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

Some Examples of Bacterial Toxins as Tools

Pathogenic bacteria produce diverse protein toxins to disturb the host's defenses. This includes the opening of epithelial barriers to establish bacterial growth in deeper tissues of the host and to modulate immune cell functions. To achieve this, many toxins share the ability to enter mammalian cells, where they catalyze the modification of cellular proteins. The enzymatic activity is diverse and ranges from ribosyl- or glycosyl-transferase activity, the deamidation of proteins, and adenylate-cyclase activity to proteolytic cleavage. Protein toxins are highly active enzymes often with tight specificity for an intracellular protein or a protein family coupled with the intrinsic capability of entering mammalian cells. A broad understanding of their molecular mechanisms established bacterial toxins as powerful tools for cell biology. Both the enzymatic part and the pore-forming/protein transport capacity are currently used as tools engineered to study signaling pathways or to transport cargo like labeled compounds, nucleic acids, peptides, or proteins directly into the cytosol. Using several representative examples, this review is intended to provide a short overview of the state of the art in the use of bacterial toxins or parts thereof as tools.

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.

Multiple Genomic Alterations, Including a Novel AFF4::IRF1 Fusion Gene, in a Treatment-Refractory Blastic Plasmacytoid Dendritic-Cell Neoplasm: A Case Report and Literature Review

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.

Blastic Plasmocytoid Dendritic Cell Neoplasm (BPDCN): Clinical Features and Histopathology with a Therapeutic Overview

Blastic Plasmacytoid Dendritic Cell Neoplasms (BPDCNs) are a rare, highly aggressive hematological malignant neoplasm that primarily involve the skin, bone marrow, lymph nodes and even extra-nodal sites. The rarity and relative poor description of cases in the literature make it necessary to review and further studies that deeply investigate this entity not only in a histopathological but also molecular field. In August-September 2023, we searched MEDLINE, PubMed and Scopus for randomized controlled trials (RCTs), narrative and systematic reviews, meta-analyses, observational studies (either longitudinal or retrospective), and case series published in English in the last 25 years using the keywords BPDCN, PDCs, Blastic NK-cell lymphoma, agranular CD4+ NK leukemia/lymphoma, agranular CD4+ CD56+ hematodermic neoplasm/tumor. Despite the progress made in recent years in the diagnosis and biological understanding of the disease, until 2018 there was no clear consensus regarding its treatment and the main therapeutic schemes used were based on chemotherapy regimens already used in the treatment of lymphomas, acute lymphoblastic leukemia (ALL) and/or acute myeloid leukemia (AML). In this narrative review, we address the definition and epidemiological features of BPDCN, provide the different theories on the etiopathogenesis with particular attention to the presumed cell of origin, discuss the main clinical manifestations that provide a sign of its presence, summarize the main histopathological and immunophenotypic characteristics with special attention to the most important markers, and finally, we provide some of the most effective information on the therapeutic treatment modalities of BPDCN.

Trends and Perspectives of Biological Drug Approvals by the FDA: A Review from 2015 to 2021

Despite belonging to a relatively new class of pharmaceuticals, biological drugs have been used since the 1980s, when they brought about a breakthrough in the treatment of chronic diseases, especially cancer. They conquered a large space in the pipeline of the pharmaceutical industry and boosted the innovation portfolio and arsenal of therapeutic compounds available. Here, we report on biological drug approvals by the US Food and Drug Administration (FDA) from 2015 to 2021. The number of drugs included in this class grew over this period, totaling 90 approvals, with an average of 13 authorizations per year. This figure contrasts with previous periods, which registered between 2 and 8 approvals per year. We highlight the great potential and advantages of biological drugs. In this context, these therapeutics show high efficacy and high selectivity, and they have brought about a significant increase in patient survival and a reduction of adverse reactions. The development and production of biopharmaceuticals pose a major challenge because these processes require cutting-edge technology, thereby making the drugs very expensive. However, we believe that, in the near future, biological medicines will be more accessible and new drugs belonging to this class will become available as new technologies emerge. Such advances will enhance the production of these biopharmaceuticals, thereby making the process increasingly profitable and less expensive, thereby bringing about greater availability of these drugs.

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.

Phenazine derivatives attenuate the stemness of breast cancer cells through triggering ferroptosis

Breast cancer stem cells (BCSCs) are positively correlated with the metastasis, chemoresistance, and recurrence of breast cancer. However, there are still no drugs targeting BCSCs in clinical using for breast cancer treatment. Here, we tried to screen out small-molecule compounds targeting BCSCs from the phenazine library established by us before. We focused on the compounds without affecting cell viability and screened out three potential compounds (CPUL119, CPUL129, CPUL149) that can significantly attenuate the stemness of breast cancer cells, as evident by the decrease of stemness marker expression, CD44+/CD24- subpopulation, mammary spheroid-formation ability, and tumor-initiating capacity. Additionally, these compounds suppressed the metastatic ability of breast cancer cells in vitro and in vivo. Combined with the transcriptome sequencing analysis, ferroptosis was shown on the top of the most upregulated pathways by CPUL119, CPUL129, and CPUL149, respectively. Mechanistically, we found that these three compounds could trigger ferroptosis by accumulating and sequestering iron in lysosomes through interacting with iron, and by regulating the expression of proteins (IRP2, TfR1, ferritin) engaged in iron transport and storage. Furthermore, inhibition of ferroptosis rescued the suppression of these three compounds on breast cancer cell stemness. This study suggests that CPUL119, CPUL129, and CPUL149 can specifically inhibit the stemness of breast cancer cells through triggering ferroptosis and may be the potential compounds for breast cancer treatment.

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.

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.

Differences and similarities between cancer and somatic stem cells: therapeutic implications

Over the last decades, the cancer survival rate has increased due to personalized therapies, the discovery of targeted therapeutics and novel biological agents, and the application of palliative treatments. Despite these advances, tumor resistance to chemotherapy and radiation and rapid progression to metastatic disease are still seen in many patients. Evidence has shown that cancer stem cells (CSCs), a sub-population of cells that share many common characteristics with somatic stem cells (SSCs), contribute to this therapeutic failure. The most critical properties of CSCs are their self-renewal ability and their capacity for differentiation into heterogeneous populations of cancer cells. Although CSCs only constitute a low percentage of the total tumor mass, these cells can regrow the tumor mass on their own. Initially identified in leukemia, CSCs have subsequently been found in cancers of the breast, the colon, the pancreas, and the brain. Common genetic and phenotypic features found in both SSCs and CSCs, including upregulated signaling pathways such as Notch, Wnt, Hedgehog, and TGF-β. These pathways play fundamental roles in the development as well as in the control of cell survival and cell fate and are relevant to therapeutic targeting of CSCs. The differences in the expression of membrane proteins and exosome-delivered microRNAs between SSCs and CSCs are also important to specifically target the stem cells of the cancer. Further research efforts should be directed toward elucidation of the fundamental differences between SSCs and CSCs to improve existing therapies and generate new clinically relevant cancer treatments.