ataca Atilla ◽

Mary K McKenna ◽

Norihiro Watanabe ◽

Maksim Mamonkin ◽

Malcolm K. Brenner ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Tumor Control ◽

Publicly Traded ◽

Advisory Committees ◽

Car T Cells ◽

Car T Cell ◽

Car T

Introduction: Efforts to safely and effectively treat acute myeloid leukemia (AML) by targeting a single leukemia associated antigen with chimeric antigen receptor T (CAR T) cells have had limited success. We determined whether combinatorial expression of chimeric antigen receptors directed to two different AML associated antigens would augment tumor eradication and prevent relapse in targets with heterogeneous expression of myeloid antigens. Methods: We generated CD123 and CD33 targeting CARs; each containing a 4-1BBz or CD28z endodomain. We analyzed the anti-tumor activity of T cells expressing each CAR alone or in co-transduction with a CLL-1 CAR with CD28z endodomain and CD8 hinge previously optimized for use in our open CAR-T cell trial for AML (NCT04219163). We analyzed CAR-T cell phenotype, expansion and transduction efficacy by flow cytometry and assessed function by in vitro and in vivo activity against AML cell lines expressing high, intermediate or low levels of the target antigens (Molm 13= CD123 high, CD33 high, CLL-1 intermediate, KG1a= CD123 low, CD33 low, CLL-1 low and HL60= CD123 low, CD33 intermediate, CLL-1 intermediate/high) For in vivo studies we used NOD.SCID IL-2Rg-/-3/GM/SF (NSGS) mice with established leukemia, determining antitumor activity by bioluminescence imaging. Results: We obtained high levels of gene transfer and expression with both single (CD33.4-1BBʓ, CD123.4-1BBʓ, CD33.CD28ʓ, CD123.CD28ʓ, CLL-1 CAR) and double transduction CD33/CD123.4-1BBʓ or CD33/CD123.CD28ʓ) although single-transductants had marginally higher total CAR expression of 70%-80% versus 60-70% after co-transduction. Constructs containing CD28 co-stimulatory domain exhibited rapid expansion with elevated peak levels compared to 41BB co-stim domain irrespective of the CAR specificity. (p<0.001) (Fig 1a). In 72h co-culture assays, we found consistently improved anti-tumor activity by CAR Ts expressing CLL-1 in combination either with CD33 or with CD123 compared to T cells expressing CLL-1 CAR alone. The benefit of dual expression was most evident when the target cell line expressed low levels of one or both target antigens (e.g. KG1a) (Fig 1b) (P<0.001). No antigen escape was detected in residual tumor. Mechanistically, dual expression was associated with higher pCD3ʓ levels compared to single CAR T cells on exposure to any given tumor (Fig 1c). Increased pCD3ʓ levels were in turn associated with augmented CAR-T degranulation (assessed by CD107a expression) in both CD4 and CD8 T cell populations and with increased TNFα and IFNɣ production (p<0.001 Fig 1d). In vivo, combinatorial targeting with CD123/CD33.CD28ʓ and CLL-1 CAR T cells improved tumor control and animal survival in lines (KG1a, MOLM13 and HL60) expressing diverse levels of the target antigens (Fig 2). Conclusion: Combinatorial targeting of T cells with CD33 or CD123.CD28z CARs and CLL-1-CAR improves CAR T cell activation associated with superior recruitment/phosphorylation of CD3ʓ, producing enhanced effector function and tumor control. The events that lead to increased pCD3ʓ after antigen engagement in the dual transduced cells may in part be due to an overall increase in CAR expression but may also reflect superior CAR recruitment after antigen engagement. We are now comparing the formation, structure, and stability of immune synapses in single and dual targeting CARs for AML. Disclosures Brenner: Walking Fish: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Tumstone: Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Founder; Maker Therapeutics: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Other: Founder; Memmgen: Membership on an entity's Board of Directors or advisory committees; Allogene: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Atilla:Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Tumstone: Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: founder; Marker Therapeuticsa: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees, Other: Founder, Patents & Royalties; Allogene: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Walking Fish: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Memgen: Membership on an entity's Board of Directors or advisory committees; KUUR: Membership on an entity's Board of Directors or advisory committees.

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T Cell Immunity Toward Viral- and Tumor-Antigens Is Preserved in MDS Patients

Blood ◽

10.1182/blood-2019-126792 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4225-4225

Author(s):

Hussein Hamad ◽

Wingchi K Leung ◽

Spyridoula Vasileiou ◽

Shivani Mukhi ◽

Quillan Huang ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Healthy Donor ◽

Tumor Antigens ◽

Ex Vivo ◽

Advisory Committees ◽

Cell Immunity ◽

Healthy Donors ◽

T Cell Lines

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by bone marrow failure and a propensity to progress to acute myeloid leukemia (AML). A core component of the underlying pathogenesis in MDS is deregulation of inflammatory cytokines, such as tumor growth factor-β (TGFβ), which impact the function of immune cells and hence their capacity to mount anti-infective or anti-tumor responses. However, little is known about antigen-specific T cell function in patients with MDS. We hypothesized that virus-specific T cell (VST) function might be preserved in patients with MDS, and that the functional capacity of T cells reactive against tumor-associated antigens aberrantly overexpressed by clonal MDS cells such as Cyclin A1 (CCNA1) and Proteinase (PR3) might also be preserved and exploited for immunotherapeutic purposes. Following informed consent, we collected peripheral blood samples from 10 patients (pts) with MDS and 17 healthy donors. Most pts (9 out of 10) were transfusion dependent and 3 subsequently underwent an allogeneic HSCT. Table 1 summarizes the other clinical characteristics, karyotypic and mutational profile at the time of blood collection. Compared with T cells isolated from healthy donors, MDS patient-derived T cells had a similar CD4 to CD8 ratio (1.5-2.5:1 for healthy donors and 3:1 for MDS pts), but displayed a more exhausted profile at baseline (CD3+TIM3+: 1% in healthy donors and 5% in MDS pts) and produced higher levels of inflammatory cytokines [IFNγ (18±3pg/ml vs 36±16pg/ml, healthy donor vs MDS; p=0.12), and IL-8 (56±32 vs 704±446 pg/ml, p=0.01)]. Next, to assess the capacity of MDS pts to mount ex vivo functional virus-directed responses, we stimulated patient-derived PBMCs (n=5) with overlapping peptide libraries (pepmixes) spanning immunogenic AdV, CMV, EBV, BK and HHV-6 antigens. Similar to healthy donor-derived T cell lines (n=5, 3 specific for 4 viruses and 2 for 5 viruses), all 5 MDS patient-derived lines demonstrated specificity for one or more of the target viruses (1 for 5 viruses, 1 for 4, 2 for 3 and 1 for 1 virus) as observed by IFNγ ELISpot assay with comparable magnitude (range Adv: 43-730 vs 384-941 in healthy donors, CMV: 0-1599 vs 0-3002, EBV: 0-1486 vs 0-541, BK: 0-839 vs 38-275 and HHV6: 0-794 vs 5-407 SFU/2x105 cells, respectively). We next examined the feasibility of expanding autologous MDS-antigen directed T cell products (n=10) to determine whether an adoptive immunotherapeutic approach might be applicable for MDS treatment. Thus, we exposed patient-derived PBMCs to autologous dendritic cells (DC) loaded with pepmixes spanning 6 MDS-associated antigens (CCNA1, survivin, WT1, PRAME, PR3 and NYESO1). After 3 rounds of stimulation, the products obtained were predominantly CD3+ T cells (mean 88±1.3%) that were polyclonal (CD4: 46±5% and CD8: 41±4%) containing predominantly memory T cells (TEM: 36±6% TCM: 37±5% and Tnaïve =13±3%). Six lines (60%) showed specific recognition to at least one of the target antigens: 4 lines specific for PRAME, 1 for CCNA1, 1 for WT1 and 1 for NYESO1 (range 0-40, 0-184, 0-1386 and 0-179 SFU/2x105 cells, respectively by IFNγ ELIspot). T cell lines were capable of specifically secreting multiple effector cytokines in response to targets (TNFα: 12% and IFNγ: 16% in response to PRAME in a representative patient-derived T cell line). Furthermore, this line was capable of killing PRAME+ targets in a 4hr 51Cr release assay [60% specific lysis, E:T 20:1]. In conclusion, functional virus-directed T cell immunity in patients with MDS is preserved, potentially explaining the lower rates of viral reactivation seen in these patients compared with other infections. Moreover, T cells specific for MDS-expressed tumor antigens can also be successfully expanded ex vivo from patients. Taken together this raises the possibility of applying an adoptive immunotherapeutic approach for the treatment of MDS. Disclosures Ramos: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Tessa Therapeutics: Research Funding. Leen:Allovir: Consultancy, Other: Cofounder, Ownership Interest; Marker Therapeutics: Consultancy, Other: Cofounder, Ownership Interest.

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Automated Manufacture of Matched Donor-Derived Allogeneic CD19 CAR T-Cells for Relapsed/Refractory B-ALL Following Allogeneic Stem Cell Transplantation: Toxicity, Efficacy and the Important Role of Lymphodepletion

Blood ◽

10.1182/blood-2019-129640 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 776-776

Author(s):

Claire Roddie ◽

Maeve A O'Reilly ◽

Maria A V Marzolini ◽

Leigh Wood ◽

Juliana Dias Alves Pinto ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Advisory Committees ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Peak Car ◽

Matched Donor

Introduction: 2nd generation CD19 CAR T cells show unprecedented efficacy in B-ALL, but several challenges remain: (1) scaling manufacture to meet patient need and (2) feasibility of generating products from lymphopenic patients post allogeneic stem cell transplant (allo-SCT). To overcome these issues we propose: (1) use of the CliniMACS Prodigy (Miltenyi Biotec), a semi-automated cGMP platform that simplifies CAR T cell manufacture and (2) the use of matched donor T cells to overcome the challenge posed by patient lymphopenia, albeit this may come with a heightened risk of graft versus host disease (GvHD). CARD (NCT02893189) is a Phase I study of matched donor derived CD19 CAR T cells generated on the CliniMACS Prodigy in 14 adult patients with relapsed/refractory (r/r) B ALL following allo-SCT. We additionally explore the requirement for lymphodepletion (LD) in the allogeneic CAR T cell setting and report on the incidence of GvHD with this therapy. Methods: Manufacturing: CARD utilises non-mobilised matched donor leucapheresate to manufacture 2nd generation CD19CAR T cells using a closed CliniMACS® Prodigy/ TransACTTM process. Study design: Eligible subjects are aged 16-70y with r/r B ALL following allo SCT. Study endpoints include feasibility of CD19CAR T cell manufacture from allo-SCT donors on the CliniMACS Prodigy and assessments of engraftment and safety including GvHD. To assess the requirement for LD prior to CD19CAR T cells in lymphopenic post-allo-SCT patients, the study is split into Cohort 1 (no LD) and Cohort 2 (fludarabine (30 mg/m2 x3) and cyclophosphamide (300mg/m2 x3)). To mitigate for the potential GvHD risk, cell dosing on study mirrors conventional donor lymphocyte infusion (DLI) schedules and is based on total CD3+ (not CAR T) cell numbers: Dose 1=1x106/kg CD3+ T cells; Dose 2= 3x106/kg CD3+ T cells; Dose 3= 1x107/kg CD3+ T cells. Results: As of 26 July 2019, 17 matched allo SCT donors were leukapheresed and 16 products were successfully manufactured and QP released. Patient demographics are as follows: (1) median patient age was 43y (range 19-64y); (2) 4/17 had prior blinatumomab and 5/17 prior inotuzumab ozogamicin; (3) 7/17 had myeloablative allo SCT and 10/17 reduced intensity allo SCT of which 6/17 were sibling donors and 12/17 were matched unrelated donors. No patients with haploidentical transplant were enrolled. To date, 12/16 patients have received at least 1 dose of CD19CAR T cells: 7/16 on Cohort 1 and 5/16 on Cohort 2 (2/16 are pending infusion on Cohort 2 and 2/16 died of fungal infection prior to infusion). Median follow-up for all 12 patients is 22.9 months (IQR 2.9-25.9; range 0.7 - 25.9). At the time of CAR T cell infusion, 7/12 patients were in morphological relapse with >5% leukemic blasts. Despite this, CD19CAR T cells were administered safely: only 2/12 patients experienced Grade 3 CRS (UPenn criteria), both in Cohort 1, which fully resolved with Tocilizumab and corticosteroids. No patients experienced ≥Grade 3 neurotoxicity and importantly, no patients experienced clinically significant GvHD. In Cohort 1 (7 patients), median peak CAR expansion by flow was 87 CD19CAR/uL blood whereas in Cohort 2 (5 patients to date), median peak CAR expansion was 1309 CD19CAR/uL blood. This difference is likely to reflect the use of LD in Cohort 2. CAR T cell persistence by qPCR in Cohort 1 is short, with demonstrable CAR in only 2/7 treated patients at Month 2. Data for Cohort 2 is immature, but this will also be reported at the meeting in addition to potential mechanisms underlying the short persistence observed in Cohort 1. Of the 10 response evaluable patients (2/12 pending marrow assessment), 9/10 (90%) achieved flow/molecular MRD negative CR at 6 weeks. 2/9 responders experienced CD19 negative relapse (one at M3, one at M5) and 3/9 responders experienced CD19+ relapse (one at M3, one at M9, one at M12). 4/10 (40%) response evaluable patients remain on study and continue in flow/molecular MRD negative remission at a median follow up of 11.9 months (range 2.9-25.9). Conclusions: Donor-derived matched allogeneic CD19 CAR T cells are straightforward to manufacture using the CliniMACS Prodigy and deliver excellent early remission rates, with 90% MRD negative CR observed at Week 6 in the absence of severe CAR associated toxicity or GvHD. Peak CAR expansion appears to be compromised by the absence of LD and this may lead to a higher relapse rate. Updated results from Cohorts 1 and 2 will be presented. Disclosures Roddie: Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. O'Reilly:Kite Gilead: Honoraria. Farzaneh:Autolus Ltd: Equity Ownership, Research Funding. Qasim:Autolus: Equity Ownership; Orchard Therapeutics: Equity Ownership; UCLB: Other: revenue share eligibility; Servier: Research Funding; Bellicum: Research Funding; CellMedica: Research Funding. Linch:Autolus: Membership on an entity's Board of Directors or advisory committees. Pule:Autolus: Membership on an entity's Board of Directors or advisory committees. Peggs:Gilead: Consultancy, Speakers Bureau; Autolus: Membership on an entity's Board of Directors or advisory committees.

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Identification of Two CAR T-Cell Populations Associated with Complete Response or Progressive Disease in Adult Lymphoma Patients Treated with Axi-Cel

Blood ◽

10.1182/blood-2019-130815 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 779-779 ◽

Cited By ~ 2

Author(s):

Zinaida Good ◽

Jay Y. Spiegel ◽

Bita Sahaf ◽

Meena B. Malipatlolla ◽

Matthew J. Frank ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Advisory Board ◽

Advisory Committees ◽

Car T Cells ◽

Scientific Advisory Board ◽

Car T ◽

Scientific Advisory

Axicabtagene ciloleucel (Axi-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for the treatment of relapsed or refractory diffuse large B-cell lymphoma (r/r DLBCL). Long-term analysis of the ZUMA-1 phase 1-2 clinical trial showed that ~40% of Axi-cel patients remained progression-free at 2 years (Locke et al., Lancet Oncology 2019). Those patients who achieved a complete response (CR) at 6 months generally remained progression-free long-term. The biological basis for achieving a durable CR in patients receiving Axi-cel remains poorly understood. Here, we sought to identify CAR T-cell intrinsic features associated with CR at 6 months in DLBCL patients receiving commercial Axi-cel at our institution. Using mass cytometry, we assessed expression of 33 surface or intracellular proteins relevant to T-cell function on blood collected before CAR T cell infusion, on day 7 (peak expansion), and on day 21 (late expansion) post-infusion. To identify cell features that distinguish patients with durable CR (n = 11) from those who developed progressive disease (PD, n = 14) by 6 months following Axi-cel infusion, we performed differential abundance analysis of multiparametric protein expression on CAR T cells. This unsupervised analysis identified populations on day 7 associated with persistent CR or PD at 6 months. Using 10-fold cross-validation, we next fitted a least absolute shrinkage and selection operator (lasso) model that identified two clusters of CD4+ CAR T cells on day 7 as potentially predictive of clinical outcome. The first cluster identified by our model was associated with CR at 6 months and had high expression of CD45RO, CD57, PD1, and T-bet transcription factor. Analysis of protein co-expression in this cluster enabled us to define a simple gating scheme based on high expression of CD57 and T-bet, which captured a population of CD4+ CAR T cells on day 7 with greater expansion in patients experiencing a durable CR (mean±s.e.m. CR: 26.13%±2.59%, PD: 10.99%±2.53%, P = 0.0014). In contrast, the second cluster was associated with PD at 6 months and had high expression of CD25, TIGIT, and Helios transcription factor with no CD57. A CD57-negative Helios-positive gate captured a population of CD4+ CAR T cells was enriched on day 7 in patients who experienced progression (CR: 9.75%±2.70%, PD: 20.93%±3.70%, P = 0.016). Co-expression of CD4, CD25, and Helios on these CAR T cells highlights their similarity to regulatory T cells, which could provide a basis for their detrimental effects. In this exploratory analysis of 25 patients treated with Axi-cel, we identified two populations of CD4+ CAR T cells on day 7 that were highly associated with clinical outcome at 6 months. Ongoing analyses are underway to fully characterize this dataset, to explore the biological activity of the populations identified, and to assess the presence of other populations that may be associated with CAR-T expansion or neurotoxicity. This work demonstrates how multidimensional correlative studies can enhance our understanding of CAR T-cell biology and uncover populations associated with clinical outcome in CAR T cell therapies. This work was supported by the Parker Institute for Cancer Immunotherapy. Figure Disclosures Muffly: Pfizer: Consultancy; Adaptive: Research Funding; KITE: Consultancy. Miklos:Celgene: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; AlloGene: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees; Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Becton Dickinson: Research Funding; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno: Membership on an entity's Board of Directors or advisory committees. Mackall:Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board.

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Human CD83 Targeted Chimeric Antigen Receptor T Cell for the Prevention of Graft Versus Host Disease and Treatment of Myeloid Leukemia

Blood ◽

10.1182/blood-2019-124031 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 196-196

Author(s):

Bishwas Shrestha ◽

Kelly Walton ◽

Jordan Reff ◽

Elizabeth M. Sagatys ◽

Nhan Tu ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Advisory Committees ◽

Graft Versus Host ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Fund Research

Distinct from pharmacologic immunosuppression, we designed a programmed cytolytic effector T cell that prevents graft versus host disease (GVHD). CD83 is expressed on allo-activated conventional T cells (Tconv) and pro-inflammatory dendritic cells (DCs), which are implicated in GVHD pathogenesis. Therefore we developed a novel human CD83 targeted chimeric antigen receptor (CAR) T cell for GVHD prophylaxis. Here we demonstrate that human CD83 CAR T cells eradicate cell mediators of GVHD, significantly increase the ratio of regulatory T cells (Treg) to allo-activated Tconv, and provide lasting protection from xenogeneic GVHD. Further, we show human, acute myeloid leukemia (AML) expresses CD83 and can be targeted by CD83 CAR T cells. A 2nd generation CD83 CAR was generated with CD3ζ and 41BB costimulatory domain that was retrovirally transduced in human T cells to generate CD83 CAR T cells. The CD83 CAR construct exhibited a high degree of transduction efficiency of about 60%. The CD83 CAR T cells demonstrated robust IFN-γ and IL-2 production, killing, and proliferation when cultured with CD83+ target cells. To test whether human CD83 CAR T cells reduce alloreactivity in vitro, we investigated their suppressive function in allogeneic mixed leukocyte reactions (alloMLR). CD83 CAR T cells were added to 5-day alloMLRs consisting of autologous T cells and allogeneic monocyte-derived DCs at ratios ranging from 3:1 to 1:10. The CD83 CAR T cells potently reduced alloreactive T cell proliferation compared to mock transduced and CD19 CAR T cells. We identified that CD83 is differentially expressed on alloreactive Tconv, compared to Tregs. Moreover, the CD83 CAR T cell efficiently depletes CD83+ Tconv and proinflammatory DCs with 48 hours of engagement. To test the efficacy of human CD83 CAR T cells in vivo, we used an established xenogeneic GVHD model, where mice were inoculated with human PBMCs (25x106) and autologous CD83 CAR (1-10x106) or mock transduced T cells. The CD83 CAR T cells were well tolerated by the mice, and significantly improved survival compared to mock transduced T cells (Figure 1A). Mice treated with CD83 CAR T cells exhibited negligible GVHD target organ damage at day +21 (Figure 1B). Mice inoculated with CD83 CAR T cells demonstrated significantly fewer CD1c+, CD83+ DCs (1.7x106 v 6.2x105, P=0.002), CD4+, CD83+ T cells (4.8x103 v 5.8x102, P=0.005), and pathogenic Th1 cells (3.1x105 v 1.1x102, P=0.005) at day +21, compared to mice treated with mock transduced T cells. Moreover, the ratio of Treg to alloreactive Tconv (CD25+ non-Treg) was significantly increased among mice treated with CD83 CAR T cells (78 v 346, P=0.02), compared to mice injected with mock transduced T cells. Further, CD83 appears to be a promising candidate to target myeloid malignancies. We observed CD83 expression on malignant myeloid K562, Thp-1, U937, and MOLM-13 cells. Moreover, the CD83 CAR T cells effectively killed AML cell lines. Many AML antigens are expressed on progenitor stem cells. Thus, we evaluated for stem cell killing in human colony forming unit (CFU) assays, which demonstrated negligible on-target, off-tumor toxicity. Therefore, the human CD83 CAR T cell is an innovative cell-based approach to prevent GVHD, while providing direct anti-tumor activity against myeloid malignancies. Figure Disclosures Blazar: Kamon Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; Five Prime Therapeutics Inc: Co-Founder, Membership on an entity's Board of Directors or advisory committees; BlueRock Therapeutics: Membership on an entity's Board of Directors or advisory committees; Abbvie Inc: Research Funding; Leukemia and Lymphoma Society: Research Funding; Childrens' Cancer Research Fund: Research Funding; KidsFirst Fund: Research Funding; Tmunity: Other: Co-Founder; Alpine Immune Sciences, Inc.: Research Funding; RXi Pharmaceuticals: Research Funding; Fate Therapeutics, Inc.: Research Funding; Magenta Therapeutics and BlueRock Therapeuetics: Membership on an entity's Board of Directors or advisory committees; Regeneron Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Davila:Atara: Research Funding; Celgene: Research Funding; Precision Biosciences: Consultancy; Bellicum: Consultancy; GlaxoSmithKline: Consultancy; Adaptive: Consultancy; Anixa: Consultancy; Novartis: Research Funding.

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A Novel Approach for Treatment of T-Cell Malignancies: Targeting T-Cell Receptor Vβ Families

Blood ◽

10.1182/blood-2020-142010 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 28-29

Author(s):

Jie Wang ◽

Katarzyna Urbanska ◽

Prannda Sharma ◽

Mathilde Poussin ◽

Reza Nejati ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

B Cell ◽

Cell Line ◽

Cell Lines ◽

Cell Receptor ◽

Brentuximab Vedotin ◽

T Cell Lymphomas ◽

T Cell Malignancies

Background: Peripheral T-cell lymphomas (PTCL) encompass a highly heterogeneous group of T-cell malignancies and are generally associated with a poor prognosis. Combination chemotherapy results in consistently poorer outcomes for T-cell lymphomas compared with B-cell lymphomas.1 There is an urgent clinical need to develop novel approaches to treatment of PTCL. While CD19- and CD20-directed immunotherapies have been successful in the treatment of B-cell malignancies, T-cell malignancies lack suitable immunotherapeutic targets. Brentuximab Vedotin, a CD30 antibody-drug conjugate, is not applicable to PTCL subtypes which do not express CD30.2 Broadly targeting pan-T cell markers is predicted to result in extensive T-cell depletion and clinically significant immune deficiency; therefore, a more tumor-specific antigen that primarily targets the malignant T-cell clone is needed. We reasoned that since malignant T cells are clonal and express the same T-cell receptor (TCR) in a given patient, and since the TCR β chain in human α/β TCRs can be grouped into 24 functional Vβ families targetable by monoclonal antibodies, immunotherapeutic targeting of TCR Vβ families would be an attractive strategy for the treatment of T-cell malignancies. Methods: We developed a flexible approach for targeting TCR Vβ families by engineering T cells to express a CD64 chimeric immune receptor (CD64-CIR), comprising a CD3ζ T cell signaling endodomain, CD28 costimulatory domain, and the high-affinity Fc gamma receptor I, CD64. T cells expressing CD64-CIR are predicted to be directed to tumor cells by Vβ-specific monoclonal antibodies that target tumor cell TCR, leading to T cell activation and induction of tumor cell death by T cell-mediated cytotoxicity. Results: This concept was first evaluated in vitro using cell lines. SupT1 T-cell lymphoblasts, which do not express a native functioning TCR, were stably transduced to express a Vβ12+ MART-1 specific TCR, resulting in a Vβ12 TCR expressing target T cell line.3 Vβ family specific cytolysis was confirmed by chromium release assays using co-culture of CD64 CIR transduced T cells with the engineered SupT1-Vβ12 cell line in the presence of Vβ12 monoclonal antibody. Percent specific lysis was calculated as (experimental - spontaneous lysis / maximal - spontaneous lysis) x 100. Controls using no antibody, Vβ8 antibody, and untransduced T cells did not show significant cytolysis (figure A). Next, the Jurkat T cell leukemic cell line, which expresses a native Vβ8 TCR, was used as targets in co-culture. Again, Vβ family target specific cytolysis was achieved in the presence of CD64 CIR T cells and Vβ8, but not Vβ12 control antibody. Having demonstrated Vβ family specific cytolysis in vitro using target T cell lines, we next evaluated TCR Vβ family targeting in vivo. Immunodeficient mice were injected with SupT1-Vβ12 or Jurkat T cells with the appropriate targeting Vβ antibody, and either CD64 CIR T cells or control untransduced T cells. The cell lines were transfected with firefly luciferase and tumor growth was measured by bioluminescence. The CD64 CIR T cells, but not untransduced T cells, in conjunction with the appropriate Vβ antibody, successfully controlled tumor growth (figure B). Our results provide proof-of-concept that TCR Vβ family specific T cell-mediated cytolysis is feasible, and informs the development of novel immunotherapies that target TCR Vβ families in T-cell malignancies. Unlike approaches that target pan-T cell antigens, this approach is not expected to cause substantial immune deficiency and could lead to a significant advance in the treatment of T-cell malignancies including PTCL. References 1. Coiffier B, Brousse N, Peuchmaur M, et al. Peripheral T-cell lymphomas have a worse prognosis than B-cell lymphomas: a prospective study of 361 immunophenotyped patients treated with the LNH-84 regimen. The GELA (Groupe d'Etude des Lymphomes Agressives). Ann Oncol Off J Eur Soc Med Oncol. 1990;1(1):45-50. 2. Horwitz SM, Advani RH, Bartlett NL, et al. Objective responses in relapsed T-cell lymphomas with single agent brentuximab vedotin. Blood. 2014;123(20):3095-3100. 3. Hughes MS, Yu YYL, Dudley ME, et al. Transfer of a TCR Gene Derived from a Patient with a Marked Antitumor Response Conveys Highly Active T-Cell Effector Functions. Hum Gene Ther. 2005;16(4):457-472. Figure Disclosures Schuster: Novartis, Genentech, Inc./ F. Hoffmann-La Roche: Research Funding; AlloGene, AstraZeneca, BeiGene, Genentech, Inc./ F. Hoffmann-La Roche, Juno/Celgene, Loxo Oncology, Nordic Nanovector, Novartis, Tessa Therapeutics: Consultancy, Honoraria.

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