Targets for chimeric antigen receptor T-cell therapy of acute myeloid leukemia

Expression and Prognostic Value of a Novel B7-H3 (CD276) Antibody in Acute Myeloid Leukemia

Despite recent advances in immunophenotyping, the prognosis of acute myeloid leukemia (AML) is still mainly estimated using age and genetic markers. As the genetic heterogeneity of AML patients is high, flow cytometry-based classification with appropriate biomarkers can efficiently complement risk stratification and treatment selection. An increased expression of B7-H3 (CD276), an immune checkpoint protein, has been reported and associated with poor prognosis. However, the available data are limited and heterogeneous. Here, we used a novel, proprietary murine anti-B7-H3 8H8 antibody for the flow cytometric analysis of B7-H3 expression in AML blasts from 77 patients. Our antibody reliably detected substantial B7-H3 expression in 62.3% of AML patients. B7-H3 expression was higher in the monocytic French-American-British (FAB) M5 group and in intermediate and poor risk patients according to the European Leukemia Network. Using receiver operating characteristics (ROCs), we identified a specific fluorescence intensity cut-off of 4.45 to discriminate between B7-H3high and B7-H3low expression. High B7-H3 expression was associated with shorter overall survival (OS) and progression-free survival (PFS). In conclusion, we have developed a novel B7-H3 antibody that serves as a new tool for the detection of B7-H3 expression in AML and may help to facilitate risk stratification and treatment selection in AML patients.

Recent advances in CAR-T cell therapy for acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a fatal and refractory haematologic cancer that primarily affects adults. It interferes with bone marrow cell proliferation. Patients have a 5 years survival rate of less than 30% despite the availability of several treatments, including chemotherapy, allogeneic haematopoietic stem cell transplantation (Allo-HSCT), and receptor antagonist drugs. Allo-HSCT is the mainstay of acute myeloid leukaemia treatment. Although it does work, there are severe side effects, such as graft-versus-host disease (GVHD). In recent years, chimeric antigen receptor (CAR)-T cell therapies have made significant progress in the treatment of cancer. These engineered T cells can locate and recognize tumour cells in vivo and release a large number of effectors through immune action to effectively kill tumour cells. CAR-T cells are among the most effective cancer treatments because of this property. CAR-T cells have demonstrated positive therapeutic results in the treatment of acute myeloid leukaemia, according to numerous clinical investigations. This review highlights recent progress in new targets for AML immunotherapy, and the limitations, and difficulties of CAR-T therapy for AML.

Production of donor-derived cytotoxic T lymphocytes with potent anti-leukemia activity for adoptive immunotherapy in high-risk pediatric patients given haploidentical hematopoietic stem cell transplantation

BACKGROUND AIMS

Somatic cell therapy based on the infusion of donor-derived cytotoxic T lymphocytes (CTL) able to recognize patients' leukemia blasts (LB) is a promising approach to control leukemia relapse after allogeneic HSCT. The success of this approach strongly depends on the ex vivo generation of high-quality donor-derived anti-leukemia CTL in compliance with Good Manufacturing Practices (GMP). We previously described a procedure for generating large numbers of donor-derived anti-leukemia CTL through stimulation of CD8-enriched lymphocytes with dendritic cells (DCs) pulsed with apoptotic LB in the presence of interleukin (IL)-12, IL-7 and IL-15. Here we report that the use of IFN-DC and the addition of IFNα2b during the priming phase significantly improve the generation of an efficient anti-leukemia T cells response in vitro.

METHODS

Using this approach, 20 high-risk pediatric patients given haploidentical HSCT for high-risk acute leukemia were enrolled and 51 batches of advanced therapy medical products (ATMP), anti-leukemia CTL, were produced.

RESULTS

Quality controls demonstrated that all batches were sterile, free of mycoplasma and conformed to acceptable endotoxin levels. Genotype analysis confirmed the molecular identity of the ATMP based on the starting biological material used for their production. The majority of ATMP were CD3+/CD8+ cells, with a memory/terminal activated phenotype, including T-central memory populations. ATMP were viable after thawing, and most ATMP batches displayed efficient capacity to lyse patients' LB and to secrete interferon-γ and tumor necrosis factor-α.

CONCLUSIONS

These results demonstrated that our protocol is highly reproducible and allows the generation of large numbers of immunologically safe and functional anti-leukemia CTL with a high level of standardization.

Chimeric antigen receptor (CAR) modified T Cells in acute myeloid leukemia: limitations and expectations

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with a poor prognosis despite the advent of novel therapies. Consequently, a major need exists for new therapeutic options, particularly for patients with relapsed/refractory (R/R) AML. In recent years, it has been possible to individualize the treatment of a subgroup of patients, particularly with the emergence of multiple targeted therapies. Nonetheless, a considerable number of patients remain without therapeutic options, and overall prognosis remains poor because of a high rate of disease relapse. In this sense, cellular therapies, especially chimeric antigen receptor (CAR)-T cell therapy, have dramatically shifted the therapeutic options for other hematologic malignancies, such as diffuse large B cell lymphoma and acute lymphoblastic leukemia. In contrast, effectively treating AML with CAR-based immunotherapy poses major biological and clinical challenges, most of them derived from the unmet need to identify target antigens with expression restricted to the AML blast without compromising the viability of the normal hematopoietic stem cell counterpart. Although those limitations have hampered CAR-T cell therapy translation to the clinic, there are several clinical trials where target antigens, such as CD123, CLL-1 or CD33 are being used to treat AML patients showing promising results. Moreover, there are continuing efforts to enhance the specificity and efficacy of CAR-T cell therapy in AML. These endeavors encompass the exploration of novel avenues, including the development of dual CAR-T cells and next-generation CAR-T cells, as well as the utilization of gene editing tools to mitigate off-tumor toxicities. In this review, we will summarize the ongoing clinical studies and the early clinical results reported with CAR-T cells in AML, as well as highlight CAR-T cell limitations and the most recent approaches to overcome these barriers. We will also discuss how and when CAR-T cells should be used in the context of AML.

Modified EASIX scores predict severe CRS/ICANS in patients with acute myeloid leukemia following CLL1 CAR-T cell therapy

Chimeric antigen receptor T (CAR-T) cell therapy targeting CLL1 has been considered a potent weapon for patients with acute myeloid leukemia (AML). This study aims to evaluate the efficacy and toxicity of CLL1 CAR-T cell therapy in a larger cohort, with particular attention to cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Among the 32 patients assessed for efficacy, complete remission occurred in 71.88% (23/32) of cases and undetectable minimal residual disease in 14 patients. The CRS developed in all patients, with 8 individuals experiencing ICANS. Severe CRS and ICANS were observed in 11 and 2 patients, respectively. Furthermore, the Endothelial Activation and Stress Index (EASIX) and its derivatives measured before and after CLL1 CAR-T cell infusion were employed for predicting the severe complications. Significant differences were observed in EASIX scores on the day before lymphodepletion (Day BL, P = 0.023), -1 (P < 0.001), +1 (P < 0.001), and +3(P = 0.014); sEASIX scores on Day BL (P = 0.007), -1 (P < 0.001), +1 (P < 0.001), and +3 (P < 0.001); and mEASIX score on Day -1 (P = 0.004) between patients with mild and severe CRS/ICANS. Additionally, there was a significant difference in mEASIX scores between responders and non-responders on Day BL (P = 0.004) and Day -1 (P = 0.044). Our findings indicate that pre- and post-infusion assessments of EASIX/mEASIX/sEASIX scores serve as reliable prognostic indicators for severe CRS/ICANS and treatment response following CLL1 CAR-T cell therapy, which can assist physicians in implementing preemptive treatment strategies for potential severe complications and screening patients who are suitable candidates for CLL1 CAR-T cell therapy. EASIX/mEASIX/sEASIX scores serve as reliable prognostic indicators for severe CRS/ICANS following CLL1 CAR-T cell therapy. The preinfusion mEASIX scores of CLL1 CAR-T cells can effectively predict treatment response.

Novel immunotherapies in the treatment of AML: is there hope?

The success of allogeneic stem cell transplantation has demonstrated the potential for immunotherapy to treat acute myeloid leukemia (AML). Although alternative T-cell-based immunotherapies have shown efficacy, they also pose the risk of on-target off-leukemia hematotoxicity. So far, adoptive autologous or allogeneic chimeric antigen receptor (CAR) T/natural killer cell therapy is almost exclusively employed as a bridge-to-transplant strategy in the context of clinical trials. For now, clinical trials predominantly target lineage-restricted antigens, but emerging approaches focus on leukemia-associated/specific intracellular target antigens, including dual and split targeting strategies. Adapter CAR T cells and T-cell-recruiting bispecific antibodies offer transient exposure with enhanced safety and multitargeting potential against antigen-escape variants. However, these have yet to demonstrate sustained responses and should be used earlier to treat low leukemia burden, preferably if measurable residual disease is present. To address immune dysregulation and enhance T-cell fitness, novel CAR T and bispecific designs, along with combinatorial strategies, might prove essential. Furthermore, genetic associations with inflammatory bone marrow signatures suggest the need for tailored platforms in defined AML subtypes. The eagerly anticipated results of trials investigating magrolimab, an anti-CD47 antibody targeting the "do not eat me" signal in p53-mutated AML, should shed further light on the potential of these evolving immunotherapeutic approaches.

Chimeric Antigen Receptor T Cell Therapy in Acute Myeloid Leukemia: Trials and Tribulations

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy that is often associated with relapse and drug resistance after standard chemotherapy or targeted therapy, particularly in older patients. Hematopoietic stem cell transplants are looked upon as the ultimate salvage option with curative intent. Adoptive cell therapy using chimeric antigen receptors (CAR) has shown promise in B cell malignancies and is now being investigated in AML. Initial clinical trials have been disappointing in AML, and we review current strategies to improve efficacy for CAR approaches. The extensive number of clinical trials targeting different antigens likely reflects the genetic heterogeneity of AML. The limited number of patients reported in multiple early clinical studies makes it difficult to draw conclusions about CAR safety, but it does suggest that the efficacy of this approach in AML lags behind the success observed in B cell malignancies. There is a clear need not only to improve CAR design but also to identify targets in AML that show limited expression in normal myeloid lineage cells.

Immunotherapy with Monoclonal Antibodies for Acute Myeloid Leukemia: A Work in Progress

In the last few years, molecularly targeted agents and immune-based treatments (ITs) have significantly changed the landscape of anti-cancer therapy. Indeed, ITs have been proven to be very effective when used against metastatic solid tumors, for which outcomes are extremely poor when using standard approaches. Such a scenario has only been partially reproduced in hematologic malignancies. In the context of acute myeloid leukemia (AML), as innovative drugs are eagerly awaited in the relapsed/refractory setting, different ITs have been explored, but the results are still unsatisfactory. In this work, we will discuss the most important clinical studies to date that adopt ITs in AML, providing the basis to understand how this approach, although still in its infancy, may represent a promising therapeutic tool for the future treatment of AML patients.

CAR-T in the Treatment of Acute Myeloid Leukemia: Barriers and How to Overcome Them

Conventional therapies for acute myeloid leukemia (AML) are characterized by high rates of relapse, severe toxicities, and poor overall survival rates. Thus, the development of new therapeutic strategies is crucial for improving the survival and quality of life of AML patients. CD19-directed chimeric antigen receptor (CAR) T-cell immunotherapy has been extremely successful in the treatment of B-cell acute lymphoid leukemia and several mature B-cell lymphomas. However, the use of CAR T-cell therapy for AML is currently prevented due to the lack of a myeloid equivalent to CD19, as currently known cell surface targets on leukemic blasts are also expressed on healthy hematopoietic stem and progenitor cells as well as their progeny. In addition, the immunosuppressive tumor microenvironment has a dampening effect on the antitumor activity of CAR-T cells. Here, we review the therapeutic challenges limiting the use of CAR T-cell therapy for AML and discuss promising novel strategies to overcome them.

Immunotherapy for myelodysplastic syndrome and acute myeloid leukemia: where do we stand?

INTRODUCTION

Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are generally characterized by a poor prognosis with currently available therapies. Immunotherapies have already seen success in treating a variety of malignant disorders, and their role in managing myeloid cancers is evolving rapidly.

AREAS COVERED

This is a review of the immunotherapies tested in MDS and AML, including immune checkpoint inhibitors, bispecific antibodies, and cell therapies such as chimeric antigen receptor (CAR) T cell therapy, T cell receptor (TCR) engineered T cells, and natural killer (NK) cells, with a focus on clinical trials conducted to date and future directions.

EXPERT OPINION

Initial clinical trials exploring checkpoint inhibitors in MDS and AML have demonstrated high toxicity and disappointing efficacy. However, ongoing trials adding novel checkpoint inhibitors to standard therapy are more promising. Technological advances are improving the outlook for bispecific antibodies, and cellular therapies like adoptive NK cell infusion have favorable efficacy and tolerability in early trials. As our understanding of the immune microenvironment in MDS and AML improves, the role for immunotherapy in the treatment of these diseases will become clearer.

Thrombotic Events Are Unusual Toxicities of Chimeric Antigen Receptor T-Cell Therapies

Chimeric antigen receptor (CAR) T-cell therapy has greatly transformed the treatment and prognosis of B-cell hematological malignancies. As CAR T-cell therapy continues to be more readily adopted and indications increase, the field's recognition of emerging toxicities will continue to grow. Among the adverse events associated with CAR T-cell therapy, cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity (ICANS) are the most common toxicities, while thrombotic events represent an under-reported, life-endangering complication. To determine thrombosis incidence post CAR T-cell therapy, we performed a multi-center, retrospective study on CAR T-cell therapy adult patients (N = 140) from Indiana University Simon Cancer Center and the University of North Carolina Medical Center treated from 2017 to 2022 for relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL, N = 3), diffuse large B-cell lymphoma (DLBCL, N = 92), follicular lymphoma (FL, N = 9), mantle cell lymphoma (MCL, N = 2), and multiple myeloma (MM, N = 34). We report 10 (7.14%) thrombotic events related to CAR T-cell therapy (DLBCL: N = 8, FL: N = 1, MM: N = 1) including 9 primary venous events and 1 arterial event that occurred with median time of 23.5 days post CAR T-cell infusion. In search of parameters associated with such events, we performed multivariate analyses of coagulation parameters (i.e., PT, PTT, and D-Dimer), scoring for adverse events (Padua Score and ISTH DIC Score) and grading for CAR T-cell toxicity severity (CRS grade and ICANS grade) and found that D-Dimer peak elevation and ICANS grade were significantly associated with post-CAR T-cell infusion thrombosis. While the pathophysiology of CAR T-cell associated coagulopathy remains unknown, our study serves to develop awareness of these emerging and unusual complications.