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

Nanobody-based naturally selected CD7-targeted CAR-T therapy for acute myeloid leukemia

ABSTRACT

Approximately 30% of patients with acute myeloid leukemia (AML) express CD7 on their myeloblasts. We have previously demonstrated that single-chain variable fragment (scFv)-based "naturally selected" CD7 chimeric antigen receptor T-cell (NS7CAR-T) therapy shows significant efficacy, with a favorable safety profile in T-cell lymphoid malignancies. Here, we derived dual variable heavy-chain domain of a heavy-chain antibody (dVHH) NS7CAR-Ts that have superior CD7 binding specificity, affinity to their scFv-based counterparts, and improved proliferative capability. In this phase 1 clinical trial, we evaluated the efficacy and safety of nanobody-based dVHH NS7CAR-Ts for patients with CD7+ refractory/relapsed AML. A cohort of 10 patients received dVHH NS7CAR-Ts across 2 dosage levels of 5 × 105/kg and 1 × 106/kg. Before enrollment, patients had undergone a median of 8 (range, 3-17) prior lines of therapy. Seven patients had prior transplants. After NS7CAR-T infusion, 7 of 10 (70%) patients achieved complete remission (CR). The median observation time was 178 days (range, 28-776). Among 7 patients who achieved CR, 3 who relapsed from prior transplants underwent a second allogeneic hematopoietic stem cell transplant (allo-HSCT). One patient remained leukemia free on day 401, and the other 2 died on day 241 and day 776, respectively, from nonrelapse-related causes. Three CR patients without consolidative (allo-HSCT) relapsed within 90 days. All the nonresponders and relapsed patients had CD7 loss. The treatment was well tolerated, with 80% experiencing mild cytokine release syndrome and none had neurotoxicity. This trial underscores the potential promising treatment of dVHH NS7CAR-Ts in providing clinical benefits with a manageable safety profile to patients with CD7+ AML, warranting further investigation. This trial was registered at www.clinicaltrials.gov as #NCT04938115.

Modified CD15/CD16-CLL1 inhibitory CAR-T cells for mitigating granulocytopenia toxicities in the treatment of acute myeloid leukemia

CLL1 Chimeric antigen receptor T-cell (CAR-T) therapy, as a promising immunotherapeutic approach, has demonstrated its potential to enhance the prognosis of patients diagnosed with acute myeloid leukemia (AML). However, due to the overexpression of CLL1 on neutrophils, CAR-T cells not only eliminated tumor cells but also eradicated neutrophils simultaneously, resulting in severe granulocytopenia and subsequent infections. Considering the distinct expression levels of CD15/CD16 on neutrophils and AML blasts, we have devised novel modified CD15 /CD16-CLL1 iCAR structures incorporating diverse inhibitory elements. Through extensive screening of structural optimization, we have successfully identified CD16-CLL1 iCAR-T cells that combine PD1 and 2B4 blockade, as well as a single VHH fragment replacing the entire CD16 scFv recognition domain. These modified cells demonstrate enhanced cytotoxicity against blasts while minimizing neutrophil elimination. Furthermore, their functionality has been effectively validated through both in vitro and in vivo experiments. In conclusion, we have successfully engineered innovative CD16-CLL1 iCAR-T cells, which preserves the cytotoxicity against tumor cells while preventing elimination of neutrophils, thereby significantly reducing the incidence of granulocytopenia during CAR-T therapy. Furthermore, our future objectives encompass the meticulous validation of both the efficacy and safety profile of this groundbreaking CAR-T therapy in clinical trials, as well as a comprehensive assessment of its potential to enhance the prognosis of patients diagnosed with AML.

Utilization of donor CLL-1 CAR-T cells for the treatment of relapsed of acute myeloid leukemia following allogeneic hematopoietic stem cell transplantation

Background

Human C-type lectin-like molecule 1 (CLL-1) represents a promising therapeutic target for Chimeric antigen receptor T (CAR-T) cells therapy in the treatment of acute myeloid leukemia (AML). In this study, we aimed to evaluate the efficacy and safety profile of donor-derived CLL-1 CAR-T cells in AML patients who experienced relapsed post-transplantation.

Methods

14 AML patients who experienced relapse following allogeneic HSCT were enrolled in our clinical trial. However, 2 patients withdrew from the study due to rapid disease progression. 12 participants received donor-derived CLL-1 CAR-T cells and were categorized into 3 groups based on the dosage of infused CAR-T cells dose (Group A:0.5×106/kg, Group B:1×106/kg, Group C:1.5×106/kg). And scRNA-seq was used to reveal CLL-1 CAR-T cells dynamics in a CAR-T cells infusion products and PBMCs at the peak of expansion for patient 4.

Results

CLL-1 CAR-T cells were well tolerated by all 12 patients. Cytokine Release Syndrome (CRS) was observed in all patients, with 5 patients experiencing grade ≥3. 3 patients developed cytokine release syndrome-associated encephalopathy (CRES), and 1 patient had a grade 4 severity level. All patients demonstrated a reduction in tumor burden, while 7 patients (58.33%) achieved MRD-CR and 2 patients (16.67%) reached MRD+CR. CAR-T cells expansion was detectable in all 12 patients, with the median time of peak expansion was 9 days (range: 7-11 days). In patient 4, compared to the pre-reinfusion state, CD4+ cells at the peak of expansion showed upregulation of cell killing-related genes and memory T cell-related genes (P < 0.01).

Conclusions

The CLL-1 CAR-T cells therapy derived from allogeneic donors demonstrates both safety and efficacy in the management of relapsed AML following allogeneic HSCT. And adjusting the ratio of CD4+ CAR-T cells and CD8+ CAR-T cells prior to infusion may help mitigate CAR-T cell-related side effects.

Clinical trial registration

https://www.chictr.org.cn/, identifier ChiCTR2000041054.

Emerging CART Therapies for Pediatric Acute Myeloid Leukemia

The prognosis of children with acute myeloid leukemia (AML) has improved incrementally over the last decades. However, at relapse, overall survival (OS) ∼40% to 50% and is even lower for patients with chemorefractory disease. Effective and less-toxic therapies are urgently needed for these children. In the last years, immune-directed therapies such as chimeric antigen receptor (CAR)-T cells were introduced, which showed outstanding clinical activity against B-cell malignancies. CART therapies are being developed for AML on the basis of the results obtained for other hematologic malignancies. The biggest challenge of CART therapy for AML is to identify a specific target antigen, since antigens expressed in AML cells are usually shared with healthy hematopoietic stem cells. An overview of prospects of CART in pediatric AML, focused on the common antigens targeted by CART in AML that have been tested or are currently under investigation, is provided in this manuscript.

Genetically modified and unmodified cellular approaches to enhance graft versus leukemia effect, without increasing graft versus host disease: the use of allogeneic cytokine-induced killer cells

Although allogeneic hematopoietic cell transplantation (HCT) represents a curative approach for many patients with hematological diseases, post-transplantation relapse occurs in 20-50% of cases, representing the primary cause of treatment failure and mortality. Alloreactive donor T cells are responsible for the graft versus leukemia (GvL) effect, which represents the key mechanism for the long-term curative effect of HCT. However, the downside is represented by graft versus host disease (GvHD), largely contributing to transplant-related mortality (TRM). Multiple factors play a role in regulating the delicate balance between GvL and GvHD, such as the optimization of the donor HLA and KIR match, the type of graft source, and the adaptive use of post-transplant cellular therapy. In addition to the standard donor lymphocyte infusion (DLI), several attempts were made to favor the GvL effect without increasing the GvHD risk. Selected DLI, NK DLI, activated DLI and more sophisticated genetically engineered cells can be employed. In this scenario, cytokine-induced killer (CIK) cells represent a suitable tool to boost GvL while minimizing GvHD. CIK cells are T lymphocytes activated in culture in the presence of monoclonal antibodies against CD3 (OKT3), interferon-gamma (IFN-g), and interleukin-2 (IL-2), characterized by the expression of markers typical of NK cells and T cells (CD3+, CD56+, with a prevalent CD8+ phenotype). CIK cells can mediate cytotoxicity through both MHC and non-MHC restricted recognition, which is the so-called "dual-functional capability" and display minimum alloreactivity. Allogeneic CIK cells showed a favorable rate of response, especially in the setting of minimal residual disease, with a rate of GvHD not exceeding 25%. Finally, the CIK cell platform can be adapted for chimeric antigen receptor (CAR) cell strategy, showing promising results in both preclinical and clinical settings. In this review, we describe the main immunological basis for the development of the GvL and the possible cellular therapy approaches used to boost it, with a particular focus on the use of CIK cells.

CAR T-cell therapy in acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive leukemic malignancy that affects myeloid lineage progenitors. Relapsed or refractory AML patients continue to have poor prognoses, necessitating the development of novel therapy alternatives. Adoptive T-cell therapy with chimeric antigen receptors (CARs) is an intriguing possibility in the field of leukemia treatment. Chimeric antigen receptor T-cell therapy is now being tested in clinical trials (mostly in phase I and phase II) using AML targets including CD33, CD123, and CLL-1. Preliminary data showed promising results. However, due to the cellular and molecular heterogeneity of AML and the co-expression of some AML targets on hematopoietic stem cells, these clinical investigations have shown substantial "on-target off-tumor" toxicities, indicating that more research is required. In this review, the latest significant breakthroughs in AML CAR T cell therapy are presented. Furthermore, the limitations of CAR T-cell technology and future directions to overcome these challenges are discussed.

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

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

Therapeutic Targeting of TIM-4-L with Engineered T Cells for Acute Myeloid Leukemia

PURPOSE

Disruption of lipid bilayer asymmetry is a common feature observed in cancer cells and offers novel routes for therapeutic targeting. We used the natural immune receptor TIM-4 to interrogate for loss of plasma membrane phospholipid polarity in primary acute myelogenous leukemia (AML) samples and evaluated the anti-leukemic activity of TIM-4-L-directed T-cell therapy in preclinical AML models.

EXPERIMENTAL DESIGN

We performed FACS analysis on 33 primary AML bone marrow specimens and correlated TIM-4-L expression frequency and intensity with molecular disease characteristics. Using Kasumi-1 and MV-4-11 AML cell lines, we further tested the anti-leukemic effects of TIM-4-L-directed engineered T cells in vitro and in vivo.

RESULTS

We found that 86% of untreated AML blasts displayed upregulation of cell surface TIM-4-L. These observations were agnostic to AML genetic classification, as samples with mutations in TP53, ASXL1, and RUNX1 displayed TIM-4-L upregulation similar to that seen in favorable and intermediate subtypes. TIM-4-L dysregulation was also stably present in AML cell lines. To evaluate the potential of targeting upregulated TIM-4-L with adoptive T-cell therapy, we constructed TIM-4-L-directed engineered T cells, which demonstrated potent anti-leukemic effects, effectively eliminating AML cell lines with a range of endogenous TIM-4-L expression levels both in vitro and in vivo.

CONCLUSIONS

These results highlight TIM-4-L as a highly prevalent target on AML across a range of genetic classifications and novel target for T-cell-based therapy in AML. Further investigations into the role of TIM-4-L in AML pathogenesis and its potential as an anti-leukemic target for clinical development are warranted.

Broadening the horizon: potential applications of CAR-T cells beyond current indications

Engineering immune cells to treat hematological malignancies has been a major focus of research since the first resounding successes of CAR-T-cell therapies in B-ALL. Several diseases can now be treated in highly therapy-refractory or relapsed conditions. Currently, a number of CD19- or BCMA-specific CAR-T-cell therapies are approved for acute lymphoblastic leukemia (ALL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), multiple myeloma (MM), and follicular lymphoma (FL). The implementation of these therapies has significantly improved patient outcome and survival even in cases with previously very poor prognosis. In this comprehensive review, we present the current state of research, recent innovations, and the applications of CAR-T-cell therapy in a selected group of hematologic malignancies. We focus on B- and T-cell malignancies, including the entities of cutaneous and peripheral T-cell lymphoma (T-ALL, PTCL, CTCL), acute myeloid leukemia (AML), chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), classical Hodgkin-Lymphoma (HL), Burkitt-Lymphoma (BL), hairy cell leukemia (HCL), and Waldenström's macroglobulinemia (WM). While these diseases are highly heterogenous, we highlight several similarly used approaches (combination with established therapeutics, target depletion on healthy cells), targets used in multiple diseases (CD30, CD38, TRBC1/2), and unique features that require individualized approaches. Furthermore, we focus on current limitations of CAR-T-cell therapy in individual diseases and entities such as immunocompromising tumor microenvironment (TME), risk of on-target-off-tumor effects, and differences in the occurrence of adverse events. Finally, we present an outlook into novel innovations in CAR-T-cell engineering like the use of artificial intelligence and the future role of CAR-T cells in therapy regimens in everyday clinical practice.

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.