CD 123 is a membrane biomarker and a therapeutic target in hematologic malignancies

Precision epitope editing: A path to advanced immunotherapies

The ability to recognize antigen epitope is crucial for generating an effective immune response. By engineering these epitopes, researchers can reduce on-target/off-tumor toxicity associated with targeted immunotherapy. Recent studies indicate that employing various gene editing tools to modify the epitopes of healthy hematopoietic stem and progenitor cells (HSPCs) can protect these cells from toxicity during tumor eradication, all while preserving their differentiation and function. This advancement greatly enhances the safety and efficacy of tumor immunotherapy.

A novel label-free method to determine equilibrium dissociation constants of antibodies binding to cell surface proteins

Solution-based affinity assays are used for the selection and characterization of proteins that could be developed into therapeutic molecules. However, these assays have limitations for cell-surface proteins as in most cases their purification requires detergent solubilization and are unlikely to assume conformations in solution that resemble their native states in cell membranes. This report describes a novel electrochemiluminescence-based method, called MSD-CAT, for the affinity analysis of antibodies binding to cell-surface receptors. MSD-CAT was used to evaluate the binding of monoclonal antibodies, Fab fragments, and bispecific antibodies targeting the cell-surface receptor interleukin 3 receptor alpha (CD123) and the results were compared to data obtained using surface plasmon resonance (SPR). The data showed that MSD-CAT can be successfully applied to determine binding affinity on cells in a label free format and without the need for laborious solubilization procedures to generate recombinant antigen. In addition, this method has the potential for high-throughput application while enabling simultaneous determination of equilibrium dissociation constant (KD) and receptor density within the same experiment.

CD33-CD123 IF-THEN Gating Reduces Toxicity while Enhancing the Specificity and Memory Phenotype of AML-Targeting CAR-T Cells

SIGNIFICANCE

Our study demonstrates the use of "IF-THEN" SynNotch-gated CAR-T cells targeting CD33 and CD123 in AML reduces off-tumor toxicity. This strategy enhances T-cell phenotype, improves expansion, preserves HSPCs, and mitigates cytokine release syndrome-addressing critical limitations of existing AML CAR-T therapies.

Advancing Chimeric Antigen Receptor T-Cell Therapy for Acute Myeloid Leukemia: Current Limitations and Emerging Strategies

Chimeric antigen receptor (CAR) T-cell therapy represents one of the most impressive advances in anticancer therapy of the last decade. While CAR T-cells are gaining ground in various B cell malignancies, their use in acute myeloid leukemia (AML) remains limited, and no CAR-T product has yet received approval for AML. The main limitation of CAR-T therapy in AML is the lack of specific antigens that are expressed in leukemic cells but not in their healthy counterparts, such as hematopoietic stem cells (HSCs), as their targeting would result in an on-target/off-tumor toxicity. Moreover, the heterogeneity of AML and the tendency of blasts to modify surface antigens' expression in the course of the disease make identification of suitable targets even more challenging. Lastly, AML's immunosuppressive microenvironment dampens CAR-T therapeutic activities. In this review, we focus on the actual pitfalls of CAR T-cell therapy in AML, and we discuss promising approaches to overcome them.

Efficient combinatorial adaptor-mediated targeting of acute myeloid leukemia with CAR T-cells

CAR T-cell products targeting lineage-specific cell-of-origin antigens, thereby eliminating both tumor and healthy counterpart cells, are currently clinically approved therapeutics in B- and plasma-cell malignancies. While they represent a major clinical improvement, they are still limited in terms of efficacy by e.g. single, sometimes low-expressed antigen targeting, and in terms of safety by e.g., lack of on-off activity. Successful cell-of-origin non-discriminative targeting of heterogeneous hematopoietic stem and progenitor cell malignancies, such as acute myeloid leukemia (AML), will require antigen-versatile targeting and off-switching of effectors in order to then allow rescue by hematopoietic stem cell transplantation (HSCT), preventing permanent myeloablation. To address this, we developed adaptor-CAR (AdFITC-CAR) T-cells targeting fluoresceinated AML antigen-binding diabody adaptors. This platform enables the use of adaptors matching the AML-antigen-expression profile and conditional activity modulation. Combining adaptors significantly improved lysis of AML cells in vitro. In therapeutic xenogeneic mouse models, AdFITC-CAR T-cells co-administered with single diabody adaptors were as efficient as direct CAR T-cells, and combinatorial use of adaptors further enhanced therapeutic efficacy against both, cell lines and primary AML. Collectively, this study provides proof-of-concept that AdFITC-CAR T-cells and combinations of adaptors can efficiently enhance immune-targeting of AML.

Radiation Therapy for Cutaneous Blastic Plasmacytoid Dendritic Cell Neoplasm: A Case Report and Review of the Literature

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive hematologic malignancy derived from plasmacytoid dendritic cells. It commonly presents as cutaneous lesions. To date, no standard treatment protocol for BPDCN exists. Traditionally treated similarly to acute leukemia or lymphoma, its prognosis remains poor. Radiation therapy is employed for isolated skin lesions, for patients that are ineligible for chemotherapy due to age or comorbidities and for post-chemotherapy recurrence. However, very limited reports are available on radiotherapy for BPDCN. We present a case involving a 94-year-old BPDCN patient treated with radiation therapy, highlighting an atypical situation of two separate radiotherapy sessions with different dosages for isolated skin lesions. Initially, 45 Gy was administered in 15 fractions (45 Gy/15 Fr), followed by a second session of 30 Gy in 10 fractions (30 Gy/10 Fr) after disease recurrence. This case is unique in detailing radiation therapy for the exceedingly rare BPDCN, particularly dose fractionation. The findings indicate that 45 Gy/15 Fr can provide adequate local control, while even a lower dose of 30 Gy/10 Fr may be effective. This case report contributes to the limited literature by proposing potential therapeutic approaches and dosage guidelines to refine future BPDCN treatment protocols.

Epitope prime editing shields hematopoietic cells from CD123 immunotherapy for acute myeloid leukemia

Acute myeloid leukemia (AML) is a malignant cancer characterized by abnormal differentiation of hematopoietic stem and progenitor cells (HSPCs). While chimeric antigen receptor T (CAR-T) cell immunotherapies target AML cells, they often induce severe on-target/off-tumor toxicity by attacking normal cells expressing the same antigen. Here, we used base editors (BEs) and a prime editor (PE) to modify the epitope of CD123 on HSPCs, protecting healthy cells from CAR-T-induced cytotoxicity while maintaining their normal function. Although BE effectively edits epitopes, complex bystander products are a concern. To enhance precision, we optimized prime editing, increasing the editing efficiency from 5.9% to 78.9% in HSPCs. Epitope-modified cells were resistant to CAR-T lysis while retaining normal differentiation and function. Furthermore, BE- or PE-edited HSPCs infused into humanized mice endowed myeloid lineages with selective resistance to CAR-T immunotherapy, demonstrating a proof-of-concept strategy for treating relapsed AML.

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.

PTPN11 Mutation Clonal Hierarchy in Acute Myeloid Leukemia

Mutations in protein tyrosine phosphatase non-receptor type 11 ( PTPN11 ) have been considered late acquired mutations in acute myeloid leukemia (AML) development. To interrogate the ontogeny of PTPN11 mutations, we utilized single-cell DNA sequencing and identified that PTPN11 mutations can occur as initiating events in some AML patients when accompanied by strong oncogenic drivers, commonly NPM1 mutations. The co-driver role of PTPN11 mutations was confirmed in a novel murine model that exhibits an AML phenotype with early expansion of a diverse set of variably differentiated myeloid cells that engrafted into immunodeficient and immunocompetent mice. This immune diversity was reconstituted from early precursor cells when engrafted into immunodeficient mice. Moreover, immune diversity was also observed in the blast component of patient samples with NPM1 and PTPN11 mutations, providing novel antigen targets for immune based approaches in this subset of AML that is resistant to multiple targeted therapies.

Increased CD123 + HLA-DR- Granulocytes in Allergic Rhinitis and Influence of Allergens on Expression of Cell Membrane Markers

BACKGROUND

It is reported that CD123 + HLA-DR- cells in PBMC are basophils, and CD203c, CD63, and FcεRI molecules are activation markers of basophils. However, little is known of CD123 + HLA-DR-cells in blood granulocytes.

OBJECTIVE

To investigate the presence of CD123 + HLA-DR- cells in the blood granulocytes and peripheral PBMC of patients with allergic rhinitis (AR), as well as the impact of allergens on the cell membrane markers of basophils.

METHODS

Flow cytometry was used to detect the expression of the membrane molecules.

RESULTS

While CD123 + HLA-DR- PBMCs are representative of basophils, their presence did not significantly change in patients with AR. In contrast, both the percentage and number of CD123 + HLA-DR- granulocytes, which make up only up to 50% of basophils, were significantly increased in patients with seasonal (sAR) and perennial AR (pAR). CD63+, CD203c+, and FcεRIα+ cells within CD123 + HLA-DR- granulocytes also showed enhanced activity in patients with AR. Allergen extracts from house dust mite allergen extract (HDME) and Artemisia sieversiana wild extract further increased the number of CD123 + HLA-DR- cells in granulocytes of sAR and pAR patients, as well as in PBMCs of pAR patients.

CONCLUSIONS

The use of CD123 + HLA-DR- granulocytes and PBMC may not be sufficient for diagnosing AR. Allergens could potentially contribute to the development of AR by influencing the number of CD123 + HLA-DR- cells, as well as the expression of CD63, CD203c, and FcεRIαin these cells.

Looking ahead to CD3, T-cell engager bispecific antibodies for hematological malignancies

INTRODUCTION

Since the approval of the bispecific antibody blinatumomab in 2017 for the treatment of acute lymphoblastic leukemia in relapse, the development of numerous bispecific antibody constructs has dramatically expanded in hematologic malignancies. Many have recently received Food Drug Administration and European Medicines Agency approvals in various stages of treatment for lymphomas, leukemias, and multiple myeloma.

AREAS COVERED

The purpose of this review is to provide an overview of bispecific antibody treatment including the mechanisms leading to effector T cells targeting tumor-associated antigens, the treatment indications, efficacies, toxicities, and challenges of the different constructs. A literature search was performed through access to PubMed and clinicaltrials.gov.

EXPERT OPINION

While there has been substantial success in the treatment of NHL, MM, and ALL, there are still hematologic malignancies such as AML where there has been limited progress. It is important to continue to investigate new designs, tumor antigen targets, and further refine where current approved bispecific antibodies fit in terms of sequencing of therapy. Hopefully, with the knowledge gained in recent years and the explosion of these therapies, patients with blood cancers will continue to benefit from these treatments for years to come.

Flotetuzumab as a salvage immunotherapy in advanced CD123-positive hematological malignancies, a phase 1 pilot study

CD123 "expression" is common in hematological malignancies, including acute lymphoblastic leukemia (ALL). Flotetuzumab is a novel, investigational CD3/CD123 DART®. We conducted a phase 1 study evaluating safety and efficacy of flotetuzumab in relapsed/refractory ALL (Cohort A) and other advanced CD123-positive hematological malignancies (excluding myeloid malignancies) (cohort B). Thirteen patients (9 in Cohort A and 4 in Cohort B) were treated at dose level 1 (500 ng/kg/day) before early closure due to discontinuation of drug development by sponsor. Two dose limiting toxicities (Grade 4 thrombocytopenia and neutropenia) occurred in one patient in Cohort B. Cytokine release syndrome occurred in most patients (85%), all being grade ≤2. Responses only occurred in Cohort B, with a partial response in one patient with Hodgkin's lymphoma and morphological complete remission in the bone marrow in one patient with blastic plasmacytoid dendritic cell neoplasm. In conclusion, flotetuzumab had a manageable safety profile in advanced CD123-positive hematological malignancies.

Recent advances in CAR-T therapy for the treatment of acute myeloid leukemia

Chimeric antigen receptor T-cell (CAR-T) therapy, which has demonstrated notable efficacy against B-cell malignancies and is approved by the US Food and Drug Administration for clinical use in this context, represents a significant milestone in cancer immunotherapy. However, the efficacy of CAR-T therapy for the treatment of acute myeloid leukemia (AML) is poor. The challenges associated with the application of CAR-T therapy for the clinical treatment of AML include, but are not limited to, nonspecific distribution of AML therapeutic targets, difficulties in the production of CAR-T cells, AML blast cell heterogeneity, the immunosuppressive microenvironment in AML, and treatment-related adverse events. In this review, we summarize the recent findings regarding various therapeutic targets for AML (CD33, CD123, CLL1, CD7, etc.) and the results of the latest clinical studies on these targets. Thereafter, we also discuss the challenges related to CAR-T therapy for AML and some promising strategies for overcoming these challenges, including novel approaches such as gene editing and advances in CAR design.

CAR-T Cells in Acute Myeloid Leukemia: Where Do We Stand?

Despite recent advances, the prognosis of acute myeloid leukemia (AML) remains unsatisfactory due to disease recurrence and the development of resistance to both conventional and novel therapies. Engineered T cells expressing chimeric antigen receptors (CARs) on their cellular surface represent one of the most promising anticancer agents. CAR-T cells are increasingly used in patients with B cell malignancies, with remarkable clinical results despite some immune-related toxicities. However, at present, the role of CAR-T cells in myeloid neoplasms, including AML, is extremely limited, as specific molecular targets for immune cells are generally lacking on AML blasts. Besides the paucity of dispensable targets, as myeloid antigens are often co-expressed on normal hematopoietic stem and progenitor cells with potentially intolerable myeloablation, the AML microenvironment is hostile to T cell proliferation due to inhibitory soluble factors. In addition, the rapidly progressive nature of the disease further complicates the use of CAR-T in AML. This review discusses the current state of CAR-T cell therapy in AML, including the still scanty clinical evidence and the potential approaches to overcome its limitations, including genetic modifications and combinatorial strategies, to make CAR-T cell therapy an effective option for AML patients.

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.

Real-world evidence on tagraxofusp for blastic plasmacytoid dendritic cell neoplasm - collected cases from a single center and case reports

Introduction

Blastic plasmacytoid dendritic cell neoplasia (BPDCN) is a rare, aggressive hematologic malignancy. Until recently, the only curative treatment consisted of intensive chemotherapy, followed by hematopoietic cell transplantation (HCT) in eligible adult cases. Tagraxofusp, a CD123-targeted protein-drug conjugate and the first approved targeted treatment for BPDCN, might enhance outcomes especially in patients not eligible for intensive therapies.

Methods

Here, we report real-world outcomes of five male patients with a median age of 79 years who received tagraxofusp as first-line treatment for BPDCN.

Results

Tagraxofusp was found to be well-tolerated in this elderly cohort, with only one patient requiring discontinuation. Three patients responded to the treatment (two patients achieved a CR and one patient achieved a partial response), of which two subsequently underwent allogeneic (allo) HCT. One patient is alive and well after ≥ 4 years after alloHCT, and one patient shows sustained CR after now 13 cycles of tagraxofusp. The other three patients died of progressive disease 4-11 months after initiation of treatment.

Discussion

In line with results from 13 published cases outside clinical trials in the literature, sustained responses were associated with CR after tagraxofusp treatment and subsequent alloHCT. Our results provide real-world evidence for safety and efficacy of tagraxofusp as first-line treatment for BPDCN.

EP300-ZNF384 transactivates IL3RA to promote the progression of B-cell acute lymphoblastic leukemia

The EP300-ZNF384 fusion gene is an oncogenic driver in B-cell acute lymphoblastic leukemia (B-ALL). In the present study, we demonstrated that EP300-ZNF384 substantially induces the transcription of IL3RA and the expression of IL3Rα (CD123) on B-ALL cell membranes. Interleukin 3 (IL-3) supplementation promotes the proliferation of EP300-ZNF348-positive B-ALL cells by activating STAT5. Conditional knockdown of IL3RA in EP300-ZF384-positive cells inhibited the proliferation in vitro, and induced a significant increase in overall survival of mice, which is attributed to impaired propagation ability of leukemia cells. Mechanistically, the EP300-ZNF384 fusion protein transactivates the promoter activity of IL3RA by binding to an A-rich sequence localized at -222/-234 of IL3RA. Furthermore, forced EP300-ZNF384 expression induces the expression of IL3Rα on cell membranes and the secretion of IL-3 in CD19-positive B precursor cells derived from healthy individuals. Doxorubicin displayed a selective killing of EP300-ZNF384-positive B-ALL cells in vitro and in vivo. Collectively, we identify IL3RA as a direct downstream target of EP300-ZNF384, suggesting CD123 is a potent biomarker for EP300-ZNF384-driven B-ALL. Targeting CD123 may be a novel therapeutic approach to EP300-ZNF384-positive patients, alternative or, more likely, complementary to standard chemotherapy regimen in clinical setting.

Novel Therapeutic Targets in Acute Myeloid Leukemia (AML)

PURPOSE OF REVIEW

This review seeks to identify and describe novel genetic and protein targets and their associated therapeutics currently being used or studied in the treatment of acute myeloid leukemia (AML).

RECENT FINDINGS

Over the course of the last 5-6 years, several targeted therapies have been approved by the FDA, for the treatment of both newly diagnosed as well as relapsed/refractory AML. These novel therapeutics, as well as several others currently under investigation, have demonstrated activity in AML and have improved outcomes for many patients. Patient outcomes in AML have slowly improved over time, though for many patients, particularly elderly patients or those with relapsed/refractory disease, mortality remains very high. With the identification of several molecular/genetic drivers and protein targets and development of therapeutics which leverage those mechanisms to target leukemic cells, outcomes for patients with AML have improved and continue to improve significantly.

Identification of Specific Cell Surface Markers on Immune Cells of Squirrel Monkeys (Saimiri sciureus)

Nonhuman primates are an important experimental model for the development of targeted biological therapeutics because of their immunological closeness to humans. However, there are very few antibody reagents relevant for delineating the different immune cell subsets based on nonhuman primate antigens directly or with cross-reactivity to those in humans. Here, we report specific expression of HLA-DR, PD-1, and CD123 on different circulating immune cell subsets in the peripheral blood that included T cells (CD3+), T cells subsets (CD4+ and CD8+), B cells (CD20+), natural killer (NK) cells (CD3-CD16+), and natural killer T cells (CD3+CD16+) along with different monocyte subsets in squirrel monkey (Saimiri sciureus). We established cross-reactivity of commercial mouse antihuman monoclonal antibodies (mAbs), with these various immune cell surface markers. These findings should aid further future comprehensive understanding of the immune parameters and identification of new biomarkers to significantly improve SQM as a model for biomedical studies.

Pivekimab sunirine (IMGN632), a novel CD123-targeting antibody-drug conjugate, in relapsed or refractory acute myeloid leukaemia: a phase 1/2 study

BACKGROUND

Pivekimab sunirine (IMGN632) is a first-in-class antibody-drug conjugate comprising a high-affinity CD123 antibody, cleavable linker, and novel indolinobenzodiazepine pseudodimer payload. CD123 is overexpressed in several haematological malignancies, including acute myeloid leukaemia. We present clinical data on pivekimab sunirine in relapsed or refractory acute myeloid leukaemia.

METHODS

This first-in-human, phase 1/2 dose-escalation and dose-expansion study enrolled participants aged 18 years or older at nine hospitals in France, Italy, Spain, and the USA with CD123+ haematological malignancies (Eastern Cooperative Oncology Group performance status of 0-1); participants reported here were in a cohort of participants with acute myeloid leukaemia who were refractory to or had relapsed on one or more previous treatments for acute myeloid leukaemia. The 3 + 3 dose-escalation phase evaluated two dosing schedules: schedule A (once every 3 weeks, on day 1 of a 3-week cycle) and fractionated schedule B (days 1, 4, and 8 of a 3-week cycle). The dose-expansion phase evaluated two cohorts: one cohort given 0·045 mg/kg of bodyweight (schedule A) and one cohort given 0·090 mg/kg of bodyweight (schedule A). The primary endpoints were the maximum tolerated dose and the recommended phase 2 dose. Antileukaemia activity (overall response and a composite complete remission assessment) was a secondary endpoint. The study is ongoing and registered with ClinicalTrials.gov, NCT03386513.

FINDINGS

Between Dec 29, 2017, and May 27, 2020, 91 participants were enrolled (schedule A, n=68; schedule B, n=23). 30 (44%) of schedule A participants were female and 38 (56%) were male; 60 (88%) were White, six (9%) were Black or African American, and two (3%) were other races. Pivekimab sunirine at doses of 0·015 mg/kg to 0·450 mg/kg in schedule A was administered in six escalating doses with no maximum tolerated dose defined; three dose-limiting toxicities were observed (reversible veno-occlusive disease; 0·180 mg/kg, n=1 and 0·450 mg/kg, n=1; and neutropenia; 0·300 mg/kg, n=1). Schedule B was not pursued further on the basis of comparative safety and antileukaemia findings with schedule A. The recommended phase 2 dose was selected as 0·045 mg/kg once every 3 weeks. At the recommended phase 2 dose (n=29), the most common grade 3 or worse treatment-related adverse events were febrile neutropenia (three [10%]), infusion-related reactions (two [7%]), and anaemia (two [7%]). Treatment-related serious adverse events occurring in 5% or more of participants treated at the recommended phase 2 dose were febrile neutropenia (two [7%]) and infusion-related reactions (two [7%]). Among 68 participants who received schedule A, one death (1%) was considered to be treatment-related (cause unknown; 0·300 mg/kg cohort). At the recommended phase 2 dose, the overall response rate was 21% (95% CI 8-40; six of 29) and the composite complete remission rate was 17% (95% CI 6-36; five of 29).

INTERPRETATION

Pivekimab sunirine showed single-agent activity across multiple doses, with a recommended phase 2 dose of 0·045 mg/kg once every 3 weeks. These findings led to a phase 1b/2 study of pivekimab sunirine plus azacitidine and venetoclax in patients with CD123-positive acute myeloid leukaemia.

FUNDING

ImmunoGen.

Blastic Plasmacytoid Dendritic Cell Neoplasm: A Comprehensive Review of the Disease, Central Nervous System Presentations, and Treatment Strategies

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy with poor outcomes. The World Health Organization (WHO) redefined BDCN as a distinct disease entity in 2016. BPDCN arises from plasmacytoid dendritic cells, manifesting primarily in the skin, bone marrow, and lymph nodes, occasionally involving the central nervous system (CNS). This presents challenges in diagnosis and treatment, with CNS involvement often overlooked in standard diagnostic workups due to BPDCN's rarity and patients often being neurologically asymptomatic at diagnosis. CNS involvement typically emerges during relapse, yet clinical trials often exclude such cases, limiting our understanding of its development and treatment. Treatment options for CNS involvement include intrathecal (IT) chemotherapies like methotrexate and cytarabine, often in combination with systemic agents. Tagraxofusp and traditional regimens for acute myeloid leukemia show limited success at preventing CNS relapse, prompting exploration of combined therapies like hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (HyperCVAD) with venetoclax and adding IT chemotherapy to other backbones. Ongoing clinical trials investigating emerging therapies offer hope despite limited focus on CNS implications. Trials incorporating CNS-involved patients aim to pioneer novel treatment approaches, potentially reshaping BPDCN management. Understanding CNS involvement's complexities in BPDCN remains crucial for tailored treatments and better patient outcomes.

Breakthrough in Blastic Plasmacytoid Dendritic Cell Neoplasm Cancer Therapy Owing to Precision Targeting of CD123

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic cancer originating from the malignant transformation of plasmacytoid dendritic cell precursors. This malignancy progresses rapidly, with frequent relapses and a poor overall survival rate, underscoring the urgent need for effective treatments. However, diagnosing and treating BPDCN have historically been challenging due to its rarity and the lack of standardized approaches. The recognition of BPDCN as a distinct disease entity is recent, and standardized treatment protocols are yet to be established. Traditionally, conventional chemotherapy and stem cell transplantation have been the primary methods for treating BPDCN patients. Advances in immunophenotyping and molecular profiling have identified potential therapeutic targets, leading to a shift toward CD123-targeted immunotherapies in both clinical and research settings. Ongoing developments with SL-401, IMGN632, CD123 chimeric antigen receptor (CAR) T-cells, and bispecific antibodies (BsAb) show promising advancements. However, the therapeutic effectiveness of CD123-targeting treatments needs improvement through innovative approaches and combinations of treatments with other anti-leukemic drugs. The exploration of combinations such as CD123-targeted immunotherapies with azacitidine and venetoclax is suggested to enhance antineoplastic responses and improve survival rates in BPDCN patients. In conclusion, this multifaceted approach offers hope for more effective and tailored therapeutic interventions against this challenging hematologic malignancy.

Genomic landscape of patients with germline RUNX1 variants and familial platelet disorder with myeloid malignancy

ABSTRACT

Familial platelet disorder with associated myeloid malignancies (FPDMM) is caused by germline RUNX1 mutations and characterized by thrombocytopenia and increased risk of hematologic malignancies. We recently launched a longitudinal natural history study for patients with FPDMM. Among 27 families with research genomic data by the end of 2021, 26 different germline RUNX1 variants were detected. Besides missense mutations enriched in Runt homology domain and loss-of-function mutations distributed throughout the gene, splice-region mutations and large deletions were detected in 6 and 7 families, respectively. In 25 of 51 (49%) patients without hematologic malignancy, somatic mutations were detected in at least 1 of the clonal hematopoiesis of indeterminate potential (CHIP) genes or acute myeloid leukemia (AML) driver genes. BCOR was the most frequently mutated gene (in 9 patients), and multiple BCOR mutations were identified in 4 patients. Mutations in 6 other CHIP- or AML-driver genes (TET2, DNMT3A, KRAS, LRP1B, IDH1, and KMT2C) were also found in ≥2 patients without hematologic malignancy. Moreover, 3 unrelated patients (1 with myeloid malignancy) carried somatic mutations in NFE2, which regulates erythroid and megakaryocytic differentiation. Sequential sequencing data from 19 patients demonstrated dynamic changes of somatic mutations over time, and stable clones were more frequently found in older adult patients. In summary, there are diverse types of germline RUNX1 mutations and high frequency of somatic mutations related to clonal hematopoiesis in patients with FPDMM. Monitoring changes in somatic mutations and clinical manifestations prospectively may reveal mechanisms for malignant progression and inform clinical management. This trial was registered at www.clinicaltrials.gov as #NCT03854318.

Novel chimeric antigen receptor targets and constructs for acute lymphoblastic leukemia: Moving beyond CD19

Acute lymphoblastic leukemia (ALL) is the second most common acute leukemia in adults with a poor prognosis with relapsed or refractory (R/R) B-cell lineage ALL (B-ALL). Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy has shown excellent response rates in RR B-ALL, but most patients relapse due to poor persistence of CAR T-cell therapy or other tumor-associated escape mechanisms. In addition, anti-CD19 CAR T-cell therapy causes several serious side effects such as cytokine release syndrome and neurotoxicity. In this review, we will discuss novel CAR targets, CAR constructs, and various strategies to boost CARs for the treatment of RR B-ALL. In addition, we discuss a few novel strategies developed to reduce the side effects of CAR.

Enabling biomedical technologies for chronic myelogenous leukemia (CML) biomarkers detection

Chronic myelogenous/myeloid leukemia (CML) is a type of cancer of bone marrow that arises from hematopoietic stem cells and affects millions of people worldwide. Eighty-five percent of the CML cases are diagnosed during chronic phase, most of which are detected through routine tests. Leukocytes, micro-Ribonucleic Acids, and myeloid markers are the primary biomarkers for CML diagnosis and are mainly detected using real-time reverse transcription polymerase chain reaction, flow cytometry, and genetic testing. Though multiple therapies have been developed to treat CML, early detection still plays a pivotal role in the overall patient survival rate. The current technologies used for CML diagnosis are costly and are confined to laboratory settings which impede their application in the point-of-care settings for early-stage detection of CML. This study provides detailed analysis and insights into the significance of CML, patient symptoms, biomarkers used for testing, and best possible detection techniques responsible for the enhancement in survival rates. A critical and detailed review is provided around potential microfluidic devices that can be adapted to detect the biomarkers associated with CML while enabling point-of-care testing for early diagnosis of CML to improve patient survival rates.

The PedAL/EuPAL Project: A Global Initiative to Address the Unmet Medical Needs of Pediatric Patients with Relapsed or Refractory Acute Myeloid Leukemia

The prognosis of children with acute myeloid leukemia (AML) has improved incrementally over the last few decades. However, at relapse, overall survival (OS) is approximately 40-50% and is even lower for patients with chemo-refractory disease. Effective and less toxic therapies are urgently needed for these children. The Pediatric Acute Leukemia (PedAL) program is a strategic global initiative that aims to overcome the obstacles in treating children with relapsed/refractory acute leukemia and is supported by the Leukemia and Lymphoma Society in collaboration with the Children's Oncology Group, the Innovative Therapies for Children with Cancer consortium, and the European Pediatric Acute Leukemia (EuPAL) foundation, amongst others. In Europe, the study is set up as a complex clinical trial with a stratification approach to allocate patients to sub-trials of targeted inhibitors at relapse and employing harmonized response and safety definitions across sub-trials. The PedAL/EuPAL international collaboration aims to determine new standards of care for AML in a first and second relapse, using biology-based selection markers for treatment stratification, and deliver essential data to move drugs to front-line pediatric AML studies. An overview of potential treatment targets in pediatric AML, focused on drugs that are planned to be included in the PedAL/EuPAL project, is provided in this manuscript.

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.

Plasmacytoid dendritic cell expansion in myeloid neoplasms: A novel distinct subset of myeloid neoplasm?

Plasmacytoid dendritic cells (pDCs) are a specific dendritic cell type stemming from the myeloid lineage. Clinically and pathologically, neoplasms associated with pDCs are classified as blastic plasmacytoid dendritic cell neoplasm (BPDCN), mature plasmacytoid dendritic myeloid neoplasm (MPDMN) and pDC expansion in myeloid neoplasms (MNs). BPDCN was considered a rare and aggressive neoplasm in the 2016 World Health Organization (WHO) classification. MPDMN, known as mature pDC-derived neoplasm, is closely related to MNs and was first recognized in the latest 2022 WHO classification, proposing a new concept that acute myeloid leukemia cases could show clonally expanded pDCs (pDC-AML). With the advances in detection techniques, an increasing number of pDC expansion in MNs have been reported, but whether the pathogenesis is similar to that of MPDMN remains unclear. This review focuses on patient characteristics, diagnosis and treatment of pDC expansion in MNs to gain further insight into this novel and unique provisional subtype.

RUNX1 loss renders hematopoietic and leukemic cells dependent on IL-3 and sensitive to JAK inhibition

Disease-initiating mutations in the transcription factor RUNX1 occur as germline and somatic events that cause leukemias with particularly poor prognosis. However, the role of RUNX1 in leukemogenesis is not fully understood, and effective therapies for RUNX1-mutant leukemias remain elusive. Here, we used primary patient samples and a RUNX1-KO model in primary human hematopoietic cells to investigate how RUNX1 loss contributes to leukemic progression and to identify targetable vulnerabilities. Surprisingly, we found that RUNX1 loss decreased proliferative capacity and stem cell function. However, RUNX1-deficient cells selectively upregulated the IL-3 receptor. Exposure to IL-3, but not other JAK/STAT cytokines, rescued RUNX1-KO proliferative and competitive defects. Further, we demonstrated that RUNX1 loss repressed JAK/STAT signaling and rendered RUNX1-deficient cells sensitive to JAK inhibitors. Our study identifies a dependency of RUNX1-mutant leukemias on IL-3/JAK/STAT signaling, which may enable targeting of these aggressive blood cancers with existing agents.

Blastic plasmacytoid dendritic cell neoplasm: a comprehensive review in pediatrics, adolescents, and young adults (AYA) and an update of novel therapies

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy that can involve the bone marrow, peripheral blood, skin, lymph nodes, and the central nervous system. Though more common in older adults, BPDCN has been reported across all age groups, including infants and children. The incidence of pediatric BPDCN is extremely low and little is known about the disease. Pediatric BPDCN is believed to be clinically less aggressive but often with more dissemination at presentation than adult cases. Unlike adults who almost always proceed to a hematopoietic stem cell transplantation in first complete remission if transplant-eligible, the majority of children can be cured with a high-risk acute lymphoblastic leukemia-like regimen. Hematopoietic stem cell transplantation is recommended for children with high-risk disease, the definition of which continues to evolve, or those in relapse and refractory settings where outcomes continue to be dismal. Novel agents used in other hematologic malignancies and CD123 targeted agents, including chimeric antigen receptor T-cells and monoclonal/bispecific antibodies, are being brought into research and practice. Our goal is to provide a comprehensive review of presentation, diagnosis, and treatment by review of pediatric cases reported for the last 20 years, and a review of novel targeted therapies and therapies under investigation for adult and pediatric patients.

Control of acute myeloid leukemia by a trifunctional NKp46-CD16a-NK cell engager targeting CD123

CD123, the alpha chain of the IL-3 receptor, is an attractive target for acute myeloid leukemia (AML) treatment. However, cytotoxic antibodies or T cell engagers targeting CD123 had insufficient efficacy or safety in clinical trials. We show that expression of CD64, the high-affinity receptor for human IgG, on AML blasts confers resistance to anti-CD123 antibody-dependent cell cytotoxicity (ADCC) in vitro. We engineer a trifunctional natural killer cell engager (NKCE) that targets CD123 on AML blasts and NKp46 and CD16a on NK cells (CD123-NKCE). CD123-NKCE has potent antitumor activity against primary AML blasts regardless of CD64 expression and induces NK cell activation and cytokine secretion only in the presence of AML cells. Its antitumor activity in a mouse CD123+ tumor model exceeds that of the benchmark ADCC-enhanced antibody. In nonhuman primates, it had prolonged pharmacodynamic effects, depleting CD123+ cells for more than 10 days with no signs of toxicity and very low inflammatory cytokine induction over a large dose range. These results support clinical development of CD123-NKCE.

Biomarkers as targets for CAR-T/NK cell therapy in AML

The most common kind of acute leukemia in adults is acute myeloid leukemia (AML), which is often treated with induction chemotherapy regimens followed by consolidation or allogeneic hematopoietic stem cell transplantation (HSCT). However, some patients continue to develop relapsed or refractory AML (R/R-AML). Small molecular targeted drugs require long-time administration. Not all the patients hold molecular targets. Novel medicines are therefore needed to enhance treatment outcomes. T cells and natural killer (NK) cells engineered with chimeric antigen receptors (CARs) that target antigens associated with AML have recently been produced and are currently being tested in both pre-clinical and clinical settings. This review provides an overview of CAR-T/NK treatments for AML.

CAR-T Cells Immunotherapies for the Treatment of Acute Myeloid Leukemia-Recent Advances

In order to increase the effectiveness of cancer therapies and extend the long-term survival of patients, more and more often, in addition to standard treatment, oncological patients receive also targeted therapy, i.e., CAR-T cells. These cells express a chimeric receptor (CAR) that specifically binds an antigen present on tumor cells, resulting in tumor cell lysis. The use of CAR-T cells in the therapy of relapsed and refractory B-type acute lymphoblastic leukemia (ALL) resulted in complete remission in many patients, which prompted researchers to conduct tests on the use of CAR-T cells in the treatment of other hematological malignancies, including acute myeloid leukemia (AML). AML is associated with a poorer prognosis compared to ALL due to a higher risk of relapse caused by the development of resistance to standard treatment. The 5-year relative survival rate in AML patients was estimated at 31.7%. The objective of the following review is to present the mechanism of action of CAR-T cells, and discuss the latest findings on the results of anti-CD33, -CD123, -FLT3 and -CLL-1 CAR-T cell therapy, the emerging challenges as well as the prospects for the future.

Bicistronic CAR-T cells targeting CD123 and CLL1 for AML to reduce the risk of antigen escape

PURPOSE

Acute myeloid leukemia (AML) is a highly heterogeneous neoplastic disease with a poor prognosis that relapses even after its treatment with chimeric antigen receptor (CAR)-T cells targeting a single antigen. CD123 and CLL1 are expressed in most AML blasts and leukemia stem cells, and their low expression in normal hematopoietic stem cells makes them ideal targets for CAR-T. In this study, we tested the hypothesis that a new bicistronic CAR targeting CD123 and CLL1 can enhance antigenic coverage and prevent antigen escape and subsequent recurrence of AML.

METHODS

CD123 and CLL1 expressions were evaluated on AML cell lines and blasts. Then, in addition to concentrating on CD123 and CLL1, we introduced the marker/suicide gene RQR8 with a bicistronic CAR. Xenograft models of disseminated AML and in vitro coculture models were used to assess the anti-leukemia efficacy of CAR-T cells. The hematopoietic toxicity of CAR-T cells was evaluated in vitro by colony cell formation assays. It was demonstrated in vitro that the combination of rituximab and NK cells caused RQR8-mediated clearance of 123CL CAR-T cells.

RESULTS

We have successfully established bicistronic 123CL CAR-T cells that can target CD123 and CLL1. 123CL CAR-T cells effectively cleared AML cell lines and blasts. They also demonstrated appreciable anti-AML activity in animal transplant models. Moreover, 123CL CAR-T cells can be eliminated in an emergency by a natural safety switch and don't target hematopoietic stem cells.

CONCLUSIONS

The bicistronic CAR-T cells targeting CD123 and CLL1 may be a useful and secure method for treating AML.

The Nup98::Nsd1 fusion gene induces CD123 expression in 32D cells

The NUP98::NSD1 fusion gene is associated with extremely poor prognosis in patients with acute myeloid leukemia (AML). NUP98::NSD1 induces self-renewal and blocks differentiation of hematopoietic stem cells, leading to development of leukemia. Despite its association with poor prognosis, targeted therapy for NUP98::NSD1-positive AML is lacking, as the details of NUP98::NSD1 function are unknown. Here, we generated 32D cells (a murine interleukin-3 (IL-3)-dependent myeloid progenitor cell line) expressing mouse Nup98::Nsd1 to explore the function of NUP98::NSD1 in AML, including comprehensive gene expression analysis. We identified two properties of Nup98::Nsd1 + 32D cells in vitro. First, Nup98::Nsd1 promoted blocking of AML cell differentiation, consistent with a previous report. Second, Nup98::Nsd1 increased dependence on IL-3 for cell proliferation, due to overexpression of the alpha subunit of the IL-3 receptor (IL3-RA, also known as CD123). Consistent with our in vitro data, IL3-RA was also upregulated in samples from patients with NUP98::NSD1-positive AML. These results highlight CD123 as a potential new therapeutic target in NUP98::NSD1-positive AML.

North American Blastic Plasmacytoid Dendritic Cell Neoplasm Consortium: position on standards of care and areas of need

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with historically poor outcomes and no worldwide consensus treatment approach. Unique among most hematologic malignancies for its frequent cutaneous involvement, BPDCN can also invade other extramedullary compartments, including the central nervous system. Generally affecting older adults, many patients are unfit to receive intensive chemotherapy, and although hematopoietic stem cell transplantation is preferred for younger, fit individuals, not all are eligible. One recent therapeutic breakthrough is that all BPDCNs express CD123 (IL3Rα) and that this accessible surface marker can be pharmacologically targeted. The first-in-class agent for BPDCN, tagraxofusp, which targets CD123, was approved in December 2018 in the United States for patients with BPDCN aged ≥2 years. Despite favorable response rates in the frontline setting, many patients still relapse in the setting of monotherapy, and outcomes in patients with relapsed/refractory BPDCN remain dismal. Therefore, novel approaches targeting both CD123 and other targets are actively being investigated. To begin to formally address the state of the field, we formed a new collaborative initiative, the North American BPDCN Consortium (NABC). This group of experts, which includes a multidisciplinary panel of hematologists/oncologists, hematopoietic stem cell transplant physicians, pathologists, dermatologists, and pediatric oncologists, was tasked with defining the current standard of care in the field and identifying the most important research questions and future directions in BPDCN. The position findings of the NABC's inaugural meetings are presented herein.

CD123 a Therapeutic Target for Acute Myeloid Leukemia and Blastic Plasmocytoid Dendritic Neoplasm

In spite of consistent progress at the level of basic research and of clinical treatment, acute myeloid leukemia (AML) still represents an unmet clinical need for adult and pediatric patients. To improve the outcomes of these patients, it is necessary to identify new therapeutic targets. IL3RA (CD123, alpha subunit of the interleukin 3 receptor) is a cell membrane protein overexpressed in several hematologic malignancies, including AML blastic plasmocytoid dendritic cell neoplasms (BPDCN). Given the higher expression of CD123 on leukemic cells compared to normal hematopoietic cells and its low/absent expression on normal hematopoietic stem cells, it appears as a suitable and attractive target for therapy. Various drugs targeting CD123 have been developed and evaluated at clinical level: interleukin-3 conjugated with diphtheria toxin; naked neutralizing anti-CD123 antibodies; drug-antibody conjugates; bispecific antibodies targeting both CD123 and CD3; and chimeric antigen receptor (CAR) T cells engineered to target CD123. Some of these agents have shown promising results at the clinical level, including tagraxofusp (CD123 conjugated with diphtheria toxin) for the treatment of BPDCN and IMGN632 (anti-CD123 drug-conjugate), and flotetuzumab (bispecific anti-CD123 and anti-CD3 monoclonal antibody) for the treatment of AML. However, the therapeutic efficacy of CD123-targeting treatments is still unsatisfactory and must be improved through new therapeutic strategies and combined treatments with other antileukemic drugs.

Antibody therapies for the treatment of acute myeloid leukemia: exploring current and emerging therapeutic targets

INTRODUCTION

Acute myeloid leukemia (AML) is the most common and deadly type of leukemia affecting adults. It is typically managed with rounds of non-targeted chemotherapy followed by hematopoietic stem cell transplants, but this is only possible in patients who can tolerate these harsh treatments and many are elderly and frail. With the identification of novel tumor-specific cell surface receptors, there is great conviction that targeted antibody therapies will soon become available for these patients.

AREAS COVERED

In this review, we describe the current landscape of known target receptors for monospecific and bispecific antibody-based therapeutics for AML. Here, we characterize each of the receptors and targeted antibody-based therapeutics in development, illustrating the rational design behind each therapeutic compound. We then discuss the bispecific antibodies in development and how they improve immune surveillance of AML. For each therapeutic, we also summarize the available pre-clinical and clinical data, including data from discontinued trials.

EXPERT OPINION

One antibody-based therapeutic has already been approved for AML treatment, the CD33-targeting antibody-drug conjugate, gemtuzumab ozogamicin. Many more are currently in pre-clinical and clinical studies. These antibody-based therapeutics can perform tumor-specific, elaborate cytotoxic functions and there is growing confidence they will soon lead to personalized, safe AML treatment options that induce durable remissions.

Genomic Landscape of Patients with Germline RUNX1 Variants and Familial Platelet Disorder with Myeloid Malignancy

Germline RUNX1 mutations lead to familial platelet disorder with associated myeloid malignancies (FPDMM), which is characterized by thrombocytopenia and a life-long risk (35-45%) of hematological malignancies. We recently launched a longitudinal natural history study for patients with FPDMM at the NIH Clinical Center. Among 29 families with research genomic data, 28 different germline RUNX1 variants were detected. Besides missense mutations enriched in Runt homology domain and loss-of-function mutations distributed throughout the gene, splice-region mutations and large deletions were detected in 6 and 7 families, respectively. In 24 of 54 (44.4%) non-malignant patients, somatic mutations were detected in at least one of the clonal hematopoiesis of indeterminate potential (CHIP) genes or acute myeloid leukemia (AML) driver genes. BCOR was the most frequently mutated gene (in 9 patients), and multiple BCOR mutations were identified in 4 patients. Mutations in 7 other CHIP or AML driver genes ( DNMT3A, TET2, NRAS, SETBP1, SF3B1, KMT2C , and LRP1B ) were also found in more than one non-malignant patient. Moreover, three unrelated patients (one with myeloid malignancy) carried somatic mutations in NFE2 , which regulates erythroid and megakaryocytic differentiation. Sequential sequencing data from 19 patients demonstrated dynamic changes of somatic mutations over time, and stable clones were more frequently found in elderly patients. In summary, there are diverse types of germline RUNX1 mutations and high frequency of somatic mutations related to clonal hematopoiesis in patients with FPDMM. Monitoring dynamic changes of somatic mutations prospectively will benefit patients’ clinical management and reveal mechanisms for progression to myeloid malignancies.

Key Points

Comprehensive genomic profile of patients with FPDMM with germline RUNX1 mutations. Rising clonal hematopoiesis related secondary mutations that may lead to myeloid malignancies.

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

Acute Myeloid Leukemia (AML) is an aggressive myeloid malignancy associated with high mortality rates (less than 30% 5-year survival). Despite advances in our understanding of the molecular mechanisms underpinning leukemogenesis, standard-of-care therapeutic approaches have not changed over the last couple of decades. Chimeric Antigen Receptor (CAR) T-cell therapy targeting CD19 has shown remarkable clinical outcomes for patients with acute lymphoblastic leukemia (ALL) and is now an FDA-approved therapy. Targeting of myeloid malignancies that are CD19-negative with this promising technology remains challenging largely due to lack of alternate target antigens, complex clonal heterogeneity, and the increased recognition of an immunosuppressive bone marrow. We carefully reviewed a comprehensive list of AML targets currently being used in both proof-of-concept pre-clinical and experimental clinical settings. We analyzed the expression profile of these molecules in leukemic as well normal tissues using reliable protein databases and data reported in the literature and we provide an updated overview of the current clinical trials with CAR T-cells in AML. Our study represents a state-of-art review of the field and serves as a potential guide for selecting known AML-associated targets for adoptive cellular therapies.

Application of engineered extracellular vesicles to overcome drug resistance in cancer

Targeted therapies have significantly improved survival rates and quality of life for many cancer patients. However, on- and off-target side toxicities in normal tissues, and precocious activation of the immune response remain significant issues that limit the efficacy of molecular targeted agents. Extracellular vesicles (EVs) hold great promise as the mediators of next-generation therapeutic payloads. Derived from cellular membranes, EVs can be engineered to carry specific therapeutic agents in a targeted manner to tumor cells. This review highlights the progress in our understanding of basic EV biology, and discusses how EVs are being chemically and genetically modified for use in clinical and preclinical studies.

Chimeric antigen receptor T-cell therapy for T-ALL and AML

Non-B-cell acute leukemia is a term that encompasses T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML). Currently, the therapeutic effectiveness of existing treatments for refractory or relapsed (R/R) non-B-cell acute leukemia is limited. In such situations, chimeric antigen receptor (CAR)-T cell therapy may be a promising approach to treat non-B-cell acute leukemia, given its promising results in B-cell acute lymphoblastic leukemia (B-ALL). Nevertheless, fratricide, malignant contamination, T cell aplasia for T-ALL, and specific antigen selection and complex microenvironment for AML remain significant challenges in the implementation of CAR-T therapy for T-ALL and AML patients in the clinic. Therefore, designs of CAR-T cells targeting CD5 and CD7 for T-ALL and CD123, CD33, and CLL1 for AML show promising efficacy and safety profiles in clinical trials. In this review, we summarize the characteristics of non-B-cell acute leukemia, the development of CARs, the CAR targets, and their efficacy for treating non-B-cell acute leukemia.

Tumor buster - where will the CAR-T cell therapy 'missile' go?

Chimeric antigen receptor (CAR) T cell (CAR-T cell) therapy based on gene editing technology represents a significant breakthrough in personalized immunotherapy for human cancer. This strategy uses genetic modification to enable T cells to target tumor-specific antigens, attack specific cancer cells, and bypass tumor cell apoptosis avoidance mechanisms to some extent. This method has been extensively used to treat hematologic diseases, but the therapeutic effect in solid tumors is not ideal. Tumor antigen escape, treatment-related toxicity, and the immunosuppressive tumor microenvironment (TME) limit their use of it. Target selection is the most critical aspect in determining the prognosis of patients receiving this treatment. This review provides a comprehensive summary of all therapeutic targets used in the clinic or shown promising potential. We summarize CAR-T cell therapies' clinical trials, applications, research frontiers, and limitations in treating different cancers. We also explore coping strategies when encountering sub-optimal tumor-associated antigens (TAA) or TAA loss. Moreover, the importance of CAR-T cell therapy in cancer immunotherapy is emphasized.

Emerging concepts of type I interferons in SLE pathogenesis and therapy

Type I interferons have been suspected for decades to have a crucial role in the pathogenesis of systemic lupus erythematosus (SLE). Evidence has now overturned several long-held assumptions about how type I interferons are regulated and cause pathological conditions, providing a new view of SLE pathogenesis that resolves longstanding clinical dilemmas. This evidence includes data on interferons in relation to genetic predisposition and epigenetic regulation. Importantly, data are now available on the role of interferons in the early phases of the disease and the importance of non-haematopoietic cellular sources of type I interferons, such as keratinocytes, renal tubular cells, glial cells and synovial stromal cells, as well as local responses to type I interferons within these tissues. These local effects are found not only in inflamed target organs in established SLE, but also in histologically normal skin during asymptomatic preclinical phases, suggesting a role in disease initiation. In terms of clinical application, evidence relating to biomarkers to characterize the type I interferon system is complex, and, notably, interferon-blocking therapies are now licensed for the treatment of SLE. Collectively, the available data enable us to propose a model of disease pathogenesis that invokes the unique value of interferon-targeted therapies. Accordingly, future approaches in SLE involving disease reclassification and preventative strategies in preclinical phases should be investigated.

Pathomorphological and clinical characteristics of blastic plasmocytoid dendritic cell neoplasm. Case report

The paper reveals the 5 cases date about blastic plasmacytoid dendritic cell neoplasm. The presented information demonstrates morphological, immunohistochemical data and clinical manifestations.

New Therapeutic Strategies for Adult Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a genetically heterogeneous hematological malignancy. Chromosomal and genetic analyses are important for the diagnosis and prognosis of AML. Some patients experience relapse or have refractory disease, despite conventional cytotoxic chemotherapies and allogeneic transplantation, and a variety of new agents and treatment strategies have emerged. After over 20 years during which no new drugs became available for the treatment of AML, the CD33-targeting antibody-drug conjugate gemtuzumab ozogamicin was developed. This is currently used in combination with standard chemotherapy or as a single agent. CPX-351, a liposomal formulation containing daunorubicin and cytarabine, has become one of the standard treatments for secondary AML in the elderly. FMS-like tyrosine kinase 3 (FLT3) inhibitors and isocitrate dehydrogenase 1/2 (IDH 1/2) inhibitors are mainly used for AML patients with actionable mutations. In addition to hypomethylating agents and venetoclax, a B-cell lymphoma-2 inhibitor is used in frail patients with newly diagnosed AML. Recently, tumor protein p53 inhibitors, cyclin-dependent kinase inhibitors, and NEDD8 E1-activating enzyme inhibitors have been gaining attention, and a suitable strategy for the use of these drugs is required. Antibody drugs targeting cell-surface markers and immunotherapies, such as antibody-drug conjugates and chimeric antigen receptor T-cell therapy, have also been developed for AML.

Bispecific CAR T-cells for B-cell malignancies

INTRODUCTION

Chimeric antigen receptor (CAR) modified T-cell therapy has revolutionized the treatment of relapsed/refractory B-cell malignancies including acute lymphoblastic leukemia and non-Hodgkin lymphoma. All of the CARs approved for clinical use in treating B-cell malignancies are directed against a single antigen, CD19. Although the initial response rates are high, a significant number of patients relapse, with antigen loss being one proposed mechanism of treatment failure. Multi-targeted CAR T approaches are now being developed to overcome this limitation of currently approved CAR products.

AREAS COVERED

Here we discuss the mechanism of antigen loss, various bispecific CAR T-cell constructs and their efficacy and safety in the pre-clinical as well as clinical settings.

EXPERT OPINION

Although CD19 CAR T-cells have significantly improved response rates in relapsed/refractory B-cell malignancies, relapse remains a major barrier to long-term survival. Bispecific CAR T-cells offer an alternative approach to mitigate relapse associated with antigen loss. In B-cell malignancies, various bispecific CAR constructs are being studied. The CD19/CD20 and CD19/CD22 bispecific CARs have shown a favorable efficacy and safety profile in phase I trials. However, larger phase II studies and longer follow ups are needed to better assess their efficacy and safety in patients with relapsed/refractory B-cell malignancies.

Miller H, Hu X, Kumar R, T. Ngo P, Yan J, B. Frieboes H. Prediction of lung cancer immunotherapy response via machine learning analysis of immune cell lineage and surface markers

BACKGROUND: Although advances have been made in cancer immunotherapy, patient benefits remain elusive. For non-small cell lung cancer (NSCLC), monoclonal antibodies targeting programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) have shown survival benefit compared to chemotherapy. Personalization of treatment would be facilitated by a priori identification of patients likely to benefit. OBJECTIVE: This pilot study applied a suite of machine learning methods to analyze mass cytometry data of immune cell lineage and surface markers from blood samples of a small cohort (n= 13) treated with Pembrolizumab, Atezolizumab, Durvalumab, or Nivolumab as monotherapy. METHODS: Four different comparisons were evaluated between data collected at an initial visit (baseline), after 12-weeks of immunotherapy, and from healthy (control) samples: healthy vs patients at baseline, Responders vs Non-Responders at baseline, Healthy vs 12-week Responders, and Responders vs Non-Responders at 12-weeks. The algorithms Random Forest, Partial Least Squares Discriminant Analysis, Multi-Layer Perceptron, and Elastic Net were applied to find features differentiating between these groups and provide for the capability to predict outcomes. RESULTS: Particular combinations and proportions of immune cell lineage and surface markers were sufficient to accurately discriminate between the groups without overfitting the data. In particular, markers associated with the B-cell phenotype were identified as key features. CONCLUSIONS: This study illustrates a comprehensive machine learning analysis of circulating immune cell characteristics of NSCLC patients with the potential to predict response to immunotherapy. Upon further evaluation in a larger cohort, the proposed methodology could help guide personalized treatment selection in clinical practice.

Characteristics and outcomes of patients with blastic plasmacytoid dendritic cell neoplasm treated with frontline HCVAD

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive blood cancer, often involving the skin, bone marrow, lymph nodes, and central nervous system (CNS) in 20% to 30% of patients. Despite significant progress in CD123- and BCL-2-targeted therapy, most patients are not cured without hematopoietic stem cell transplant (HSCT), and CNS relapses occur quite frequently. Combination approaches with targeted and chemotherapy agents plus incorporation of prophylactic CNS-directed therapy are urgently needed. In this setting, we sought to analyze outcomes using the cytotoxic chemotherapy backbone regimen hyperfractionated cyclophosphamide, vincristine, adriamycin, and dexamethasone (HCVAD). We conducted a retrospective analysis of patients with BPDCN (n = 100), evaluating complete remission (CR) and median overall survival (OS) among 3 groups: those who received frontline HCVAD-based therapy (n = 35), SL-401 (n = 37), or other regimens (n = 28). HCVAD-based regimens yielded higher CR (80% vs 59% vs 43%; P = .01). There was no significant difference in OS (28.3 vs 13.7 vs 22.8 months; P = .41) or remission duration probability among treatment groups (38.6 vs not reached vs 10.2 months; P = .24). HSCT was performed in 51% vs 49% vs 38%, respectively (P = .455). These results suggest a continued important role for HCVAD-based chemotherapy in BPDCN, even in the modern targeted-therapy era, with high CR rates in the frontline setting. Further studies must establish the clinical activity, feasibility, and safety of doublet/triplet combinations of targeted therapies plus cytotoxic agents and the addition of CNS prophylaxis, with the ultimate goal of durable long-term remission for patients with BPDCN.