Abstract 2933: Pre-clinical model of eradication of B cell leukemia with lentiviral transduced anti-CD19 chimeric immunoreceptor-modified T cells
Authors: Barrett David M. , Carpenito Carmine , Zhao Yang Bing , Kalos Michael , June Carl H. , Grupp Stephan A. 
Published: February 2011

CD19 is a membrane glycoprotein found on human B lymphocytes at all stages of maturation, and is not lost during malignant transformation to precursor-B cell Acute Lymphoblastic Leukemia (ALL). T cells engineered with chimeric immunoreceptors (CIR) consisting of an extracellular scFv domain against CD19 fused to the T cell receptor ζ signal transduction domain represent a promising adoptive immunotherapy against leukemias refractory to traditional chemotherapy. Previous studies from our group and others have demonstrated that inclusion of signaling domains from costimulatory molecules such as CD28 or CD137 (41BB) can improve the antileukemic efficacy and in vivo persistence of CIR-modified T cells. To critically evaluate the anti-tumor efficacy of anti-CD19-targeting CIR that contained various signaling domains alone or in combination we utilized the highly immunodeficient NOG mouse model and an aggressive CD19+ leukemia cell line (Nalm-6) and treated with primary human CD8+ and CD4+ lymphocytes gene modified to express anti-CD19 CIR with TcR zeta alone, CD28-TcRzeta, CD137-TcRzeta, and CD28- CD137-TcR signalling domains.

NOG mice were injected with 1×106 Nalm-6 on Day 1, a dose that produces 100% engraftment in the bone marrow by Day 7 (95% CI 0.15-1.2% of total bone marrow cells CD19+) with 100% mortality by Day 25 if untreated. T cells were expanded ex vivo using anti-CD3/CD28 beads and subjected to lentiviral gene transfer of various CIRs, and 1×107 T cells were injected on Day 7 (7×106 CAR +). Mice were followed weekly by quantitative flow cytometric analysis of peripheral blood for CD3, CD4, CD8 and CD19 positive human cells. A separate cohort of animals were treated with either Nalm-6 or T cells transduced with firefly luciferase to track biodistribution and treatment response.

Mice treated with T cells engineered to express each of the anti-CD19 CAR demonstarted statistically significant improved survival over control animals, with animals succumbing either to leukemia, or in a construct dependent manner, GVHD. Additionally, a hierarchy of survival advantage was observed among the anti-CD19 constructs, with the CD19-CD28-CD137-ζ CAR mediating most enhanced survival, with 37% of those mice surviving until the end of the study at Day 125. In vivo bioluminescent imaging demonstrated that T cell migration and expansion depends on antigen recognition and presence of the ζ chain in the CIR, and that leukemia clearance is unexpectedly rapid (&lt; 3 days).

These data indicate it is possible to eradicate established bone marrow disease with a single injection of lentiviral transduced CIR T cells. Future efforts will focus on leukemia rechallenge to evaluate in vivo persistence and surveillance capabilities of these CIR T cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2933.