Targeting hedgehog in hematologic malignancy. Blood. 2012;119:2196-2204. [PMID: 22223823 DOI: 10.1182/blood-2011-10-383752]

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.

Glasdegib plus intensive or non-intensive chemotherapy for untreated acute myeloid leukemia: results from the randomized, phase 3 BRIGHT AML 1019 trial

This is the primary report of the randomized, placebo-controlled phase 3 BRIGHT AML 1019 clinical trial of glasdegib in combination with intensive chemotherapy (cytarabine and daunorubicin) or non-intensive chemotherapy (azacitidine) in patients with untreated acute myeloid leukemia. Overall survival (primary endpoint) was similar between the glasdegib and placebo arms in the intensive (n = 404; hazard ratio [HR] 1.05; 95% confidence interval [CI]: 0.782-1.408; two-sided p = 0.749) and non-intensive (n = 325; HR 0.99; 95% CI: 0.768-1.289; two-sided p = 0.969) studies. The proportion of patients who experienced treatment-emergent adverse events was similar for glasdegib versus placebo (intensive: 99.0% vs. 98.5%; non-intensive: 99.4% vs. 98.8%). The most common treatment-emergent adverse events were nausea, febrile neutropenia, and anemia in the intensive study and anemia, constipation, and nausea in the non-intensive study. The addition of glasdegib to either cytarabine and daunorubicin or azacitidine did not significantly improve overall survival and the primary efficacy endpoint for the BRIGHT AML 1019 phase 3 trial was not met. Clinical trial registration: ClinicalTrials.gov: NCT03416179.

Acute Myeloid Leukemia Treatment in the Elderly: A Comprehensive Review of the Present and Future

BACKGROUND

Acute myeloid leukemia (AML) is a disease of the hematopoietic system that remains a therapeutic challenge despite advances in our understanding of the underlying cancer biology in the past decade. It is also an affliction of the elderly that predominantly affects patients over 60 years of age. Standard therapy involves intensive chemotherapy that is often difficult to tolerate in older populations. Fortunately, recent developments in molecular targeting have shown promising results in treating leukemia, paving the way for novel treatment strategies that are easier to tolerate.

SUMMARY

Venetoclax, a BCL-2 inhibitor, when combined with a hypomethylating agent, has proven to be a highly effective and well-tolerated drug and established itself as a new standard for treating AML in patients who are unfit for standard intensive therapy. Other targeted therapies include clinically proven and FDA-approved agents, such as IDH1/2 inhibitors, FLT3 inhibitors, and Gemtuzumab, as well as newer and more experimental drugs such as magrolimab, PI-kinase inhibitors, and T-cell engaging therapy. Some of the novel agents such as magrolimab and menin inhibitors are particularly promising, providing therapeutic options to a wider population of patients than ever before. Determining who will benefit from intense or novel low-intense therapy remains a challenge, and it requires careful assessment of individual patient's fitness and disease characteristics.

KEY MESSAGES

This article reviews past and current treatment strategies that harness various mechanisms of leukemia-targeting agents and introduces novel therapies on the horizon aimed at exploring therapeutic options for the elderly and unfit patient population. It also provides a strategy to select the best available therapy for elderly patients with both newly diagnosed and relapsed/refractory AML.

Insights into the New Molecular Updates in Acute Myeloid Leukemia Pathogenesis

As our understanding of the biologic basis of acute myeloid leukemia evolves, so do the classification systems used to describe this group of cancers. Early classification systems focused on the morphologic features of blasts and other cell populations; however, the explosion in genomic technologies has led to rapid growth in our understanding of these diseases and thus the refinement of classification systems. Recently, two new systems, the International Consensus Classification system and the 5th edition of the World Health Organization classification of tumors of hematopoietic and lymphoid tissues, were published to incorporate the latest genomic advances in blood cancer. This article reviews the major updates in acute myeloid leukemia in both systems and highlights the biologic insights that have driven these changes.

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.

Acute myeloid leukemia: 2023 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Acute myeloid leukemia (AML) is a frequently fatal bone marrow stem cell cancer characterized by unbridled proliferation of malignant marrow stem cells with associated infection, anemia, and bleeding. An improved understanding of pathophysiology, improvements in measurement technology and at least 10 recently approved therapies have led to revamping the diagnostic, prognostic, and therapeutic landscape of AML.

DIAGNOSIS

One updated and one new classification system were published in 2022, both emphasizing the integration of molecular analysis into daily practice. Differences between the International Consensus Classification and major revisions from the previous 2016 WHO system provide both challenges and opportunities for care and clinical research.

RISK ASSESSMENT AND MONITORING

The European Leukemia Net 2022 risk classification integrates knowledge from novel molecular findings and recent trial results, as well as emphasizing dynamic risk based on serial measurable residual disease assessment. However, how to leverage our burgeoning ability to measure a small number of potentially malignant myeloid cells into therapeutic decision making is controversial.

RISK ADAPTED THERAPY

The diagnostic and therapeutic complexity plus the availability of newly approved agents requires a nuanced therapeutic algorithm which should integrate patient goals of care, comorbidities, and disease characteristics including the specific mutational profile of the patient's AML. The framework we suggest only represents the beginning of the discussion.

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.

Ehrlichia SLiM ligand mimetic activates Hedgehog signaling to engage a BCL-2 anti-apoptotic cellular program

Ehrlichia chaffeensis (E. chaffeensis) has evolved eukaryotic ligand mimicry to repurpose multiple cellular signaling pathways for immune evasion. In this investigation, we demonstrate that TRP120 has a novel repetitive short linear motif (SLiM) that activates the evolutionarily conserved Hedgehog (Hh) signaling pathway to inhibit apoptosis. In silico analysis revealed that TRP120 has sequence and functional similarity with Hh ligands and a candidate Hh ligand SLiM was identified. siRNA knockdown of Hh signaling and transcriptional components significantly reduced infection. Co-immunoprecipitation and surface plasmon resonance demonstrated that rTRP120-TR interacted directly with Hh receptor Patched-2 (PTCH2). E. chaffeensis infection resulted in early upregulation of Hh transcription factor GLI-1 and regulation of Hh target genes. Moreover, soluble recombinant TRP120 (rTRP120) activated Hh and induced gene expression consistent with the eukaryotic Hh ligand. The TRP120-Hh-SLiM (NPEVLIKD) induced nuclear translocation of GLI-1 in THP-1 cells and primary human monocytes and induced a rapid and expansive activation of Hh pathway target genes. Furthermore, Hh activation was blocked by an α-TRP120-Hh-SLiM antibody. TRP120-Hh-SLiM significantly increased levels of Hh target, anti-apoptotic protein B-cell lymphoma 2 (BCL-2), and siRNA knockdown of BCL-2 dramatically inhibited infection. Blocking Hh signaling with the inhibitor Vismodegib, induced a pro-apoptotic cellular program defined by decreased mitochondria membrane potential, significant reductions in BCL-2, activation of caspase 3 and 9, and increased apoptotic cells. This study reveals a novel E. chaffeensis SLiM ligand mimetic that activates Hh signaling to maintain E. chaffeensis infection by engaging a BCL-2 anti-apoptotic cellular program.

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.

New Drugs Bringing New Challenges to AML: A Brief Review

The better understanding of the genomic landscape in acute myeloid leukaemia (AML) has progressively paved the way for precision medicine in AML. There is a growing number of drugs with novel mechanisms of action and unique side-effect profiles. This review examines the impact of evolving novel therapies on survival in AML and the challenges that ensue.

Towards precision medicine for AML

With rapid advances in sequencing technologies, tremendous progress has been made in understanding the molecular pathogenesis of acute myeloid leukaemia (AML), thus revealing enormous genetic and clonal heterogeneity, and paving the way for precision medicine approaches. The successful development of precision medicine for patients with AML has been exemplified by the introduction of targeted FLT3, IDH1/IDH2 and BCL-2 inhibitors. When used as single agents, these inhibitors display moderate antileukaemic activity. However, augmented clinical activity has been demonstrated when they are administered in combination with drugs with broader mechanisms of action targeting epigenetic and/or other oncogenic signalling pathways or with conventional cytotoxic agents. The development of immunotherapies has been hampered by the expression of antigens that are expressed by both leukaemic and non-malignant haematopoietic progenitor cells; nonetheless, a diverse range of immunotherapies are now entering clinical development. This myriad of emerging agents also creates challenges, such as how to safely combine agents with different mechanisms of action, the need to circumvent primary and secondary resistance, and new challenges in future clinical trial design. In this Review, we discuss the current state of precision medicine for AML, including both the potential to improve patient outcomes and the related challenges.

Synergistic inhibitory effect of Smo inhibitor jervine and its combination with decitabine can target Hedgehog signaling pathway to inhibit myelodysplastic syndrome cell line

OBJECTIVE

Hypomethylating agents (HMAs) have been reported to target the Sonic Hedgehog (Shh) signaling pathway in myelodysplastic syndrome (MDS). However, the synergistic inhibitory effect of Smo inhibitor jervine and its combination with decitabine in MUTZ-1 cell lines remains lacking.

METHODS

We used a CCK-8 assay to detect the in-vitro proliferation rate of MUTZ-1 cell lines. Besides, the Annexin V-FITC/PI double staining flow cytometry was utilized to detect the apoptosis rate and cell cycle changes. The expression levels of mRNA were quantified by using qRT-PCR, and the western blot was employed to detect the expression of proteins.

RESULTS

We found that the single-agent jervine or decitabine can significantly inhibit the proliferation rate of MUTZ-1 cell lines, and this inhibitory effect is time-dependent and concentration-dependent. The combined intervention of the jervine and decitabine can more significantly inhibit cell proliferation, induce cell apoptosis, and block the G1 phase of the cell cycle. The combined intervention of the two drugs significantly reduced Smo and G1i-1 mRNA expression in MUTZ-1 cells. Furthermore, after combining both of the drug treatments, the proteins levels of Smo, G1i-1, PI3K, p-AKT, Bcl2, and Cyclin Dl were significantly downregulated, and Caspase-3 is upregulated, indicating that jervine with its combination of decitabine might be effective for controlling the proliferation, apoptosis, and cell cycle.

CONCLUSION

The Smo inhibitor jervine and its combination with decitabine have a synergistic effect on the proliferation, cell cycle, and apoptosis of MUTZ-1 cells, and its mechanism may be achieved by interfering with the Shh signaling pathway.

UTX maintains the functional integrity of the murine hematopoietic system by globally regulating aging-associated genes

Epigenetic regulation is essential for the maintenance of the hematopoietic system, and its deregulation is implicated in hematopoietic disorders. In this study, UTX, a demethylase for lysine 27 on histone H3 (H3K27) and a component of COMPASS-like and SWI/SNF complexes, played an essential role in the hematopoietic system by globally regulating aging-associated genes. Utx-deficient (UtxΔ/Δ) mice exhibited myeloid skewing with dysplasia, extramedullary hematopoiesis, impaired hematopoietic reconstituting ability, and increased susceptibility to leukemia, which are the hallmarks of hematopoietic aging. RNA-sequencing (RNA-seq) analysis revealed that Utx deficiency converted the gene expression profiles of young hematopoietic stem-progenitor cells (HSPCs) to those of aged HSPCs. Utx expression in hematopoietic stem cells declined with age, and UtxΔ/Δ HSPCs exhibited increased expression of an aging-associated marker, accumulation of reactive oxygen species, and impaired repair of DNA double-strand breaks. Pathway and chromatin immunoprecipitation analyses coupled with RNA-seq data indicated that UTX contributed to hematopoietic homeostasis mainly by maintaining the expression of genes downregulated with aging via demethylase-dependent and -independent epigenetic programming. Of note, comparison of pathway changes in UtxΔ/Δ HSPCs, aged muscle stem cells, aged fibroblasts, and aged induced neurons showed substantial overlap, strongly suggesting common aging mechanisms among different tissue stem cells.

Acute Myeloid Leukemia Mutations and Future Mechanistic Target to Overcome Resistance

OPINION STATEMENT

Cytogenetics and mutation identification in acute myeloid leukemia have allowed for more targeted therapy. Many therapies have been approved by the FDA in the last 3 years including gilteritinib and azacitidine but the overall survival has remained stagnant at 25%. The inability to achieve complete remission was related to the residual leukemic stem cells (LSCs). Thus, the relationship between bone marrow niche and LSCs must be further explored to prevent treatment relapse/resistance. The development of immunotherapy and nanotechnology may play a role in future therapy to achieve the complete remission. Nano-encapsulation of drugs can improve drugs' bioavailability, help drugs evade resistance, and provide combination therapy directly to the cancer cells. Studies indicate targeting surface antigens such as CLL1 and CD123 using chimeric antibody receptor T cells can improve survival outcomes. Finally, new discoveries indicate that inhibiting integrin αvβ3 and acid ceramidase may prove to be efficacious.

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.

Precision medicine in myeloid malignancies

Myeloid malignancies have always been at the forefront of an improved understanding of the molecular pathogenesis of cancer. In accordance, over the last years, basic research focusing on the aberrations underlying malignant transformation of myeloid cells has provided the basis for precision medicine approaches and subsequently has led to the development of powerful therapeutic strategies. In this review article, we will recapitulate what has happened since in the 1980s the use of all-trans retinoic acid (ATRA), as a first targeted cancer therapy, has changed one of the deadliest leukemia subtypes, acute promyelocytic leukemia (APL), into one that can be cured without classical chemotherapy today. Similarly, imatinib, the first molecularly designed cancer therapy, has revolutionized the management of chronic myeloid leukemia (CML). Thus, targeted treatment approaches have become the paradigm for myeloid malignancy, but many questions still remain unanswered, especially how identical mutations can be associated with different phenotypes. This might be linked to the impact of the cell of origin, gene-gene interactions, or the tumor microenvironment including the immune system. Continuous research in the field of myeloid neoplasia has started to unravel the molecular pathways that are not only crucial for initial treatment response, but also resistance of leukemia cells under therapy. Ongoing studies focusing on leukemia cell vulnerabilities do already point to novel (targetable) "Achilles heels" that can further improve myeloid cancer therapy.

An update of new small-molecule anticancer drugs approved from 2015 to 2020

A high incidence of cancer has given rise to the development of more anti-tumor drugs. From 2015 to 2020, fifty-six new small-molecule anticancer drugs, divided into ten categories according to their anti-tumor target activities, have been approved. These include TKIs (30 drugs), MAPK inhibitors (3 drugs), CDK inhibitors (3 drugs), PARP inhibitors (3 drugs), PI3K inhibitors (3 drugs), SMO receptor antagonists (2 drugs), AR antagonists (2 drugs), SSTR inhibitors (2 drugs), IDH inhibitors (2 drugs) and others (6 drugs). Among them, PTK inhibitors (30/56) have led to a paradigm shift in cancer treatment with less toxicity and more potency. Each of their structures, approval statuses, applications, SAR analyses, and original research synthesis routes have been summarized, giving us a more comprehensive map for further efforts to design more specific targeted agents for reducing cancer in the future. We believe this review will help further research of potential antitumor agents in clinical usage.

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.

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.

A review of FDA-approved acute myeloid leukemia therapies beyond '7 + 3'

Introduction: The standard anthracycline and cytarabine-based chemotherapy for acute myeloid leukemia (AML) has changed relatively little since the 1970s and produces unsatisfactory outcomes in many patients. In the past two decades, a better understanding of the pathophysiology and heterogeneity of this disease has led to promising new therapies, resulting in a flurry of new drug approvals.Areas covered: The MEDLINE database, ClinicalTrials.gov and conference proceedings were reviewed for the most salient literature concerning FDA-approved drugs for AML beyond standard chemotherapy: gemtuzumab ozogamicin, hypomethylating agents, Fms-like tyrosine kinase 3 (FLT3) inhibitors, isocitrate dehydrogenase (IDH) inhibitors, venetoclax, liposomal cytarabine and daunorubicin (CPX-351), and hedgehog pathway inhibitors. Key evidence for their efficacy is discussed. For each drug category, indications, typical usage and responses, major toxicities, and future directions for research are highlighted.Expert opinion: The treatment paradigm for AML is rapidly evolving. Promising new drugs targeting driver mutations have improved outcomes in specific AML subgroups. In parallel, advances in low-intensity therapies have allowed patients unfit for standard induction chemotherapy to achieve meaningful disease control. Further work is ongoing to identify synergistic drug combinations as well as optimal treatment selection guided by individual patient and disease features.

Emerging drugs for the treatment of chronic myelomonocytic leukemia

Introduction: Chronic myelomonocytic leukemia (CMML) is a clonal hematologic disorder with heterogenous prognosis, but with no curative therapies with exception of allogeneic transplant. Therapeutic options for patients with CMML are limited, and although hypomethylating agents such as azacitidine and decitabine are the standard of care, only 40% of patients achieve a response, and most responses are transient. Over the last 5 years, significant advances have been made in the understanding of the clonal landscape of CMML, some of the mechanisms associated to resistance to HMA, and other key biological processes involved in disease pathogenesis. Areas covered: The current article reviews the most relevant emerging therapies currently undergoing clinical trials for the treatment of previously untreated or relapsed CMML. Expert opinion: The presence of recurrent somatic mutations in CMML represents therapeutic opportunities to utilize specific small molecule inhibitors such as IDH, FLT3, MEK/ERK, PLK1, or splicing inhibitors and modulators. In addition, other novel agents such as immune therapies, BCL2 or MCL1 inhibitors and other monoclonal antibodies could lead to therapeutic advances. Identifying specific patient populations likely to benefit from some of these interventions, and development of optimal combinations will remain the challenge when determining their role in therapy.

Normal Hematopoiesis Is a Balancing Act of Self-Renewal and Regeneration

The hematopoietic system is highly organized to maintain its functional integrity and to meet lifelong organismal demands. Hematopoietic stem cells (HSCs) must balance self-renewal with differentiation and the regeneration of the blood system. It is a complex balancing act between these competing HSC functions. Although highly quiescent at steady state, HSCs become activated in response to inflammatory cytokines and regenerative challenges. This activation phase leads to many intrinsic stresses such as replicative, metabolic, and oxidative stress, which can cause functional decline, impaired self-renewal, and exhaustion of HSCs. To cope with these insults, HSCs use both built-in and emergency-triggered stress-response mechanisms to maintain homeostasis and to defend against disease development. In this review, we discuss how the hematopoietic system operates in steady state and stress conditions, what strategies are used to maintain functional integrity, and how deregulation in the balance between self-renewal and regeneration can drive malignant transformation.

Acute Alcohol Intoxication Impairs Sonic Hedgehog-Gli1 Signaling and Activation of Primitive Hematopoietic Precursor Cells in the Early Stage of Host Response to Bacteremia

BACKGROUND

Activation of hematopoietic stem cells [HSCs, lineage(lin)- stem cell growth factor receptor (c-kit)+ stem cell antigen-1(Sca-1)+ , or LKS cells in mice] is critical for initiating the granulopoietic response. This study determined the effect of alcohol exposure on sonic hedgehog (SHH) signaling in the regulation of HSC activation during bacteremia.

METHODS

Acute alcohol intoxication was induced in mice by intraperitoneal (i.p.) injection of 20% alcohol (5 g alcohol/kg body weight). Control mice received i.p. saline. Thirty minutes later, mice were intravenously (i.v.) injected with Escherichia coli (E. coli, 1 to 5 × 107 CFUs/mouse) or saline.

RESULTS

SHH expression by lineage-negative bone marrow cells (BMCs) was significantly increased 24 hours after E. coli infection. Extracellular signal-regulated kinase 1/2 (ERK1/2)-specificity protein 1 (Sp1) signaling promotes SHH expression. ERK1/2 was markedly activated in BMCs 8 hours following E. coli infection. Alcohol suppressed both the activation of ERK1/2 and up-regulation of SHH expression following E. coli infection. E. coli infection up-regulated GLI family zinc finger 1 (Gli1) gene expression by BMCs and increased Gli1 protein content in LKS cells. The extent of Gli1 expression was correlated with the activity of proliferation in LKS cells. Alcohol inhibited up-regulation of Gli1 expression and activation of LKS cells in response to E. coli infection. Alcohol also interrupted the granulopoietic response to bacteremia.

CONCLUSION

These data show that alcohol disrupts SHH-Gli1 signaling and HSC activation in the early stage of the granulopoietic response, which may serve as an important mechanism underlying the impairment of immune defense against bacterial infection in host excessively consuming alcohol.

Downregulation of GLI3 Expression Mediates Chemotherapy Resistance in Acute Myeloid Leukemia

Aberrant activation of the hedgehog (HH) pathway is observed in many neoplasms, including acute myeloid leukemia (AML). The glioma-associated oncogene homolog (GLI) transcription factors are the main downstream effectors of the HH signaling cascade and are responsible for the proliferation and maintenance of leukemic stem cells, which support chemotherapy resistance and leukemia relapse. Cytarabine (Ara-C)-resistant variants of AML cell lines were established through long-term cultivation with successively increasing Ara-C concentrations. Subsequently, differences in GLI expression were analyzed by RT-qPCR. GLI3 mRNA levels were detectable in parental Kasumi-1, OCI-AML3, and OCI-AML5 cells, whereas GLI3 expression was completely silenced in all resistant counterparts. Therefore, we generated GLI3-knockdown cell lines using small hairpin RNAs (shRNA) and evaluated their sensitivity to Ara-C in vitro. The knockdown of GLI3 partly abolished the effect of Ara-C on colony formation and induction of apoptosis, indicating that GLI3 downregulation results in Ara-C resistance. Moreover, we analyzed the expression of several genes involved in Ara-C metabolism and transport. Knockdown of GLI3 resulted in the upregulation of SAM and HD domain-containing protein 1 (SAMHD1), cytidine deaminase (CDA), and ATP-binding cassette C11 (ABCC11)/multidrug resistance-associated protein 8 (MRP8), each of which has been identified as a predictive marker for Ara-C response in acute myeloid leukemia. Our results demonstrate that GLI3 downregulation is a potential mechanism to induce chemotherapy resistance in AML.

Glasdegib: A Novel Hedgehog Pathway Inhibitor for Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive myeloid disorder that is associated with a generally poor prognosis. Effective treatment options have been limited for older patients with AML who are not able to undergo intensive remission induction chemotherapy due to advanced age or comorbidities. New and novel agents are needed to improve treatment outcomes for this patient population. Glasdegib is a novel Hedgehog signaling pathway inhibitor approved by the U.S. Food & Drug Administration for the treatment of patients with newly diagnosed AML who are 75 years of age or older or who have comorbidities that preclude intensive induction chemotherapy. Glasdegib is approved in combination with low-dose cytarabine (LDAC). This approval is based on the results of a multicenter, open-label, randomized trial of glasdegib plus LDAC vs. LDAC monotherapy in which the addition of glasdegib resulted in an improvement in median overall survival.

The Time Has Come for Targeted Therapies for AML: Lights and Shadows

Acute myeloid leukemia (AML) is a complex disease characterized by genetic and clinical heterogeneity and high mortality. After 40 years during which the standard of care for patients evolved very little, the therapeutic landscape has recently seen rapid changes, with the approval of eight new drugs by the Food and Drug Administration (FDA) within the last 2 years, providing new opportunities, as well as new challenges, for treating clinicians. These therapies include FLT3 inhibitors midostaurin and gilteritinib, CPX-351 (liposomal cytarabine and daunorubicin), gemtuzumab ozogamicin (GO, anti-CD33 monoclonal antibody conjugated with calicheamicin), IDH1/IDH2 inhibitors ivosidenib and enasidenib, Hedgehog inhibitor glasdegib, and BCL-2 inhibitor venetoclax. In this review, we summarize currently available data on these new drugs and discuss the rapidly evolving therapeutic armamentarium for AML, focusing on targeted therapies.

Population Pharmacokinetics of Glasdegib in Patients With Advanced Hematologic Malignancies and Solid Tumors

Glasdegib is an inhibitor of the Hedgehog pathway recently approved in the United States for the treatment of acute myeloid leukemia. A population pharmacokinetic analysis was conducted to characterize the kinetic behavior of glasdegib and its sources of variability (covariates) by utilizing data from 269 patients with cancer treated with oral glasdegib doses ranging from 5 to 640 mg/d. Nonlinear mixed-effects modeling was conducted using NONMEM (v.7.3) and Perl-speaks NONMEM (v.4.2.0). The estimated apparent total clearance, apparent central volume of distribution, and apparent peripheral volume of distribution were 6.27 L/h, 3.32 L, and 279.2 L, respectively. Age, sex, race, and hepatic function were not significant covariates on glasdegib pharmacokinetic parameters. Baseline body weight, percentage bone marrow blasts, creatinine clearance, and use of moderate or strong cytochrome P450 3A inhibitors were statistically significant covariates on apparent total clearance; however, the magnitude of the effects was not considered clinically meaningful.

Sonidegib, a Smoothened Inhibitor, Promotes Apoptosis and Suppresses Proliferation of Natural Killer/T-Cell Lymphoma

Background

Dysregulation of the Hedgehog (Hh) pathway modulates various aspects of hematologic and solid tumors, but its effects in human Natural killer/T-cell lymphoma (NKTCL) are unclear. Moreover, no study has examined the consequences of pharmacologically inhibiting Hh signaling in NKTCL cell lines.

Material/Methods

In this study, the expression of Smoothened (Smo) and Glioma-associated oncogene 1 (Gli1) in NKTCL tissue were scrutinized. Two human NKTCL cell lines, SNK6 and SNT8, were subjected to various doses of sonidegib (a Smo inhibitor) and incubated for distinct durations. The cell apoptosis was examined by flow cytometry, CCK-8 assay was run to assess proliferation, and protein levels were quantified by Western blotting.

Results

Both Smo and Gli1 expression were higher in NKTCL tissue than in Lymphoid Reactive Hyperplasia (LRH). Sonidegib significantly suppressed proliferation in NKTCL cells and the effect was dose-dependent. Further analysis revealed that sonidegib treatment elevated the number of apoptotic cells in a dose- and time-dependent manner. In addition, sonidegib downregulated Smo and Gli1expression in NKTCL cells.

Conclusions

The Hh pathway is crucial to the development of NKTCL and thus holds huge promise as a treatment for this disease.

Novel therapy in Acute myeloid leukemia (AML): moving toward targeted approaches

Acute myeloid leukemia (AML) is a heterogenous and complex disease characterized by rapid cellular proliferation, an aggressive clinical course, and generally high mortality. While progress has been made in the understanding of the genetic and molecular biology of the disease, the standard of care for patients had only changed minimally over the past 40 years. Recently, rapid movement of potentially useful agents from bench to bedside has translated into new therapies either recently approved or in clinical trials. These therapies include improved chemotherapies, mutationally targeted inhibitors, pro-apoptotic agents, microenvironment targeting molecules, cell cycle checkpoint inhibitors, and epigenetic regulators. Furthermore, advances in immunotherapy employ monoclonal and bispecific antibodies, chimeric antigen receptor (CAR) T cells, checkpoint inhibitors, and vaccines provide an alternative pathway for AML treatment. In this review, we discuss the recent results of completed or ongoing clinical trials with these novel therapeutic agents in AML.

Recent Treatment Advances and the Role of Nanotechnology, Combination Products, and Immunotherapy in Changing the Therapeutic Landscape of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common acute leukemia that is becoming more prevalent particularly in the older (65 years of age or older) population. For decades, "7 + 3" remission induction therapy with cytarabine and an anthracycline, followed by consolidation therapy, has been the standard of care treatment for AML. This stagnancy in AML treatment has resulted in less than ideal treatment outcomes for AML patients, especially for elderly patients and those with unfavourable profiles. Over the past two years, six new therapeutic agents have received regulatory approval, suggesting that a number of obstacles to treating AML have been addressed and the treatment landscape for AML is finally changing. This review outlines the challenges and obstacles in treating AML and highlights the advances in AML treatment made in recent years, including Vyxeos®, midostaurin, gemtuzumab ozogamicin, and venetoclax, with particular emphasis on combination treatment strategies. We also discuss the potential utility of new combination products such as one that we call "EnFlaM", which comprises an encapsulated nanoformulation of flavopiridol and mitoxantrone. Finally, we provide a review on the immunotherapeutic landscape of AML, discussing yet another angle through which novel treatments can be designed to further improve treatment outcomes for AML patients.

Genomic testing, tumor microenvironment and targeted therapy of Hedgehog-related human cancers

Hedgehog signals are transduced through Patched receptors to the Smoothened (SMO)-SUFU-GLI and SMO-Gi-RhoA signaling cascades. MTOR-S6K1 and MEK-ERK signals are also transduced to GLI activators through post-translational modifications. The GLI transcription network up-regulates target genes, such as BCL2, FOXA2, FOXE1, FOXF1, FOXL1, FOXM1, GLI1, HHIP, PTCH1 and WNT2B, in a cellular context-dependent manner. Aberrant Hedgehog signaling in tumor cells leads to self-renewal, survival, proliferation and invasion. Paracrine Hedgehog signaling in the tumor microenvironment (TME), which harbors cancer-associated fibroblasts, leads to angiogenesis, fibrosis, immune evasion and neuropathic pain. Hedgehog-related genetic alterations occur frequently in basal cell carcinoma (BCC) (85%) and Sonic Hedgehog (SHH)-subgroup medulloblastoma (87%) and less frequently in breast cancer, colorectal cancer, gastric cancer, pancreatic cancer, non-small-cell lung cancer (NSCLC) and ovarian cancer. Among investigational SMO inhibitors, vismodegib and sonidegib are approved for the treatment of patients with BCC, and glasdegib is approved for the treatment of patients with acute myeloid leukemia (AML). Resistance to SMO inhibitors is caused by acquired SMO mutations, SUFU deletions, GLI2 amplification, other by-passing mechanisms of GLI activation and WNT/β-catenin signaling activation. GLI-DNA-interaction inhibitors (glabrescione B and GANT61), GLI2 destabilizers (arsenic trioxide and pirfenidone) and a GLI-deacetylation inhibitor (4SC-202) were shown to block GLI-dependent transcription and tumorigenesis in preclinical studies. By contrast, SMO inhibitors can remodel the immunosuppressive TME that is dominated by M2-like tumor-associated macrophages (M2-TAMs), myeloid-derived suppressor cells and regulatory T cells, and thus, a Phase I/II clinical trial of the immune checkpoint inhibitor pembrolizumab with or without vismodegib in BCC patients is ongoing.

Concise Review: Exploiting Unique Biological Features of Leukemia Stem Cells for Therapeutic Benefit

Cancer stem cells play a critical role in disease initiation and insensitivity to chemotherapy in numerous hematologic malignancies and some solid tumors, and these stem cells need to be eradicated to achieve a cure. Key to successful targeting of cancer stem cells is to identify and functionally test critical target genes and to fully understand their associated molecular network in these stem cells. Human chronic myeloid leukemia (CML) is well accepted as one of the typical types of hematopoietic malignancies that are derived from leukemia stem cells (LSCs), serving as an excellent model disease for understanding the biology of LSCs and developing effective, selective, and curative strategies through targeting LSCs. Here, we discuss LSCs in CML with a focus on identification of unique biological features of these stem cells to emphasize the feasibility and significance of specific targeting of LSCs while sparing normal stem cell counterparts in leukemia therapy. stem cells translational medicine2019;8:768&774

Absolute Oral Bioavailability of Glasdegib (PF-04449913), a Smoothened Inhibitor, in Randomized Healthy Volunteers

Glasdegib (PF‐04449913) is an oral small‐molecule inhibitor of the Hedgehog signaling pathway under development for treating myeloid malignancies. This was an open‐label phase 1, randomized, 2‐sequence, 2‐treatment, 2‐period, crossover study evaluating the absolute bioavailability of glasdegib in healthy volunteers under fasting condition (NCT03270878). In period 1, 12 eligible subjects received either a single oral dose of glasdegib 100 mg (tablet) or a single intravenous (IV) dose of glasdegib 50 mg. Following ≥6‐day washout, subjects received the treatment that they did not receive in the first period. Blood samples were collected for up to 96 hours after dosing. Drug plasma concentrations were determined by high‐performance liquid chromatography–tandem mass spectrometry. Glasdegib pharmacokinetic parameters were calculated using noncompartmental analysis. The mean terminal half‐life was 14.3 hours for oral tablet treatment vs 13.8 hours for glasdegib IV treatment. The absolute oral bioavailability measured as the ratios (oral/IV) of adjusted geometric mean (90% confidence interval) of dose normalized area under the plasma concentration–time curve was 77.12% (71.83%‐82.81%). Two adverse events (1 mild and 1 moderate in severity) were reported by 2 subjects following oral tablet administration; these were fully resolved by the end of the study.

A phase 2 trial of the oral smoothened inhibitor glasdegib in refractory myelodysplastic syndromes (MDS)

Hypomethylating agent (HMA) failure myelodysplastic syndrome (MDS) patients have poor outcomes and urgent need for novel therapies. Hedgehog pathway signaling upregulation plays a central role in myeloid neoplasm pathogenesis and leukemia stem cell survival. We evaluated the efficacy and safety of the smoothened inhibitor glasdegib in HMA-failure MDS (n = 35, median age 73 years). According to the International Prognostic Scoring System and the MD Anderson Global Risk Model, 54% and 77% had higher risk disease, respectively. Overall response was 6% (n = 2), and best response was marrow complete remission with hematologic improvement in both patients. Median OS and median follow-up were 10.4 and 42.8 months, respectively. Drug response/stable disease (SD) resulted in better OS than treatment failure (20.6 [95% CI, 10.4-] vs 3.9 months [95% CI, 0.7-9.1]; P< .0001). Response/SD was confirmed to be an independent covariate for improved OS (P <  .0001). Grade 3 or higher infections occurred in 11% of patients (n = 4); non-hematologic toxicities were rare. Early mortality (< 30 days) occurred in 11% of patients (n = 4). Glasdegib was well tolerated among HMA-failure MDS patients, although single-agent activity was limited. SD or better resulted in notably superior OS. These results support further investigation of glasdegib, potentially in novel drug combinations, in MDS patients.

State of the art of Smo antagonists for cancer therapy: advances in the target receptor and new ligand structures

Since the Hedgehog signaling pathway has been associated with cancer, it has emerged as a therapeutic target for cancer therapy. The main target among the key Hedgehog proteins is the GPCR-like Smo receptor. Therefore, some Smo antagonists that have entered clinical trials, including the US FDA-approved drugs vismodegib and sonidegib, to treat basal cell carcinoma and medulloblastoma. However, early resistance of these drugs has spawned the need to understand the molecular bases of this phenomena. We therefore reviewed details about Smo receptor structures and the best Smo antagonist chemical structures. In addition, we discussed strategies that should be considered to develop new, safer generations of Smo antagonists that avoid current clinical limitations.

Targeting the cross-talk between the hedgehog and NF-κB signaling pathways in multiple myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy. Aberrant activation of the Hedgehog (Hh) and NF-κB signaling pathways is observed in MM and plays a pivotal role in the development of MM by promoting myeloma cell growth, survival, and drug resistance. In this study, we found that the Sonic Hh (SHh) ligand in the bone marrow microenvironment is responsible for the enhancement of NF-κB activity in MM cell lines NCI-H929 and U266. Notably, we discovered that Hh signaling regulates NF-κB through its classical pathway (SHh/PTCH1/SMO/GLI1) in MM cells. Meanwhile, non-classical pathway by SMO recruitment of TRAF6 to ubiquitination is also involved in it. Moreover, the SMO inhibitor cyclopamine enhances the cytotoxic effects of bortezomib in MM cell lines. Our study reveals the cross-talk between Hh members and the NF-κB pathway in the myeloma cells and provides a theoretical basis for combined utilization of Hh members and proteasome inhibition in MM.

Randomized comparison of low dose cytarabine with or without glasdegib in patients with newly diagnosed acute myeloid leukemia or high-risk myelodysplastic syndrome

Glasdegib is a Hedgehog pathway inhibitor. This phase II, randomized, open-label, multicenter study (ClinicalTrials.gov, NCT01546038) evaluated the efficacy of glasdegib plus low-dose cytarabine (LDAC) in patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome unsuitable for intensive chemotherapy. Glasdegib 100 mg (oral, QD) was administered continuously in 28-day cycles; LDAC 20 mg (subcutaneous, BID) was administered for 10 per 28 days. Patients (stratified by cytogenetic risk) were randomized (2:1) to receive glasdegib/LDAC or LDAC. The primary endpoint was overall survival. Eighty-eight and 44 patients were randomized to glasdegib/LDAC and LDAC, respectively. Median (80% confidence interval [CI]) overall survival was 8.8 (6.9–9.9) months with glasdegib/LDAC and 4.9 (3.5–6.0) months with LDAC (hazard ratio, 0.51; 80% CI, 0.39–0.67, P = 0.0004). Fifteen (17.0%) and 1 (2.3%) patients in the glasdegib/LDAC and LDAC arms, respectively, achieved complete remission (P < 0.05). Nonhematologic grade 3/4 all-causality adverse events included pneumonia (16.7%) and fatigue (14.3%) with glasdegib/LDAC and pneumonia (14.6%) with LDAC. Clinical efficacy was evident across patients with diverse mutational profiles. Glasdegib plus LDAC has a favorable benefit–risk profile and may be a promising option for AML patients unsuitable for intensive chemotherapy.

Glasdegib in combination with cytarabine and daunorubicin in patients with AML or high-risk MDS: Phase 2 study results

Glasdegib is a Hedgehog pathway inhibitor. This ongoing, open‐label, phase 2 study (NCT01546038) evaluated glasdegib plus cytarabine/daunorubicin in patients with untreated acute myeloid leukemia (AML) or high‐risk myelodysplastic syndromes (MDS). Patients received glasdegib 100 mg orally, once daily in continuous 28‐day cycles from day −3, with intravenous cytarabine 100 mg/m² on days 1‐7 and daunorubicin 60 mg/m² on days 1‐3. Patients in remission then received consolidation therapy (2‐4 cycles of cytarabine 1 g/m² twice daily on days 1, 3, 5 of each cycle), followed by maintenance glasdegib (maximum 6 cycles). Primary endpoint was complete remission (CR) in patients aged ≥55 years. Secondary endpoints included overall survival (OS), safety and outcome by mutational status. Patients had a median (range) age of 64.0 (27‐75) years, 60.0% were male, and 84.5% were white. In 69 evaluable patients, 46.4% (80% confidence interval [CI]: 38.7‐54.1) achieved investigator‐reported CR. Among patients ≥55 years old (n = 60), 40.0% (80% CI 31.9‐48.1) achieved CR. Among all 69 patients, median OS was 14.9 (80% CI 13.4‐19.3) months, with 12‐month survival probability 66.6% (80% CI 58.5‐73.4). The most common treatment‐related adverse events (≥50% patients) were diarrhea and nausea. There were no significant associations between mutational status (12 genes) and clinical response, suggesting potential benefit across diverse molecular profiles. Glasdegib plus cytarabine/daunorubicin was well tolerated and associated with clinical activity in patients with untreated AML or high‐risk MDS. A randomized phase 3 trial of glasdegib in combination with chemotherapy (7 + 3 schedule) is ongoing.

FoxO6 regulates Hippo signaling and growth of the craniofacial complex

The mechanisms that regulate post-natal growth of the craniofacial complex and that ultimately determine the size and shape of our faces are not well understood. Hippo signaling is a general mechanism to control tissue growth and organ size, and although it is known that Hippo signaling functions in neural crest specification and patterning during embryogenesis and before birth, its specific role in postnatal craniofacial growth remains elusive. We have identified the transcription factor FoxO6 as an activator of Hippo signaling regulating neonatal growth of the face. During late stages of mouse development, FoxO6 is expressed specifically in craniofacial tissues and FoxO6-/- mice undergo expansion of the face, frontal cortex, olfactory component and skull. Enlargement of the mandible and maxilla and lengthening of the incisors in FoxO6-/- mice are associated with increases in cell proliferation. In vitro and in vivo studies demonstrated that FoxO6 activates Lats1 expression, thereby increasing Yap phosphorylation and activation of Hippo signaling. FoxO6-/- mice have significantly reduced Hippo Signaling caused by a decrease in Lats1 expression and decreases in Shh and Runx2 expression, suggesting that Shh and Runx2 are also linked to Hippo signaling. In vitro, FoxO6 activates Hippo reporter constructs and regulates cell proliferation. Furthermore PITX2, a regulator of Hippo signaling is associated with Axenfeld-Rieger Syndrome causing a flattened midface and we show that PITX2 activates FoxO6 expression. Craniofacial specific expression of FoxO6 postnatally regulates Hippo signaling and cell proliferation. Together, these results identify a FoxO6-Hippo regulatory pathway that controls skull growth, odontogenesis and face morphology.

Hedgehog Signaling Pathway and Autophagy in Cancer

Hedgehog (Hh) pathway controls complex developmental processes in vertebrates. Abnormal activation of Hh pathway is responsible for tumorigenesis and maintenance of multiple cancers, and thus addressing this represents promising therapeutic opportunities. In recent years, two Hh inhibitors have been approved for basal cell carcinoma (BCC) treatment and show extraordinary clinical outcomes. Meanwhile, a series of novel agents are being developed for the treatment of several cancers, including lung cancer, leukemia, and pancreatic cancer. Unfortunately, Hh inhibition fails to show satisfactory benefits in these cancer types compared with the success stories in BCC, highlighting the need for better understanding of Hh signaling in cancer. Autophagy, a conserved biological process for cellular component elimination, plays critical roles in the initiation, progression, and drug resistance of cancer, and therefore, implied potential to be targeted. Recent evidence demonstrated that Hh signaling interplays with autophagy in multiple cancers. Importantly, modulating this crosstalk exhibited noteworthy capability to sensitize primary and drug-resistant cancer cells to Hh inhibitors, representing an emerging opportunity to reboot the efficacy of Hh inhibition in those insensitive tumors, and to tackle drug resistance challenges. This review will highlight recent advances of Hh pathway and autophagy in cancers, and focus on their crosstalk and the implied therapeutic opportunities.

FusionPathway: Prediction of pathways and therapeutic targets associated with gene fusions in cancer

Numerous gene fusions have been uncovered across multiple cancer types. Although the ability to target several of these fusions has led to the development of some successful anti-cancer drugs, most of them are not druggable. Understanding the molecular pathways of a fusion is important in determining its function in oncogenesis and in developing therapeutic strategies for patients harboring the fusion. However, the molecular pathways have been elucidated for only a few fusions, in part because of the labor-intensive nature of the required functional assays. Therefore, we developed a domain-based network approach to infer the pathways of a fusion. Molecular interactions of a fusion are first predicted by using its protein domain composition, and its associated pathways are then inferred from these molecular interactions. We demonstrated the capabilities of this approach by primarily applying it to the well-studied BCR-ABL1 fusion. The approach was also applied to two undruggable fusions in sarcoma, EWS-FL1 and FUS-DDIT3. We successfully identified known genes and pathways associated with these fusions and satisfactorily validated these predictions using several benchmark sets. The predictions of EWS-FL1 and FUS-DDIT3 also correlate with results of high-throughput drug screening. To our best knowledge, this is the first approach for inferring pathways of fusions.

We present a computational framework, FusionPathway, to infer the oncogenesis pathways of a fusion and help develop therapeutic strategies in these pathways for patients harboring the fusion. In this work, we successfully validated the capabilities of this approach through its application to the well-studied BCR-ABL1 fusion and two undruggable fusions in sarcoma, EWS-FL1 and FUS-DDIT3. Especially, the predictions of EWS-FL1 and FUS-DDIT3 correlate well with results of high-throughput drug screening in sarcoma cells. Therefore, FusionPathway can be an effective method to infer pathways and potential therapeutic targets that are associated with those undruggable fusions. Our results of BCR-ABL1 also suggest that FusionPathway may be able to help elucidate pathway-dependent mechanisms of resistances to those kinase fusion-targeting therapies and develop strategies to overcome the resistances. In addition, the developed R package of FusionPathways (https://github.com/perwu/FusionPathway/) can help people easily apply our approach to study other important fusions in cancer.

Sonic Hedgehog Signaling Regulates Hematopoietic Stem/Progenitor Cell Activation during the Granulopoietic Response to Systemic Bacterial Infection

Activation and reprogramming of hematopoietic stem/progenitor cells play a critical role in the granulopoietic response to bacterial infection. Our current study determined the significance of Sonic hedgehog (SHH) signaling in the regulation of hematopoietic precursor cell activity during the host defense response to systemic bacterial infection. Bacteremia was induced in male Balb/c mice via intravenous injection (i.v.) of Escherichia coli (5 × 10⁷ CFUs/mouse). Control mice received i.v. saline. SHH protein level in bone marrow cell (BMC) lysates was markedly increased at both 24 and 48 h of bacteremia. By contrast, the amount of soluble SHH ligand in marrow elutes was significantly reduced. These contrasting alterations suggested that SHH ligand release from BMCs was reduced and/or binding of soluble SHH ligand to BMCs was enhanced. At both 12 and 24 h of bacteremia, SHH mRNA expression by BMCs was significantly upregulated. This upregulation of SHH mRNA expression was followed by a marked increase in SHH protein expression in BMCs. Activation of the ERK1/2–SP1 pathway was involved in mediating the upregulation of SHH gene expression. The major cell type showing the enhancement of SHH expression in the bone marrow was lineage positive cells. Gli1 positioned downstream of the SHH receptor activation serves as a key component of the hedgehog (HH) pathway. Primitive hematopoietic precursor cells exhibited the highest level of baseline Gli1 expression, suggesting that they were active cells responding to SHH ligand stimulation. Along with the increased expression of SHH in the bone marrow, expression of Gli1 by marrow cells was significantly upregulated at both mRNA and protein levels following bacteremia. This enhancement of Gli1 expression was correlated with activation of hematopoietic stem/progenitor cell proliferation. Mice with Gli1 gene deletion showed attenuation in activation of marrow hematopoietic stem/progenitor cell proliferation and inhibition of increase in blood granulocytes following bacteremia. Our results indicate that SHH signaling is critically important in the regulation of hematopoietic stem/progenitor cell activation and reprogramming during the granulopoietic response to serious bacterial infection.

Phase Ib Study of Glasdegib, a Hedgehog Pathway Inhibitor, in Combination with Standard Chemotherapy in Patients with AML or High-Risk MDS

Purpose: This open-label, multicenter, dose-finding, phase Ib study (NCT01546038) evaluated the safety, pharmacokinetics, pharmacodynamics, and clinical activity of the novel Hedgehog pathway Smoothened inhibitor glasdegib (PF-04449913) in patients (N = 52) with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS).Experimental Design: Glasdegib 100 or 200 mg was administered orally, once daily in 28-day cycles, in combination with low-dose cytarabine (arm A) or decitabine (arm B) to newly diagnosed patients considered not suitable for standard induction chemotherapy, and in combination with cytarabine/daunorubicin (arm C) to fit patients. The study followed a standard 3+3 dose-escalation design. The primary endpoint was dose-limiting toxicity (DLT). Ten additional patients were enrolled in expansion cohorts of arms A (n = 23) and C (n = 22) to confirm the recommended phase II dose (RP2D).Results: No DLTs were observed in arms A and B; 1 DLT (grade 4 neuropathy) occurred in arm C. The most common treatment-related nonhematologic adverse events were mostly grades 1 and 2 in all arms. Muscle spasms, dysgeusia, and alopecia were generally mild. Overall, 16 patients (31%) achieved a complete remission (CR)/CR with incomplete blood count recovery. Note that 100 mg daily was selected as the RP2D for glasdegib in combination with standard chemotherapies in the absence of an estimated MTD in this setting.Conclusions: Treatment with glasdegib in combination with standard chemotherapy was generally well-tolerated and consistent with prior findings, warranting further evaluation of glasdegib-based combinations in patients with AML or high-risk MDS. Clin Cancer Res; 24(10); 2294-303. ©2018 AACR.

Evaluation of the effect of new formulation, food, or a proton pump inhibitor on the relative bioavailability of the smoothened inhibitor glasdegib (PF-04449913) in healthy volunteers

PURPOSE

This phase I open-label study investigated the oral bioavailability of two novel maleate salt-based glasdegib (PF-04449913) tablet formulations (small- and large-particle size) relative to the current clinical formulation (diHCl salt-based). In addition, the effect of a gastric pH-altering agent (rabeprazole) and food on the pharmacokinetics of the large-particle size formulation of glasdegib were evaluated. The pharmacokinetics of glasdegib oral solution was also assessed.

METHODS

Thirty-four healthy subjects received glasdegib 100 mg as three different formulations in the fasted state (diHCl salt or small- or large-particle size maleate formulation); 13 received the large-particle maleate formulation (fed), and 14 concurrently with rabeprazole (fasted); six subjects received glasdegib 50 mg oral solution (fasted).

RESULTS

For both new tablet formulations of glasdegib, ratios (Test:Reference) of adjusted geometric means (90% confidence interval) of area under the concentration-time curve from 0 to infinity and maximum plasma concentration were within 80-125% compared with the diHCl formulation (fasted). For the large-particle size formulation (fed), these ratios were 86.3% (81.0-92.0%) and 75.7% (65.3-87.7%), respectively, compared with fasted. When the large-particle maleate formulation was administered concurrently with rabeprazole versus alone (fasted), these ratios were 111.9% (102.8-121.9%) and 87.2% (75.9-100.3%), respectively. The pharmacokinetics of oral solution was similar to the tablet.

CONCLUSIONS

The maleate salt-based tablet formulations were bioequivalent to the diHCl tablet formulation. The extent of the observed effect of a high-fat, high-calorie meal or concurrent rabeprazole treatment on glasdegib exposure is not considered clinically meaningful.

Antagonism between Hedgehog and Wnt signaling pathways regulates tumorigenicity

The crosstalk of multiple cellular signaling pathways is crucial in animal development and tissue homeostasis, and its dysregulation may result in tumor formation and metastasis. The Hedgehog (Hh) and Wnt signaling pathways are both considered to be essential regulators of cell proliferation, differentiation and oncogenesis. Recent studies have indicated that the Hh and Wnt signaling pathways are closely associated and involved in regulating embryogenesis and cellular differentiation. Hh signaling acts upstream of the Wnt signaling pathway, and negative regulates Wnt activity via secreted frizzled-related protein 1 (SFRP1), and the Wnt/β-catenin pathway downregulates Hh activity through glioma-associated oncogene homolog 3 transcriptional regulation. This evidence suggests that the imbalance of Hh and Wnt regulation serves a crucial role in cancer-associated processes. The activation of SFRP1, which inhibits Wnt, has been demonstrated to be an important cross-point between the two signaling pathways. The present study reviews the complex interaction between the Hh and Wnt signaling pathways in embryogenesis and tumorigenicity, and the role of SFRP1 as an important mediator associated with the dysregulation of the Hh and Wnt signaling pathways.