Classification and clinical behavior of blastic plasmacytoid dendritic cell neoplasms according to their maturation-associated immunophenotypic profile

Spontaneous Remission of Blastic Plasmacytoid Dendritic Cell Neoplasm: A Case Report

Spontaneous remissions (SRs) in blastic plasmacytoid dendritic cell neoplasms (BPDCNs) are infrequent, poorly documented, and transient. We report a 40-year-old man presenting with bycitopenia and soft tissue infection. The bone marrow exhibited 3% abnormal cells. Immunophenotyping of these cells revealed the antigens CD45+ (dim), CD34+, CD117+, CD123+ (bright), HLA-DR+ (bimodal), CD56+ (bright), CD33+, CD13+, CD2+, and CD22+ (dim) and the partial expression of the CD10+, CD36+, and CD7+ antigens. All other myeloid, monocytic, and lymphoid antigens were negative. Genetic studies showed a complex karyotype and mutations in the TP53R337C and KRASG12D genes. On hospital admission, the patient showed a subcutaneous nodule on the right hand and left lower limb. Flow cytometry multiparameter (FCM) analysis showed the presence of 29% abnormal cells with the previously described immunophenotype. The patient was diagnosed with BPDCN. The patient was treated with broad-spectrum antibiotics for soft tissue infection, which delayed therapy for BPDCN. No steroids or chemotherapeutic or hypomethylating agents were administered. His blood cell counts improved and skin lesions disappeared, until the patient relapsed five months after achieving spontaneous remission. About 60% of abnormal cells were identified. No changes in immunophenotype or the results of genetic studies were observed. The patient underwent a HyperCVAD chemotherapy regimen for six cycles. Consolidation therapy was performed via allogeneic bone marrow transplantation with an HLA-unrelated donor. One year after the bone marrow transplant, the patient died due to the progression of his underlying disease, coinciding with a respiratory infection caused by SARS-CoV-2. In the available literature, SRs are often linked to infections or other stimulators of the immune system, suggesting that powerful immune activation could play a role in controlling the leukemic clone. Nevertheless, the underlying mechanism of this phenomenon is not clearly understood. We hypothesize that the immune system would force the leukemic stem cell (LSC) to undergo a state of quiescence. This loss of replication causes the LSC progeny to die off, resulting in the SR of BPDCN.

Diagnostic management of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in close interaction with therapeutic considerations

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.

Recent Advances in the Biology and CD123-Directed Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm

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.

Treatment of patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN): focus on the use of tagraxofusp and clinical considerations

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.

Efficacy and manageable safety of tagraxofusp in blastic plasmacytoid dendritic cell neoplasm: a case series of pediatric and adolescent/young adult patients

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: 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.

A CD56- immunoblastoid variant of blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive malignant hematologic neoplasm arising from plasmacytoid dendritic cells. It is a very rare tumor that constitutes less than 0.1% of all hematologic malignancies. Most patients with BPDCN present clinically with cutaneous lesions as the first sign of disease. Immunophenotypic variability with aberrant marker profiles has been reported. We report a case of a transcription factor 4 (TCF-4) + BPDCN, with negative CD56 expression in an 85-year-old woman with multiple skin nodules. A punch biopsy revealed a diffuse, monomorphous, and non-epidermotropic cell infiltrate involving the entire dermis. The infiltrate was composed of intermediate-sized cells with immunoblastoid morphology, which is an unusual morphologic variant. The neoplastic cells were strongly positive for CD45 and co-expressed CD4, CD123, TCF-4, BCL-2, and CD10. The Ki-67 proliferative rate was very high (90%). Negative immunostains included CD56, an unusual finding in BPDCN. This case illustrates the challenges encountered in the diagnosis of this entity, particularly in unusual morphologic variants and phenotypes. The elucidation of molecular signatures and development of targeted therapies for its management have been recently introduced and differ from acute myeloid leukemias. Hence, accurate diagnosis of BPDCN is critical for dermatopathologists.

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.

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) in an Elderly Female: A Rare Case

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is a rare hematologic malignancy derived from type 2 Dendritic cells (immature Plasmacytoid dendritic cells). It is an aggressive lymphoma and most commonly presents as nonpruritic cutaneous lesions. It can also involve the bone marrow, lymph nodes, or circulating peripheral blasts. Here we present a 61-year-old female with skin bruises all over her body for the last three months associated with fatigue, night sweats, and unintentional weight loss. Her initial diagnosis was Acute Myeloid Leukemia (AML), but later she was diagnosed with BPDCN on tumor biopsy consistent with CD56+ neoplasm. The patient was treated with cyclophosphamide with steroid bridge. She was follow-up every week for the disseminated intravascular coagulation panel and monitored for tumor lysis syndrome. The management of the BPDCN is still unclear due to the condition's rarity. tagraxofusp has been used for remission induction as it has a higher response rate with an acceptable toxicity profile than conventional chemotherapy. Allogeneic hematopoietic stem cell transplantation (HCT) is recommended in patients with the first remission. For patients with relapsed/refractory disease, tagraxofusp demonstrates a good overall response, followed by HCT.

Blastic plasmacytoid dendritic cell neoplasm in an adolescent female: a rare entity with challenging diagnosis and management

Blastic plasmacytoid dendritic cell neoplasm is a rare and aggressive haematopoietic neoplasm with poor prognosis. It usually presents with cutaneous lesions and symptoms secondary to bone marrow involvement. Due to rarity and lack of standard treatment protocols, these cases are difficult to diagnose and treat. We report a case of a female in early adolescence who presented with skin nodules on the leg. The diagnosis was established by immunophenotypic studies. We discuss the investigations and treatment options available to diagnose and treat this malignancy.

Evaluation of diagnostic efficacy of NRP-1/CD304 in hematological diseases

BACKGROUND

Previous studies had explored the diagnostic or prognostic value of NRP-1/CD304 in blastic plasmacytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML), and B-cell acute lymphoblastic leukemia (B-ALL), whereas the expression and application value of NRP-1/CD304 in other common hematological diseases have not been reported.

METHODS

Bone marrow samples from 297 newly diagnosed patients with various hematological diseases were collected to detect the expression of NRP-1/CD304 by flow cytometry (FCM). The diagnostic efficacy of NRP-1/ CD304-positive diseases was analyzed by receiver operating characteristic (ROC) curve, and the area under the ROC curve (AUC) was compared.

RESULTS

In the research cohort, the total positive rate of NRP-1/CD304 was 14.81% (44/297), mainly distributed in BPDCN (100%, 6/6), B-ALL (48.61%, 35/72), and AML (4.48%, 3/67), with statistically significant differences (p < 0.01). Other diseases, such as T-cell acute lymphoblastic leukemia (T-ALL), B-cell non-Hodgkin lymphoma (B-NHL), T/NK-cell lymphoma and plasma cell neoplasms, did not express NRP-1/CD304. The AUC of NRP-1/CD304 was 0.936 (95% CI 0.898-0.973), 0.723 (95% CI 0.646-0.801), and 0.435 (95% CI 0.435) in BPDCN, B-ALL and AML, respectively. Besides, CD304 was commonly expressed in B-ALL with BCR-ABL1 gene rearrangement (p = 0.000), and CD304 expression was positively correlated with CD34 co-expression (p = 0.009) and CD10 co-expression (p = 0.007).

CONCLUSIONS

NRP-1/CD304 is only expressed in BPDCN, B-ALL and AML, but not in other common hematological diseases. This indicates that NRP-1/CD304 has no obvious diagnostic and follow-up study value in hematological diseases other than BPDCN, B-ALL, and AML.

Clinical features, immune profile and induction chemotherapy options for blastic plasmacytoid dendritic cell neoplasm: a systematic review and meta-analysis

Aim: Blastic plasmacytoid dendritic cell neoplasm is a rarely occurring hematologic malignancy with a dismal prognosis. Methods: We conducted a meta-analysis for a total of 1312 patients from 24 retrospective studies. Results: The complete remission (CR) rate of acute lymphoblastic leukemia-like induction chemotherapy was 82%, and the overall survival (OS) was 15.75 months; the CR rate of acute myeloid leukemia-like chemotherapy was 51%, and the OS was 7.18 months; and the CR rate of cyclophosphamide, doxorubicin, vincristine and prednisone-like chemotherapy was 50%, and the OS was 12.06 months. Conclusion: Acute lymphoblastic leukemia-like induction chemotherapy has the best CR rate and OS.

Plasmacytoid dendritic cells in the setting of myeloid neoplasms: Diagnostic guide to challenging pathologic presentations

In this article, we describe three broad pathologic presentations of plasmacytoid dendritic cells (pDCs) that may be encountered in clinical practice, in which an association between pDCs and myeloid neoplasms is identified: (1) myeloid neoplasms with mature pDC expansion, most commonly seen in chronic myelomonocytic leukaemia (CMML); (2) myeloid neoplasms with pDC differentiation, in which pDCs show a spectrum of maturation from early immature pDCs to mature forms, most commonly seen in acute myeloid leukaemia (AML); (3) myeloid neoplasms associated with blastic plasmacytoid dendritic cell neoplasm (BPDCN), either stemming from the same precursor or representing an independent clonal process. Additionally, we also discuss AML with pDC-like phenotype, in which myeloblasts show immunophenotypic features that may mimic those seen in pDCs. Using these presentations, we provide a diagnostic algorithm for appropriate pathologic classification, while attempting to clarify and homogenize nomenclatures pertaining to different biologic states of pDCs.

Diagnosis, treatment, and genetic characteristics of blastic plasmacytoid dendritic cell neoplasm: A review

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a highly aggressive and extremely rare hematologic disease with a poor prognosis, involving mainly the skin and bone marrow. The immunophenotype of these tumor cells is characterized by the expression of CD4, CD56, CD123, TCL-1, and CD303. To date, no consensus has been reached on the standard of care for BPDCN. Currently, clinical treatment is mainly based on high-dose chemotherapy combined with hematopoietic stem cell transplantation. However, this treatment method has limitations for elderly, frail, and relapsed/refractory patients. In recent years, breakthroughs in molecular biology and genetics have not only provided new ideas for the diagnosis of BPDCN but also helped develop targeted treatment strategies for this disease. The emergence of targeted drugs has filled the gap left by traditional therapies and shown great clinical promise. This article focuses on the latest advances in genetics and targeted therapies for BPDCN, especially the emerging therapies that may provide new ideas for the clinical treatment of BPDCN.

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.

Blastic plasmacytoid dendritic cell neoplasm: A clinicopathological diagnostic dilemma report of three cases with review of literature

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a highly aggressive hematologic neoplasm and classified under acute myeloid leukemia. Here, we describe the clinicopathological features of three cases of BPDCN: two with classical and one uncommon immunophenotype. A-35-year-old female (case 1) presented with complaint of nasal mass and generalized lymphadenopathy. Biopsy from axillary lymph node showed infiltration by cells with scant cytoplasm which were immunopositive for LCA, CD4, CD43, and ALK1. Flowcytometry showed positivity for CD45, CD4, CD33, and CD123 while negative for rest all markers. The other two cases have classical immunophenotype. In clinical practice, nasal mass with lymphadenopathy suggests natural killer T-cell/peripheral T-cell lymphoma. Again immunohistochemical positivity for CD4, CD43, and ALK while negativity for CD3 suggests anaplastic large cell lymphoma. In this case, morphology and extensive bone marrow involvement raise the suspicion. Fowcytometry positivity for HLADR, CD123, and CD33 helps in making diagnosis.

Patients with blastic plasmacytoid dendritic cell neoplasm in pregnancy: A rare case report

RATIONALE

Previous clinical reports of patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN) in pregnancy are rare.

PATIENT CONCERNS

The present study presents the case of 37-year-old women exhibiting third trimester with progressive painless, abdominal skin nodules.

INTERVENTIONS AND OUTCOMES

A 37-year-old pregnant woman with BPDCN and partial placenta previa and racket-shaped placenta. After comprehensive evaluation, the pregnancy status ends at 37 weeks and 6 days by cesarean section of lower uterus and no abnormality in the newborn.

LESSONS

Pregnant women diagnosed with BPDCN in the third trimester should terminate the pregnancy promptly for further treatment.

Long-Term Benefits of Tagraxofusp for Patients With Blastic Plasmacytoid Dendritic Cell Neoplasm

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically on the based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive myeloid malignancy. We report long-term results, including data from the continued access phase, of the largest prospective BPDCN trial evaluating the CD123-targeted therapy tagraxofusp (TAG) in adults with treatment-naive and relapsed/refractory BPDCN. The primary outcome was complete response (CR) + clinical CR (CRc: CR with residual skin abnormality not indicative of active disease). Eighty-four (65 treatment-naive and 19 relapsed/refractory) of 89 patients received TAG 12 μg/kg once daily; the median follow-up was 34.0 months. For treatment-naive patients, the overall response rate was 75%; 57% achieved CR + CRc. The median time to remission was 39 (range, 14-131) days, and the median CR + CRc duration was 24.9 (95% CI, 3.8 to not reached) months. Nineteen patients (51%) with CR + CRc were bridged to stem-cell transplant, with a median CR + CRc duration of 22.2 (range, 1.5-57.4) months. Most common adverse events were increased alanine (64%) or aspartate (60%) aminotransferase and hypoalbuminemia (51%); most occurred in cycle 1 and were transient. Capillary leak syndrome occurred in 21% of patients (grade ≥ 3: 7%). In first-line patients with BPDCN, TAG monotherapy resulted in high and durable responses, allowing many to bridge to stem-cell transplant. TAG was generally well-tolerated with a predictable and manageable safety profile.

Immunophenotypic and Molecular Features of Acute Myeloid Leukemia with Plasmacytoid Dendritic Cell Differentiation Are Distinct from Blastic Plasmacytoid Dendritic Cell Neoplasm

Acute myeloid leukemia (AML) with ≥2% plasmacytoid dendritic cells (pDC) has been recently described as AML with pDC differentiation (pDC-AML) characterized by pDC expansion with frequent RUNX1 mutations. In this study, we investigated a cohort of 53 pDC-AML cases representing about 3% of all AML cases. We characterized their immunophenotype and genetic profiles and compared these findings with blastic plasmacytoid dendritic cell neoplasm (BPDCN). pDC-differentiation/expansion was preferentially observed in AML with an immature myeloid or myelomonocytic immunophenotype, where myeloblasts were frequently positive for CD34 (98%), CD117 (94%), HLA-DR (100%) and TdT (79%), with increased CD123 (89%) expression. The median number of pDCs in pDC-AML was 6.6% (range, 2% to 26.3%) and their immunophenotype reminiscent of pDCs in early or intermediate stages of differentiation. The immunophenotype of pDCs in pDC-AML was different from BPDCN (n = 39), with major disparities in CD34 (96% vs. 0%), CD56 (8% vs. 97%) and TCL1 (12% vs. 98%) and significant differences in frequency of CD4, CD13, CD22, CD25, CD36, CD38, CD117 and CD303 expression. At the molecular level, the genetic landscapes of pDC-AML and BPDCN also differ, with RUNX1 mutations detected in 64% of pDC-AML versus 2% of BPDCN. Disparities in TET2 (21% vs. 56%), FLT3 (23% vs. 0%), DNMT3A (32% vs. 10%) and ZRSR2 (2% vs. 16%) (all p < 0.05) were also detected. The distinct immunophenotypic and mutation profiles of pDC-AML and BPDCN indicate that the neoplastic pDCs in pDC-AML and BPDCN derived from different subsets of pDC precursors.

Clinical Insights into the Management of Blastic Plasmacytoid Dendritic Cell Neoplasm

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.

Allogeneic hematopoietic cell transplantation for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN)

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is an aggressive hematological malignancy; however, some patients achieve durable remission with allogeneic hematopoietic cell transplantation (allo-HCT). We report on all 17 patients with BPDCN who underwent allo-HCT at our center between 2000 and 2020. The median age was 39 (18-67) years. All (n = 16, 94%), except one patient, had systemic disease involving bone marrow and/or other organs. Ten patients (59%) were in first complete remission (CR1) at allo-HCT. The donor source was matched related or unrelated in ten (59%) and alternate donor in seven (41%) patients. Five (31%) patients developed acute graft-versus-host disease (GVHD), all grade I-II. The cumulative incidence (CI) of chronic GVHD at five-year was 34%. The CI of non-relapse mortality at one-year was 29%. Progression-free survival (PFS) rates at two-year and five-year were 49% (95% CI = 22-71%) and 39% (95% CI = 14-64%), respectively. The two-year and five-year overall survival (OS) rates were 65% (95% CI = 38-82%) and 40% (95% CI = 12-68%), respectively. The five-year rate for both PFS and OS was 80% in CR1 patients versus 0% in patients not in CR1. In conclusion, allo-HCT provides long-lasting remissions in BPDCN patients, particularly when performed in CR1.

Blastic plasmacytoid dendritic cell neoplasm with skin and bone marrow involvement: Report of three cases

BACKGROUND

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematopoietic malignancy. BPDCN is difficult to diagnose because of the overlap in morphologic and immunophenotypic features with various cutaneous lymphatic hematopoietic tumors.

CASE SUMMARY

We report on three BPDCN cases, all characterized by skin nodules and examined by histology, immunohistochemical detection, in situ hybridization for Epstein-Barr virus, and follow-up. We also review the relevant literature. All patients were positive for CD56 and negative for Epstein-Barr encoded small RNA. Two patients had bone marrow involvement. Chemotherapy is the main treatment for BPDCN, but case 1 showed bone marrow suppression and case 2 developed recurrence after chemotherapy. Case 1 survived for 7 mo, case 2 for 17 mo, and case 3 for 9 mo.

CONCLUSION

An accurate pathological diagnosis is a precondition for treatment, and the diagnosis of BPDCN should be based on a combination of clinical symptoms, pathological characteristics, immunophenotype, and other auxiliary examinations. It is necessary to clarify the clinicopathological features and biological behavior of BPDCN to improve its understanding by both clinicians and pathologists. Case 2 survived significantly longer than the other two cases, suggesting that the treatment received by case 2 was more effective.

Targeting CD123 in BPDCN: an emerging field

INTRODUCTION

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy with historically poor outcomes for patients, often refractory to traditional chemotherapy. Recent research has focused on targeted therapy to improve responses and limit potential toxicity.

AREAS COVERED

CD123 (also known as IL-3 Rα) is a cell surface marker and attractive therapeutic target for many myeloid malignancies, particularly BPDCN, whose cells ubiquitously overexpress CD123. We review the history of CD123 research regarding BPDCN, recent advances including FDA approval of tagraxofusp (formerly SL-401) for BPDCN, and ongoing clinical studies utilizing novel therapeutic strategies to target CD123.

EXPERT OPINION

The approval of tagraxofusp for the treatment of BPDCN in December 2018 drastically changed the treatment landscape for patients with this rare neoplasm. While tagraxofusp is better tolerated than traditional multi-agent chemotherapy regimens, it requires close monitoring and sound clinical judgment by providers to prevent and mitigate severe treatment-related complications with special attention to the recognition and management of capillary leak syndrome (CLS). Several other promising strategies for targeting CD123 in BPDCN are currently under investigation, including antibody-drug conjugates, T-cell engagers, and CAR-T cellular therapeutics. These CD123 targeted approaches may soon become standard of care for patients with this difficult to treat malignancy.

Blastic Plasmacytoid Dendritic Cell Neoplasm: Progress in Cell Origin, Molecular Biology, Diagnostic Criteria and Therapeutic Approaches

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy characterized by recurrent skin nodules, an aggressive clinical course with rapid involvement of hematological organs, and a poor prognosis with poor overall survival. BPDCN is derived from plasmacytoid dendritic cells (pDCs) and its pathogenesis is unclear. The tumor cells show aberrant expression of CD4, CD56, interleukin-3 receptor alpha chain (CD123), blood dendritic cell antigen 2 (BDCA 2/CD303), blood dendritic cell antigen 4 (BDCA4) and transcription factor (E protein) E2-2 (TCF4). The best treatment drugs are based on experience by adopting those used for either leukemia or lymphoma. Relapse with drug resistance generally occurs quickly. Stem cell transplantation after the first complete remission is recommended and tagraxofusp is the first targeted therapy. In this review, we summarize the differentiation of BPDCN from its cell origin, its connection with normal pDCs, clinical characteristics, genetic mutations and advances in treatment of BPDCN. This review provides insights into the mechanisms of and new therapeutic approaches for BPDCN.

Novel Therapeutic Approaches in Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN): Era of Targeted Therapy

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy arising from the aberrant transformation of plasmacytoid dendritic cells (pDCs) and involving skin, bone marrow, lymph nodes, and central nervous system. Characteristically unique from other myeloid neoplasms, BPDCN cells express CD4, CD56, and CD123 as well as TCL-1 and TCF4 in almost all cases. Historically, this malignancy has exhibited a poor prognosis, with median survival of less than 2 years. Traditional treatment approaches have involved conventional cytotoxic chemotherapy followed by hematopoietic stem cell transplantation; however, patients frequently relapse with chemotherapy-resistant disease. We have recently entered a modern era of therapy with targeting of CD123, with first-in-class agent tagraxofusp, a CD123- targeted agent approved by the US Food and Drug Administration for therapy of patients with BPDCN ages 2 and older. Relapsed and refractory BPDCN remains an elusive therapeutic challenge, but better understanding of the underlying pathophysiology has led to the development of other CD123-targeted agents and combination therapy, as well as agents targeting beyond CD123. Specifically, the use of venetoclax in targeting BCL2 has been promising in BPDCN treatment. This review will focus on the underlying diagnostic markers of BPDCN which have led to novel targeted treatment strategies, as well as future directions in therapy we can expect in coming years.

Approval of tagraxofusp-erzs for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and clinically challenging hematologic malignancy with dismal outcomes. With a median age of ∼70 years, the majority of patients with BPDCN have experienced historically suboptimal responses with intensive chemotherapy regimens. The major scientific breakthrough in this field was the recognition of overexpression of a surface receptor, CD123/interleukin 3 (IL-3) receptor α, in all patients. Importantly, a novel therapeutic agent consisting of a truncated diphtheria toxin (DT) payload fused to recombinant human IL-3 was being developed, one that targeted CD123, initially known as DT-IL-3 (later known as SL401; tagraxofusp; tagraxofusp-erzs [Elzonris]). The identification of this agent, and subsequent clinical trials specifically dedicated to patients with BPDCN (including a pilot study, followed by a larger phase 1/2 multicenter study [90% overall response rate [ORR] in frontline and 67% ORR in relapsed/refractory setting]), in part led to approval of tagraxofusp-erzs on 21 December 2018. Tagraxofusp-erzs was the first agent approved for BPDCN (for patients ages 2 years and older), and importantly, established this drug as the first CD123-targeted agent ever approved. The most notable toxicity of tagraxofusp-erzs is occurrence of the capillary leak syndrome, which occurs frequently at all grades, and has also been observed to be life-threatening, appropriately leading to a US Food and Drug Administration "black box" warning in the package insert. The preclinical and clinical aspects of drug development of tagraxofusp-erzs as monotherapy leading to drug approval are reviewed herein, with discussion of future directions of this novel agent, including consideration for rational combinations in BPDCN and beyond.

Severe tumor lysis syndrome during the induction therapy for the treatment of blastic plasmacytoid dendritic cell neoplasm arising from myelodysplastic/myeloproliferative neoplasms

BPDCN shows clinically heterogeneous characteristics. And as other hematological malignancies, symptoms of BPDCN suggesting a high tumor burden, such as high white blood cell count or splenomegaly, should be carefully considered to prevent TLS.

Pediatric blastic plasmacytoid dendritic cell neoplasm: report of four cases and review of literature

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematological malignancy with poor outcome. Four children with BPDCN treated at our hospital were enrolled. All the four cases presented with cutaneous lesions. Bone marrow and central nervous system was involved in 50% and 25% of patients, respectively. The whole exome sequencing analysis revealed that KMT2 family genes were the most frequently mutated (4/4, 100%), followed by IKZF2 (2/4, 50%). The point mutation p.D348N was found in three patients and one patient had p.C394Y mutation in the KMT2C gene. Translocation of KMT2A-MLLT3 was found in Case 2. Case 1 had complex karyotype, who was induced by acute myeloid leukemia-like regimens. Although he received allogeneic hematopoietic stem cell transplantation twice as well as CD123 chimeric antigen receptor T cell therapy, the disease still progressed and he died 37 months after diagnosis. The other three patients were treated with Interfant-99 protocol. They tolerated the therapy well without significant toxicities and now in complete remission so far with a median follow up time of 9 months. More studies are needed to address the question whether the complex karyotype and KMT2 family genes are the causes of the relapse and refractory in BPDCN.

Blastic plasmacytoid dendritic cell neoplasms: results of an international survey on 398 adult patients

The purpose of this study is to describe the clinical and prognostic features and to evaluate the outcome of different therapeutic approaches among patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN) who have been diagnosed and treated in different institutions. A total of 398 patients from 75 centers were included in the study. Treatment consisted of non-Hodgkin lymphoma (NHL)-like regimens in 129 (32.8%) patients and acute leukemia (AL)-like regimens in 113 (23.5%) patients. In 61 (15.5%) and 16 (4.1%) patients, chemotherapy was followed by allogeneic and autologous hematopoietic stem cell transplantation (HSCT), respectively. Twenty-seven (6.9%) patients received radiotherapy, 6 (1.5%) received new agents, and 62 (15.7%) received palliative care. After a median follow-up of 12 months, median overall survival (OS) was 18 months. Patients who received NHL/AL-like regimens, followed by allogeneic HSCT, had the best outcome; median OS was not reached. OS was 65 months for patients who underwent autologous HSCT; 18 months and 14 months, respectively, for those treated with AL-like and NHL-like regimens without consolidation; and 4 months for those receiving palliative care (P < .001). In BPDCN, chemotherapy with lymphoma- or AL-like regimens, followed by transplantation, represents the therapeutic strategy associated with the best outcome. Consolidation with allogeneic HSCT, when feasible, appears superior to autologous HSCT.

Tagraxofusp and anti-CD123 in blastic plasmacytoid dendritic cell neoplasm: a new hope

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy, characterized by poor prognosis if treated with conventional therapy. Allogenic hematologic stem cell transplant can improve survival and can be curative, but it is available in a small percentage of patients given that the median age at diagnosis is 70 years. In this scenario it is assumed that only the development of precision medicine-driven therapy will change BPDCN patient prognosis. CD123 (the α-subunit of interleukin (IL)-3 receptor) is over-expressed on BPDCN cells surface and seems to be the ideal marker to develop antibody-based therapies. Tagraxofusp (Elzonris^®), a recombinant immunotoxin consisting of human interleukin-3 fused to a truncated diphtheria toxin, has been approved by FDA in December 2018 for the treatment of BPDCN in adult and pediatric patients. tagraxofusp has shown promising clinical activity, with a high overall response rate and quite manageable safety profile even in elderly patients. It seems to improve overall survival too, but comparative trials are necessary to confirm this. Adverse events are commonly reported and the most important are transaminitis, thrombocytopenia and capillary leak syndrome (CLS). Therefore, to prevent the onset of severe CLS is recommended to reserve tagraxofusp for patients with preserved hepatic and cardiac functions, and to strictly observe serum albumin level. Further studies are required to resolve many several unanswered questions about tagraxofusp. In this review, we will resume and discuss pharmacological characteristic of tagraxofusp, results of clinical trials leading to its approval by FDA in 2018 and future perspectives about its use in BPDCN and other hematological malignancies.

How should we diagnose and treat blastic plasmacytoid dendritic cell neoplasm patients?

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia for which we developed a nationwide network to collect data from new cases diagnosed in France. In a retrospective, observational study of 86 patients (2000-2013), we described clinical and biological data focusing on morphologies and immunophenotype. We found expression of markers associated with plasmacytoid dendritic cell origin (HLA-DRhigh, CD303+, CD304+, and cTCL1+) plus CD4 and CD56 and frequent expression of isolated markers from the myeloid, B-, and T-lymphoid lineages, whereas specific markers (myeloperoxidase, CD14, cCD3, CD19, and cCD22) were not expressed. Fifty-one percent of cytogenetic abnormalities impact chromosomes 13, 12, 9, and 15. Myelemia was associated with an adverse prognosis. We categorized chemotherapeutic regimens into 5 groups: acute myeloid leukemia (AML)-like, acute lymphoid leukemia (ALL)-like, lymphoma (cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP])-like, high-dose methotrexate with asparaginase (Aspa-MTX) chemotherapies, and not otherwise specified (NOS) treatments. Thirty patients received allogeneic hematopoietic cell transplantation (allo-HCT), and 4 patients received autologous hematopoietic cell transplantation. There was no difference in survival between patients receiving AML-like, ALL-like, or Aspa-MTX regimens; survival was longer in patients who received AML-like, ALL-like, or Aspa-MTX regimens than in those who received CHOP-like regimens or NOS. Eleven patients are in persistent complete remission after allo-HCT with a median survival of 49 months vs 8 for other patients. Our series confirms a high response rate with a lower toxicity profile with the Aspa-MTX regimen, offering the best chance of access to hematopoietic cell transplantation and a possible cure.

Updates in Novel Therapies for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

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. 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.

Tagraxofusp as treatment for patients with blastic plasmacytoid dendritic cell neoplasm

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.

Tagraxofusp for the Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN): A Brief Report on Emerging Data

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare myeloid malignancy, for which conventional chemotherapy has poor outcomes. CD123, the α-subunit of interleukin (IL)-3 receptor, is constantly overexpressed at the surface of tumoral cells. Tagraxofusp (or SL-401) is a recombinant cytotoxin which consists of human interleukin-3 fused to a truncated diphtheria toxin. It is currently the only novel therapy with a prospective evaluation of efficacy and safety in the treatment of BPDCN and is also the only one to achieve FDA approval. In this short review, the results of tagraxofusp are summarized and perspectives of its use in BPDCN and in other malignancies are discussed. The safety profile is also summarized, since capillary leak syndrome is the main toxic effect of the drug, along with more common toxicities including an increase in transaminases and thrombocytopenia.

Dendritic Cell Leukemia: a Review

PURPOSE OF REVIEW

The purpose of this review was to summarize the clinical, diagnostic, and therapeutic features of blastic plasmacytoid dendritic cell neoplasm (BPDCN).

RECENT FINDINGS

Several case reports and series revealed new clinical, molecular, diagnostic, and therapeutic aspects of the disease. The clinical presentation diversity has been confirmed, with frequent leukemic non-cutaneous or rare atypical manifestations. The clonal evolution in the development of BPDCN has not been sufficiently elucidated. Although certain immunophenotypic markers (CD4, TCL1, CD123, CD56, CD303) are indicative of BPDCN, the diagnosis remains in certain cases challenging. Adult (ALL)-type chemotherapy followed by hematopoietic stem cell transplantation (HSCT) is related to a favorable outcome, while chemotherapy alone seems enough in children. Future studies should continue to investigate whether CD123-directed therapies could be utilized. BPDCN is a rare aggressive malignancy that needs an aggressive induction therapy. Although a diagnostic consensus is still lacking, and large retrospective studies are also needed to obtain standardized treatment guidelines, the future perspectives are encouraging, because of novel therapeutic agents that are under investigation.

Dual Expression of TCF4 and CD123 Is Highly Sensitive and Specific For Blastic Plasmacytoid Dendritic Cell Neoplasm

The diagnosis of blastic plasmacytoid dendritic cell neoplasm (BPDCN) has been based on the expression status of multiple markers, including CD123. TCF4 was discovered recently to be an obligatory master regulator of plasmacytoid dendritic cells. We postulated that a tissue-based assay designed to detect dual CD123 and TCF4 expression would provide a highly reliable and practical marker for BPDCN in biopsy material. We designed, optimized, and validated a dual-color TCF4/CD123 immunohistochemistry stain for use in formalin-fixed paraffin-embedded tissue sections. The performance characteristics of the TCF4/CD123 stain were evaluated in 48 confirmed BPDCN cases. TCF4/CD123 coexpression was detected reproducibly in plasmacytoid dendritic cells. In BPDCN, the TCF4/CD123 stain showed coexpression in all (48/48; 100%) cases analyzed. Cases with concurrent samples from different anatomic sites showed comparable staining characteristics. In contrast, of 464 non-BPDCN cases comprising a wide range of hematolymphoid neoplasms and cutaneous lesions that might enter in the differential diagnosis of BPDCN, we identified dual expression of TCF4 and CD123 in only 1 case of B-lymphoblastic leukemia/lymphoma. On the basis of these findings, the TCF4/CD123 dual-color immunohistochemical stain had an analytic sensitivity of 100% and a specificity of 99.8%. Receiver operator characteristic analysis demonstrated an area under the curve of 1.000 (95% confidence interval: 0.999-1.000). In summary, the dual-color TCF4/CD123 immunohistochemistry stain provides a robust standalone and cost-effective assay for the diagnosis of BPDCN.

Blastic Plasmacytoid Dendritic Cell Neoplasm: The European Perspective

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) has to be considered an orphan tumoral disease. BPDCN is a good model concerning the structuring and the organization of a concerted medical program on a nation-based, transnational, or international level. In 2019 in France the diagnosis process for BPDCN was clearly established. Two prospective clinical trials are ongoing. Because of the difficulties in diagnostic procedures and the rarity of the disease it is important that European countries collaborate to build a real European network to ensure the best and equitable medical care to all BPDCN patients.

Blastic Plasmacytoid Dendritic Cell Neoplasm: Clinical Presentation and Diagnosis

Clinical and biological presentation of patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN) is depicted to highlight criteria that might alert physicians. Diagnosis of BPDCN is still challenging and requires (1) immunophenotyping of blood or bone marrow aspiration using several markers (CD4, CD56, HLA-DR, myeloid and lymphoid lineage markers) and should include pDC markers such as CD123, cTCL1, CD303, and CD304, and/or (2) pathologic analysis of cutaneous lesions, also with immunohistochemistry using markers specific to BPDCN.

Chemotherapy Options for Blastic Plasmacytoid Dendritic Cell Neoplasm

BPDCN is ultimately a bone marrow disease requiring induction-type eradication therapy followed by hematopoietic stem cell transplant (HSCT) to achieve long-lasting remissions or cure. Various regimens have been applied to this disease with varying success. A cumulative review of the literature suggests more intense regimens have greater efficacy with acute lymphoblastic leukemia regimens preferred to acute myeloid leukemia regimens. This approach benefits fit patients who are eligible for HSCT; however, most BPDCN patients require other treatment options. The recent FDA approval of the CD123-targeted agent tagraxofusp provides a novel therapeutic alternative to traditional chemotherapy but with potential toxicities.

New perspectives in genetics and targeted therapy for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is one rare but clinically aggressive hematological malignancy, and it is typically characterized by skin lesion and bone marrow involvement. Diagnosis of BPDCN relies on the immunophenotype positive for four of CD4, CD56, CD123, TCL1 and BDCA-2, and commonly without the expression of MPO, cytoplasmic CD3, CD13, CD64, cytoplasmic CD79a, CD19 and CD20. Commonly, BPDCN is characterized by high CD123 expression, aberrant NF-κB activation, dependence on TCF4-/BRD4-network, and deregulated cholesterol metabolism. Under conventional therapy, the survival duration is only improved in a small number of BPDCN patients. Therefore, targeted therapy should be developed. Up to now, tagraxofusp is the leading edge and has been approved for BPDCN treatment. However, most of other targeted therapy agents were still not pushed to clinical trials for BPDCN. In this review, we emphatically discuss recent perspectives on BPDCN genetic features and developments of its targeted therapy.

Role of tagraxofusp in treating blastic plasmacytoid dendritic cell neoplasm (BPDCN)

Introduction: Advances and drug development in rare diseases, such as blastic plasmacytoid dendritic cell neoplasm (BPDCN), has historically been limited by small numbers of patients in the target population. In recent years, the development of tagraxofusp (SL-401) (ELZONRIS, Stemline Therapeutics) for the treatment of adult and pediatric BPDCN has been a successful story that led to US FDA approval in December 2018.Areas covered: In this evaluation of tagraxofusp, we briefly review chemistry; pharmacokinetics and pharmacodynamics, as we focus on the clinical experience and future directions.Expert Opinion: Tagraxofusp has been a welcome new addition and a successful initial development step in the targeted treatment of BPDCN. In phase I/II clinical trial, major responses were observed in 90% of treatment-naïve patients, with 72% of the responses observed as complete remissions. Limitations on the usage of tagraxofusp and strategies to handle those limitations were further explored in this review.

Recent developments in the treatment of blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive hematologic malignancy derived from precursors of dendritic cells and involves most frequently the skin, bone marrow and lymph nodes. Diagnosis depends upon identification of specific tumor markers including CD4, CD56 and CD123. Historically, the median survival has been less than 2 years in most reported series. While for many years, conventional chemotherapy followed by stem cell transplantation was the standard of care, recently tagraxofusp, a cytotoxin directed against CD123, received United States Food and Drug Administration approval specifically for patients with BPDCN. In this review, we will discuss the markers used for diagnosis of BPDCN and focus on the new targeted treatments available. Specifically in BPDCN, tagraxofusp was highly effective with a safety profile found to be acceptable overall, with the noted occurrence of capillary leak syndrome. Future directions in therapy approaches for patients with BPDCN will include the development of other CD123-targeted agents, agents targeting beyond CD123 and investigation of rational combination approaches of CD123-directed therapy with other therapies.