HSPA5 and acute myeloid leukemia: Progression was due to lack of CAR T cell persistence and not the development of antigen loss variants, since recurrent AML cells continued to express cell surface GRP78, and we could not detect CAR T cells in the peripheral blood, bone marrow, and/or spleen at the time of relapse (Fig. 6d, for gating strategy see Supplementary Fig. 9).