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Emanating from a discrete category within the lympho-hematopoietic tumor system, as established by the World Health Organization in 2008, the blastic plasmacytoid dendritic cell neoplasm constitutes an uncommon malignant hematological disorder. It is routinely misidentified on account of its conspicuous dermatological manifestation, yet may insidiously permeate bone marrow and lymph nodes, involving peripheral blood and diverse extra-nodal tissues. Instances of mammary gland encroachment are extraordinarily infrequent. The current document delineates a case of a 14-year-old female patient contending with blastic plasmacytoid dendritic cell neoplasm, whose primary symptom was a mammary nodule, and whose breast and bone marrow/blood involvement were synchronous, in attempt to increase clinical vigilance. [ABSTRACT FROM AUTHOR]

Tagraxofusp is a first‐in‐class CD123‐directed conjugate of an amended diphtheria toxin platform and recombinant interleukin 3. Binding and subsequent internalization of the drug result in cell death via disruption of intracellular protein synthesis. CD123 is a surface marker that is expressed in several hematological malignancies, especially blastic plasmacytoid dendritic cell neoplasm (BPDCN), where its expression is ubiquitous. A pivotal study of tagraxofusp in BPDCN resulted in its approval for the treatment of BPDCN, the first treatment approved for this indication. Since the introduction of tagraxofusp, research has focused on the management of adverse effects, combination therapy to improve outcomes in fit patients, and dosing and combination strategies to mitigate toxicities while preserving efficacy, especially among older patients. The successful targeting of CD123 in BPDCN has also encouraged research into a variety of other CD123‐positive hematological neoplasms, including acute myeloid leukemia (AML), and informed the development of other novel agents targeting CD123. This review examines the clinical data leading to the development and approval of tagraxofusp in BPDCN, how it is being used in combination to improve outcomes in BPDCN and AML, and its developing role in other hematological malignancies. Tagraxofusp is a first‐in‐class CD123‐directed immunotherapy for blastic plasmacytoid dendritic cell neoplasm. This review outlines the studies leading to its approval, how it is being used in combination and in other hematological malignancies, and novel CD123‐directed therapies. [ABSTRACT FROM AUTHOR]

BPDCN is an aggressive myeloid malignancy with a poor prognosis. It derives from the precursors of plasmacytoid dendritic cells and is characterized by CD123 overexpression, which is seen in all patients with BPDCN. The CD123-directed therapy tagraxofusp is the only approved treatment for BPDCN; it was approved in the US as monotherapy for the treatment of patients aged ≥2 years with treatment-naive or relapsed/refractory BPDCN. Herein, we review the available data supporting the utility of tagraxofusp in treating patients with BPDCN. In addition, we present best practices and real-world insights from clinicians in academic and community settings in the US on how they use tagraxofusp to treat BPDCN. Several case studies illustrate the efficacy of tagraxofusp and discuss its safety profile, as well as the prevention, mitigation, and management of anticipated adverse events. [ABSTRACT FROM AUTHOR]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare malignancy derived from plasmacytoid dendritic cells, can mimic both acute leukemia and aggressive T-cell lymphoma. Therapy of this highly aggressive hematological disease should be initiated as soon as possible, especially in light of novel targeted therapies that have become available. However, differential diagnosis of BPDCN remains challenging. This retrospective study aimed to highlight the challenges to timely diagnoses of BPDCN. We documented the diagnostic and clinical features of 43 BPDCN patients diagnosed at five academic hospitals from 2001–2022. The frequency of BPDCN diagnosis compared to AML was 1:197 cases. The median interval from the first documented clinical manifestation to diagnosis of BPDCN was 3 months. Skin (65%) followed by bone marrow (51%) and blood (45%) involvement represented the most common sites. Immunophenotyping revealed CD4 + , CD45 + , CD56 + , CD123 + , HLA-DR + , and TCL-1 + as the most common surface markers. Overall, 86% (e.g. CD33) and 83% (e.g., CD7) showed co-expression of myeloid and T-cell markers, respectively. In the median, we detected five genomic alterations per case including mutational subtypes typically involved in AML: DNA methylation (70%), signal transduction (46%), splicing factors (38%), chromatin modification (32%), transcription factors (32%), and RAS pathway (30%), respectively. The contribution of patients (30%) proceeding to any form of upfront stem cell transplantation (SCT; autologous or allogeneic) was almost equal resulting in beneficial overall survival rates in those undergoing allogeneic SCT (p = 0.0001). BPDCN is a rare and challenging entity sharing various typical characteristics of other hematological diseases. Comprehensive diagnostics should be initiated timely to ensure appropriate treatment strategies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Blastic plasmacytoid dendritic cell neoplasm (BPDCN) predominantly occurs in adults ≥60 years old; 10–20% of cases are pediatric or adolescent/young adult (AYA) patients. Tagraxofusp (TAG, Elzonris®) is the only approved treatment for BPDCN; in the United States it is approved for patients aged ≥2 years. Data on treating pediatric and AYA BPDCN patients are limited. We present a case series of pediatric and AYA patients with BPDCN treated with TAG. Eight patients (five newly diagnosed; three relapsed/refractory [R/R]), aged 2–21 years, received 12 mcg/kg TAG. Seven patients were female; most had skin (n = 6) and/or bone marrow (n = 4) involvement. No new safety signals were identified. Grade 3 adverse events were headache (n = 1) and transaminitis (n = 2). Three patients with newly diagnosed BPDCN achieved complete response, one achieved partial response, and one had stable disease (SD). One patient with R/R BPDCN achieved a minor response; one had SD. Seven patients (88%) were bridged to stem cell transplant: 80% of newly diagnosed patients and 100% of R/R patients. Five patients remained alive at last follow‐up. These cases highlight the efficacy and safety of TAG in pediatric and AYA patients for whom there is no other approved BPDCN therapy.

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. [ABSTRACT FROM AUTHOR]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic neoplasm (less than 1% of primary cutaneous lymphomas and acute leukemia) with a highly aggressive clinical course and frequent skin, bone marrow and central nervous system involvement. Even though there is often an early response to chemotherapy, leukemic dissemination relapses are very common and result in poor outcomes, with a median overall survival of 8 to 14 months in the first-line setting using standard combination chemotherapy regimens. Almost 90% of patients experience skin involvement as their initial site of infection, where BPDCN may stay restricted for weeks or even months until a swift secondary phase involving multiple organs takes place. Consequently, it is crucial to suspect and identify early skin lesions, as well as to conduct and report a skin biopsy as soon as possible. In order to diagnose and treat BPDCN, a multidisciplinary strategy involving collaboration between pathologists, hematologists, and dermatologists is unquestionably essential. [ABSTRACT FROM AUTHOR]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with an aggressive clinical course and poor prognosis. The genetic abnormalities in BPDCN are heterogeneous; therefore, its molecular pathogenesis and the prognostic importance of genomic alterations associated with the disease are not well defined. Here we report a case of BPDCN with a novel AFF4::IRF1 fusion predicted to lead to a loss-of-function of the IRF1 tumor suppressor, somatic mutations of ASXL1, TET2, and MYD88, as well as multiple intrachromosomal deletions. The patient showed resistance to Tagraxofusp and Venetoclax, and he died about 16 months after diagnosis. Considering the predicted effect of the AFF4::IRF1 fusion on IRF1's antitumor effects and immune regulation, and the possibility of its relevance to the aggressive course observed in this case, we propose further evaluation of the clinical significance of this fusion in BPDCN in future cooperative group studies and the consideration of therapeutic strategies aimed at restoring IRF1-dependent antineoplastic effects in such cases. [ABSTRACT FROM AUTHOR]

Tagraxofusp (or SL‐401) is a recombinant molecule composed of human interleukin‐3 that binds CD123 on neoplastic cells fused to a truncated diphtheria toxin (DT). Tagraxofusp's most significant success has come from studies involving patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive disease that is usually refractory to conventional chemotherapy. Tagraxofusp had an acceptable safety profile and high efficacy in early phase I/II studies on patients with BPDCN. Another phase II study confirmed the good response rates, resulting in Food and Drugs Administration and European Medicine Agency approval of tagraxofusp for the treatment of BPDCN. Considering its high efficacy and its manageable safety profile, tagraxofusp has been suddenly explored in other myeloid malignancies with high expression of cell surface CD123, both in monotherapy or combination strategies. The triplet tagraxofusp‐azacytidine‐venetoclax appears to be of particular interest among these combinations. Furthermore, combination strategies may be used to overcome tagraxofusp resistance. The downregulation of DPH1 (diphthamide biosynthesis 1), the enzyme responsible for the conversion of histidine 715 on eEF2 to diphthamide, which is then the direct target of ADP ribosylation DT, is typically associated with this resistance phenomenon. It has been discovered that azacitidine can reverse DHP1 expression and restore sensitivity to tagraxofusp. In conclusion, the success of tagraxofusp in BPDCN paved the way for its application even in other CD123‐positive malignancies. Nowadays, several ongoing trials are exploring the use of tagraxofusp in different myeloid neoplasms. This review aims to summarize the actual role of tagraxofusp in BPDCN and other CD123‐positive myeloid malignancies. [ABSTRACT FROM AUTHOR]

IntroductionBlastic 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.MethodsHere, 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.ResultsTagraxofusp 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.DiscussionIn 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.

In recent years, targeted (biological) therapies have become available also for primary cutaneous T-cell lymphomas (PCTCLs) including anti-CD30 (brentuximab vedotin) in mycosis fungoides, primary cutaneous anaplastic large T-cell lymphoma, lymphomatoid papulosis; anti-CCR4 (mogamulizumab) in Sezary syndrome; anti-CD123 (tagraxofusp) in blastic plasmocytoid cell neoplasm. Moreover, anti-PD1 (nivolumab), anti-PDL1 (pembrolizumab, atezolizumab), anti-CD52 (alemtuzumab), anti-KIR3DL2-CD158k (lacutamab), and anti-CD70 (cusatuzumab) have been tested or are under investigations in phase II trials. The expression of these epitopes on neoplastic cells in skin biopsies or blood samples plays a central role in the management of PCTCL patients. This narrative review aims to provide readers with an update on the latest advances in the newest therapeutic options for PCTCLs. [ABSTRACT FROM AUTHOR]

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Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic neoplasm (less than 1% of primary cutaneous lymphomas and acute leukemia) with a highly aggressive clinical course and frequent skin, bone marrow and central nervous system (CNS) involvement. Despite a frequent initial response to chemotherapy, relapses with eventual leukemic dissemination are extremely common, leading to poor outcomes and a median overall survival (OS) ranging from 8 to 14 months in first line setting, with standard combination chemotherapy regimens. The skin is the first affected site (in almost 90% of patients) where BPDCN may remain confined for weeks or even months (sanctuary?) until a rapid second step with multiorgan involvement occurs. Therefore, it is of uppermost importance to suspect and recognize early skin lesions and to perform and report a skin biopsy as soon as possible. A multidisciplinary approach with coordination among dermatologists, pathologists and hematologists is definitively crucial in diagnosis and management of BPDCN.

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.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with an aggressive clinical course and poor prognosis. The genetic abnormalities in BPDCN are heterogeneous; therefore, its molecular pathogenesis and the prognostic importance of genomic alterations associated with the disease are not well defined. Here we report a case of BPDCN with a novel AFF4::IRF1 fusion predicted to lead to a loss-of-function of the IRF1 tumor suppressor, somatic mutations of ASXL1, TET2, and MYD88, as well as multiple intrachromosomal deletions. The patient showed resistance to Tagraxofusp and Venetoclax, and he died about 16 months after diagnosis. Considering the predicted effect of the AFF4::IRF1 fusion on IRF1’s antitumor effects and immune regulation, and the possibility of its relevance to the aggressive course observed in this case, we propose further evaluation of the clinical significance of this fusion in BPDCN in future cooperative group studies and the consideration of therapeutic strategies aimed at restoring IRF1-dependent antineoplastic effects in such cases.

Yumeng Zhang,1,2 Lubomir Sokol2 1Department of Internal Medicine, University of South Florida, Tampa, FL, USA; 2Department of Malignant Hematology, Moffitt Cancer Center, Tampa, FL, USACorrespondence: Yumeng Zhang; Lubomir Sokol, Email yumeng.zhang@moffitt.org; Lubomir.Sokol@moffitt.orgAbstract: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is aggressive hematologic malignancy derived from plasmacytoid dendritic cell precursors of myeloid cell lineage. Patients frequently present with bruise-like skin lesions, which typically are followed months later by progressive cytopenias. Historically, BPDCN prognosis has been dismal, with median overall survival ranging from 9 to 13 months. In the past 2 decades, our understanding of BPDCN pathogenesis has led to the successful development of novel therapeutics. In December 2018, the FDA approved tagraxofusp-erzs for adults and pediatric patients older than 2 years who have either treatment-naïve or relapsed/refractory BPDCN. Acute lymphoblastic leukemia (ALL)-based chemotherapy regimens also provide comparable outcomes to tagraxofusp. In our practice, for patients with good performance status, we use tagraxofusp, ALL-based chemotherapy regimens, or clinical trials as frontline induction therapy, followed by consolidation with allogeneic stem cell transplant once the first complete response has been achieved. Our induction regimen also includes intrathecal chemotherapy for central nervous system prophylaxis. Patients with poor performance status who are treatment-naïve or patients with relapsed/refractory disease have limited therapeutic options, and we strongly recommend enrollment in clinical trials; several novel agents and combinations are currently under clinical investigation for both treatment-naïve and relapsed/refractory BPDCN.Keywords: tagraxofusp, chemotherapy, allogeneic, transplantation

Abstract Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy. It is associated with poor prognosis and heterogenous presentation. The CD123‐directed cytotoxin, Tagraxofusp, is a targeted therapy for BPDCN. Here, we report an 81‐year‐old female diagnosed with BPDCN. The patient was treated with Tagraxofusp and underwent a remarkably long remission (>20 months) without stem‐cell transplantation. She, however, experienced blue toe syndrome and left foot gangrene. We postulate that these previously unreported side effects were caused by microembolization. Characterization of the incidence of thrombo‐ and microembolizations in such a context, as well as prophylactic management options, are warranted.

In recent years, targeted (biological) therapies have become available also for primary cutaneous T-cell lymphomas (PCTCLs) including anti-CD30 (brentuximab vedotin) in mycosis fungoides, primary cutaneous anaplastic large T-cell lymphoma, lymphomatoid papulosis; anti-CCR4 (mogamulizumab) in Sezary syndrome; anti-CD123 (tagraxofusp) in blastic plasmocytoid cell neoplasm. Moreover, anti-PD1 (nivolumab), anti-PDL1 (pembrolizumab, atezolizumab), anti-CD52 (alemtuzumab), anti-KIR3DL2-CD158k (lacutamab), and anti-CD70 (cusatuzumab) have been tested or are under investigations in phase II trials. The expression of these epitopes on neoplastic cells in skin biopsies or blood samples plays a central role in the management of PCTCL patients. This narrative review aims to provide readers with an update on the latest advances in the newest therapeutic options for PCTCLs.

Abstract: Targeted therapy in oncology brings with it the promise to maximize cancer cell cytotoxicity with minimal off-target effects. Antibody-drug conjugates (ADCs), an important group of such targeted agents, consist of a monoclonal antibody conjugated to a potent cytotoxic drug. In the field of leukemia, ADCs form an important component of therapeutic arsenal through the use of gemtuzumab ozogamicin in acute myeloid leukemia and inotuzumab ozogamicin (InO) in B-cell acute lymphoblastic leukemia, 2 approved agents. A recombinant fusion protein, tagraxofusp, which function similar to ADC, has gained approval for therapy in blastic plasmacytic dendritic cell neoplasm. The use of such agents as monotherapy or as part of a combination therapy has led to improved response rates and outcomes in certain specific disease subtypes and has led to further studies to identify novel cellular targets and improved delivery of cytotoxic agents using ADC. In this review, we will discuss about ADCs in myeloid leukemia and understand their development and current use in the field. [ABSTRACT FROM AUTHOR]

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is a rare hematologic cancer, accounting for less than 1% of acute leukemias in the U.S. Diagnosis involves detecting markers like CD123, CD4, CD56, TCL1, and TCF4. Treatment typically involved acute leukemia therapies, but Tagraxofusp, a targeted therapy, was recently approved. Despite advancements, prognosis remains grim, with a median survival of around 1 year. Atraumatic splenic rupture (ASR) is a rare complication of this condition, with only five cases reported from 1994 to 2018. Here we present a case of BPDCN complicated by ASR. This case emphasizes the challenges of diagnosing and treating BPDCN, noting its rarity and absence of standard therapy. Tagraxofusp has shown promising results but presents safety concerns like capillary leak syndrome, particularly in elderly patients with comorbidities., Competing Interests: Conflict of interest: The authors have no conflict of interest, financial or otherwise., (© 2024 Greater Baltimore Medical Center.)

Simple Summary: Until recently, there were no approved therapies for the aggressive blood cancer blastic plasmacytoid dendritic cell neoplasm (BPDCN). Survival for patients diagnosed with BPDCN is under two years, and improved treatments are needed. In 2018, tagraxofusp became the first approved drug for BPDCN. Tagraxofusp is an interleukin 3-dipththeria toxin recombinant fusion protein that targets CD123, a component of the interleukin 3 receptor, on the surface of BPDCN cells. Here, we discuss the development of tagraxofusp and other newer agents that also target CD123. We also present rationale for several other cell surface proteins, expressed on BPDCN, that are targets for therapies already in development for other cancers and that might be also considered for evaluation in BPDCN. Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia derived from plasmacytoid dendritic cells (pDCs). It is associated with a remarkably poor prognosis and unmet need for better therapies. Recently, the first-in-class CD123-targeting therapy, tagraxofusp, was approved for treatment of BPDCN. Other CD123-targeting strategies are in development, including bispecific antibodies and combination approaches with tagraxofusp and other novel agents. In other blood cancers, adoptive T-cell therapy using chimeric antigen receptor (CAR)-modified T cells represents a promising new avenue in immunotherapy, showing durable remissions in some relapsed hematologic malignancies. Here, we report on novel and innovative therapies in development to target surface molecules in BPDCN currently in clinical trials or in preclinical stages. We also discuss new cell surface targets that may have implications for future BPDCN treatment. [ABSTRACT FROM AUTHOR]

Blastic plasmacytoid dendritic-cell neoplasm (BPDCN) is an extremely rare disease that originates from dendritic cells and is associated with a poor overall survival (OS). Diagnostic and therapeutic standards are less well-established in comparison to other leukemic conditions and standards of care are lacking. Morphologic and molecular similarities to acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) are hard to distinguish. We here report a BPDCN patient with a long, challenging diagnostic period. While bone marrow biopsies initially failed to prove the correct diagnosis, a cutaneous biopsy finally identified a CD45+/CD56+/CD4+/CD123+/CD33+/MPO− population suggestive of BPDCN which was confirmed by flow cytometry. Molecular analysis revealed an ASXL-1, TET2 and SRSF2-mutation, cytogenetic analysis showed a normal karyotype. Treatment with the recently approved CD123-cytotoxin Tagraxofusp showed initially a very good response. This case reflects diagnostic and therapeutic difficulties in BPDCN as very rare, easily misdiagnosed neoplasia and the need for precise diagnostic care. [ABSTRACT FROM AUTHOR]

The IL-3 alpha chain receptor (CD123) is a cell surface protein that is widely expressed by various subtypes of acute leukemia, including acute myeloid leukemia (AML), acute lymphoblastic leukemia and blastic plasmacytoid dendritic cell neoplasm. Notably, CD123 is preferentially overexpressed in leukemia stem cells (LSC) in contrast to normal hematopoietic stem cells, and this differential expression allows for the selective eradication of LSC and leukemic blasts through therapeutic targeting of CD123, with less impact on hematopoietic cells. The level of CD123 expression in AML correlates with both treatment response and outcomes. Therefore, targeting CD123 represents a promising universal therapeutic target in advanced acute leukemias irrespective of the individual leukemia phenotype. There are currently 31 ongoing clinical trials examining the utility of CD123-based targeted therapies. Here we focus our review on current efforts to target CD123 in acute leukemia through various therapeutic constructs.

Introduction: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy that originates from plasmacytoid dendritic cells. It can involve skin, bone marrow, and/or lymph nodes. There is no consensus recommendation regarding treatment especially in the relapsed setting. Tagraxofusp, a CD123 directed agent, was recently approved by the Food and Drug Administration to treat BPDCN. We report a case of an elderly patient with diagnosis of BPDCN who was treated initially with tagraxofusp followed by azacitidine and venetoclax combination on relapse. Case report: A 79 year old male presented with violaceous skin lesions. He had no other symptoms. Biopsy of these lesions was consistent with a diagnosis of BPDCN. Further testing showed no extracutaneous involvement. Management and outcome: Tagraxofusp was started at full dose (12 mcg/kg). This dose was not tolerated well. Patient could only tolerate the lowest dose (5 mcg/kg). Toxicities included elevated liver function tests, hyperglycemia, capillary leak syndrome, and pancreatitis. Dose escalation on progression was not possible due to side effects. Treatment was switched to venetoclax and azacitidine. Combination treatment was tolerated very well and patient showed major cutaneous response after 5 cycles and continues to do well. Discussion: Tagraxofusp is a novel therapy that needs more real-world experience. This case describes the clinical course of an elderly patient on tagraxofusp. We also review the literature of azacytidine/venetoclax combination as a potential yet tolerable treatment option for this rare disease entity. This is the fourth case in literature to be treated with this combination. [ABSTRACT FROM AUTHOR]

BACKGROUND: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, clinically aggressive, and often fatal hematologic malignancy. BPDCN is not a new entity, but it has been renamed and reclassified, which, in part, contributes to it being underrecognized. In 2018, tagraxofusp became the first U.S. Food and Drug Administration-approved therapy for BPDCN. OBJECTIVES: This article aims to educate oncology nurses about tagraxofusp's dosing regimen, side effects, and how to manage patients undergoing treatment in inpatient and outpatient settings. METHODS: The authors reviewed content related to the safety and clinical management of tagraxofusp, as well as content that supports patient and provider education. FINDINGS: Capillary leak syndrome (CLS) is the most serious adverse event reported with tagraxofusp; therefore, nurses should stop tagraxofusp administration until all CLS-related symptoms have resolved. Hypersensitivity reactions and hepatotoxicity have also been observed in patients treated with tagraxofusp and should be monitored during treatment cycles. [ABSTRACT FROM AUTHOR]

The interleukin-3 receptor [alpha] subunit, CD123, is expressed in many hematologic malignancies including acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). Tagraxofusp (SL-401) is a CD123-targeted therapy consisting of interleukin-3 fused to a truncated diphtheria toxin payload. Factors influencing response to tagraxofusp other than CD123 expression are largely unknown. We interrogated tagraxofusp resistance in patients and experimental models and found that it was not associated with CD123 loss. Rather, resistant AML and BPDCN cells frequently acquired deficiencies in the diphthamide synthesis pathway, impairing tagraxofusp's ability to ADP- ribosylate cellular targets. Expression of DPH1, encoding a diphthamide pathway enzyme, was reduced by DNA CpG methylation in resistant cells. Treatment with the DNA methyltransferase inhibitor azacitidine restored DPH1 expression and tagraxofusp sensitivity. We also developed a drug-dependent ADP-ribosylation assay in primary cells that correlated with tagraxofusp activity and may represent an additional novel biomarker. As predicted by these results and our observation that resistance also increased mitochondrial apoptotic priming, we found that the combination of tagraxofusp and azacitidine was effective in patient-derived xenografts treated in vivo. These data have important implications for clinical use of tagraxofusp and led to a phase 1 study combining tagraxofusp and azacitidine in myeloid malignancies., Introduction CD123, or the interleukin-3 (IL-3) receptor (IL-3R) [alpha] chain, is a cell-surface marker associated with a variety of hematologic malignancies and is often enriched on tumor cells compared with [...]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive myeloid malignancy of the dendritic cell lineage that affects patients of all ages, though the incidence appears to be highest in patients over the age of 60 years. Diagnosis is based on the presence of plasmacytoid dendritic cell precursors expressing CD123, the interleukin-3 (IL-3) receptor alpha, and a distinct histologic appearance. Timely diagnosis remains a challenge, due to lack of disease awareness and overlapping biologic and clinical features with other hematologic malignancies. Prognosis is poor with a median overall survival of 8 to 14 months, irrespective of disease presentation pattern. Historically, the principal treatment was remission induction therapy followed by a stem cell transplant (SCT) in eligible patients. However, bridging to SCT is often not achieved with induction chemotherapy regimens. The discovery that CD123 is universally expressed in BPDCN and is considered to have a pathogenetic role in its development paved the way for the successful introduction of tagraxofusp, a recombinant human IL-3 fused to a truncated diphtheria toxin payload, as an initial treatment for BPDCN. Tagraxofusp was approved in 2018 by the United States Food and Drug Administration for the treatment of patients aged 2 years and older with newly diagnosed and relapsed/refractory BPDCN, and by the European Medicines Agency in 2021 for first-line treatment of adults. The advent of tagraxofusp has opened a new era of precision oncology in the treatment of BPDCN. Herein, we present an overview of BPDCN biology, its diagnosis, and treatment options, illustrated by clinical cases., Competing Interests: Disclosures Naveen Pemmaraju: Pacylex Pharmaceuticals, Astellas Pharma US, ImmunoGen, Inc, Bristol-Myers Squibb Co., Cimeio Therapeutics AG, EUSA Pharma, Menarini Group, Blueprint Medicines, CTI BioPharma, ClearView Healthcare Partners, Novartis Pharmaceutical, Neopharm, Celgene Corporation, AbbVie Pharmaceuticals, Pharma Essentia, Curio Science, DAVA Oncology, Imedex, Intellisphere, CancerNet, Harborside Press, Aptitude Health, Medscape, Magdalen Medical Publishing, OncLive, CareDx, Patient Power, Physician Education Resource (PER): Consultancy/Scientific Advisory Board/Speaking; United States Department of Defense, National Institute of Health/National Cancer Institute (NIH/NCI): Research (Grant); Affymetrix: Research Funding; Dan's House of Hope: Membership on an entity's Board of Directors/Management; ASH Committee on Communications, ASCO Cancer.Net Editorial Board: Leadership; Karger Publishers: Licences; HemOnc Times/Oncology Times: Uncompensated. Eric Deconinck: Stemline Therapeutics: Consultancy, honoraria; ImmunoGen: Consultancy, honoraria; Chugai: Research funding; Novartis: Research funding. Priyanka Mehta: Pfizer, AbbVie, Celgene, Daiichi Sankyo, Jazz Pharmaceuticals, Stemline Therapeutics: Advisory board/honoraria. Irwin Walker: Sanofi: Research funding. Marco Herling: AbbVie, BeiGene, Jazz, Janssen, Stemline Therapeutics, Takeda: Consultancy; Mundipharma EDO, Janpix, Novartis, Roche: Funding of preclinical research. Francine Garnache-Ottou: Stemline Therapeutics, LFB: Consultancy. Nadia Gabarin: Declarations of interest: none. Clinton Campbell: Declarations of interest: none. Johannes Duell: Stemline: Lecturing Yakir Moshe: AbbVie: Advisory board, research funding, speaker; Astellas, Medison: Advisory board, speaker; Gilead, Novartis, Stemline: Advisory board Tariq Mughal: Informa Publishing, Oxford University Press: Royalties. Consultant: Stemline Therapeutics Inc, New York, NY, USA. Mohamad Mohty: Jazz Pharmaceuticals: Research funding, honoraria. Emanuele Angelucci: Menarini/Stemline, Novartis: Honoraria; bluebird bio, Glaxo, Gilead, Roche: Board of Directors or advisory committees; Vifor Pharma, BMS, Vertex Inc.: Participation DMC., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy that previously lacked standardized therapeutic approaches. CD123 (interleukin-3 receptor alpha unit) is highly expressed in many hematologic malignancies, including BPDCN. Tagraxofusp-ezrs (tagraxofusp from herein) is an agent that consists of interleukin-3 fused to a truncated diphtheria toxin, targeting CD123. The Food and Drug Administration recently approved tagraxofusp as therapy for BPDCN for adults and children aged 2 years and older.Areas Covered: We discuss the history and clinical background of BPDCN along with tagraxofusp as its first-line therapy. We review the clinical efficacy and safety profile of tagraxofusp in adults including proposed sensitivity and resistance. Finally, we summarize tagraxofusp use in the pediatric population.Expert Opinion: Tagraxofusp is a newly approved therapy for BPDCN, a hematologic malignancy that has overall historically poor outcomes. With its significant efficacy, many patients were successfully bridged to stem cell transplantation in the clinical trial leading to its ultimate approval. Clinical awareness for major toxicities, including capillary leak syndrome will be a critical aspect of using this novel agent. In the future, investigation of its use in other hematologic malignancies and expansion of clinical trials in pediatric populations with BPDCN are warranted. [ABSTRACT FROM AUTHOR]

Purpose of Review: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, clinically aggressive hematologic malignancy that has heterogeneous presentation and can involve the skin, lymph nodes, and bone marrow. Recent advancements in our patho-biologic understanding of the disease have led to the development of new targeted therapies for BPDCN. In this review, we aimed to describe some of the novel treatments that are being put forward for the management of BPDCN. Recent Findings: Tagraxofusp is the first CD123-targeted therapy approved as the first ever targeted treatment of BPDCN in patients aged 2 years and older. This agent was approved based on a pivotal clinical trial that showed that it was associated with high rates of clinical responses in both treatment-naïve and treatment-experienced patients. The most serious adverse event was occurrence of the capillary leak syndrome. Other targeted therapies are actively being investigated in clinical trials. These include other CD123-targeted approaches, as well as active investigation in targets beyond CD123, such as the BCL-2 inhibitor, venetoclax. Summary: BPDCN is a rare hematologic clonal disorder with historically poor outcomes. Newer targeted therapies have been recently introduced, with promising results and novel toxicities that are important to recognize and understand. Stem cell transplantation after achievement of complete remission remains the mainstay of therapy among younger/fit, eligible patients, regardless of treatment modality used. [ABSTRACT FROM AUTHOR]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) predominantly occurs in adults ≥60 years old; 10-20% of cases are pediatric or adolescent/young adult (AYA) patients. Tagraxofusp (TAG, Elzonris ® ) is the only approved treatment for BPDCN; in the United States it is approved for patients aged ≥2 years. Data on treating pediatric and AYA BPDCN patients are limited. We present a case series of pediatric and AYA patients with BPDCN treated with TAG. Eight patients (five newly diagnosed; three relapsed/refractory [R/R]), aged 2-21 years, received 12 mcg/kg TAG. Seven patients were female; most had skin ( n = 6) and/or bone marrow ( n = 4) involvement. No new safety signals were identified. Grade 3 adverse events were headache ( n = 1) and transaminitis ( n = 2). Three patients with newly diagnosed BPDCN achieved complete response, one achieved partial response, and one had stable disease (SD). One patient with R/R BPDCN achieved a minor response; one had SD. Seven patients (88%) were bridged to stem cell transplant: 80% of newly diagnosed patients and 100% of R/R patients. Five patients remained alive at last follow-up. These cases highlight the efficacy and safety of TAG in pediatric and AYA patients for whom there is no other approved BPDCN therapy., Competing Interests: Naveen Pemmaraju: Consultancy: Pacylex Pharmaceuticals, ImmunoGen, Inc, Bristol‐Myers Squibb Co., Blueprint Medicines, ClearView Healthcare Partners, Protagonist Therapeutics, Inc., Affymetrix, Incyte, Novartis Pharmaceuticals, LFB Biotechnologies, Stemline Therapeutics, Inc., Celgene Corporation, AbbVie Pharmaceuticals, MustangBio, Roche Diagnostics, DAVA Oncology, Aptitude Health, CareDx, Inc.; Other: Research Support and Research Funding: Novartis Pharmaceuticals; Research Funding: Affymetrix; Membership on an entity's Board of Directors or advisory committees: Stemline Therapeutics, Inc., AbbVie Pharmaceuticals, ASH Communications Committee, ASCO Leukemia Advisory Panel, HemOnc Times/Oncology Times, Dan's House of Hope; Other and Research Funding: Stemline Therapeutics, Inc., AbbVie Pharmaceuticals, Cellectis S.A. ADR, Daiichi Sankyo, Inc., Plexxikon, Samus; Other: MustangBio, Springer Science+Business Media, SagerStrong Foundation. Branko Cuglievan: Nothing to disclose. Joseph Lasky: Nothing to disclose. Albert Kheradpour: Nothing to disclose. Nobuko Hijiya: Consultancy: Stemline Therapeutics, Inc., Novartis; DSMB: Novartis, Incyte. Research Support (to institution): Novartis, Pfizer. Anthony S. Stein: Advisory Board: Sanofi; Speaker's Bureau: Amgen. Soheil Meshinchi: Nothing to disclose. Craig A. Mullen: Nothing to disclose. Emanuele Angelucci: Honoraria: Menarini/Stemline, Novartis; Board of Directors or advisory committees: bluebird bio, Glaxo, Gilead, Roche; Participation DMC: Vifor Pharma, BMS, Vertex Inc. Luciana Vinti: Advisory and Consultancy: Amgen, Clinigen; Speaker's Bureau: Amgen, Takeda; Research grant or Funding: Merck Sharp and Dohme. Tariq I. Mughal: Consultant to Stemline Therapeutics Inc, New York, NY, USA; Other: Oxford University Press, Informa (financial benefit and/or patents). Anna B. Pawlowska: Nothing to disclose., (© 2024 The Authors. eJHaem published by British Society for Haematology and John Wiley & Sons Ltd.)

Introduction: CD123 or interleukin 3 receptor alpha is overexpressed in multiple hematologic malignancies. Tagraxofusp is an intravenously administered CD123-directed cytotoxin consisting of the fusion of interleukin-3 with a truncated diphtheria toxin payload and was recently approved by the Food and Drug Administration for the treatment of adults and children aged 2 and older with blastic plasmacytoid dendritic cell neoplasm (BPDCN). Areas Covered: In this review, we discuss the use of tagraxofusp in BPDCN, and active clinical trials involving this agent in several hematologic malignancies are also presented. Tagraxofusp has significant efficacy in patients with BPDCN and manageable safety profile, with the most commonly reported adverse events being asymptomatic elevation of alanine and aspartate aminotransferase levels, hypoalbuminemia, peripheral edema, and thrombocytopenia. The most serious side effect is capillary leak syndrome that can be lethal in some cases but the risk may be mitigated by early recognition and intervention. Expert Opinion: Tagraxofusp has been introduced as a novel treatment of BPDCN, a rare hematologic malignancy, for which no standard therapy previously existed. Many patients treated with this agent were able to be bridged to stem cell transplantation, including older patients. In the future, combinations of tagraxofusp with other targeted agents will be explored. [ABSTRACT FROM AUTHOR]

The interleukin 3 receptor (CD123) is a transmembrane protein that is absent or hardly expressed on normal hematopoietic stem cells, but highly expressed on the surface of cancer cells in several hematologic malignancies. In this issue of the JCI, Togami et al. investigated the mechanism of resistance to the recently approved anti-CD123 agent tagraxofusp, which consists of interleukin 3 fused to a truncated diphtheria toxin (DT) molecule. The authors demonstrated that loss of the intracellular target for DT, diphthamide, a conservative modification of histidine 715 in eukaryotic elongation factor 2, resulted in tagraxofusp resistance. Specifically, hypermethylation of the DPH1 gene, encoding a key enzyme in diphthamide synthesis, resulted in diphthamide loss. Notably, treatment with a DNA hypomethylating agent restored DPH1 expression and resensitized cells to tagraxofusp. The recognition of this resistance mechanism may have important clinical implications and lead to the development of more effective multiagent therapies., Searching for an ideal cancer-specific 'target' Monoclonal antibodies, introduced to the oncology armamentarium over 2 decades ago, initiated a golden era of targeted cancer immunotherapy. A plethora of therapies, including [...]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy that derives from precursors of plasmacytoid dendritic cells and is characterized by disseminated, erythematous or bluish-livid plaques or nodi. Because of the disease's rarity the diagnosis and treatment still pose a significant challenge. We present a case of a patient with BPDCN and show clinical and diagnostic characteristics as well as potential treatment regimes., (© 2023. The Author(s).)

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic neoplasm (less than 1% of primary cutaneous lymphomas and acute leukemia) with a highly aggressive clinical course and frequent skin, bone marrow and central nervous system involvement. Even though there is often an early response to chemotherapy, leukemic dissemination relapses are very common and result in poor outcomes, with a median overall survival of 8 to 14 months in the first-line setting using standard combination chemotherapy regimens. Almost 90% of patients experience skin involvement as their initial site of infection, where BPDCN may stay restricted for weeks or even months until a swift secondary phase involving multiple organs takes place. Consequently, it is crucial to suspect and identify early skin lesions, as well as to conduct and report a skin biopsy as soon as possible. In order to diagnose and treat BPDCN, a multidisciplinary strategy involving collaboration between pathologists, hematologists, and dermatologists is unquestionably essential., Competing Interests: Conflict of interest: the authors declare no potential conflict of interest., (Copyright © 2024, the Author(s).)