Survival outcomes and clinical benefit in patients with acute myeloid leukemia treated with glasdegib and low-dose cytarabine according to response to therapy

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/β-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

Glasdegib with intensive/nonintensive chemotherapy in Japanese patients with untreated acute myeloid leukemia or high-risk myelodysplastic syndromes

Glasdegib is a potent, selective, oral inhibitor of the hedgehog signaling pathway. In this phase I study, previously untreated Japanese patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndromes were treated with glasdegib (100 mg once daily) combinations: low-dose cytarabine (20 mg twice daily; cohort 1, n = 6; expansion cohort, n = 15); daunorubicin and cytarabine (60 mg/m2 i.v.; cohort 2, n = 6); or azacitidine (100 mg/m2 i.v.; cohort 3, n = 6). Patients, except cohort 2, were ineligible for intensive chemotherapy. The primary end-point was dose-limiting toxicity in cohorts 1-3 and disease-modifying response in the expansion cohort. Disease-modifying response rate was tested with the null hypothesis of 6.8%, which was set based on the results from the phase II BRIGHT AML 1003 study (NCT01546038). No dose-limiting toxicities were observed in cohorts 1 or 3; one patient in cohort 2 experienced a dose-limiting toxicity of grade 3 erythroderma. The most common grade ≥3 treatment-related adverse events were neutropenia and thrombocytopenia (66.7% each) in cohort 1 and thrombocytopenia (60.0%) in the expansion cohort. In the expansion cohort, the disease-modifying response rate was 46.7% (90% confidence interval, 24.4-70.0; p < 0.0001), with all patients achieving either a complete response or complete response with incomplete blood count recovery. Median overall survival was 13.9 months. In this study, the primary disease-modifying response end-point with glasdegib plus low-dose cytarabine was met. The study confirms the safety and efficacy of glasdegib plus low-dose cytarabine in Japanese patients with AML ineligible for intensive chemotherapy.

Targeting cancer hallmark vulnerabilities in hematologic malignancies by interfering with Hedgehog/GLI signaling

Understanding the genetic alterations, disrupted signaling pathways, and hijacked mechanisms in oncogene-transformed hematologic cells is critical for the development of effective and durable treatment strategies against liquid tumors. In this review, we focus on the specific involvement of the Hedgehog (HH)/GLI pathway in the manifestation and initiation of various cancer features in hematologic malignancies, including multiple myeloma, T- and B-cell lymphomas, and lymphoid and myeloid leukemias. By reviewing canonical and noncanonical, Smoothened-independent HH/GLI signaling and summarizing preclinical in vitro and in vivo studies in hematologic malignancies, we elucidate common molecular mechanisms by which HH/GLI signaling controls key oncogenic processes and cancer hallmarks such as cell proliferation, cancer stem cell fate, genomic instability, microenvironment remodeling, and cell survival. We also summarize current clinical trials with HH inhibitors and discuss successes and challenges, as well as opportunities for future combined therapeutic approaches. By providing a bird's eye view of the role of HH/GLI signaling in liquid tumors, we suggest that a comprehensive understanding of the general oncogenic effects of HH/GLI signaling on the formation of cancer hallmarks is essential to identify critical vulnerabilities within tumor cells and their supporting remodeled microenvironment, paving the way for the development of novel and efficient personalized combination therapies for hematologic malignancies.

A comparative safety review of targeted therapies for acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) treatment has primarily focused on 7 + 3 chemotherapy, but in the last decade there has been a significant increase in new therapies, mostly targeted agents, approved for the treatment of AML. We performed a comparative analysis of the unique safety profile of each of these new agents.

AREAS COVERED

We conducted a review of the current literature on public databases (PubMed, ClinicalTrials.gov, and U.S. Food and Drug Administration) regarding new AML drugs that were approved from 2017 to 2023.

EXPERT OPINION

The diagnosis of AML typically carries a poor prognosis but with an increase in the number of drugs that are now available, patients' outcomes are improving. With novel mechanisms of action, the use of these agents introduces different safety profiles, occasionally with adverse events not previously seen with standard chemotherapy or at different frequencies. An understanding of the drugs available and the safety concerns associated with each one is crucial to selecting the best available option for each patient, and early recognition and appropriate management of drug-related adverse effects.

The pathogenesis and development of targeted drugs in acute T lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is mainly classified into acute T- and B-lymphoblastic leukaemia according to the source of its lymphocytes, thymus and bone. Among them, the incidence of adult T-cell accounts for about 25% of adult acute lymphoblastic leukaemia, but the degree of malignancy is high and the treatment rate and prognosis are poor. At this stage, there are few targeted drugs and the commonly used broad-spectrum chemotherapeutic drugs have poor efficacy and many adverse drug reactions. Understanding and investigating the pathogenesis of T-acute lymphoblastic leukaemia is very important for further developing new targeting drugs and improving existing drugs. Dysregulated signalling pathways are the main aetiological factors of T-acute lymphoblastic leukaemia. They play crucial roles in promoting tumour initiation, progression, drug design and therapy responses. This is primarily because signalling pathways are indispensable for many cellular biological processes, including tumour growth, migration, invasion, metastasis and others. As a result, small molecule inhibitors targeting the major kinase components of the signalling pathway have received a lot of attention and have been developed and evaluated in preclinical models and clinical trials. Already marketed drugs are also being repurposed in combination therapies to further improve efficacy and overcome tumour cell resistance. In this review, we have aimed to examine the latest and most classical signalling pathways in the aetiology of T-acute lymphoblastic leukaemia and shed light on potential targets for novel therapeutic agents to act on.

Amsacrine-based induction therapy in AML patients with cardiac comorbidities: a retrospective single-center analysis

Intensive chemotherapy is the backbone of induction treatment in patients with acute myeloid leukemia (AML). However, AML patients with concomitant cardiac disease may not be eligible for anthracycline-based therapies. In a small cohort of patients, we have previously shown that anthracycline-free, amsacrine-based chemotherapy TAA (thioguanine, cytarabine, amsacrine) may be as effective as cytarabine/daunorubicin for induction therapy in these patients. In this systematic retrospective single-center analysis, we documented the outcome of 31 patients with significant cardiac comorbidities including coronary heart disease or cardiomyopathy receiving TAA as induction chemotherapy. Median (range) ejection fraction (EF) was 48% (30-67%) in this cohort. Patients with EF below 30% were considered unfit for intensive induction therapy. Event-free survival (EFS), overall survival (OS), and relapse-free survival (RFS) were 1.61, 5.46, and 13.6 months respectively. Poor outcome was primarily related to a high early mortality rate within the first 30 days of therapy, mainly caused by infectious complications. TAA cannot be recommended as a substitute of standard induction for AML patients with significant concomitant cardiac disease. In the era of novel agents, alternative strategies (e.g., hypomethylating agents plus venetoclax) should be considered when anthracycline-based regimens are not suitable.

Understanding the Roles of the Hedgehog Signaling Pathway during T-Cell Lymphopoiesis and in T-Cell Acute Lymphoblastic Leukemia (T-ALL)

The Hedgehog (HH) signaling network is one of the main regulators of invertebrate and vertebrate embryonic development. Along with other networks, such as NOTCH and WNT, HH signaling specifies both the early patterning and the polarity events as well as the subsequent organ formation via the temporal and spatial regulation of cell proliferation and differentiation. However, aberrant activation of HH signaling has been identified in a broad range of malignant disorders, where it positively influences proliferation, survival, and therapeutic resistance of neoplastic cells. Inhibitors targeting the HH pathway have been tested in preclinical cancer models. The HH pathway is also overactive in other blood malignancies, including T-cell acute lymphoblastic leukemia (T-ALL). This review is intended to summarize our knowledge of the biological roles and pathophysiology of the HH pathway during normal T-cell lymphopoiesis and in T-ALL. In addition, we will discuss potential therapeutic strategies that might expand the clinical usefulness of drugs targeting the HH pathway in T-ALL.

Precision Medicine in Myeloid Malignancies: Hype or Hope?

PURPOSE OF REVIEW

We review how understanding the fitness and comorbidity burden of patients, and molecular landscape of underlying acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) at the time of diagnosis is now integral to treatment.

RECENT FINDINGS

The upfront identification of patients' fitness and molecular profile facilitates selection of targeted and novel agents, enables risk stratification, allows consideration of allogeneic hematopoietic cell transplantation in high-risk patients, and provides treatment selection for older (age ≥ 75) or otherwise unfit patients who may not tolerate conventional treatment. The use of measurable residual disease (MRD) assessment improves outcome prediction and can also guide therapeutic strategies such as chemotherapy maintenance and transplant. In recent years, several novel drugs have received FDA approval for treating patients with AML with or without specific mutations. A doublet and triplet combination of molecular targeted and other novel treatments have resulted in high response rates in early trials. Following the initial success in AML, novel drugs are undergoing clinical trials in MDS. Unprecedented advances have been made in precision medicine approaches in AML and MDS. However, lack of durable responses and long-term disease control in many patients still present significant challenges, which can only be met, to some extent, with innovative combination strategies throughout the course of treatment from induction to consolidation and maintenance.

Hedgehog/GLI signaling in hematopoietic development and acute myeloid leukemia-From bench to bedside

While the underlying genetic alterations and biology of acute myeloid leukemia (AML), an aggressive hematologic malignancy characterized by clonal expansion of undifferentiated myeloid cells, have been gradually unraveled in the last decades, translation into clinical treatment approaches has only just begun. High relapse rates remain a major challenge in AML therapy and are to a large extent attributed to the persistence of treatment-resistant leukemic stem cells (LSCs). The Hedgehog (HH) signaling pathway is crucial for the development and progression of multiple cancer stem cell driven tumors, including AML, and has therefore gained interest as a therapeutic target. In this review, we give an overview of the major components of the HH signaling pathway, dissect HH functions in normal and malignant hematopoiesis, and specifically elaborate on the role of HH signaling in AML pathogenesis and resistance. Furthermore, we summarize preclinical and clinical HH inhibitor studies, leading to the approval of the HH pathway inhibitor glasdegib, in combination with low-dose cytarabine, for AML treatment.

Drug and apoptosis resistance in cancer stem cells: a puzzle with many pieces

Resistance to anticancer agents and apoptosis results in cancer relapse and is associated with cancer mortality. Substantial data have provided convincing evidence establishing that human cancers emerge from cancer stem cells (CSCs), which display self-renewal and are resistant to anticancer drugs, radiation, and apoptosis, and express enhanced epithelial to mesenchymal progression. CSCs represent a heterogeneous tumor cell population and lack specific cellular targets, which makes it a great challenge to target and eradicate them. Similarly, their close relationship with the tumor microenvironment creates greater complexity in developing novel treatment strategies targeting CSCs. Several mechanisms participate in the drug and apoptosis resistance phenotype in CSCs in various cancers. These include enhanced expression of ATP-binding cassette membrane transporters, activation of various cytoprotective and survival signaling pathways, dysregulation of stemness signaling pathways, aberrant DNA repair mechanisms, increased quiescence, autophagy, increased immune evasion, deficiency of mitochondrial-mediated apoptosis, upregulation of anti-apoptotic proteins including c-FLIP [cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein], Bcl-2 family members, inhibitors of apoptosis proteins, and PI3K/AKT signaling. Studying such mechanisms not only provides mechanistic insights into these cells that are unresponsive to drugs, but may lead to the development of targeted and effective therapeutics to eradicate CSCs. Several studies have identified promising strategies to target CSCs. These emerging strategies may help target CSC-associated drug resistance and metastasis in clinical settings. This article will review the CSCs drug and apoptosis resistance mechanisms and how to target CSCs.

Profile of Glasdegib for the Treatment of Newly Diagnosed Acute Myeloid Leukemia (AML): Evidence to Date

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy primarily affecting older adults. Historically, the highest rates of response have been achieved with intensive induction chemotherapy; however, a significant portion of older or unfit adults with AML are unable to tolerate intensive therapy or have chemotherapy-resistant disease, creating a large need for active and less intensive treatment strategies. Glasdegib, an oral inhibitor of the transmembrane protein Smoothened (SMO) involved in the Hedgehog (Hh) signaling pathway, was approved in 2018 for older or unfit adults with AML and attained a role in clinical practice after showing an overall survival (OS) advantage when combined with the established agent low-dose cytarabine (LDAC). Since that time, however, several other highly active lower intensity therapies such as venetoclax plus a hypomethylating agent (HMA) have garnered a dominant role in the treatment of this patient population. In this review, we summarize the role of glasdegib in the current treatment landscape of newly diagnosed AML and discuss ongoing investigations into its role in novel combination therapies.

Application of precision medicine in clinical routine in haematology-Challenges and opportunities

Precision medicine is revolutionising patient care in cancer. As more knowledge is gained about the impact of specific genetic lesions on diagnosis, prognosis and treatment response, diagnostic precision and the possibility for optimal individual treatment choice have improved. Identification of hallmark genetic aberrations such as the BCR::ABL1 gene fusion in chronic myeloid leukaemia (CML) led to the rapid development of efficient targeted therapy and molecular follow-up, vastly improving survival for patients with CML during recent decades. The assessment of translocations, copy number changes and point mutations are crucial for the diagnosis and risk stratification of acute myeloid leukaemia and myelodysplastic syndromes. Still, the often heterogeneous and complex genetic landscape of haematological malignancies presents several challenges for the implementation of precision medicine to guide diagnosis, prognosis and treatment choice. This review provides an introduction and overview of the important molecular characteristics and methods currently applied in clinical practice to guide clinical decision making in haematological malignancies of myeloid and lymphoid origin. Further, experimental ways to guide the choice of targeted therapy for refractory patients are reviewed, such as functional precision medicine using drug profiling. An example of the use of pipeline studies where the treatment is chosen according to the molecular characteristics in rare solid malignancies is also provided. Finally, the future opportunities and remaining challenges of precision medicine in the real world are discussed.

MiR-140 targets lncRNA FAM230B to suppress cell proliferation in acute myeloid leukemia running title: MiR-140 targets FAM230B in AML

BACKGROUND

FAM230B serves as an oncogenic lncRNA in both gastric cancer and papillary thyroid cancer, while its role in acute myeloid leukemia (AML) is unclear. We predicted that FAM230B could be a target of miR-140, a well-characterized tumor suppressor, and analyzed their interaction in AML.

METHODS

Differential expressions of FAM230B and miR-140 in bone marrow mononuclear cells (BMMNCs) were determined by RT-qPCR. Correlations were analyzed by Pearson's correlation coefficient. Subcellular FAM230B location was determined using cellular fractionation assay. The direct interaction between FAM230B and miR-140 was confirmed by RNA pull-down assay. The roles of FAM230B and miR-140 in cell proliferation were explored using BrdU assay.

RESULTS

High FAM230B expression level and low miR-140 expression level were observed in AML. FAM230B and miR-140 were inversely correlated and directly interacted with each other. FAM230B could be detected in both cytoplasm and nuclear samples. MiR-140 overexpression downregulated FAM230B expression and suppressed the enhancing effects of FAM230B overexpression on cell proliferation.

CONCLUSION

MiR-140 may target FAM230B to suppress cell proliferation in AML.

Refining AML Treatment: The Role of Genetics in Response and Resistance Evaluation to New Agents

Simple Summary

Acute myeloid leukemia (AML) is an aggressive cancer of the hematopoietic system. At present, we know that AML is heterogeneous and varies from one patient to another, often characterized by specific changes in the DNA (mutations). Likewise, we know that the mutational landscape of the disease predicts its response to certain therapies and that it can change under the influence of therapy. Since 2017, the number of potential drugs intended to treat AML has substantially increased and so has our knowledge about the role of certain mutations in the prediction of disease response, relapse and resistance. In this article, we review the current state of knowledge of genetic aberrations with respect to clinical decision making.

Abstract

The number of treatment options for acute myeloid leukemia (AML) has greatly increased since 2017. This development is paralleled by the broad implantation of genetic profiling as an integral part of clinical studies, enabling us to characterize mutation–response, mutation–non-response, or mutation–relapse patterns. The aim of this review is to provide a concise overview of the current state of knowledge with respect to newly approved AML treatment options and the association of response, relapse and resistance with genetic alterations. Specifically, we will highlight current genetic data regarding FLT3 inhibitors, IDH inhibitors, hypomethylating agents (HMA), the BCL-2 inhibitor venetoclax (VEN), the anti-CD33 antibody conjugate gemtuzumab ozogamicin (GO) and the liposomal dual drug CPX-351.

Update on glasdegib in acute myeloid leukemia - broadening horizons of Hedgehog pathway inhibitors

Numerous new emerging therapies, including oral targeted chemotherapies, have recently entered the therapeutic arsenal against acute myeloid leukemia (AML). The significant shift toward the use of these novel therapeutics, administered either alone or in combination with intensive or low-intensity chemotherapy, changes the prospects for the control of this disease, especially for elderly patients. Glasdegib, an oral Hedgehog pathway inhibitor, showed satisfactory response rates associated with moderate toxicity and less early mortality than standard induction regimens in this population. It was approved in November 2018 by the FDA and in June 2020 by the EMA for use in combination with low-dose cytarabine as a treatment of newly-diagnosed AML in patients aged ≥ 75 and/or unfit for intensive induction chemotherapy. The current paper proposes an extensive, up-to-date review of the preclinical and clinical development of glasdegib. Elements of its routine clinical use and the landscape of ongoing clinical trials are also stated.

6-month follow-up of VIALE-C demonstrates improved and durable efficacy in patients with untreated AML ineligible for intensive chemotherapy (141/150)

VIALE-C compared the safety and efficacy of venetoclax or placebo plus low-dose cytarabine (+LDAC) in patients with untreated AML ineligible for intensive chemotherapy. Overall, 211 patients were enrolled (n = 143, venetoclax; n = 68, placebo). At the primary analysis, the study did not meet its primary endpoint of a statistically significant improvement in overall survival (OS), however, ~60% of patients had been on study for ≤6-months. Here, we present an additional 6-months of follow-up of VIALE-C (median follow-up 17.5 months; range 0.1-23.5). Median OS was (venetoclax +LDAC vs. placebo +LDAC) 8.4 vs. 4.1 months (HR = 0.70, 95% CI 0.50,0.99; P = 0.040); a 30% reduction in the risk of death with venetoclax. Complete response (CR)/CR with incomplete hematologic recovery (CRi) rates were 48.3% vs. 13.2%. Transfusion independence rates (RBC) were 43% vs.19% and median event-free survival was 4.9 vs. 2.1 months (HR = 0.61; 95% CI 0.44,0.84; P = 0.002). These results represent improved efficacy over the primary analysis. Incidence of grade ≥3 adverse events were similar between study arms and overall safety profiles were comparable to the primary analysis. These data support venetoclax +LDAC as a frontline treatment option for patients with AML ineligible for intensive chemotherapy.This trial was registered at www.clinicaltrials.gov as #NCT03069352.

Hedgehog Signaling in Myeloid Malignancies

Simple Summary

The Hedgehog signaling pathway is aberrantly activated in many myeloid malignancies, and pathway inhibition is clinically beneficial in specific patients with acute myeloid leukemia. However, even with the approval of these agents, the role of Hedgehog signaling in other myeloid disorders is less clear. In this review, we summarize the laboratory studies that have examined Hedgehog signaling in normal and malignant hematopoiesis as well as the clinical studies that have been carried out in several myeloid leukemias. Finally, we explore potential strategies to further expand the use of pathway inhibitors as therapies for these diseases.

Abstract

Myeloid malignancies arise from normal hematopoiesis and include several individual disorders with a wide range of clinical manifestations, treatment options, and clinical outcomes. The Hedgehog (HH) signaling pathway is aberrantly activated in many of these diseases, and glasdegib, a Smoothened (SMO) antagonist and HH pathway inhibitor, has recently been approved for the treatment of acute myeloid leukemia (AML). The efficacy of SMO inhibitors in AML suggests that they may be broadly active, but clinical studies in other myeloid malignancies have been largely inconclusive. We will discuss the biological role of the HH pathway in normal hematopoiesis and myeloid malignancies and review clinical studies targeting HH signaling in these diseases. In addition, we will examine SMO-independent pathway activation and highlight potential strategies that may expand the clinical utility of HH pathway antagonists.

Patterns of undertreatment among patients with acute myeloid leukemia (AML): considerations for patients eligible for non-intensive chemotherapy (NIC)

Acute myeloid leukemia (AML) is a life-threatening malignancy that is more prevalent in the elderly. Because the patient population is heterogenous and advanced in age, choosing the optimal therapy can be challenging. There is strong evidence supporting antileukemic therapy, including standard intensive induction chemotherapy (IC) and non-intensive chemotherapy (NIC), for older patients with AML, and guidelines recommend treatment selection based on a patient’s individual and disease characteristics as opposed to age alone. Nonetheless, historic evidence indicates that a high proportion of patients who may be candidates for NIC receive no active antileukemic treatment (NAAT), instead receiving only best supportive care (BSC). We conducted a focused literature review to assess current real-world patterns of undertreatment in AML. From a total of 25 identified studies reporting the proportion of patients with AML receiving NAAT, the proportion of patients treated with NAAT varied widely, ranging from 10 to 61.4% in the US and 24.1 to 35% in Europe. Characteristics associated with receipt of NAAT included clinical factors such as age, poor performance status, comorbidities, and uncontrolled concomitant conditions, as well as sociodemographic factors such as female sex, unmarried status, and lower income. Survival was diminished among patients receiving NAAT, with reported median overall survival values ranging from 1.2 to 4.8 months compared to 5 to 14.4 months with NIC. These findings suggest a proportion of patients who are candidates for NIC receive NAAT, potentially forfeiting the survival benefit of active antileukemic treatment.

Eradication of Measurable Residual Disease in AML: A Challenging Clinical Goal

In non-promyelocytic (non-M3) AML measurable residual disease (MRD) detected by multi-parameter flow cytometry and molecular technologies, which are guided by Consensus-based guidelines and discover very low leukemic cell numbers far below the 5% threshold of morphological assessment, has emerged as the most relevant predictor of clinical outcome. Currently, it is well-established that MRD positivity after standard induction and consolidation chemotherapy, as well as during the period preceding an allogeneic hematopoietic stem cell transplant (allo-HSCT), portends to a significantly inferior relapse-free survival (RFS) and overall survival (OS). In addition, it has become absolutely clear that conversion from an MRD-positive to an MRD-negative state provides a favorable clinical outcome similar to that associated with early MRD negativity. Thus, the complete eradication of MRD, i.e., the clearance of the few leukemic stem cells-which, due to their chemo-radiotherapy resistance, might eventually be responsible of disease recurrence-has become an un-met clinical need in AML. Nowadays, this goal might potentially be achieved thanks to the development of novel innovative treatment strategies, including those targeting driver mutations, apoptosis, methylation patterns and leukemic proteins. The aim of this review is to analyze these strategies and to suggest any potential combination able to induce MRD negativity in the pre- and post-HSCT period.

Reporters of Cancer Stem Cells as a Tool for Drug Discovery

In view of the importance of cancer stem cells (CSCs) in chemoresistance, metastasis and recurrence, the biology of CSCs were explored in detail. Based on that, several modalities were proposed to target them. In spite of the several clinical trials, a successful CSC-targeting drug is yet to be identified. The number of molecules screened and entered for clinical trial for CSC-targeting is comparatively low, compared to other drugs. The bottle neck is the lack of a high-throughput adaptable screening strategy for CSCs. This review is aimed to identify suitable reporters for CSCs that can be used to identify the heterogeneous CSC populations, including quiescent CSCs, proliferative CSCs, drug resistant CSCs and metastatic CSCs. Analysis of the tumor microenvironment regulating CSCs revealed that the factors in CSC-niche activates effector molecules that function as CSC markers, including pluripotency markers, CD133, ABCG2 and ALDH1A1. Among these factors OCT4, SOX2, NANOG, ABCG2 and ALDH1A1 are ideal for making reporters for CSCs. The pluripotency molecules, like OCT4, SOX2 and NANOG, regulate self-renewal, chemoresistance and metastasis. ABCG2 is a known regulator of drug resistance while ALDH1A1 modulates self-renewal, chemoresistance and metastasis. Considering the heterogeneity of CSCs, including a quiescent population and a proliferative population with metastatic ability, we propose the use of a combination of reporters. A dual reporter consisting of a pluripotency marker and a marker like ALDH1A1 will be useful in screening drugs that target CSCs.

Inhibition of EZH2 by chidamide exerts antileukemia activity and increases chemosensitivity through Smo/Gli-1 pathway in acute myeloid leukemia

Background

Epigenetic dysregulation plays important roles in leukemogenesis and the progression of acute myeloid leukemia (AML). Histone acetyltransferases (HATs) and histone deacetylases (HDACs) reciprocally regulate the acetylation and deacetylation of nuclear histones. Aberrant activation of HDACs results in uncontrolled proliferation and blockade of differentiation, and HDAC inhibition has been investigated as epigenetic therapeutic strategy against AML.

Methods

Cell growth was assessed with CCK-8 assay, and apoptosis was evaluated by flow cytometry in AML cell lines and CD45 + and CD34 + CD38- cells from patient samples after staining with Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI). EZH2 was silenced with short hairpin RNA (shRNA) or overexpressed by lentiviral transfection. Changes in signaling pathways were detected by western blotting. The effect of chidamide or EZH2-specific shRNA (shEZH2) in combination with adriamycin was studied in vivo in leukemia-bearing nude mouse models.

Results

In this study, we investigated the antileukemia effects of HDAC inhibitor chidamide and its combinatorial activity with cytotoxic agent adriamycin in AML cells. We demonstrated that chidamide suppressed the levels of EZH2, H3K27me3 and DNMT3A, exerted potential antileukemia activity and increased the sensitivity to adriamycin through disruption of Smo/Gli-1 pathway and downstream signaling target p-AKT in AML cells and stem/progenitor cells. In addition to decreasing the levels of H3K27me3 and DNMT3A, inhibition of EZH2 either pharmacologically by chidamide or genetically by shEZH2 suppressed the activity of Smo/Gli-1 pathway and increased the antileukemia activity of adriamycin against AML in vitro and in vivo.

Conclusions

Inhibition of EZH2 by chidamide has antileukemia activity and increases the chemosensitivity to adriamycin through Smo/Gli-1 pathway in AML cells (Fig. 5). These findings support the rational combination of HDAC inhibitors and chemotherapy for the treatment of AML.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02789-3.

Clinical benefit of glasdegib plus low-dose cytarabine in patients with de novo and secondary acute myeloid leukemia: long-term analysis of a phase II randomized trial

This analysis from the phase II BRIGHT AML 1003 trial reports the long-term efficacy and safety of glasdegib + low-dose cytarabine (LDAC) in patients with acute myeloid leukemia ineligible for intensive chemotherapy. The multicenter, open-label study randomized (2:1) patients to receive glasdegib + LDAC (de novo, n = 38; secondary acute myeloid leukemia, n = 40) or LDAC alone (de novo, n = 18; secondary acute myeloid leukemia, n = 20). At the time of analysis, 90% of patients had died, with the longest follow-up since randomization 36 months. The combination of glasdegib and LDAC conferred superior overall survival (OS) versus LDAC alone; hazard ratio (HR) 0.495; (95% confidence interval [CI] 0.325–0.752); p = 0.0004; median OS was 8.3 versus 4.3 months. Improvement in OS was consistent across cytogenetic risk groups. In a post-hoc subgroup analysis, a survival trend with glasdegib + LDAC was observed in patients with de novo acute myeloid leukemia (HR 0.720; 95% CI 0.395–1.312; p = 0.14; median OS 6.6 vs 4.3 months) and secondary acute myeloid leukemia (HR 0.287; 95% CI 0.151–0.548; p < 0.0001; median OS 9.1 vs 4.1 months). The incidence of adverse events in the glasdegib + LDAC arm decreased after 90 days’ therapy: 83.7% versus 98.7% during the first 90 days. Glasdegib + LDAC versus LDAC alone continued to demonstrate superior OS in patients with acute myeloid leukemia; the clinical benefit with glasdegib + LDAC was particularly prominent in patients with secondary acute myeloid leukemia. ClinicalTrials.gov identifier: NCT01546038.

Glasdegib in combination with low-dose Cytarabine for the outpatient treatment of relapsed or refractory acute myeloid leukemia in unfit patients

We retrospectively collected clinical data on 31 relapsed or refractory acute myeloid leukemia (R/R AML) patients who were treated with outpatient glasdegib and low-dose Cytarabine (LDAraC) at our institution. The median age was 67 years (45–86). The median Eastern Cooperative Oncology Group performance status was 2 (1–3). The patients had previously received a median number of 2 (1–4) treatment lines, 61% (19/31) had been treated with intensive chemotherapy, 29% (9/31) had relapsed after allogeneic stem cell transplantation, and 45% (14/31) had had venetoclax exposure. Adverse cytogenetics were identified in 45% (14/31) of the cases. The CR + CRp rate was 21% (6/29) among evaluable patients. The median overall survival was 3.9 months for all patients. Different median overall survival times were observed in responders, patients achieving stable disease and those diagnosed with progressive disease: not reached vs 3.9 months vs 0.8 months, respectively (p < 0.001). The most common adverse events were pneumonia (29%, 9/31), sepsis (23%, 7/31), and febrile neutropenia (16%, 5/31). Glasdegib + LDAraC is a fairly safe, non-intensive, outpatient regimen inducing complete remission and resulting in prolonged survival in some R/R AML patients.

Glasdegib in newly diagnosed acute myeloid leukemia

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive blood cancer that proves fatal for the majority of affected individuals. Older patients are particularly vulnerable due to more unfavorable disease biology and diminished ability to tolerate intensive induction chemotherapy (ICT). Safer, more efficacious therapies are desperately needed.

AREAS COVERED

We briefly summarize the challenges facing AML treatment and introduce the rapidly expanding therapeutic landscape. Our focus is on the Hedgehog (Hh) pathway and how preclinical evidence has spurred the clinical development of selective inhibitors for oncology indications. Glasdegib is the first Hh pathway inhibitor approved for the treatment of a hematologic malignancy, and we review its pharmacology, safety, efficacy, and potential clinical impact in AML patients.

EXPERT OPINION

Advances in the mechanistic understanding of AML have started to translate into improved therapeutic options for patients with contraindications to ICT. Glasdegib improved overall survival in this population when combined with low-dose cytarabine. While an encouraging development for these difficult to treat patients, alternative combination therapy approaches such as venetoclax plus azacitidine have gained greater clinical traction. Further investigation of glasdegib combination strategies and predictive biomarkers, particularly in regard to overcoming chemoresistance and preventing relapse, is needed to better define its clinical utility.

Forsaken Pharmaceutical: Glasdegib in Acute Myeloid Leukemia and Myeloid Diseases

Advancements in the understanding of the pathogenesis of acute myeloid leukemia (AML) have led to the introduction and approval of a number of novel drugs in AML. Glasdegib, an oral hedgehog pathway inhibitor, was approved in 2018 in combination with low-dose cytarabine for the treatment of newly diagnosed AML in patients unfit for intensive chemotherapy. In this review, we discuss the preclinical rationale for glasdegib, important clinical trials that led to glasdegib's approval, and future trials of glasdegib in AML and other myeloid diseases. Notably, 2 large randomized, placebo-controlled phase 3 trials (AML BRIGHT 1019) are currently recruiting patients with newly diagnosed AML to evaluate glasdegib in combination with intensive chemotherapy or azacitidine, depending on the patient's ability to tolerate induction chemotherapy. While glasdegib and low-dose cytarabine have been eclipsed by venetoclax and hypomethylating agent combinations for newly diagnosed AML in the United States, we discuss other areas where glasdegib may still have an opportunity to improve outcomes in this devastating disease.

Maintenance therapy in acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

Relapse remains the main cause of treatment failure in acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Emerging evidence has demonstrated that AML patients might benefit from maintenance therapy post-transplantation, especially for high-risk AML patients. In this mini-review, we will summarize targeted drugs, such as hypomethylating agents, FLT3 inhibitors and isocitrate dehydrogenase inhibitors, as maintenance therapy post-transplantation in AML patients undergoing allo-HSCT.

Targeting multiple signaling pathways: the new approach to acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and the second most common form of acute leukemia in children. Despite this, very little improvement in survival rates has been achieved over the past few decades. This is partially due to the heterogeneity of AML and the need for more targeted therapeutics than the traditional cytotoxic chemotherapies that have been a mainstay in therapy for the past 50 years. In the past 20 years, research has been diversifying the approach to treating AML by investigating molecular pathways uniquely relevant to AML cell proliferation and survival. Here we review the development of novel therapeutics in targeting apoptosis, receptor tyrosine kinase (RTK) signaling, hedgehog (HH) pathway, mitochondrial function, DNA repair, and c-Myc signaling. There has been an impressive effort into better understanding the diversity of AML cell characteristics and here we highlight important preclinical studies that have supported therapeutic development and continue to promote new ways to target AML cells. In addition, we describe clinical investigations that have led to FDA approval of new targeted AML therapies and ongoing clinical trials of novel therapies targeting AML survival pathways. We also describe the complexity of targeting leukemia stem cells (LSCs) as an approach to addressing relapse and remission in AML and targetable pathways that are unique to LSC survival. This comprehensive review details what we currently understand about the signaling pathways that support AML cell survival and the exceptional ways in which we disrupt them.

An evaluation of overall survival in patients with newly diagnosed acute myeloid leukemia and the relationship with glasdegib treatment and exposure

PURPOSE

Glasdegib, an oral inhibitor of the Hedgehog signaling pathway, is approved in the United States in combination with low-dose cytarabine (LDAC) to treat patients with newly diagnosed acute myeloid leukemia (AML) ineligible to receive intensive chemotherapy. This population pharmacokinetic/pharmacodynamic analysis characterized the time course of survival with glasdegib + LDAC relative to LDAC alone, and explored whether the differences in glasdegib exposure at the clinical dose of 100 mg once daily (QD) significantly affected overall survival (OS).

METHODS

Data from the BRIGHT AML 1003 trial in patients with AML were included in treatment-response (glasdegib + LDAC, n = 78; LDAC alone, n = 38) and exposure-response (glasdegib + LDAC, n = 75) analyses.

RESULTS

The analyses demonstrate that patients treated with glasdegib + LDAC (vs LDAC alone) at any time point during the study period were 58% less likely to die, translating to prolonging of median OS by ~ 5 months (hazard ratio 0.42 [95% confidence interval 0.28-0.66]). Variability in glasdegib exposures did not impact the risk of death. Additionally, potential covariates such as patient demographics, prior treatment with a hypomethylating agent, baseline safety laboratory values, and disease characteristics, did not impact the probability of OS.

CONCLUSION

Together these results confirm that glasdegib + LDAC treatment (vs. LDAC alone) is associated with a significant survival benefit in patients with newly diagnosed AML, and that variability in glasdegib doses (e.g., for dose reductions) and exposures do not compromise the survival benefit of glasdegib 100 mg QD.

CLINICAL TRIAL NUMBER

NCT01546038.