A novel TCR like CAR with specificity for PR1/HLA A2 effectively targets myeloid leukemia in vitro when expressed in human adult peripheral blood and cord blood T cells.
BACKGROUND AIMS The PR1 peptide, derived from the leukemia associated antigens proteinase 3 and neutrophil elastase, is overexpressed on HLA A2 in acute myeloid leukemia (AML) We developed a T cell receptor (TCR) like monoclonal antibody (8F4) that binds the PR1/HLA A2 complex on the surface of AML cells, efficiently killing them in vitro and eliminating them in preclinical models. Humanized 8F4 (h8F4) with high affinity for the PR1/HLA A2 epitope was used to construct an h8F4 chimeric antigen receptor (CAR) that was transduced into T cells to mediate anti leukemia activity. METHODS Human T cells were transduced to express the PR1/HLA A2 specific CAR (h8F4 CAR T cells) containing the scFv of h8F4 fused to the intracellular signaling endo domain of CD3 zeta chain through the transmembrane and intracellular costimulatory domain of CD28. RESULTS Adult human normal peripheral blood (PB) T cells were efficiently transduced with the h8F4 CAR construct and predominantly displayed an effector memory phenotype with a minor population (12% of central memory cells in vitro. Umbilical cord blood (UCB) T cells could also be efficiently transduced with the h8F4 CAR. The PB and UCB derived h8F4 CAR T cells specifically recognized the PR1/HLA A2 complex and were capable of killing leukemia cell lines and primary AML blasts in an HLA A2 dependent manner. CONCLUSIONS Human adult PB and UCB derived T cells expressing a CAR derived from the TCR like 8F4 antibody rapidly and efficiently kill AML in vitro. Our data could lead to a new treatment paradigm for AML in which targeting leukemia stem cells could transfer long term immunity to protect against relapse.
Cytotherapy