[Observation on the efficacy of consolidation chemotherapy combined with allogeneic natural killer cell infusion in the treatment of low and moderate risk acute myeloid leukemia]

MRD-directed and risk-adapted individualized stratified treatment of AML

Measurable residual disease (MRD) has been widely recognized as a biomarker for deeply evaluating complete remission (CR), predicting relapse, guiding pre-emptive interventions, and serving as an endpoint surrogate for drug testing. However, despite the emergence of new technologies, there remains a lack of comprehensive understanding regarding the proper techniques, sample materials, and optimal time points for MRD assessment. In this review, we summarized the MRD methods, sample sources, and evaluation frequency according to the risk category of the European Leukemia Net (ELN) 2022. Additionally, we emphasize the importance of properly utilizing and combining these technologies. We have also refined the flowchart outlining each time point for pre-emptive interventions and intervention paths. The evaluation of MRD in acute myeloid leukemia (AML) is sophisticated, clinically applicable, and technology-dependent, and necessitates standardized approaches and further research.

piggyBac system to co-express NKG2D CAR and IL-15 to augment the in vivo persistence and anti-AML activity of human peripheral blood NK cells

Promising progress has been made in adoptive transfer of allogeneic natural killer (NK) cells to treat relapsed or refractory acute myeloid leukemia (AML). In this regard, chimeric antigen receptor (CAR)-modification of NK cells is considered as a compelling approach to augment the specificity and cytotoxicity of NK cells against AML. Using a non-viral piggyBac transposon technology and human peripheral blood-derived primary NK cells, we generated CAR-NK cells to target NKG2D ligands and demonstrated their in vitro activity in lysing cancer cells expressing the ligands and in vivo efficacy in inhibiting tumor growth in a xenograft KG-1 AML model. We further generated CAR-NK cells co-expressing transgenes for the NKG2D CAR and interleukin-15 (IL-15). The ectopic expression of IL-15 improved the in vitro and in vivo persistence of NKG2D CAR-NK cells, leading to enhanced in vivo tumor control and significant prolongation of mouse survival in the KG-1 AML model. Collectively, our findings demonstrate the ectopic expression of IL-15 as an important means to improve the antileukemic activity of NKG2D CAR-NK cells. Our study further illustrates the feasibility of using the piggyBac non-viral platform as an efficient and cost-effective way for CAR-NK cell manufacturing.

From CAR-T Cells to CAR-NK Cells: A Developing Immunotherapy Method for Hematological Malignancies

The approval of CD19 chimeric antigen receptor (CAR)-engineered T (CAR-T) cell products in B-cell malignancies represents a breakthrough in CAR-T cell immunotherapy. However, the remaining limitations concerning the graft-versus-host disease (GVHD) and other adverse effects (e.g., cytokine release syndromes [CRS] and neurotoxicity) still restrict their wider applications. Natural killer (NK) cells have been identified as promising candidates for CAR-based cellular immunotherapy because of their unique characteristics. No HLA-matching restriction and abundant sources make CAR-engineered NK (CAR-NK) cells potentially available to be off-the-shelf products that could be readily available for immediate clinical use. Therefore, researchers have gradually shifted their focus from CAR-T cells to CAR-NK cells in hematological malignancies. This review discusses the current status and applications of CAR-NK cells in hematological malignancies, as well as the unique advantages of CAR-NK cells compared with CAR-T cells. It also discusses challenges and prospects regarding clinical applications of CAR-NK cells.

Cellular immunotherapy for hematological malignancy: recent progress and future perspectives

Advancements in the field of cellular immunotherapy have accelerated in recent years and have changed the treatment landscape for a variety of hematologic malignancies. Cellular immunotherapy strategies exploit the patient's immune system to kill cancer cells. The successful use of CD19 chimeric antigen receptor (CAR) T-cells in treating B-cell malignancies is the paradigm of this revolution, and numerous ongoing studies are investigating and extending this approach to other malignancies. However, resistance to CAR-T-cell therapy and non-durable efficacy have prevented CAR-T-cells from becoming the ultimate therapy. Because natural killer (NK) cells play an essential role in antitumor immunity, adoptively transferred allogeneic NK and CAR-modified NK cell therapy has been attempted in certain disease subgroups. Allogenic hematopoietic stem cell transplantation (allo-HSCT) is the oldest form of cellular immunotherapy and the only curative option for hematologic malignancies. Historically, the breadth of application of allo-HSCT has been limited by a lack of identical sibling donors (ISDs). However, great strides have recently been made in the success of haploidentical allografts worldwide, which enable everyone to have a donor. Haploidentical donors can achieve comparable outcomes to those of ISDs and even better outcomes in certain circumstances because of a stronger graft vs. tumor effect. Currently, novel strategies such as CAR-T or NK-based immunotherapy can be applied as a complement to allo-HSCT for curative effects, particularly in refractory cases. Here, we introduce the developments in cellular immunotherapy in hematology.

Natural killer cell-based immunotherapy for acute myeloid leukemia

Despite considerable progress has been achieved in the treatment of acute myeloid leukemia over the past decades, relapse remains a major problem. Novel therapeutic options aimed at attaining minimal residual disease-negative complete remission are expected to reduce the incidence of relapse and prolong survival. Natural killer cell-based immunotherapy is put forward as an option to tackle the unmet clinical needs. There have been an increasing number of therapeutic dimensions ranging from adoptive NK cell transfer, chimeric antigen receptor-modified NK cells, antibodies, cytokines to immunomodulatory drugs. In this review, we will summarize different forms of NK cell-based immunotherapy for AML based on preclinical investigations and clinical trials.