Abstract Book 2010 - CIMT Annual Meeting

044 Kalos | Cellular therapy
Clearance of established leukemia in a mouse xenograft model
by a single injection of primary T cells gene-modified to express
chimeric antigen receptors that target CD19
Michael Kalos 1 , David M. Barrett 2 , Carmine Carpenito 1 , Stephan A. Grupp 2 and Carl June 1
1 Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA
2 Division of Oncology, Children’s Hospital of Philadelphia, Philadelphia, PA
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We are evaluating the potential to use T-cells re-
directed by genetic engineering to target human
tumors. Chimeric antigen receptors (CAR), developed
by combining antigen binding domains from
antibodies or T cell receptors (TcR) to T cell signalling
domains offer a potentially powerful platform
to mediate tumor re-targeting.
To re-target T cells against B cell malignancies we
are focusing on the CD19 molecule, a membrane
glycoprotein found on human B lymphocytes and
expressed by the vast majority of B cell tumors. We
have generated a CAR that consists of an extracellular
scFv domain derived from an antibody that
targets CD19 linked to the intracellular signalling
domain of the TcR zeta chain. To criticaly evaluate
the effects of including signaling domains from T cell
costimulatory on CAR functionality and anti-CD19targeting
CAR we introduced signalling domains
from CD28 or CD137 (41BB) domains into the anti-
CD19 CAR, transduced such CAR into primary
human CD8+ and CD4+ T cells, and evaluated
the ability of the transduced T cells to eradicate
established aggressive CD19+ leukemia cell line
Nalm-6 in the highly immunodeficient NOG mouse
model. We evaluated primary lymphocytes gene
modified to express anti-CD19-targeting CAR that
contain TcRζ —alone, CD28-TcRζ, CD137-TcRζ—,
and CD28-CD137-TcRζ — signaling domains.
Mice treated with a single dose of T cells engineered
to express each of the anti-CD19 CAR demonstrated
statistically significant improved survival over con-
trols animals. The CD19-CD28-CD137-ζ — CAR mediated
the longest median overall survival and the
most mice surviving until the end of the study at
Day 180. In vivo bioluminescent imaging shows the
kinetics of leukemia clearance to be rapid (within
72 hours), and proves a sensitive tool for tracking
disease relapse.
These data demonstrate the potential of CAR directed
to the CD19 molecule to effectively redirect T
cells to eradicate established bone marrow disease
with a single injection of CAR modified cells. Future
efforts will focus on enhancing in vivo persistence
and surveillance capabilities of these CAR T-cells,
as well as investigating the ability of CAR T cells to
clear repeated challenges of leukemia.