[HTML][HTML] Myeloid conditioning with c-kit-targeted CAR-T cells enables donor stem cell engraftment

Y Arai, U Choi, CI Corsino, SM Koontz, M Tajima… - Molecular Therapy, 2018 - cell.com
Y Arai, U Choi, CI Corsino, SM Koontz, M Tajima, CL Sweeney, MA Black, SA Feldman…
Molecular Therapy, 2018cell.com
We report a novel approach to bone marrow (BM) conditioning using c-kit-targeted chimeric
antigen receptor T (c-kit CAR-T) cells in mice. Previous reports using anti-c-kit or anti-CD45
antibody linked to a toxin such as saporin have been promising. We developed a distinctly
different approach using c-kit CAR-T cells. Initial studies demonstrated in vitro killing of
hematopoietic stem cells by c-kit CAR-T cells but poor expansion in vivo and poor migration
of CAR-T cells into BM. Pre-treatment of recipient mice with low-dose cyclophosphamide …
We report a novel approach to bone marrow (BM) conditioning using c-kit-targeted chimeric antigen receptor T (c-kit CAR-T) cells in mice. Previous reports using anti-c-kit or anti-CD45 antibody linked to a toxin such as saporin have been promising. We developed a distinctly different approach using c-kit CAR-T cells. Initial studies demonstrated in vitro killing of hematopoietic stem cells by c-kit CAR-T cells but poor expansion in vivo and poor migration of CAR-T cells into BM. Pre-treatment of recipient mice with low-dose cyclophosphamide (125 mg/kg) together with CXCR4 transduction in the CAR-T cells enhanced trafficking to and expansion in BM (<1%–13.1%). This resulted in significant depletion of the BM c-kit+ population (9.0%–0.1%). Because congenic Thy1.1 CAR-T cells were used in the Thy1.2-recipient mice, anti-Thy1.1 antibody could be used to deplete CAR-T cells in vivo before donor BM transplant. This achieved 20%–40% multilineage engraftment. We applied this conditioning to achieve an average of 28% correction of chronic granulomatous disease mice by wild-type BM transplant. Our findings provide a proof of concept that c-kit CAR-T cells can achieve effective BM conditioning without chemo-/radiotherapy. Our work also demonstrates that co-expression of a trafficking receptor can enhance targeting of CAR-T cells to a designated tissue.
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