How I treat refractory/relapsed diffuse large B-cell lymphomas with CD19-directed chimeric antigen receptor T cells.

Chimeric antigen receptor (CAR) T cells targeting CD19 represent a promising salvage immunotherapy for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL), offering ~40% of long-term responses. In everyday clinical practice, haematologists involved in CAR T cell treatment of patients with R/R DLBCL have to deal with diagnostically complex cases and difficult therapeutic choices. The availability of novel immunotherapeutic agents for R/R DLBCL and recent advances in understanding CAR T-cell failure mechanisms demand a rational approach to identify the best choice for bridging therapy and managing post-CAR T-cell therapy relapses. Moreover, positron emission tomography/computerised tomography may result in false-positive interpretation, highlighting the importance of post-treatment biopsy. In this review, we discuss all above issues, presenting four instructive cases, with the aim to provide criteria and new perspectives for CAR T-cell treatment of DLBCL.

Selective homing of CAR-CIK cells to the bone marrow niche enhances control of the acute myeloid leukemia burden.

Acute myeloid leukemia (AML) is a hematological malignancy derived from neoplastic myeloid progenitor cells characterized by abnormal clonal proliferation and differentiation. Although novel therapeutic strategies have recently been introduced, the prognosis of AML is still unsatisfactory. So far, the efficacy of chimeric antigen receptor (CAR)-T-cell therapy in AML has been hampered by several factors, including the poor accumulation of the blood-injected cells in the leukemia bone marrow (BM) niche in which chemotherapy-resistant leukemic stem cells reside. Thus, we hypothesized that overexpression of CXCR4, whose ligand CXCL12 is highly expressed by BM stromal cells within this niche, could improve T-cell homing to the BM and consequently enhance their intimate contact with BM-resident AML cells, facilitating disease eradication. Specifically, we engineered conventional CD33.CAR-cytokine-induced killer cells (CIKs) with the wild-type (wt) CXCR4 and the variant CXCR4R334X, responsible for leukocyte sequestration in the BM of patients with warts, hypogammaglobulinemia, immunodeficiency, and myelokathexis syndrome. Overexpression of both CXCR4wt and CXCR4mut in CD33.CAR-CIKs resulted in significant improvement of chemotaxis toward recombinant CXCL12 or BM stromal cell-conditioned medium, with no observed impairment of cytotoxic potential in vitro. Moreover, CXCR4-overexpressing CD33.CAR-CIKs showed enhanced in vivo BM homing, associated with a prolonged retention for the CXCR4R334X variant. However, only CD33.CAR-CIKs coexpressing CXCR4wt but not CXCR4mut exerted a more sustained in vivo antileukemic activity and extended animal survival, suggesting a noncanonical role for CXCR4 in modulating CAR-CIK functions independent of BM homing. Taken together, these data suggest that arming CAR-CIKs with CXCR4 may represent a promising strategy for increasing their therapeutic potential for AML.

IL-3-zetakine combined with a CD33 costimulatory receptor as a dual CAR approach for safer and selective targeting of AML.

Acute myeloid leukemia (AML) still represents an unmet clinical need for adult and pediatric patients. Adoptive cell therapy by chimeric antigen receptor (CAR)-engineered T cells demonstrated a high therapeutic potential, but further development is required to ensure a safe and durable disease remission in AML, especially in elderly patients. To date, translation of CAR T-cell therapy in AML is limited by the absence of an ideal tumor-specific antigen. CD123 and CD33 are the 2 most widely overexpressed leukemic stem cell biomarkers but their shared expression with endothelial and hematopoietic stem and progenitor cells increases the risk of undesired vascular and hematologic toxicities. To counteract this issue, we established a balanced dual-CAR strategy aimed at reducing off-target toxicities while retaining full functionality against AML. Cytokine-induced killer (CIK) cells, coexpressing a first-generation low affinity anti-CD123 interleukin-3-zetakine (IL-3z) and an anti-CD33 as costimulatory receptor without activation signaling domains (CD33.CCR), demonstrated a powerful antitumor efficacy against AML targets without any relevant toxicity on hematopoietic stem and progenitor cells and endothelial cells. The proposed optimized dual-CAR cytokine-induced killer cell strategy could offer the opportunity to unleash the potential of specifically targeting CD123+/CD33+ leukemic cells while minimizing toxicity against healthy cells.

Case Report: Subtotal Lymphoid and Total Marrow Irradiation as Bridge Therapy to CD19-Directed CAR T Cells in a Chemorefractory DLBCL With Leukemic Involvement.

CAR T cell therapy has transformed the salvage approach for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). Maintaining disease control before CAR T cell infusion during product manufacturing (so-called bridging therapy) is an important step to optimizing outcome. Among possible bridging therapies, radiation therapy (RT) represents a valuable option, particularly when the disease is limited. Here, we report for the first time on a patient with chemorefractory-transformed DLBCL showing nodal, extranodal, and massive bone marrow (BM) lymphoma infiltration associated with leukemic involvement, a successful bridge therapy to CD19-directed CAR T cell therapy by subtotal lymphoid/total marrow irradiation plus thiothepa followed by reinfusion of CD34+ autologous hematopoietic stem cells. Such a novel bridging regimen allowed a significant reduction of nodal and BM tumor volume while improving blood cell count before CAR T cell infusion. The PET-CT scan and BM evaluation performed at 1, 3, and 6 months after treatment showed complete remission of the disease. A relapse occurred at almost 1 year in lymph nodes because of CD19 antigen escape while the BM remained free of disease. This extended radiotherapy approach may be an effective bridging therapy for chemorefractory DLBCL patients eligible for CAR T cells who present with a high tumor burden, including massive BM involvement associated with leukemic involvement. This preliminary evidence is worth confirming in additional patients.

Current status and future perspectives in targeted therapy of NPM1-mutated AML.

Nucleophosmin 1 (NPM1) is a nucleus-cytoplasmic shuttling protein which is predominantly located in the nucleolus and exerts multiple functions, including regulation of centrosome duplication, ribosome biogenesis and export, histone assembly, maintenance of genomic stability and response to nucleolar stress. NPM1 mutations are the most common genetic alteration in acute myeloid leukemia (AML), detected in about 30-35% of adult AML and more than 50% of AML with normal karyotype. Because of its peculiar molecular and clinico-pathological features, including aberrant cytoplasmic dislocation of the NPM1 mutant and wild-type proteins, lack of involvement in driving clonal hematopoiesis, mutual exclusion with recurrent cytogenetic abnormalities, association with unique gene expression and micro-RNA profiles and high stability at relapse, NPM1-mutated AML is regarded as a distinct genetic entity in the World Health Organization (WHO) classification of hematopoietic malignancies. Starting from the structure and functions of NPM1, we provide an overview of the potential targeted therapies against NPM1-mutated AML and discuss strategies aimed at interfering with the oligomerization (compound NSC348884) and the abnormal traffic of NPM1 (avrainvillamide, XPO1 inhibitors) as well as at inducing selective NPM1-mutant protein degradation (ATRA/ATO, deguelin, (-)-epigallocatechin-3-gallate, imidazoquinoxaline derivatives) and at targeting the integrity of nucleolar structure (actinomycin D). We also discuss the current therapeutic results obtained in NPM1-mutated AML with the BCL-2 inhibitor venetoclax and the preliminary clinical results using menin inhibitors targeting HOX/MEIS1 expression. Finally, we review various immunotherapeutic approaches in NPM1-mutated AML, including immune check-point inhibitors, CAR and TCR T-cell-based therapies against neoantigens created by the NPM1 mutations.

Novel NPM1 exon 5 mutations and gene fusions leading to aberrant cytoplasmic nucleophosmin in AML.

Nucleophosmin (NPM1) mutations in acute myeloid leukemia (AML) affect exon 12, but also sporadically affect exons 9 and 11, causing changes at the protein C-terminal end (tryptophan loss, nuclear export signal [NES] motif creation) that lead to aberrant cytoplasmic NPM1 (NPM1c+), detectable by immunohistochemistry. Combining immunohistochemistry and molecular analyses in 929 patients with AML, we found non-exon 12 NPM1 mutations in 5 (1.3%) of 387 NPM1c+ cases. Besides mutations in exons 9 (n = 1) and 11 (n = 1), novel exon 5 mutations were discovered (n = 3). Another exon 5 mutation was identified in an additional 141 patients with AML selected for wild-type NPM1 exon 12. Three NPM1 rearrangements (NPM1/RPP30, NPM1/SETBP1, NPM1/CCDC28A) were detected and characterized among 13 979 AML samples screened by cytogenetic/fluorescence in situ hybridization and RNA sequencing. Functional studies demonstrated that in AML cases, new NPM1 proteins harbored an efficient extra NES, either newly created or already present in the fusion partner, ensuring its cytoplasmic accumulation. Our findings support NPM1 cytoplasmic relocation as critical for leukemogenesis and reinforce the role of immunohistochemistry in predicting AML-associated NPM1 genetic lesions. This study highlights the need to develop new assays for molecular diagnosis and monitoring of NPM1-mutated AML.

CD123 Is Consistently Expressed on NPM1-Mutated AML Cells.

NPM1-mutated (NPM1mut) acute myeloid leukemia (AML) comprises about 30% of newly diagnosed AML in adults. Despite notable advances in the treatment of this frequent AML subtype, about 50% of NPM1mut AML patients treated with conventional treatment die due to disease progression. CD123 has been identified as potential target for immunotherapy in AML, and several anti-CD123 therapeutic approaches have been developed for AML resistant to conventional therapies. As this antigen has been previously reported to be expressed by NPM1mut cells, we performed a deep flow cytometry analysis of CD123 expression in a large cohort of NPM1mut and wild-type samples, examining the whole blastic population, as well as CD34+CD38- leukemic cells. We demonstrate that CD123 is highly expressed on NPM1mut cells, with particularly high expression levels showed by CD34+CD38- leukemic cells. Additionally, CD123 expression was further enhanced by FLT3 mutations, which frequently co-occur with NPM1 mutations. Our results identify NPM1-mutated and particularly NPM1/FLT3 double-mutated AML as disease subsets that may benefit from anti-CD123 targeted therapies.

Targeting CD33 in Chemoresistant AML Patient-Derived Xenografts by CAR-CIK Cells Modified with an Improved SB Transposon System.

The successful implementation of chimeric antigen receptor (CAR)-T cell therapy in the clinical context of B cell malignancies has paved the way for further development in the more critical setting of acute myeloid leukemia (AML). Among the potentially targetable AML antigens, CD33 is insofar one of the main validated molecules. Here, we describe the feasibility of engineering cytokine-induced killer (CIK) cells with a CD33.CAR by using the latest optimized version of the non-viral Sleeping Beauty (SB) transposon system "SB100X-pT4." This offers the advantage of improving CAR expression on CIK cells, while reducing the amount of DNA transposase as compared to the previously employed "SB11-pT" version. SB-modified CD33.CAR-CIK cells exhibited significant antileukemic activity in vitro and in vivo in patient-derived AML xenograft models, reducing AML development when administered as an "early treatment" and delaying AML progression in mice with established disease. Notably, by exploiting an already optimized xenograft chemotherapy model that mimics human induction therapy in mice, we demonstrated for the first time that CD33.CAR-CIK cells are also effective toward chemotherapy resistant/residual AML cells, further supporting its future clinical development and implementation within the current standard regimens.