CAR-T Cell Therapy for Acute Myeloid Leukemia: Preclinical Rationale, Current Clinical Progress, and Barriers to Success

Targeting the membrane-proximal C2-set domain of CD33 for improved CAR T cell therapy

Current CD33-targeted immunotherapies typically recognize the membrane-distal V-set domain of CD33. Here, we show that decreasing the distance between T cell and leukemia cell membrane increases the efficacy of CD33 chimeric antigen receptor (CAR) T cells. We therefore generated and optimized second-generation CAR constructs containing single-chain variable fragments from antibodies raised against the membrane-proximal C2-set domain, which bind CD33 regardless of whether the V-set domain is present (CD33PAN antibodies). CD33PAN CAR T cells resulted in efficient tumor clearance and improved survival of immunodeficient mice bearing human AML cell xenografts and, in an AML model with limited CD33 expression, forced escape of CD33neg leukemia. Compared to CD33V-set CAR T cells, CD33PAN CAR T cells showed greater in vitro and in vivo efficacy against several human AML cell lines with differing levels of CD33 without increased expression of exhaustion markers. CD33PAN moieties were detected at a higher frequency on human leukemic stem cells, and CD33PAN CAR T cells had greater in vitro efficacy against primary human AML cells. Together, our studies demonstrate improved efficacy with CAR T cells binding CD33 close to the cell membrane, providing the rationale to investigate CD33PAN CAR T cells further toward possible clinical application.

Proteasome inhibition enhances the anti-leukemic efficacy of chimeric antigen receptor (CAR) expressing NK cells against acute myeloid leukemia

BACKGROUND

Relapsed and refractory acute myeloid leukemia (AML) carries a dismal prognosis. CAR T cells have shown limited efficacy in AML, partially due to dysfunctional autologous T cells and the extended time for generation of patient specific CAR T cells. Allogeneic NK cell therapy is a promising alternative, but strategies to enhance efficacy and persistence may be necessary. Proteasome inhibitors (PI) induce changes in the surface proteome which may render malignant cells more vulnerable to NK mediated cytotoxicity. Here, we investigated the potential benefit of combining PIs with CAR-expressing allogeneic NK cells against AML.

METHODS

We established the IC50 concentrations for Bortezomib and Carfilzomib against several AML cell lines. Surface expression of class-I HLA molecules and stress-associated proteins upon treatment with proteasome inhibitors was determined by multiparameter flow cytometry. Using functional in vitro assays, we explored the therapeutic synergy between pre-treatment with PIs and the anti-leukemic efficacy of NK cells with or without expression of AML-specific CAR constructs against AML cell lines and primary patient samples. Also, we investigated the tolerability and efficacy of a single PI application strategy followed by (CAR-) NK cell infusion in two different murine xenograft models of AML.

RESULTS

AML cell lines and primary AML patient samples were susceptible to Bortezomib and Carfilzomib mediated cytotoxicity. Conditioned resistance to Azacitidine/Venetoclax did not confer primary resistance to PIs. Treating AML cells with PIs reduced the surface expression of class-I HLA molecules on AML cells in a time-and-dose dependent manner. Stress-associated proteins were upregulated on the transcriptional level and on the cell surface. NK cell mediated killing of AML cells was enhanced in a synergistic manner. PI pre-treatment increased effector-target cell conjugate formation and Interferon-γ secretion, resulting in enhanced NK cell activity against AML cell lines and primary samples in vitro. Expression of CD33- and CD70-specific CARs further improved the antileukemic efficacy. In vivo, Bortezomib pre-treatment followed by CAR-NK cell infusion reduced AML growth, leading to prolonged overall survival.

CONCLUSIONS

PIs enhance the anti-leukemic efficacy of CAR-expressing allogeneic NK cells against AML in vitro and in vivo, warranting further exploration of this combinatorial treatment within early phase clinical trials.

HA-1-targeted T-cell receptor T-cell therapy for recurrent leukemia after hematopoietic stem cell transplantation

ABSTRACT

Relapse is the leading cause of death after allogeneic hematopoietic stem cell transplantation (HCT) for leukemia. T cells engineered by gene transfer to express T cell receptors (TCR; TCR-T) specific for hematopoietic-restricted minor histocompatibility (H) antigens may provide a potent selective antileukemic effect post-HCT. We conducted a phase 1 clinical trial using a novel TCR-T product targeting the minor H antigen, HA-1, to treat or consolidate treatment of persistent or recurrent leukemia and myeloid neoplasms. The primary objective was to evaluate the feasibility and safety of administration of HA-1 TCR-T after HCT. CD8+ and CD4+ T cells expressing the HA-1 TCR and a CD8 coreceptor were successfully manufactured from HA-1-disparate HCT donors. One or more infusions of HA-1 TCR-T following lymphodepleting chemotherapy were administered to 9 HCT recipients who had developed disease recurrence after HCT. TCR-T cells expanded and persisted in vivo after adoptive transfer. No dose-limiting toxicities occurred. Although the study was not designed to assess efficacy, 4 patients achieved or maintained complete remissions following lymphodepletion and HA-1 TCR-T, with 1 patient still in remission at >2 years. Single-cell RNA sequencing of relapsing/progressive leukemia after TCR-T therapy identified upregulated molecules associated with T-cell dysfunction or cancer cell survival. HA-1 TCR-T therapy appears feasible and safe and shows preliminary signals of efficacy. This clinical trial was registered at ClinicalTrials.gov as #NCT03326921.

Immune-dysregulation harnessing in myeloid neoplasms

Myeloid malignancies arise in bone marrow microenvironments and shape these microenvironments in favor of malignant development. Immune suppression is one of the most important stages in myeloid leukemia progression. Leukemic clone expansion and immune dysregulation occur simultaneously in bone marrow microenvironments. Complex interactions emerge between normal immune system elements and leukemic clones in the bone marrow. In recent years, researchers have identified several of these pathological interactions. For instance, recent works shows that the secretion of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), from bone marrow stromal cells contributes to immune dysregulation and the selective proliferation of JAK2V617F+ clones in myeloproliferative neoplasms. Moreover, inflammasome activation and sterile inflammation result in inflamed microenvironments and the development of myelodysplastic syndromes. Additional immune dysregulations, such as exhaustion of T and NK cells, an increase in regulatory T cells, and impairments in antigen presentation are common findings in myeloid malignancies. In this review, we discuss the role of altered bone marrow microenvironments in the induction of immune dysregulations that accompany myeloid malignancies. We also consider both current and novel therapeutic strategies to restore normal immune system function in the context of myeloid malignancies.

Alliance between titans: combination strategies of CAR-T cell therapy and oncolytic virus for the treatment of hematological malignancies

There have been several clinical studies using chimeric antigen receptor (CAR)-T cell therapy for different hematological malignancies. It has transformed the therapy landscape for hematologic malignancies dramatically. Nonetheless, in acute myeloid leukemia (AML) and T cell malignancies, it still has a dismal prognosis. Even in the most promising locations, recurrence with CAR-T treatment remains a big concern. Oncolytic viruses (OVs) can directly lyse tumor cells or cause immune responses, and they can be manipulated to create therapeutic proteins, increasing anticancer efficacy. Oncolytic viruses have been proven in a rising number of studies to be beneficial in hematological malignancies. There are limitations that cannot be avoided by using either treatment alone, and the combination of CAR-T cell therapy and oncolytic virus therapy may complement the disadvantages of individual application, enhance the advantages of their respective treatment methods and improve the treatment effect. The alternatives for combining two therapies in hematological malignancies are discussed in this article.

CAR-NK cell therapy in AML: Current treatment, challenges, and advantage

Over the last decade, discovery of novel therapeutic method has been attention by the researchers and has changed the therapeutic perspective of hematological malignancies. Although NK cell play a pivotal role in the elimination of abnormal and cancerous cells, there are evidence that NK cell are disarm in hematological malignancy. Chimeric antigen receptor NK (CAR-NK) cell therapy, which includes the engineering of NK cells to detect tumor-specific antigens and, as a result, clear of cancerous cells, has created various clinical advantage for several human malignancies treatment. In the current review, we summarized NK cell dysfunction and CAR-NK cell based immunotherapy to treat AML patient.

A chemically adjustable BMP6-IL6 axis in mesenchymal stem cells drives acute myeloid leukemia cell differentiation

Chemotherapy alone or in combination with allogeneic stem cell transplantation has been the standard of care for acute myeloid leukemia (AML) for decades. Leukemia relapse with limited treatment options remains the main cause of treatment failure. Therefore, an effective and safe approach to improve treatment outcomes is urgently needed for most AML patients. Mesenchymal stem cells (MSCs) have been reported to efficiently induce apoptosis and shape the fate of acute myeloid leukemia cells. Here, we identified LG190155 as a potent compound that enhances the antileukemia efficiency of MSCs. Pretreatment of MSCs with LG190155 significantly provoked differentiation in both AML patient-derived primary leukemia cells and AML cell lines and reduced the tumor burden in the AML mouse model. Using the quantitative proteomic technique, we discovered a pivotal mechanism that mediates AML cell differentiation, in which autocrine bone morphogenetic protein 6 (BMP6) in MSCs boosted IL-6 secretion and further acted on leukemic cells to trigger differentiation. Furthermore, the activity of the BMP6-IL6 axis was dramatically enhanced by activating vitamin D receptor (VDR) in MSCs. Our data illustrated an effective preactivated approach to reinforcing the antileukemia effect of MSCs, which could serve as an effective therapeutic strategy for AML.

Recent progress in chimeric antigen receptor therapy for acute myeloid leukemia

Although CAR-T cell therapy has been particularly successful as a treatment for B cell malignancies, effectively treating acute myeloid leukemia with CAR remains a greater challenge. Multiple preclinical studies and clinical trials are underway, including on AML-related surface markers that CAR-T cells can target, such as CD123, CD33, NKG2D, CLL1, CD7, FLT3, Lewis Y and CD70, all of which provide opportunities for developing CAR-T therapies with improved specificity and efficacy. We also explored specific strategies for CAR-T cell treatment of AML, including immune checkpoints, suicide genes, dual targeting, genomic tools and the potential for universal CAR. In addition, CAR-T cell therapy for AML still has certain risks and challenges, including cytokine release syndrome (CRS) and haematotoxicity. Despite these challenges, as a new targeting method for AML treatment, CAR-T cell therapy still has great prospects. Ongoing research aims to further optimize this treatment mode.

Current Advancements in Anti-Cancer Chimeric Antigen Receptor T Cell Immunotherapy and How Nanotechnology May Change the Game

Chimeric antigen receptor (CAR)-T cell immunotherapy represents a cutting-edge advancement in the landscape of cancer treatment. This innovative therapy has shown exceptional promise in targeting and eradicating malignant tumors, specifically leukemias and lymphomas. However, despite its groundbreaking successes, (CAR)-T cell therapy is not without its challenges. These challenges, particularly pronounced in the treatment of solid tumors, include but are not limited to, the selection of appropriate tumor antigens, managing therapy-related toxicity, overcoming T-cell exhaustion, and addressing the substantial financial costs associated with treatment. Nanomedicine, an interdisciplinary field that merges nanotechnology with medical science, offers novel strategies that could potentially address these limitations. Its application in cancer treatment has already led to significant advancements, including improved specificity in drug targeting, advancements in cancer diagnostics, enhanced imaging techniques, and strategies for long-term cancer prevention. The integration of nanomedicine with (CAR)-T cell therapy could revolutionize the treatment landscape by enhancing the delivery of genes in (CAR)-T cell engineering, reducing systemic toxicity, and alleviating the immunosuppressive effects within the tumor microenvironment. This review aims to explore how far (CAR)-T cell immunotherapy has come alone, and how nanomedicine could strengthen it into the future. Additionally, the review will examine strategies to limit the off-target effects and systemic toxicity associated with (CAR)-T cell therapy, potentially enhancing patient tolerance and treatment outcomes.

Blood-brain barrier breakdown, central nervous system cell damage, and infiltrated T cells as major adverse effects in CAR-T-related deaths: a literature review

Background

CAR-T-related deaths observed worldwide are rare. The underlying pathogenetic mechanisms are the subject of study, as are the findings that enable diagnosis. A systematic literature search of the PubMed database and a critical review of the collected studies were conducted from the inception of this database until January 2023. The aim of the study is to determine when death is related to CAR-T cell therapy and to develop a shareable diagnostic algorithm.

Methods

The database was searched by combining and meshing the terms ("CAR-t" OR "CART") AND ("Pathology" OR "Histology" OR "Histological" OR "Autopsy") AND ("Heart" OR "Cardiac" OR "Nervous System" OR "Kidney" OR "Liver") with 34 results and also the terms: [(Lethal effect) OR (Death)] AND (CAR-T therapy) with 52 results in titles, abstracts, and keywords [all fields]. One hundred scientific articles were examined, 14 of which were additional records identified through other sources. Fifteen records were included in the review.

Results

Neuronal death, neuronal edema, perivascular edema, perivascular and intraparenchymal hemorrhagic extravasation, as well as perivascular plasmatodendrosis, have been observed in cases with fatal cerebral edema. A cross-reactivity of CAR-T cells in cases of fatal encephalopathy can be hypothesized when, in addition to the increased vascular permeability, there is also a perivascular lymphocyte infiltrate, which appears to be a common factor among most authors.

Conclusion

Most CAR-T-related deaths are associated with blood-brain barrier breakdown, central nervous system cell damage, and infiltrated T cells. Further autopsies and microscopic investigations would shed more light on the lethal toxicity related to CAR-T cells. A differential diagnosis of CAR-T-related death is crucial to identifying adverse events. In this article, we propose an algorithm that could facilitate the comparison of findings through a systematic approach. Despite toxicity cases, CAR-T therapy continues to stand out as the most innovative treatment within the field of oncology, and emerging strategies hold the promise of delivering safer therapies in future.

Chimeric Antigen Receptor T-Cell Therapy in Acute Myeloid Leukemia: State of the Art and Recent Advances

Chimeric antigen receptors (CAR)-T-cell therapy represents the most important innovation in onco-hematology in recent years. The progress achieved in the management of complications and the latest generations of CAR-T-cells have made it possible to anticipate in second-line the indication of this type of treatment in large B-cell lymphoma. While some types of B-cell lymphomas and B-cell acute lymphoid leukemia have shown extremely promising results, the same cannot be said for myeloid leukemias-in particular, acute myeloid leukemia (AML), which would require innovative therapies more than any other blood disease. The heterogeneities of AML cells and the immunological complexity of the interactions between the bone marrow microenvironment and leukemia cells have been found to be major obstacles to the clinical development of CAR-T in AML. In this review, we report on the main results obtained in AML clinical trials, the preclinical studies testing potential CAR-T constructs, and future perspectives.

Early and Late Toxicities of Chimeric Antigen Receptor T-Cells

As chimeric antigen receptor (CAR) T-cell therapy is increasingly integrated into clinical practice across a range of malignancies, identifying and treating inflammatory toxicities will be vital to success. Early experiences with CD19-targeted CAR T-cell therapy identified cytokine release syndrome and neurotoxicity as key acute toxicities and led to unified initiatives to mitigate the influence of these complications. In this section, we provide an update on the current state of CAR T-cell-related toxicities, with an emphasis on emerging acute toxicities affecting additional organ systems and considerations for delayed toxicities and late effects.

Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells

Discrimination between hematopoietic stem cells and leukemic stem cells remains a major challenge for acute myeloid leukemia immunotherapy. CAR T cells specific for the CD117 antigen can deplete malignant and healthy hematopoietic stem cells before consolidation with allogeneic hematopoietic stem cell transplantation in absence of cytotoxic conditioning. Here we exploit non-viral technology to achieve early termination of CAR T cell activity to prevent incoming graft rejection. Transient expression of an anti-CD117 CAR by mRNA conferred T cells the ability to eliminate CD117+ targets in vitro and in vivo. As an alternative approach, we used a Sleeping Beauty transposon vector for the generation of CAR T cells incorporating an inducible Caspase 9 safety switch. Stable CAR expression was associated with high proportion of T memory stem cells, low levels of exhaustion markers, and potent cellular cytotoxicity. Anti-CD117 CAR T cells mediated depletion of leukemic cells and healthy hematopoietic stem cells in NSG mice reconstituted with human leukemia or CD34+ cord blood cells, respectively, and could be terminated in vivo. The use of a non-viral technology to control CAR T cell pharmacokinetic properties is attractive for a first-in-human study in patients with acute myeloid leukemia prior to hematopoietic stem cell transplantation.

NPM1-mutated acute myeloid leukemia: New pathogenetic and therapeutic insights and open questions

The nucleophosmin (NPM1) gene encodes for a multifunctional chaperone protein that is localized in the nucleolus but continuously shuttles between the nucleus and cytoplasm. NPM1 mutations occur in about one-third of AML, are AML-specific, usually involve exon 12 and are frequently associated with FLT3-ITD, DNMT3A, TET2, and IDH1/2 mutations. Because of its unique molecular and clinico-pathological features, NPM1-mutated AML is regarded as a distinct leukemia entity in both the International Consensus Classification (ICC) and the 5th edition of the World Health Organization (WHO) classification of myeloid neoplasms. All NPM1 mutations generate leukemic mutants that are aberrantly exported in the cytoplasm of the leukemic cells and are relevant to the pathogenesis of the disease. Here, we focus on recently identified functions of the NPM1 mutant at chromatin level and its relevance in driving HOX/MEIS gene expression. We also discuss yet controversial issues of the ICC/WHO classifications, including the biological and clinical significance of therapy-related NPM1-mutated AML and the relevance of blasts percentage in defining NPM1-mutated AML. Finally, we address the impact of new targeted therapies in NPM1-mutated AML with focus on CAR T cells directed against NPM1/HLA neoepitopes, as well as XPO1 and menin inhibitors.

The landscape of novel strategies for acute myeloid leukemia treatment: Therapeutic trends, challenges, and future directions

Acute myeloid leukemia (AML) is a highly heterogeneous subtype of hematological malignancies with a wide spectrum of cytogenetic and molecular abnormalities, which makes it difficult to manage and cure. Along with the deeper understanding of the molecular mechanisms underlying AML pathogenesis, a large cohort of novel targeted therapeutic approaches has emerged, which considerably expands the medical options and changes the therapeutic landscape of AML. Despite that, resistant and refractory cases caused by genomic mutations or bypass signalling activation remain a great challenge. Therefore, discovery of novel treatment targets, optimization of combination strategies, and development of efficient therapeutics are urgently required. This review provides a detailed and comprehensive discussion on the advantages and limitations of targeted therapies as a single agent or in combination with others. Furthermore, the innovative therapeutic approaches including hyperthermia, monoclonal antibody-based therapy, and CAR-T cell therapy are also introduced, which may provide safe and viable options for the treatment of patients with AML.

Immunogenic cell death inducer peptides: A new approach for cancer therapy, current status and future perspectives

Immunogenic Cell Death (ICD) is a type of cell death that kills tumor cells by stimulating the adaptive immune response against other tumor cells. ICD depends on the endoplasmic reticulum (ER) stress and the secretion of Damage-Associated Molecular Patterns (DAMP) by the dying tumor cell. DAMPs recruit innate immune cells such as Dendritic Cells (DC), triggering a cancer-specific immune response such as cytotoxic T lymphocytes (CTLs) to eliminate remaining cancer cells. ICD is accompanied by several hallmarks in dying cells, such as surface translocation of ER chaperones, calreticulin (CALR), and extracellular secretion of DAMPs such as high mobility group protein B1 (HMGB1) and adenosine triphosphate (ATP). Therapeutic peptides can kill bacteria and tumor cells thus affecting the immune system. They have high specificity and affinity for their targets, small size, appropriate cell membrane penetration, short half-life, and simple production processes. Peptides are interesting agents for immunomodulation since they may overcome the limitations of other therapeutics. Thus, the development of peptides affecting the TME and active antitumoral immunity has been actively pursued. On the other hand, several peptides have been recently identified to trigger ICD and anti-cancer responses. In the present review, we review previous studies on peptide-induced ICD, their mechanism, their targets, and markers. They include anti-microbial peptides (AMPs), cationic or mitochondrial targeting, checkpoint inhibitors, antiapoptotic inhibitors, and "don't eat me" inhibitor peptides. Also, peptides will be investigated potentially inducing ICD that is divided into ER stressors, ATPase inhibitors, and anti-microbial peptides.

In vitro differentiation of myeloid suppressor cells (MDSC-like) from an immature myelomonocytic precursor THP-1

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population with a potent suppressor profile that regulates immune responses. These cells are one of the main components of the microenvironment of several diseases, including solid and hematologic tumors, autoimmunities, and chronic inflammation. However, their wide use in studies is limited due to they comprehend a rare population, which is difficult to isolate, expand, differentiate, and maintain in culture. Additionally, this population has a complex phenotypic and functional characterization.

OBJECTIVE

To develop a protocol for the in vitro production of MDSC-like population from the differentiation of the immature myeloid cell line THP-1.

METHODS

We stimulated THP-1 with G-CSF (100 ng/mL) and IL-4 (20 ng/mL) for seven days to differentiate into the MDSC-like profile. At the end of the protocol, we characterized these cells phenotypically and functionally by immunophenotyping, gene expression analysis, cytokine release dosage, lymphocyte proliferation, and NK-mediated killing essays.

RESULTS

We differentiate THP-1 cells in an MDSC-like population, named THP1-MDSC-like, which presented immunophenotyping and gene expression profiles compatible with that described in the literature. Furthermore, we verified that this phenotypic and functional differentiation did not deviate to a macrophage profile of M1 or M2. These THP1-MDSC-like cells secreted several immunoregulatory cytokines into the microenvironment, consistent with the suppressor profile related to MDSC. In addition, the supernatant of these cells decreased the proliferation of activated lymphocytes and impaired the apoptosis of leukemic cells induced by NK cells.

CONCLUSIONS

We developed an effective protocol for MDSC in vitro production from the differentiation of the immature myeloid cell line THP-1 induced by G-CSF and IL-4. Furthermore, we demonstrated that THP1-MDSC-like suppressor cells contribute to the immune escape of AML cells. Potentially, these THP1-MDSC-like cells can be applied on a large-scale platform, thus being able to impact the course of several studies and models such as cancer, immunodeficiencies, autoimmunity, and chronic inflammation.

Challenges and optimal strategies of CAR T therapy for hematological malignancies

ABSTRACT

Remarkable improvement relative to traditional approaches in the treatment of hematological malignancies by chimeric antigen receptor (CAR) T-cell therapy has promoted sequential approvals of eight commercial CAR T products within last 5 years. Although CAR T cells' productization is now rapidly boosting their extensive clinical application in real-world patients, the limitation of their clinical efficacy and related toxicities inspire further optimization of CAR structure and substantial development of innovative trials in various scenarios. Herein, we first summarized the current status and major progress in CAR T therapy for hematological malignancies, then described crucial factors which possibly compromise the clinical efficacies of CAR T cells, such as CAR T cell exhaustion and loss of antigen, and finally, we discussed the potential optimization strategies to tackle the challenges in the field of CAR T therapy.

Outcomes with chimeric antigen receptor t-cell therapy in relapsed or refractory acute myeloid leukemia: a systematic review and meta-analysis

Background

We conducted a systematic review and meta-analysis to evaluate outcomes following chimeric antigen receptor T cell (CAR-T) therapy in relapsed/refractory acute myeloid leukemia (RR-AML).

Methods

We performed a literature search on PubMed, Cochrane Library, and Clinicaltrials.gov. After screening 677 manuscripts, 13 studies were included. Data was extracted following PRISMA guidelines. Pooled analysis was done using the meta-package by Schwarzer et al. Proportions with 95% confidence intervals (CI) were computed.

Results

We analyzed 57 patients from 10 clinical trials and 3 case reports. The pooled complete and overall response rates were 49.5% (95% CI 0.18-0.81, I² =65%) and 65.2% (95% CI 0.36-0.91, I² =57%). The pooled incidence of cytokine release syndrome, immune-effector cell associated neurotoxicity syndrome, and graft-versus-host disease was estimated as 54.4% (95% CI 0.17-0.90, I² =77%), 3.9% (95% CI 0.00-0.19, I² =22%), and 1.6% (95%CI 0.00-0.21, I² =33%), respectively.

Conclusion

CAR-T therapy has demonstrated modest efficacy in RR-AML. Major challenges include heterogeneous disease biology, lack of a unique targetable antigen, and immune exhaustion.

Establishment and validation of a carbohydrate metabolism-related gene signature for prognostic model and immune response in acute myeloid leukemia

Introduction

The heterogeneity of treatment response in acute myeloid leukemia (AML) patients poses great challenges for risk scoring and treatment stratification. Carbohydrate metabolism plays a crucial role in response to therapy in AML. In this multicohort study, we investigated whether carbohydrate metabolism related genes (CRGs) could improve prognostic classification and predict response of immunity and treatment in AML patients.

Methods

Using univariate regression and LASSO-Cox stepwise regression analysis, we developed a CRG prognostic signature that consists of 10 genes. Stratified by the median risk score, patients were divided into high-risk group and low-risk group. Using TCGA and GEO public data cohorts and our cohort (1031 non-M3 patients in total), we demonstrated the consistency and accuracy of the CRG score on the predictive performance of AML survival.

Results

The overall survival (OS) was significantly shorter in high-risk group. Differentially expressed genes (DEGs) were identified in the high-risk group compared to the low-risk group. GO and GSEA analysis showed that the DEGs were mainly involved in immune response signaling pathways. Analysis of tumor-infiltrating immune cells confirmed that the immune microenvironment was strongly suppressed in high-risk group. The results of potential drugs for risk groups showed that inhibitors of carbohydrate metabolism were effective.

Discussion

The CRG signature was involved in immune response in AML. A novel risk model based on CRGs proposed in our study is promising prognostic classifications in AML, which may provide novel insights for developing accurate targeted cancer therapies.

Safe and effective off-the-shelf immunotherapy based on CAR.CD123-NK cells for the treatment of acute myeloid leukaemia

Background

Paediatric acute myeloid leukaemia (AML) is characterized by poor outcomes in patients with relapsed/refractory disease, despite the improvements in intensive standard therapy. The leukaemic cells of paediatric AML patients show high expression of the CD123 antigen, and this finding provides the biological basis to target CD123 with the chimeric antigen receptor (CAR). However, CAR.CD123 therapy in AML is hampered by on-target off-tumour toxicity and a long “vein-to-vein” time.

Methods

We developed an off-the-shelf product based on allogeneic natural killer (NK) cells derived from the peripheral blood of healthy donors and engineered them to express a second-generation CAR targeting CD123 (CAR.CD123).

Results

CAR.CD123-NK cells showed significant anti-leukaemia activity not only in vitro against CD123⁺ AML cell lines and CD123⁺ primary blasts but also in two animal models of human AML-bearing immune-deficient mice. Data on anti-leukaemia activity were also corroborated by the quantification of inflammatory cytokines, namely granzyme B (Granz B), interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α), both in vitro and in the plasma of mice treated with CAR.CD123-NK cells.

To evaluate and compare the on-target off-tumour effects of CAR.CD123-T and NK cells, we engrafted human haematopoietic cells (hHCs) in an immune-deficient mouse model. All mice infused with CAR.CD123-T cells died by Day 5, developing toxicity against primary human bone marrow (BM) cells with a decreased number of total hCD45⁺ cells and, in particular, of hCD34⁺CD38⁻ stem cells. In contrast, treatment with CAR.CD123-NK cells was not associated with toxicity, and all mice were alive at the end of the experiments. Finally, in a mouse model engrafted with human endothelial tissues, we demonstrated that CAR.CD123-NK cells were characterized by negligible endothelial toxicity when compared to CAR.CD123-T cells.

Conclusions

Our data indicate the feasibility of an innovative off-the-shelf therapeutic strategy based on CAR.CD123-NK cells, characterized by remarkable efficacy and an improved safety profile compared to CAR.CD123-T cells. These findings open a novel intriguing scenario not only for the treatment of refractory/resistant AML patients but also to further investigate the use of CAR-NK cells in other cancers characterized by highly difficult targeting with the most conventional T effector cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01376-3.

CD7-directed CAR T-cell therapy: a potential immunotherapy strategy for relapsed/refractory acute myeloid leukemia

Relapsed/refractory acute myeloid leukemia (AML) patients generally have a dismal prognosis and the treatment remains challenging. Due to the expression of CD7 on 30% AML and not on normal myeloid and erythroid cells, CD7 is an attractive target for immunotherapy of AML. CD7-targeted CAR T-cells had demonstrated encouraging efficacy in xenograft models of AML. We report here on the use of autologous CD7 CAR T-cells in the treatment of a relapsed/refractory AML patient with complex karyotype, TP53 deletion, FLT3-ITD mutation, and SKAP2-RUNX1 fusion gene. Before the CAR T-cell therapy, the patient achieved partial remission with IA regimen and attained complete remission after reinduction therapy (decitabine and venentoclax). Relapse occurred after consolidation (CLAG regimen). Then she failed CLIA regimen combined with venetoclax and exhibited resistance to FLT3 inhibitors. Bone marrow showed 20% blasts (CD7+ 95.6%). A total dose of 5 × 10⁶/kg CD7 CAR T-cells was administered after the decitabine +FC regimen. Seventeen days after CAR T-cells infusion, she achieved morphologic leukemia-free state. The patient developed grade 3 cytokine release syndrome. No severe organ toxicity or immune effector cell-associated neurotoxicity syndrome was observed. In summary, the autologous CD7 CAR T-cell therapy could be considered a potential approach for AML with CD7 expression (NCT04762485).

Trial registration Clinical Trials.gov, NCT04762485. Registered on February 21, 2021, prospectively registered

New Perspectives in Treating Acute Myeloid Leukemia: Driving towards a Patient-Tailored Strategy

For decades, intensive chemotherapy (IC) has been considered the best therapeutic option for treating acute myeloid leukemia (AML), with no curative option available for patients who are not eligible for IC or who have had failed IC. Over the last few years, several new drugs have enriched the therapeutic arsenal of AML treatment for both fit and unfit patients, raising new opportunities but also new challenges. These include the already approved venetoclax, the IDH1/2 inhibitors enasidenib and ivosidenib, gemtuzumab ozogamicin, the liposomal daunorubicin/cytarabine formulation CPX-351, and oral azacitidine. Venetoclax, an anti BCL2-inhibitor, in combination with hypomethylating agents (HMAs), has markedly improved the management of unfit and elderly patients from the perspective of improved quality of life and better survival. Venetoclax is currently under investigation in combination with other old and new drugs in early phase trials. Recently developed drugs with different mechanisms of action and new technologies that have already been investigated in other settings (BiTE and CAR-T cells) are currently being explored in AML, and ongoing trials should determine promising agents, more synergic combinations, and better treatment strategies. Access to new drugs and inclusion in clinical trials should be strongly encouraged to provide scientific evidence and to define the future standard of treatment in AML.

A Bibliometric and Knowledge-Map Analysis of CAR-T Cells From 2009 to 2021

Objectives

A bibliometric and knowledge-map analysis is used to explore hotspots’ evolution and development trends in the CAR-T cell field. By looking for research hotspots and new topics, we can provide new clues and ideas for researchers in this field.

Methods

The articles and reviews regarding CAR-T cells were retrieved and obtained from the Web of Science Core Collection (WOSCC) on October 28th, 2021. CtieSpace [version 5.8.R3 (64-bit)] and VOSviewer (version 1.6.17) were used to conduct the bibliometric and knowledge-map analysis.

Results

660 authors from 488 institutions in 104 countries/regions published 6,867 papers in 1,212 academic journals. The United States was absolutely in the leading position in this research field. The institution that contributed the most publications was the University of Pennsylvania. Carl H June published the most articles, while Shannon L Maude had the most co-citations. However, there was little cooperation between countries. After 2012, cooperation among various institutions was also small. The journals that published the most CAR-T cell-related papers were Frontiers in immunology and Cancers. Nevertheless, Blood and The New England Journal of Medicine were the most commonly co-cited journals. The most influential research hotspots were the research of CAR-T cells in hematological malignancies, the related research of cytokine release syndrome (CRS), CD19, and the anti-tumor activity and efficacy of CAR-T cells. The latest hotspots and topics included the study of CAR-T cells in solid tumors, universal CAR-T cells, CAR-NK cells, CD22, and anakinra (the IL-1 receptor antagonist). The research of CAR-T cells in solid tumors was a rapidly developing hot field. Emerging topics in this field mainly included the study of CAR-T cells in glioblastoma (related targets: IL13Rα2, EGFRvIII, and HER2), neuroblastoma (related target: GD2), sarcoma (related target: HER2), and pancreatic cancer (related target: mesothelin), especially glioblastoma.

Conclusion

As an anti-tumor therapy with great potential and clinical application prospects, CAR-T cell therapy is still in a stage of rapid development. The related field of CAR-T cells will remain a research hotspot in the future.

In-Vivo Induced CAR-T Cell for the Potential Breakthrough to Overcome the Barriers of Current CAR-T Cell Therapy

Chimeric antigen receptor T cell (CAR-T cell) therapy has shown impressive success in the treatment of hematological malignancies, but the systemic toxicity and complex manufacturing process of current autologous CAR-T cell therapy hinder its broader applications. Universal CAR-T cells have been developed to simplify the production process through isolation and editing of allogeneic T cells from healthy persons, but the allogeneic CAR-T cells have recently encountered safety concerns, and clinical trials have been halted by the FDA. Thus, there is an urgent need to seek new ways to overcome the barriers of current CAR-T cell therapy. In-vivo CAR-T cells induced by nanocarriers loaded with CAR-genes and gene-editing tools have shown efficiency for regressing leukemia and reducing systemic toxicity in a mouse model. The in-situ programming of autologous T-cells avoids the safety concerns of allogeneic T cells, and the manufacture of nanocarriers can be easily standardized. Therefore, the in-vivo induced CAR-T cells can potentially overcome the abovementioned limitations of current CAR-T cell therapy. Here, we provide a review on CAR structures, gene-editing tools, and gene delivery techniques applied in immunotherapy to help design and develop new in-vivo induced CAR-T cells.

The Hematology of Tomorrow Is Here-Preclinical Models Are Not: Cell Therapy for Hematological Malignancies

Simple Summary

Cell therapy is revolutionizing the prospect of deadly hematological malignancies such as high-risk acute myeloid leukemia. Stem cell therapy of allogeneic source from compatible human leukocyte antigen donor has exceptional success promoting durable remissions, but the rate of relapse is currently still high and there is transplant-related mortality. This review presents the current knowledge on the clinical use of mesenchymal stromal cells to improve outcomes in hematopoietic stem cell transplants. As an alternative or adjuvant approach to prevent relapse, we summarize the status of the promising forms of cellular immunotherapy aimed at targeting not only the bulk but also the cells of origin of leukemia. Finally, we discuss the available in vivo models for disease modelling and treatment efficacy prediction in these contexts.

Abstract

The purpose of this review is to present the current knowledge on the clinical use of several forms of cell therapy in hematological malignancies and the preclinical models available for their study. In the context of allogeneic hematopoietic stem cell transplants, mesenchymal stromal cells are pursued to help stem cell engraftment and expansion, and control graft versus host disease. We further summarize the status of promising forms of cellular immunotherapy including CAR T cell and CAR NK cell therapy aimed at eradicating the cells of origin of leukemia, i.e., leukemia stem cells. Updates on other forms of cellular immunotherapy, such as NK cells, CIK cells and CAR CIK cells, show encouraging results in AML. The considerations in available in vivo models for disease modelling and treatment efficacy prediction are discussed, with a particular focus on their strengths and weaknesses for the study of healthy and diseased hematopoietic stem cell reconstitution, graft versus host disease and immunotherapy. Despite current limitations, cell therapy is a rapidly evolving field that holds the promise of improved cure rates, soon. As a result, we may be witnessing the birth of the hematology of tomorrow. To further support its development, improved preclinical models including humanized microenvironments in mice are urgently needed.

Prevention and Treatment of Acute Myeloid Leukemia Relapse after Hematopoietic Stem Cell Transplantation: The State of the Art and Future Perspectives

Allogeneic hematopoietic stem cell transplantation (HSCT) for high-risk acute myeloid leukemia (AML) represents the only curative option. Progress has been made in the last two decades in the pre-transplant induction therapies, supportive care, selection of donors and conditioning regimens that allowed to extend the HSCT to a larger number of patients, including those aged over 65 years and/or lacking an HLA-identical donor. Furthermore, improvements in the prophylaxis of the graft-versus-host disease and of infection have dramatically reduced transplant-related mortality. The relapse of AML remains the major reason for transplant failure affecting almost 40-50% of the patients. From 10 to 15 years ago to date, treatment options for AML relapsing after HSCT were limited to conventional cytotoxic chemotherapy and donor leukocyte infusions (DLI). Nowadays, novel agents and targeted therapies have enriched the therapeutic landscape. Moreover, very recently, the therapeutic landscape has been enriched by manipulated cellular products (CAR-T, CAR-CIK, CAR-NK). In light of these new perspectives, careful monitoring of minimal-residual disease (MRD) and prompt application of pre-emptive strategies in the post-transplant setting have become imperative. Herein, we review the current state of the art on monitoring, prevention and treatment of relapse of AML after HSCT with particular attention on novel agents and future directions.

Immune-Based Therapeutic Strategies for Acute Myeloid Leukemia

Simple Summary

This review summarizes various therapeutic immune approaches representing their targets, the efficacy and toxicity in the treatment of acute myeloid leukemia. In particular, immune checkpoint inhibitors, bispecific T-cell engager antibodies and chimeric antigen receptor-T-cell approaches are highlighted.

Abstract

The development and design of immune-based strategies have become an increasingly important topic during the last few years in acute myeloid leukemia (AML), based on successful immunotherapies in solid cancer. The spectrum ranges from antibody drug conjugates, immune checkpoint inhibitors blocking programmed cell death protein 1 (PD1), cytotoxic T lymphocyte antigen 4 (CTLA4) or T cell immunoglobulin and mucin domain containing-3 (TIM3), to T-cell based monoclonal and bispecific T-cell engager antibodies, chimeric antigen receptor-T-cell (CAR-T) approaches and leukemia vaccines. Currently, there are many substances in development and multiple phase I/II studies are ongoing. These trials will help us to deepen our understanding of the pathogenesis of AML and facilitate the best immunotherapeutic strategy in AML. We discuss here the mode of action of immune-based therapies and provide an overview of the available data.

Engineering CAR-NK cells to secrete IL-15 sustains their anti-AML functionality but is associated with systemic toxicities

Background

The prognosis of patients with recurrent/refractory acute myelogenous leukemia (AML) remains poor and cell-based immunotherapies hold promise to improve outcomes. Natural Killer (NK) cells can elicit an antileukemic response via a repertoire of activating receptors that bind AML surface ligands. NK-cell adoptive transfer is safe but thus far has shown limited anti-AML efficacy. Here, we aimed to overcome this limitation by engineering NK cells to express chimeric antigen receptors (CARs) to boost their anti-AML activity and interleukin (IL)-15 to enhance their persistence.

Methods

We characterized in detail NK-cell populations expressing a panel of AML (CD123)-specific CARs and/or IL-15 in vitro and in AML xenograft models.

Results

CARs with 2B4.ζ or 4-1BB.ζ signaling domains demonstrated greater cell surface expression and endowed NK cells with improved anti-AML activity in vitro. Initial in vivo testing revealed that only 2B4.ζ Chimeric Antigen Receptor (CAR)-NK cells had improved anti-AML activity in comparison to untransduced (UTD) and 4-1BB.ζ CAR-NK cells. However, the benefit was transient due to limited CAR-NK-cell persistence. Transgenic expression of secretory interleukin (sIL)-15 in 2B4.ζ CAR and UTD NK cells improved their effector function in the setting of chronic antigen simulation in vitro. Multiparameter flow analysis after chronic antigen exposure identified the expansion of unique NK-cell subsets. 2B4.ζ/sIL-15 CAR and sIL-15 NK cells maintained an overall activated NK-cell phenotype. This was confirmed by transcriptomic analysis, which revealed a highly proliferative and activated signature in these NK-cell groups. In vivo, 2B4.ζ/sIL-15 CAR-NK cells had potent anti-AML activity in one model, while 2B4.ζ/sIL-15 CAR and sIL-15 NK cells induced lethal toxicity in a second model.

Conclusion

Transgenic expression of CD123-CARs and sIL-15 enabled NK cells to function in the setting of chronic antigen exposure but was associated with systemic toxicities. Thus, our study provides the impetus to explore inducible and controllable expression systems to provide cytokine signals to AML-specific CAR-NK cells before embarking on early-phase clinical testing.

Immune Phenomena in Myeloid Neoplasms: An "Egg or Chicken" Question

Immune phenomena are increasingly reported in myeloid neoplasms, and include autoimmune cytopenias/diseases and immunodeficiency, either preceding or complicating acute myeloid leukemia, myelodysplastic syndromes (MDS), chronic myeloproliferative neoplasms, and bone marrow failure (BMF) syndromes. Autoimmunity and immunodeficiency are the two faces of a dysregulated immune tolerance and surveillance and may result, along with contributing environmental and genetic factors, in an increased incidence of both tumors and infections. The latter may fuel both autoimmunity and immune activation, triggering a vicious circle among infections, tumors and autoimmune phenomena. Additionally, alterations of the microbiota and of mesenchymal stem cells (MSCs) pinpoint to the importance of a permissive or hostile microenvironment for tumor growth. Finally, several therapies of myeloid neoplasms are aimed at increasing host immunity against the tumor, but at the price of increased autoimmune phenomena. In this review we will examine the epidemiological association of myeloid neoplasms with autoimmune diseases and immunodeficiencies, and the pivotal role of autoimmunity in the pathogenesis of MDS and BMF syndromes, including the paroxysmal nocturnal hemoglobinuria conundrum. Furthermore, we will briefly examine autoimmune complications following therapy of myeloid neoplasms, as well as the role of MSCs and microbiota in these settings.

CAR T-Cell Therapy in Hematological Malignancies

Chimeric antigen receptor (CAR) T-cells (CAR T-cells) are a promising therapeutic approach in treating hematological malignancies. CAR T-cells represent engineered autologous T-cells, expressing a synthetic CAR, targeting tumor-associated antigens (TAAs) independent of major histocompatibility complex (MHC) presentation. The most common target is CD19 on B-cells, predominantly used for the treatment of lymphoma and acute lymphocytic leukemia (ALL), leading to approval of five different CAR T-cell therapies for clinical application. Despite encouraging clinical results, treatment of other hematological malignancies such as acute myeloid leukemia (AML) remains difficult. In this review, we focus especially on CAR T-cell application in different hematological malignancies as well as strategies for overcoming CAR T-cell dysfunction and increasing their efficacy.

Driving CAR T Stem Cell Targeting in Acute Myeloid Leukemia: The Roads to Success

Current treatment outcome for acute myeloid leukemia (AML) patients is unsatisfactory and characterized by high rates of relapse and poor overall survival. Increasing evidence points to a crucial role of leukemic stem cells (LSC) and the bone marrow (BM) leukemic niche, in which they reside, in AML evolution and chemoresistance. Thus, future strategies aiming at improving AML therapeutic protocols are likely to be directed against LSC and their niche. Chimeric antigen receptor (CAR) T-cells have been extremely successful in the treatment of relapsed/refractory acute lymphoblastic leukemia and B-cell non-Hodgkin lymphoma and comparable results in AML are highly desirable. At present, we are at the dawn of CAR T-cell application in AML, with several preclinical studies and few early phase clinical trials. However, the lack of leukemia-specific targets and the genetic and phenotypic heterogeneity of the disease combined with the leukemia-induced remodeling of the BM microenvironment are limiting CAR T-cell exploitation in AML. Here, we reviewed AML-LSC and AML-BM niche features in the context of their therapeutic targeting using CAR T-cells. We summarized recent progress in CAR T-cell application to the treatment of AML, and we discussed the remaining therapeutic challenges and promising novel strategies to overcome them.