Proteins created from recurrent fusion genes like CBFB-MYH11 are prevalent in acute myeloid leukemia (AML), often necessary for leukemogenesis, persistent throughout the disease course, and highly leukemia specific, making them attractive neoantigen targets for immunotherapy. A nonameric peptide derived from a prevalent CBFB-MYH11 fusion protein was found to be immunogenic in HLA-B*40:01+ donors. High-avidity CD8+ T cell clones isolated from healthy donors killed CBFB-MYH11+ HLA-B*40:01+ AML cell lines and primary human AML samples in vitro. CBFB-MYH11–specific T cells also controlled CBFB-MYH11+ HLA-B*40:01+ AML in vivo in a patient-derived murine xenograft model. High-avidity CBFB-MYH11 epitope–specific T cell receptors (TCRs) transduced into CD8+ T cells conferred antileukemic activity in vitro. Our data indicate that the CBFB-MYH11 fusion neoantigen is naturally presented on AML blasts and enables T cell recognition and killing of AML. We provide proof of principle for immunologically targeting AML-initiating fusions and demonstrate that targeting neoantigens has clinical relevance even in low–mutational frequency cancers like fusion-driven AML. This work also represents a first critical step toward the development of TCR T cell immunotherapy targeting fusion gene–driven AML.
Melinda A. Biernacki, Kimberly A. Foster, Kyle B. Woodward, Michael E. Coon, Carrie Cummings, Tanya M. Cunningham, Robson G. Dossa, Michelle Brault, Jamie Stokke, Tayla M. Olsen, Kelda Gardner, Elihu Estey, Soheil Meshinchi, Anthony Rongvaux, Marie Bleakley