Development of a gene edited next-generation hematopoietic cell transplant to enable acute myeloid leukemia treatment by solving off-tumor toxicity

Protection of CD33-modified hematopoietic stem cell progeny from CD33-directed CAR T cells in rhesus macaques

ABSTRACT

The treatment of monogenetic disorders, such as hemoglobinopathies and lysosomal storage diseases, has markedly improved with the advent of cell and gene therapies, particularly allogeneic or gene-modified autologous stem cell transplantations. However, therapeutic efficacy is reliant on maintaining engraftment above a critical threshold. To maintain such engraftment levels, we and others have pursued approaches to shield edited cells from antibody or chimeric antigen receptor (CAR) T-cell-mediated selection. Here, we focused on CD33, which is expressed early on hematopoietic stem and progenitor cells (HSPCs) as well as on myeloid progenitors. Rhesus macaques were engrafted with HSPCs edited to ablate CD33 using either CRISPR/CRISPR-associated protein 9 or adenine base editor. Both editing strategies showed similar post-transplant recovery kinetics and yielded equivalent levels of engraftment. We then created a V-set domain-specific CAR construct (CAR33), validated its functionality in vitro, and treated both animals with autologous CAR33 T cells. CAR33 T cells expanded after infusion and caused specific depletion of CD33WT but not CD33null progeny, leading to a transient enrichment for gene-edited cells in the blood. No depletion was seen in the bone marrow stem cell compartment with CD34+CD90+ HSCs expressing lower levels of CD33 in comparison to monocytes. Thus, we show proof of concept and safety of an epitope editing-based enrichment/protection strategy in macaques.

Cellular and immunotherapies for myelodysplastic syndromes

In this review article, we outline the current landscape of immune and cell therapy-based approaches for patients with myelodysplastic syndromes (MDS). Given the well characterized graft-versus-leukemia (GVL) effect observed with allogeneic hematopoietic cell transplantation, and the known immune escape mechanisms observed in MDS cells, significant interest exists in developing immune-based approaches to treat MDS. These attempts have included antibody-based drugs that block immune escape molecules, such as inhibitors of the PD-1/PD-L1 and TIM-3/galectin-9 axes that mediate interactions between MDS cells and T-lymphocytes, as well as antibodies that block the CD47/SIRPα interaction, which mediates macrophage phagocytosis. Unfortunately, these approaches have been largely unsuccessful. There is significant potential for T-cell engaging therapies and chimeric antigen receptor T (CAR-T) cells, but there are also several limitations to these approaches that are unique to MDS. However, many of these limitations may be overcome by the next generation of cellular therapies, including those with engineered T-cell receptors or natural killer (NK)-cell based platforms. Regardless of the approach, all these immune cells are subject to the complex bone marrow microenvironment in MDS, which harbours a variable and heterogeneous mix of pro-inflammatory cytokines and immunosuppressive elements. Understanding this interaction will be paramount to ensuring the success of immune and cellular therapies in MDS.

Finding potential targets in cell-based immunotherapy for handling the challenges of acute myeloid leukemia

Acute myeloid leukemia (AML) is a hostile hematological malignancy under great danger of relapse and poor long-term survival rates, despite recent therapeutic advancements. To deal with this unfulfilled clinical necessity, innovative cell-based immunotherapies have surfaced as promising approaches to improve anti-tumor immunity and enhance patient outcomes. In this comprehensive review, we provide a detailed examination of the latest developments in cell-based immunotherapies for AML, including chimeric antigen receptor (CAR) T-cell therapy, T-cell receptor (TCR)-engineered T-cell therapy, and natural killer (NK) cell-based therapies. We critically evaluate the unique mechanisms of action, current challenges, and evolving strategies to improve the efficacy and safety of these modalities. The review emphasizes how promising these cutting-edge immune-based strategies are in overcoming the inherent complexities and heterogeneity of AML. We discuss the identification of optimal target antigens, the importance of mitigating on-target/off-tumor toxicity, and the need to enhance the persistence and functionality of engineered immune effector cells. All things considered, this review offers a thorough overview of the rapidly evolving field of cell-based immunotherapy for AML, underscoring the significant progress made and the ongoing efforts to translate these innovative approaches into more effective and durable treatments for this devastating disease.

T cell-redirecting therapies in hematological malignancies: Current developments and novel strategies for improved targeting

T cell-redirecting therapies (TCRTs), such as chimeric antigen receptor (CAR) or T cell receptor (TCR) T cells and T cell engagers, have emerged as a highly effective treatment modality, particularly in the B and plasma cell-malignancy setting. However, many patients fail to achieve deep and durable responses; while the lack of truly unique tumor antigens, and concurrent on-target/off-tumor toxicities, have hindered the development of TCRTs for many other cancers. In this review, we discuss the recent developments in TCRT targets for hematological malignancies, as well as novel targeting strategies that aim to address these, and other, challenges.

CRISPR technology in human diseases

Gene editing is a growing gene engineering technique that allows accurate editing of a broad spectrum of gene-regulated diseases to achieve curative treatment and also has the potential to be used as an adjunct to the conventional treatment of diseases. Gene editing technology, mainly based on clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR-associated protein systems, which is capable of generating genetic modifications in somatic cells, provides a promising new strategy for gene therapy for a wide range of human diseases. Currently, gene editing technology shows great application prospects in a variety of human diseases, not only in therapeutic potential but also in the construction of animal models of human diseases. This paper describes the application of gene editing technology in hematological diseases, solid tumors, immune disorders, ophthalmological diseases, and metabolic diseases; focuses on the therapeutic strategies of gene editing technology in sickle cell disease; provides an overview of the role of gene editing technology in the construction of animal models of human diseases; and discusses the limitations of gene editing technology in the treatment of diseases, which is intended to provide an important reference for the applications of gene editing technology in the human disease.