Anti-TIM3 chimeric antigen receptor-natural killer cells preferentially target primitive acute myeloid leukemia cells with minimal fratricide and exhaustion

Acute myeloid leukemia (AML) is an aggressive and genetically heterogeneous disease with poor clinical outcomes. Refractory AML is common, and relapse remains a major challenge, attributable to the presence of therapy-resistant leukemic stem cells (LSCs), which possess self-renewal and repopulating capability. Targeting LSCs is currently the most promising avenue for long-term management of AML. Likewise, chimeric antigen receptor (CAR)-natural killer (NK) cells have emerged as a promising alternative to CAR-T cells due to their intrinsic potential as off-the-shelf products and safer clinical profiles. Here, we introduced a third-generation CAR harboring TIM3 scFv, CD28, 4-1BB, and CD3 zeta (CAR-TIM3) into human NK-92 cells, the only FDA-approved NK cell line for clinical trials. TIM3 was chosen as a target antigen owing to its differential expression in LSCs and normal hematopoietic stem/progenitor cells (HSPCs). The established CAR-TIM3 NK-92 cells effectively targeted TIM3 and displayed potent anti-tumor activity against various primitive AML cells, subsequently causing a reduction in leukemic clonogenic growth in vitro, while having minimal effects on HSPCs. CAR-TIM3 NK-92 cells significantly reduced leukemic burden in vivo and interestingly suppressed the engraftment of AML cells into the mouse liver and bone marrow. Surprisingly, we found that CAR-TIM3 NK-92 cells expressed relatively low surface TIM3, leading to a low fratricidal effect. As TIM3 and PD-1 are immune checkpoints involved in NK cell dysfunction, we further tested and found that CAR-TIM3 NK-92 cells are beneficial for alleviating NK cell exhaustion. Our findings highlight the potential application of CAR-TIM3 NK cells for cellular immunotherapy for TIM3+ AML.