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808 Pre-Clinical Activity of Allogeneic Anti-CD22 CAR-T Cells for the Treatment of B-Cell Acute Lymphoblastic Leukemia

Program: Oral and Poster Abstracts
Type: Oral
Session: 614. Acute Lymphoblastic Leukemia: Therapy, excluding Transplantation: CAR-T Cell Immunotherapy
Monday, December 11, 2017: 5:15 PM
Bldg C, Lvl 1, Hall C4 (Georgia World Congress Center)

Julia Wells, PhD1*, Tianyu Cai, PhD2*, Cécile Schiffer-Manniou, PhD3*, Stéphanie Filipe, PhD3*, Agnès Gouble, PhD3*, Roman Galetto, PhD3*, Nitin Jain, MD1, Elias J. Jabbour, MD 4, Julianne Smith, PhD5 and Marina Konopleva, MD, PhD1

1Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX
2Department of Leukemia, University of Texas MD Anderson Cancer Center, Houston, TX
3Cellectis SA, Paris, France
4Department of Leukemia, University of Texas M.D. Anderson Cancer Ctr., Houston, TX
5Cellectis Inc, New York, NY

Autologous T-cells engineered with chimeric antigen receptors (CARs) against CD19 are proving to be an efficacious immunotherapy for patients with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). At present, CAR technology is administered through the custom-made manufacturing of therapeutic products from each patient’s own T-cells. However, this patient-specific autologous paradigm is a significant limiting factor in the large-scale deployment of CAR technology. In this study, we utilized allogeneic "off-the-shelf" engineered CAR T-cells from third-party healthy donors. The CD22 surface antigen is commonly expressed in B-ALL patients as well as in healthy B-cells. Here, its potential as a CAR target was investigated using allogeneic off-the shelf engineered CAR T-cells against human CD22 (UCART22).

UCART22 cells harbor surface expression of an anti-CD22 CAR (CD22 scFv-41BB-CD3z) and the RQR8 ligand, a safety feature rendering the T-cells sensitive to the monoclonal antibody rituximab. To reduce the potential for alloreactivity, the cell surface expression of the T-cell receptor (TCR) is abrogated through the inactivation of the TCRα constant (TRAC) gene using Cellectis’ TALEN® gene-editing technology.

The level of CD22 cell surface molecules was measured using BD Quantbrite beads for both patient peripheral blood samples and B-ALL cell lines. B-ALL cell lines (n=8) expressed a greater amount of CD22 molecules per cell than patient samples (n=14) (5,028 +/- 1,342 compared to 951 +/-160 molecules/cell, p=0.044), with highest expression of CD22 in two Ph-like B-ALL cell lines (MUTZ5, shown in Figure1A and MHH-CALL4).

The in vitro cytotoxic activity of UCART22 cells was evaluated by co-culturing UCART22 or non-transduced CAR(-) TCRαβ(-) control T-cells (NTD) with B-ALL cell lines and primary human samples, at a maximum 10:1 effector to target ratio (represented in Figure1B). Using flow cytometry, significant antigen-specific cytotoxic activity of UCART22 cells was found compared to NTD controls and correlated with CD22 expression factored by the %kolmogorov-smirnov max difference in CD22-PE fluorescence compared to unstained controls (Pearson correlation r-squared for cell lines= 0.6850, p=0.0001 and r-squared for patient samples=0.6204, p=0.0008).

Secretion of 13 cytokines was measured after 1:1 co-incubation of effector and target cells. UCART22 cells stimulated by CD22(+) B-ALL, but not NTD cells, secreted high levels of IFNγ, TNFα, IL-5, IL-17A and IL-17F in the culture supernatants, with cytokine levels being proportionate to CD22 abundance (represented in Figure1C).

In addition, immune compromised mice engrafted with Daudi cells, a CD22(+) expressing Burkitt’s lymphoma cell line, were treated with UCART22 cells. Treatment doses of 1-10x10^6 cells per mouse reduced disease burden (Figure 1D), measured by bioluminescence imaging, and extended survival in a dose-dependent fashion compared to saline or NTD treated controls. Additional PDX studies using B-ALL patient derived xenografts are ongoing and will be presented. Altogether, these results show supporting evidence for the future use of allogenic UCART22 in B-ALL immunotherapy.

Disclosures: Schiffer-Manniou: Cellectis SA: Employment. Filipe: Cellectis: Employment. Gouble: Cellectis SA: Employment. Galetto: Cellectis SA: Employment. Jain: ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Verastem: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Abbvie: Research Funding; Incyte: Research Funding; Genentech: Research Funding; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jabbour: Bristol-Myers Squibb: Consultancy. Smith: Cellectis Inc: Employment. Konopleva: Stemline: Research Funding.

*signifies non-member of ASH