Immune checkpoint inhibitors in acute myeloid leukemia

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.

The Immune Resistance Signature of Acute Myeloid Leukemia and Current Immunotherapy Strategies

Acute myeloid leukemia (AML) is a complex hematopoietic clonal disorder with limited curative options beyond stem cell transplantation. The success of transplant is intimately linked with the graft versus leukemia effect from the alloreactive donor immune cells including, T and NK cells. The immune system plays a dynamic role in leukemia survival and resistance. Despite our growing understanding of the immune microenvironment, responses to immune-based therapies differ greatly between patients. Herein, we review the biology of immune evasion mechanisms in AML, discuss the current landscape of immunotherapeutic strategies, and discuss the implications of therapeutic targets. This review focuses on T and NK cell-based therapy, including modified and non-modified NK cells, CAR-T and CAR-NK cells, antibodies, and checkpoint blockades. Understanding the complex interchange between immune tolerance and the emergence of tumor resistance will improve patient outcomes.

T cell-mediated tumor killing sensitivity gene signature-based prognostic score for acute myeloid leukemia

BACKGROUND AND OBJECTIVE

Acute myeloid leukemia (AML) is an aggressive, heterogenous hematopoetic malignancies with poor long-term prognosis. T-cell mediated tumor killing plays a key role in tumor immunity. Here, we explored the prognostic performance and functional significance of a T-cell mediated tumor killing sensitivity gene (GSTTK)-based prognostic score (TTKPI).

METHODS

Publicly available transcriptomic data for AML were obtained from TCGA and NCBI-GEO. GSTTK were identified from the TISIDB database. Signature GSTTK for AML were identified by differential expression analysis, COX proportional hazards and LASSO regression analysis and a comprehensive TTKPI score was constructed. Prognostic performance of the TTKPI was examined using Kaplan-Meier survival analysis, Receiver operating curves, and nomogram analysis. Association of TTKPI with clinical phenotypes, tumor immune cell infiltration patterns, checkpoint expression patterns were analysed. Drug docking was used to identify important candidate drugs based on the TTKPI-component genes.

RESULTS

From 401 differentially expressed GSTTK in AML, 24 genes were identified as signature genes and used to construct the TTKPI score. High-TTKPI risk score predicted worse survival and good prognostic accuracy with AUC values ranging from 75 to 96%. Higher TTKPI scores were associated with older age and cancer stage, which showed improved prognostic performance when combined with TTKPI. High TTKPI was associated with lower naïve CD4 T cell and follicular helper T cell infiltrates and higher M2 macrophages/monocyte infiltration. Distinct patterns of immune checkpoint expression corresponded with TTKPI score groups. Three agents; DB11791 (Capmatinib), DB12886 (GSK-1521498) and DB14773 (Lifirafenib) were identified as candidates for AML.

CONCLUSION

A T-cell mediated killing sensitivity gene-based prognostic score TTKPI showed good accuracy in predicting survival in AML. TTKPI corresponded to functional and immunological features of the tumor microenvironment including checkpoint expression patterns and should be investigated for precision medicine approaches.

Comprehensive analysis of cuproptosis-associated LncRNAs predictive value and related CeRNA network in acute myeloid leukemia

Background

Acute myeloid leukemia (AML) is characterized by a high recurrence and mortality rate. Cuproptosis is involved in cell death regulation in in a variety of solid tumors. Long non-coding RNAs that regulate cuproptosis genes in the pathogenesis of acute leukemia have yet to be explored.

Methods

First, cuproptosis genes with distinct expression levels were discovered by contrasting AML with normal samples from the TCGA and GTEx cohorts. Pearson correlation and univariate Cox-regression analysis were performed to identify cuproptosis-associated lncRNAs with significant prognostic values. Then the least absolute shrinkage and selection operator (LASSO) Cox regression was utilized to establish a multi-gene signature to predict AML prognosis. Next, Kaplan-Meier estimator, receiver operating characteristic curve, and a nomogram were performed to evaluate the predictive capacity of the risk signature. Functional enrichment analyses were employed to assess their function. Moreover, qRT-PCR testing of lncRNA expression in AML samples was conducted. The competing endogenous RNA (ceRNA) network was constructed to find the target genes.

Results

A risk model based on the signature of three cuproptosis-associated lncRNAs was developed. The results showed that the model possessed excellent prognostic potential. The nomogram raised the accuracy in predicting AML survival. In addition, functional enrichment analyses demonstrated an enrichment of inflammatory and immune-related pathways. Moreover, correlations between the risk signature and clinicopathological variables, tumor mutational burden, RNA stemness score, immune profile, and drug sensitivity were observed. Furthermore, we discovered that TRAF3IP2-AS1 may function as a ceRNA to regulate cuproptosis and ferroptosis gene expression.

Conclusion

The risk signature established in this study could serve as a reliable biosignature for AML prognosis. And the findings presented here may facilitate research on cuproptosis in AML.

Acute myeloid leukemias with JAK2/STAT mutations are associated with PD-L1 upregulation

Even though overexpression of the immune checkpoint protein, programmed cell death ligand-1 (PD-L1), is observed in solid tumors, its expression patterns in acute myeloid leukemia remain understudied. As activation of the JAK/STAT pathway has been shown to enhance PD-L1 expression in preclinical models, we evaluated biopsies from AML patients with activating mutations in JAK2/STATs. PD-L1 expression was significantly upregulated in JAK2/STAT mutant cases when compared to JAK2 wildtype controls as demonstrated by PD-L1 immunohistochemistry staining and quantified using the combined positive score (CPS) system. There is significant overexpression of phosphorylated STAT3 expression in patients with oncogenic JAK2 activation and a positive correlation between p-STAT3 and PD-L1 expression. In conclusion, we demonstrate the CPS scoring system could be applied as a quantitative measure of PD-L1 expression in leukemias and that JAK2/STATs mutant AML can be potential candidates for checkpoint inhibitor trials.

Discovery of Small-Molecule TIM-3 Inhibitors for Acute Myeloid Leukemia Using Pharmacophore-Based Virtual Screening

T-cell immunoglobulin and mucin domain 3 (TIM-3) is a negative immune checkpoint that represents a promising target for cancer immunotherapy. Although encouraging results have been observed for TIM-3 inhibition in the context of acute myeloid leukemia (AML), targeting TIM-3 is currently restricted to monoclonal antibodies (mAbs). To fill this gap, we implemented a pharmacophore-based screening approach to identify small-molecule TIM-3 inhibitors. Our approach resulted in the identification of hit compounds with TIM-3 binding affinity. Subsequently, we used the structure-activity relationship (SAR) by a catalog approach to identify compound A-41 with submicromolar TIM-3 binding affinity. Remarkably, A-41 demonstrated the ability to block TIM-3 interactions with key ligands and inhibited the immunosuppressive function of TIM-3 using an in vitro coculture assay. This work will pave the way for future drug discovery efforts aiming at the development of small-molecule inhibitors TIM-3 for AML.

Regulation of hematopoietic and leukemia stem cells by regulatory T cells

Adult bone marrow (BM) hematopoietic stem cells (HSCs) are maintained in a quiescent state and sustain the continuous production of all types of blood cells. HSCs reside in a specialized microenvironment the so-called HSC niche, which equally promotes HSC self-renewal and differentiation to ensure the integrity of the HSC pool throughout life and to replenish hematopoietic cells after acute injury, infection or anemia. The processes of HSC self-renewal and differentiation are tightly controlled and are in great part regulated through cellular interactions with classical (e.g. mesenchymal stromal cells) and non-classical niche cells (e.g. immune cells). In myeloid leukemia, some of these regulatory mechanisms that evolved to maintain HSCs, to protect them from exhaustion and immune destruction and to minimize the risk of malignant transformation are hijacked/disrupted by leukemia stem cells (LSCs), the malignant counterpart of HSCs, to promote disease progression as well as resistance to therapy and immune control. CD4⁺ regulatory T cells (Tregs) are substantially enriched in the BM compared to other secondary lymphoid organs and are crucially involved in the establishment of an immune privileged niche to maintain HSC quiescence and to protect HSC integrity. In leukemia, Tregs frequencies in the BM even increase. Studies in mice and humans identified the accumulation of Tregs as a major immune-regulatory mechanism. As cure of leukemia implies the elimination of LSCs, the understanding of these immune-regulatory processes may be of particular importance for the development of future treatments of leukemia as targeting major immune escape mechanisms which revolutionized the treatment of solid tumors such as the blockade of the inhibitory checkpoint receptor programmed cell death protein 1 (PD-1) seems less efficacious in the treatment of leukemia. This review will summarize recent findings on the mechanisms by which Tregs regulate stem cells and adaptive immune cells in the BM during homeostasis and in leukemia.

Advances in immune therapies in hematological malignancies

Immunotherapy in cancer takes advantage of the exquisite specificity, potency, and flexibility of the immune system to eliminate alien tumor cells. It involves strategies to activate the entire immune defense, by unlocking mechanisms developed by tumor cells to escape from surrounding immune cells, as well as engineered antibody and cellular therapies. What is important to note is that these are therapeutics with curative potential. The earliest example of immune therapy is allogeneic stem cell transplantation, introduced in 1957, which is still an important modality in hematology, most notably in myeloid malignancies. In this review, we discuss developmental trends of immunotherapy in hematological malignancies, focusing on some of the strategies that we believe will have the most impact on future clinical practice in this field. In particular, we delineate novel developments for therapies that have already been introduced into the clinic, such as immune checkpoint inhibition and chimeric antigen receptor T-cell therapies. Finally, we discuss the therapeutic potential of emerging strategies based on T-cell receptors and adoptive transfer of allogeneic natural killer cells.

New Frontiers in Monoclonal Antibodies for the Targeted Therapy of Acute Myeloid Leukemia and Myelodysplastic Syndromes

Acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) represent an unmet clinical need whose prognosis is still dismal. Alterations of immune response play a prominent role in AML/MDS pathogenesis, revealing novel options for immunotherapy. Among immune system regulators, CD47, immune checkpoints, and toll-like receptor 2 (TLR2) are major targets. Magrolimab antagonizes CD47, which is overexpressed by AML and MDS cells, thus inducing macrophage phagocytosis with clinical activity in AML/MDS. Sabatolimab, an inhibitor of T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3), which disrupts its binding to galectin-9, has shown promising results in AML/MDS, enhancing the effector functions of lymphocytes and triggering tumor cell death. Several other surface molecules, namely CD33, CD123, CD45, and CD70, can be targeted with monoclonal antibodies (mAbs) that exert different mechanisms of action and include naked and conjugated antibodies, bispecific T-cell engagers, trispecific killer engagers, and fusion proteins linked to toxins. These novel mAbs are currently under investigation for use as monotherapy or in combination with hypomethylating agents, BCL2 inhibitors, and chemotherapy in various clinical trials at different phases of development. Here, we review the main molecular targets and modes of action of novel mAb-based immunotherapies, which can represent the future of AML and higher risk MDS treatment.

CPX-351: An Old Scheme with a New Formulation in the Treatment of High-Risk AML

Simple Summary

Secondary AML (s-AML) including therapy-related acute myeloid leukemia (t-AML) and acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) represent approximately one quarter of all AML cases. These AML subcategories are predominantly associated with advanced age and present a specific biologic profile including adverse genetics and a multidrug resistance phenotype, which often determine dramatically poor outcomes after conventional chemotherapy. In 2017, the FDA approved CPX-351, a liposomal formulation of cytarabine and daunorubicin at a fixed 5:1 molar ratio, for the treatment of adults with newly diagnosed t-AML and MRC-AML. Since the approval, many trials have been conducted or are still ongoing in order to assess the role of CPX-351 as frontline treatment in different AML subcategories, as a potential bridge to transplant or in combination with target therapies. In this review, we will discuss the current role of CPX-351 in treating these high-risk AML, focusing on how its use may potentially change the treatment paradigms of AML.

Abstract

Therapy-related acute myeloid leukemia (t-AML) and acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) represent aggressive diseases characterized by a dismal prognosis if compared with de novo acute myeloid leukemia, especially in older patients. In these AML subsets, standard chemotherapy regimens produce poor response rates and unsatisfactory outcomes. Historically, conventional approaches consisted of an anthracycline combined with continuous infusion of cytarabine for 7 days, the “3+7” regimen. Several attempts have been conducted to ameliorate this combination regimen but inconsistent improvements in response rates and no significant changes in overall survival have been observed, until the recent introduction of targeted molecules. A liposomal formulation of traditional chemotherapy agents cytarabine and daunorubicin, termed CPX-351, enhances pharmacodynamics and synergistic effects through the maintenance of the optimal 5:1 molar ratio, which extends the treatment’s half-life and increases the bone marrow tropism of the drug. The use of CPX-351 in newly diagnosed AML-MRC and t-AML patients aged 60–75 years has demonstrated superior remission rates compared to conventional chemotherapy and improvements in event-free and overall survival. Recently, published data from a 5-year follow-up highlighted evidence that CPX-351 has the ability to produce and contribute to long-term remission and survival in older patients with newly diagnosed high-risk/secondary AML. Future perspectives include evaluation of dose intensification with CPX-351 in high-risk settings, combining this agent with targeted therapies, and better understanding the mechanism of improved responses in t-AML and AML-MRC. In this review, we will examine the role of CPX-351 inside the new AML therapeutic scenario and how its employment could potentially modify the treatment algorithm of high-risk and elderly patients with AML

Infectious Complications Among Patients With AML Treated With Immune Checkpoint Inhibitors

BACKGROUND

The incidence and spectrum of infections in acute myeloid leukemia (AML) patients treated with immune checkpoint inhibitors (CPIs) in combination with a hypomethylating agents (HMAs) is not known. Nivolumab is a PD-1 checkpoint inhibitor approved in many solid tumors and lymphoma.

MATERIALS/METHODS

We performed a retrospective cohort study of 75 adult patients at MD Anderson Cancer Center with relapsed/refractory AML treated with azacitidine and nivolumab or with nivolumab and ipilimumab from March 2016 through March 2020 and described the infectious complications that occurred during their treatment.

RESULTS

Sixty-four (85%) patients developed an infection during the study period, and bacterial infections were by far the most common type of infection. A comparison of risk factors and characteristic between the 75 patients on CPIs who developed infection and those who did not found that corticosteroid use (odds ratio [OR], 28; 95% confidence interval [CI], 1.6-490; P =.02) and lymphopenia (OR, 4; 95% CI, 1-15.5; P =.04) were significantly associated with infections.

CONCLUSION

Patient with relapsed/refractory AML treated with salvage CPI-based therapy were more likely to develop infections when treated with corticosteroids in the setting of an immune-related adverse event, compared to those who were not.

Targeting the cluster of differentiation 47/signal-regulatory protein alpha axis in myeloid malignancies

PURPOSE OF REVIEW

The antitumor activity of macrophages is regulated by a balance of prophagocytic and antiphagocytic signals. Cluster of differentiation 47 (CD47), the dominant macrophage immune checkpoint ('do not eat me' signal), interacts with its receptor signal-regulatory protein alpha (SIRPα) to suppress phagocytic activities. This axis plays a pivotal role in immune evasion in myeloid malignancies as well as multiple cancers providing strong rationale for therapeutic exploitation.

RECENT FINDINGS

Preclinical studies have revealed overexpression of CD47 on leukemic stem cells and myeloblasts from patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), which contributes to immune surveillance evasion and is associated with poor outcomes. Blockade of CD47 with different approaches has demonstrated proof-of-concept antitumor activities mainly through phagocytic clearance. Early phase clinical trials combining the anti-CD47 mAb magrolimab with the hypomethylating agent azacitidine have showed synergistic activities, deep and durable responses, as well as a tolerable safety profile in these patients, including those with TP53 mutations.

SUMMARY

Targeting CD47/SIRPα axis, in combination with other therapeutic agents, represents a promising treatment approach for patients with myeloid malignancies, particularly the challenging TP53-mutated subgroup.

Modulation of the Gal-9/TIM-3 Immune Checkpoint with α-Lactose. Does Anomery of Lactose Matter?

Simple Summary

The disaccharide lactose is a common excipient in pharmaceutical products. In addition, the two anomers α- and β-lactose can exert immuno-modulatory effects. α-Lactose functions as a major regulator of the T-cell immunoglobulin mucin-3 (Tim-3)/Galectin-9 (Gal-9) immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of TIM-3 with monoclonal antibodies or small molecules represents a promising approach to combat onco-hematological diseases, in particular myelodysplastic syndromes, and acute myeloid leukemia. Alternatively, the activity of the checkpoint can be modulated via targeting of Gal-9 with both α- and β-lactose. In fact, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. This review discusses the capacity of lactose and Gal-9 to modulate the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. The immuno-regulatory roles of lactose and Gal-9 are highlighted.

Abstract

The disaccharide lactose is an excipient commonly used in pharmaceutical products. The two anomers, α- and β-lactose (α-L/β-L), differ by the orientation of the C-1 hydroxyl group on the glucose unit. In aqueous solution, a mutarotation process leads to an equilibrium of about 40% α-L and 60% β-L at room temperature. Beyond a pharmaceutical excipient in solid products, α-L has immuno-modulatory effects and functions as a major regulator of TIM-3/Gal-9 immune checkpoint, through direct binding to the β-galactoside-binding lectin galectin-9. The blockade of the co-inhibitory checkpoint TIM-3 expressed on T cells with anti-TIM-3 antibodies represents a promising approach to combat different onco-hematological diseases, in particular myelodysplastic syndromes and acute myeloid leukemia. In parallel, the discovery and development of anti-TIM-3 small molecule ligands is emerging, including peptides, RNA aptamers and a few specifically designed heterocyclic molecules. An alternative option consists of targeting the different ligands of TIM-3, notably Gal-9 recognized by α-lactose. Modulation of the TIM-3/Gal-9 checkpoint can be achieved with both α- and β-lactose. Moreover, lactose is a quasi-pan-galectin ligand, capable of modulating the functions of most of the 16 galectin molecules. The present review provides a complete analysis of the pharmaceutical and galectin-related biological functions of (α/β)-lactose. A focus is made on the capacity of lactose and Gal-9 to modulate both the TIM-3/Gal-9 and PD-1/PD-L1 immune checkpoints in oncology. Modulation of the TIM-3/Gal-9 checkpoint is a promising approach for the treatment of cancers and the role of lactose in this context is discussed. The review highlights the immuno-regulatory functions of lactose, and the benefit of the molecule well beyond its use as a pharmaceutical excipient.

The prospective prognostic value of the immune checkpoint BTLA expression in adult acute myeloid leukemia patients

Background

One of the crucial functions of the immune system is to prevent tumorigenesis, yet cancer occurs when malignant cells manage to evade immune surveillance via multiple strategies. Accordingly, this study aimed at assessing the potential significance of the novel immune checkpoint B and T lymphocyte attenuator (BTLA) as a prognostic marker in acute myeloid leukemia (AML), in addition to how it relates to response to treatment and patients’ survival. Thus, mRNA expression of BTLA was investigated on peripheral blood in 60 AML patients and 15 healthy controls.

Results

BTLA expression was found to be significantly elevated (p = 0.024) in the tested AML cases in comparison with healthy controls. Moreover, BTLA was over-expressed in the CD13, CD33, and HLA-DR positive cases as compared to their negative counterparts (p = 0.003; p < 0.001, and p = 0.001, respectively), and cases showing BTLA over-expression had significantly poorer overall survival times (p = 0.001) as confirmed by Kaplan–Meier survival analysis.

Conclusion

These observations suggest that BTLA over-expression may be associated with reduced immunity against tumors and could be recommended as a promising biomarker for unfavorable prognosis in AML.