Phase 1 dose escalation multicenter trial of pracinostat alone and in combination with azacitidine in patients with advanced hematologic malignancies

Pracinostat combined with azacitidine in newly diagnosed adult acute myeloid leukemia (AML) patients unfit for standard induction chemotherapy: PRIMULA phase III study

Non-intensive therapies such as the hypomethylating agent (HMA) azacitidine (AZA) have been used in patients with AML ineligible for intensive induction chemotherapy (IC) or stem cell transplant due to advanced age, comorbidities, and/or risk factors. However, response rates and survival remain dismal. Pre-clinical studies indicate the epigenetic combination of HMAs and HDAC inhibitors induce re-expression of silenced genes synergistically. The activity of pracinostat, an oral pan-HDAC inhibitor, has been shown in xenograft tumor models of AML and promising efficacy was seen in a Phase 2 study. This Phase 3 study (NCT03151408) evaluated the efficacy/safety of pracinostat administered with AZA in adult patients with newly diagnosed AML ineligible to receive IC. Patients were randomized to either pracinostat plus AZA or placebo/AZA and stratified by cytogenetic risk and ECOG status. As planned, an interim analysis was performed when 232/390 events (deaths) occurred. A total of 406 patients were randomized (203/group) at the time of the analysis. Median overall survival was 9.95 months for both treatment groups (p=0.8275). There was no significant difference between treatments in secondary efficacy endpoints, reflecting a lack of clinical response. This study did not show a benefit of adding pracinostat to AZA in elderly patients unfit for IC.

A novel prognostic signature contributes to precision treatment in colon adenocarcinoma with KRAS mutation

BACKGROUND

Approximately 40% of colon cancer harbor Kirsten rat sarcoma viral oncogene ( KRAS ) mutations, but the prognostic value of KRAS mutations in colon cancer is still controversial.

METHODS

We enrolled 412 colon adenocarcinoma (COAD) patients with KRAS mutations, 644 COAD patients with KRAS wild-type and 357 COAD patients lacking information on KRAS status from five independent cohorts. A random forest model was developed to estimate the KRAS status. The prognostic signature was established using least absolute shrinkage and selection operator-Cox regression and evaluated by Kaplan-Meier survival analysis, multivariate-Cox analysis, receiver operating characteristic curve and nomogram. The expression data of KRAS -mutant COAD cell lines from the Cancer Cell Line Encyclopedia database and the corresponding drug sensitivity data from the Genomics of Drug Sensitivity in Cancer database were used for potential target and agent exploration.

RESULTS

We established a 36-gene prognostic signature classifying the KRAS -mutant COAD as high and low risk. High risk patients had inferior prognoses compared to those with low risk, while the signature failed to distinguish the prognosis of COAD with KRAS wild-type. The risk score was the independent prognostic factor for KRAS -mutant COAD and we further fabricated the nomograms with good predictive efficiency. Moreover, we suggested FMNL1 as a potential drug target and three drugs as potential therapeutic agents for KRAS -mutant COAD with high risk.

CONCLUSION

We established a precise 36-gene prognostic signature with great performance in prognosis prediction of KRAS -mutant COAD providing a new strategy for personalized prognosis management and precision treatment for KRAS -mutant COAD.

Epigenetic targeting to enhance acute myeloid leukemia-directed immunotherapy

AML is a malignant disease of hematopoietic progenitor cells with unsatisfactory treatment outcome, especially in patients that are ineligible for intensive chemotherapy. Immunotherapy, comprising checkpoint inhibition, T-cell engaging antibody constructs, and cellular therapies, has dramatically improved the outcome of patients with solid tumors and lymphatic neoplasms. In AML, these approaches have been far less successful. Discussed reasons are the relatively low mutational burden of AML blasts and the difficulty in defining AML-specific antigens not expressed on hematopoietic progenitor cells. On the other hand, epigenetic dysregulation is an essential driver of leukemogenesis, and non-selective hypomethylating agents (HMAs) are the current backbone of non-intensive treatment. The first clinical trials that evaluated whether HMAs may improve immune checkpoint inhibitors' efficacy showed modest efficacy except for the anti-CD47 antibody that was substantially more efficient against AML when combined with azacitidine. Combining bispecific antibodies or cellular treatments with HMAs is subject to ongoing clinical investigation, and efficacy data are awaited shortly. More selective second-generation inhibitors targeting specific chromatin regulators have demonstrated promising preclinical activity against AML and are currently evaluated in clinical trials. These drugs that commonly cause leukemia cell differentiation potentially sensitize AML to immune-based treatments by co-regulating immune checkpoints, providing a pro-inflammatory environment, and inducing (neo)-antigen expression. Combining selective targeted epigenetic drugs with (cellular) immunotherapy is, therefore, a promising approach to avoid unintended effects and augment efficacy. Future studies will provide detailed information on how these compounds influence specific immune functions that may enable translation into clinical assessment.

Acute myeloid leukemia in the medically unfit elderly patients

Acute Myeloid Leukemia is a clonal proliferative disorder whose incidence increases with age. While studies have shown that the elderly medically unfit patients have poorer outcomes with intensive chemotherapy, a vast majority of them are deemed ineligible for intensive chemotherapy. Multiple studies have also shown that poor performance status prior to treatment initiation affects the prognosis. An accurate comprehensive assessment is hence vital to the selection of such patients. The chemotherapy agents that have been used for AML in the medically unfit patients have also changed significantly in the past few years. In this review we focus on the importance of comprehensive geriatric assessment prior to chemotherapy initiation among patients who are 75 years and older and the treatment approaches available for the medically unfit, Acute Myeloid Leukemia patients.

An Update of Epigenetic Drugs for the Treatment of Cancers and Brain Diseases: A Comprehensive Review

Epigenetics has long been recognized as a significant field in biology and is defined as the investigation of any alteration in gene expression patterns that is not attributed to changes in the DNA sequences. Epigenetic marks, including histone modifications, non-coding RNAs, and DNA methylation, play crucial roles in gene regulation. Numerous studies in humans have been carried out on single-nucleotide resolution of DNA methylation, the CpG island, new histone modifications, and genome-wide nucleosome positioning. These studies indicate that epigenetic mutations and aberrant placement of these epigenetic marks play a critical role in causing the disease. Consequently, significant development has occurred in biomedical research in identifying epigenetic mechanisms, their interactions, and changes in health and disease conditions. The purpose of this review article is to provide comprehensive information about the different types of diseases caused by alterations in epigenetic factors such as DNA methylation and histone acetylation or methylation. Recent studies reported that epigenetics could influence the evolution of human cancer via aberrant methylation of gene promoter regions, which is associated with reduced gene function. Furthermore, DNA methyltransferases (DNMTs) in the DNA methylation process as well as histone acetyltransferases (HATs)/histone deacetylases (HDACs) and histone methyltransferases (HMTs)/demethylases (HDMs) in histone modifications play important roles both in the catalysis and inhibition of target gene transcription and in many other DNA processes such as repair, replication, and recombination. Dysfunction in these enzymes leads to epigenetic disorders and, as a result, various diseases such as cancers and brain diseases. Consequently, the knowledge of how to modify aberrant DNA methylation as well as aberrant histone acetylation or methylation via inhibitors by using epigenetic drugs can be a suitable therapeutic approach for a number of diseases. Using the synergistic effects of DNA methylation and histone modification inhibitors, it is hoped that many epigenetic defects will be treated in the future. Numerous studies have demonstrated a link between epigenetic marks and their effects on brain and cancer diseases. Designing appropriate drugs could provide novel strategies for the management of these diseases in the near future.

Prediction of survival with lower intensity therapy among older patients with acute myeloid leukemia

BACKGROUND

The aim of this study was to develop a prognostic model for survival in older/unfit patients with newly diagnosed acute myeloid leukemia (AML) who were treated with lower-intensity chemotherapy regimens.

METHODS

The authors reviewed all older/unfit patients with newly diagnosed AML who received lower-intensity chemotherapy from 2000 until 2020 at their institution. A total of 1462 patients were included. They were divided (3:1 basis) into a training (n = 1088) and a validation group (n = 374).

RESULTS

In the training cohort of 1088 patients (median age, 72 years), the multivariate analysis identified 11 consistent independent adverse factors associated with survival: older age, therapy-related myeloid neoplasm, existence of previous myelodysplastic syndrome or myeloproliferative neoplasms, poor performance status, pulmonary comorbidity, anemia, thrombocytopenia, elevated lactate dehydrogenase, cytogenetic abnormalities, and the presence of infection at diagnosis, and therapy not containing venetoclax. The 3-year survival rates were 52%, 24%, 10%, and 1% in favorable, intermediate, poor, and very poor risk, respectively. This survival model was validated in an independent cohort. In a subset of patients in whom molecular mutation profiles were performed in more recent times, adding the mutation profiles after accounting for the effects of previous factors identified IDH2 (favorable), NPM1 (favorable), and TP53 (unfavorable) mutations as molecular prognostic factors.

CONCLUSION

The proposed survival model with lower-intensity chemotherapy in older/unfit patients with newly diagnosed AML may help to advise patients on their expected outcome, to propose different strategies in first complete remission, and to compare the results of different existing or future investigational therapies.

PLAIN LANGUAGE SUMMARY

Lower intensity therapy can be considered for older patients to avoid severe toxicities and adverse events. However, survival prediction in AML was commonly developed in patients who received intensive chemotherapy. In this study, we have proposed a survival model to guide therapeutic approach in older patients who received lower-intensity therapy.

Phase 1 study of belinostat and adavosertib in patients with relapsed or refractory myeloid malignancies

PURPOSE

Belinostat is an intravenous histone deacetylase inhibitor with approval for T-cell lymphomas. Adavosertib is a first in class oral Wee1 inhibitor. Preclinical studies of the combination demonstrated synergy in various human acute myeloid leukemia (AML) lines as well as AML xenograft mouse models.

EXPERIMENTAL DESIGN

This was a phase 1 dose-escalation study of belinostat and adavosertib in patients with relapsed/refractory AML and myelodysplastic syndrome (MDS). Patients received both drugs on days 1-5 and 8-12 of a 21-day cycle. Safety and toxicity were monitored throughout the study. Plasma levels of both drugs were measured for pharmacokinetic analysis. Response was determined by standard criteria including bone marrow biopsy.

RESULTS

Twenty patients were enrolled and treated at 4 dose levels. A grade 4 cytokine release syndrome at dose level 4 (adavosertib 225 mg/day; belinostat 1000 mg/m2) qualified as a dose-limiting toxicity event. The most common non-hematologic treatment-related adverse events were nausea, vomiting, diarrhea, dysgeusia, and fatigue. No responses were seen. The study was terminated prior to maximum tolerated dose/recommended phase 2 dose determination.

CONCLUSIONS

The combination of belinostat and adavosertib at the tested dose levels was feasible but without efficacy signals in the relapsed/refractory MDS/AML population.

Epimutations and Their Effect on Chromatin Organization: Exciting Avenues for Cancer Treatment

The three-dimensional architecture of genomes is complex. It is organized as fibers, loops, and domains that form high-order structures. By using different chromosome conformation techniques, the complex relationship between transcription and genome organization in the three-dimensional organization of genomes has been deciphered. Epigenetic changes, such as DNA methylation and histone modification, are the hallmark of cancers. Tumor initiation, progression, and metastasis are linked to these epigenetic modifications. Epigenetic inhibitors can reverse these altered modifications. A number of epigenetic inhibitors have been approved by FDA that target DNA methylation and histone modification. This review discusses the techniques involved in studying the three-dimensional organization of genomes, DNA methylation and histone modification, epigenetic deregulation in cancer, and epigenetic therapies targeting the tumor.

Functional Drug Screening of Small Molecule Inhibitors of Epigenetic Modifiers in Refractory AML Patients

The use of inhibitors of epigenetic modifiers in the treatment of acute myeloid leukemia (AML) has become increasingly appealing due to the highly epigenetic nature of the disease. We evaluated a library of 164 epigenetic compounds in a cohort of 9 heterogeneous AML patients using an ex vivo drug screen. AML blasts were isolated from bone marrow biopsies according to established protocols and treatment response to the epigenetic library was evaluated. We find that 11 histone deacetylase (HDAC) inhibitors, which act upon mechanisms of cell cycle arrest and apoptotic pathways through inhibition of zinc-dependent classes of HDACs, showed efficacy in all patient-derived samples. Other compounds, including bromodomain and extraterminal domain (BET) protein inhibitors, showed efficacy in most samples. Specifically, HDAC inhibitors are already clinically available and can be repurposed for use in AML. Results in this cohort of AML patient-derived samples reveal several epigenetic compounds with high anti-blast activity in all samples, despite the molecular diversity of the disease. These results further enforce the notion that AML is a predominantly epigenetic disease and that similar epigenetic mechanisms may underlie disease development and progression in all patients, despite differences in genetic mutations.

E-Cadherin-Deficient Epithelial Cells Are Sensitive to HDAC Inhibitors

Inactivating germline mutations in the CDH1 gene (encoding the E-cadherin protein) are the genetic hallmark of hereditary diffuse gastric cancer (HDGC), and somatic CDH1 mutations are an early event in the development of sporadic diffuse gastric cancer (DGC) and lobular breast cancer (LBC). In this study, histone deacetylase (HDAC) inhibitors were tested for their ability to preferentially inhibit the growth of human cell lines (MCF10A and NCI-N87) and murine organoids lacking CDH1 expression. CDH1^-/- breast and gastric cells were more sensitive to the pan-HDAC inhibitors entinostat, pracinostat, mocetinostat and vorinostat than wild-type cells, with an elevated growth inhibition that was, in part, attributable to increased apoptosis. CDH1-null cells were also sensitive to more class-specific HDAC inhibitors, but compared to the pan-inhibitors, these effects were less robust to genetic background. Increased sensitivity to entinostat was also observed in gastric organoids with both Cdh1 and Tp53 deletions. However, the deletion of Tp53 largely abrogated the sensitivity of the Cdh1-null organoids to pracinostat and mocetinostat. Finally, entinostat enhanced Cdh1 expression in heterozygous Cdh1^+/- murine organoids. In conclusion, entinostat is a promising drug for the chemoprevention and/or treatment of HDGC and may also be beneficial for the treatment of sporadic CDH1-deficient cancers.

Epigenetic dysregulation in myeloid malignancies

Epigenetic deregulation is now a well-recognized -though not yet fully understood- mechanism that contributes to the development and progression of myeloid malignancies. In the past 15 years, next generation sequencing studies have revealed patterns of aberrant DNA methylation, altered chromatin states, and mutations in chromatin modifiers across the spectrum of myeloid malignancies. Studies into the mechanisms that drive these diseases through mouse modeling have helped identify new avenues for therapeutic interventions, from initial treatment to resistant, relapsed disease. This is particularly significant when chemotherapy with cytotoxic agents remains the general standard of care. In this review, we will discuss some of the recent findings of epigenetic mechanisms and how these are informing the development of more targeted strategies for therapeutic intervention in myeloid malignancies.

Small molecules in targeted cancer therapy: advances, challenges, and future perspectives

Due to the advantages in efficacy and safety compared with traditional chemotherapy drugs, targeted therapeutic drugs have become mainstream cancer treatments. Since the first tyrosine kinase inhibitor imatinib was approved to enter the market by the US Food and Drug Administration (FDA) in 2001, an increasing number of small-molecule targeted drugs have been developed for the treatment of malignancies. By December 2020, 89 small-molecule targeted antitumor drugs have been approved by the US FDA and the National Medical Products Administration (NMPA) of China. Despite great progress, small-molecule targeted anti-cancer drugs still face many challenges, such as a low response rate and drug resistance. To better promote the development of targeted anti-cancer drugs, we conducted a comprehensive review of small-molecule targeted anti-cancer drugs according to the target classification. We present all the approved drugs as well as important drug candidates in clinical trials for each target, discuss the current challenges, and provide insights and perspectives for the research and development of anti-cancer drugs.

Study of the antilymphoma activity of pracinostat reveals different sensitivities of DLBCL cells to HDAC inhibitors

Histone deacetylase inhibitors (HDACis) are antitumor agents with distinct efficacy in hematologic tumors. Pracinostat is a pan-HDACi with promising early clinical activity. However, similar to other HDACis, its activity as a single agent is limited. Diffuse large B-cell lymphoma (DLBCL) includes distinct molecular subsets or metabolically defined subtypes that rely in different ways on the B-cell receptor signaling pathway, oxidative phosphorylation, and glycolysis for their survival. The antitumor activity of pracinostat has not been determined in lymphomas. We performed preclinical in vitro activity screening of 60 lymphoma cell lines that included 25 DLBCLs. DLBCL cells belonging to distinct metabolic subtypes were treated with HDACis for 6 hours or 14 days followed by transcriptional profiling. DLBCL xenograft models enabled assessment of the in vivo antilymphoma activity of pracinostat. Combination treatments with pracinostat plus 10 other antilymphoma agents were performed. Western blot was used to assess acetylation levels of histone and nonhistone proteins after HDACi treatment. Robust antiproliferative activity was observed across all lymphoma histotypes represented. Focusing on DLBCL, we identified a low-sensitivity subset that almost exclusively consists of the oxidative phosphorylation (OxPhos)-DLBCL metabolic subtype. OxPhos-DLBCL cells also showed poorer sensitivity to other HDACis, including vorinostat. Transcriptomic analysis revealed fewer modulated transcripts but an enrichment of antioxidant pathway genes after HDACi treatment of OxPhos-DLBCLs compared with high-sensitivity B-cell receptor (BCR)-DLBCLs. Pharmacologic inhibition of antioxidant production rescued sensitivity of OxPhos-DLBCLs to pracinostat whereas BCR-DLBCLs were unaffected. Our study provides novel insights into the antilymphoma activity of pracinostat and identifies a differential response of DLBCL metabolic subtypes to HDACis.

Do histone deacytelase inhibitors and azacitidine combination hold potential as an effective treatment for high/very-high risk myelodysplastic syndromes?

INTRODUCTION

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disorder, predominantly seen in elderly patients with variable clinical outcome and high tendency for leukemic transformation. Allogeneic hematopoietic stem cell transplantation (alloHCT) is the only potential curative option but limited to a selected group of patients, for the rest, disease control is the goal and enrollment in clinical trial is always encouraged. Mechanistically, azacitidine (AZA) and histone deacetylase inhibitors (HDACi) is a promising combination for patient with high-risk MDS to improve clinical outcome, but the combination has yet to demonstrate its efficacy in randomized clinical trials.

AREAS COVERED

In this review the authors discuss the salient features, pharmacokinetics, safety, and efficacy data of AZA and HDACi combination in patients with MDS. Future strategies on how to possibly improve clinical outcome of patients with MDS using AZA and HDACi combination are discussed.

EXPERT OPINION

Pre-clinical and clinical data demonstrated synergistic activity of AZA and HDACi in patients with MDS. So far, the efficacy of this combination is undermined by toxicity; mainly gastrointestinal. Careful patient selection and alternative dosing schedule is needed in future clinical trials to evaluate clinical outcome.

Recent developments in epigenetic cancer therapeutics: clinical advancement and emerging trends

Epigenetic drug discovery field has evidenced significant advancement in the recent times. A plethora of small molecule inhibitors have progressed to clinical stage investigations and are being explored exhaustively to ascertain conclusive benefits in diverse malignancies. Literature precedents indicates that substantial amount of efforts were directed towards the use of epigenetic tools in monotherapy as well as in combination regimens at the clinical level, however, the preclinical/preliminary explorations were inclined towards the identification of prudent approaches that can leverage the anticancer potential of small molecule epigenetic inhibitors as single agents only. This review article presents an update of FDA approved epigenetic drugs along with the epigenetic inhibitors undergoing clinical stage investigations in different cancer types. A detailed discussion of the pragmatic strategies that are expected to steer the progress of the epigenetic therapy through the implementation of emerging approaches such as PROTACS and CRISPR/Cas9 along with logical ways for scaffold fabrication to selectively approach the enzyme isoforms in pursuit of garnering amplified antitumor effects has been covered. In addition, the compilation also presents the rational strategies for the construction of multi-targeting scaffold assemblages employing previously identified pharmacophores as potential alternatives to the combination therapy.

Synthesis of Novel Tryptamine Derivatives and Their Biological Activity as Antitumor Agents

We synthesized five novel tryptamine derivatives characterized by the presence of an azelayl chain or of a 1,1,1-trichloroethyl group, in turn connected to another heterocyclic scaffold. The combination of tryptamin-, 1,1,1-trichloroethyl- and 2-aminopyrimidinyl- moieties produced compound 9 identified as the most active compound in hematological cancer cell lines (IC₅₀ = 0.57-65.32 μM). Moreover, keeping constant the presence of the tryptaminic scaffold and binding it to the azelayl moiety, the compounds maintain biological activity. Compound 13 is still active against hematological cancer cell lines and shows a selective effect only on HT29 cells (IC₅₀ = 0.006 µM) among solid tumor models. Compound 14 loses activity on all leukemic lines, while showing a high level of toxicity on all solid tumor lines tested (IC₅₀ 0.0015-0.469 µM).

Phase 1 study of belinostat (PXD-101) and bortezomib (Velcade, PS-341) in patients with relapsed or refractory acute leukemia and myelodysplastic syndrome

We report the results of a phase 1 dose-escalation study of belinostat and bortezomib in adult patients with acute leukemia or MDS or CML with blast crisis. Thirty-eight patients received IV belinostat days 1-5 and 8-12 with IV bortezomib days 1, 4, 8, and 11 every 21 days. QTc prolongation was the only identified DLT. The RP2Ds were 1.3 mg/m² bortezomib and 1000 mg/m² belinostat. One patient with highly refractory MLL-ENL rearranged biphenotypic AML with multiple karyotypic aberrations had a complete pathologic and karyotypic response. One patient with post-MPN AML remained on study with stable disease (SD) for 32 cycles. Whole-exome sequencing revealed no aberrations in the first patient and a hyper-mutator genotype in the second. Eighteen patients had a best response of SD. We conclude that this treatment strategy is feasible but has limited activity in this population. Nevertheless, the factors that predict exceptional responses to this strategy warrant further investigation.

Small Molecules Targeting HATs, HDACs, and BRDs in Cancer Therapy

Evidence for research over the past decade shows that epigenetic regulation mechanisms run through the development and prognosis of tumors. Therefore, small molecular compounds targeting epigenetic regulation have become a research hotspot in the development of cancer therapeutic drugs. According to the obvious abnormality of histone acetylation when tumors occur, it suggests that histone acetylation modification plays an important role in the process of tumorigenesis. Currently, as a new potential anti-cancer therapeutic drugs, many active small molecules that target histone acetylation regulatory enzymes or proteins such as histone deacetylases (HDACs), histone acetyltransferase (HATs) and bromodomains (BRDs) have been developed to restore abnormal histone acetylation levels to normal. In this review, we will focus on summarizing the changes of histone acetylation levels during tumorigenesis, as well as the possible pharmacological mechanisms of small molecules that target histone acetylation in cancer treatment.

Thirty Years of HDAC Inhibitors: 2020 Insight and Hindsight

It is now 30 years since the first report of a potent zinc-dependent histone deacetylase (HDAC) inhibitor appeared. Since then, five HDAC inhibitors have received regulatory approval for cancer chemotherapy while many others are in clinical development for oncology as well as other therapeutic indications. This Perspective reviews the biological and medicinal chemistry advances over the past 3 decades with an emphasis on the design of selective inhibitors that discriminate between the 11 human HDAC isoforms.

Targeting acute myeloid leukemia stem cells: Current therapies in development and potential strategies with new dimensions

High relapse rate of acute myeloid leukemia (AML) is still a crucial problem despite considerable advances in anti-cancer therapies. One crucial cause of relapse is the existence of leukemia stem cells (LSCs) with self-renewal ability, which contribute to repeated treatment resistance and recurrence. Treatments targeting LSCs, especially in combination with existing chemotherapy regimens or hematopoietic stem cell transplantation might help achieve a higher complete remission rate and improve overall survival. Many novel agents of different therapeutic strategies that aim to modulate LSCs self-renewal, proliferation, apoptosis, and differentiation are under investigation. In this review, we summarize the latest advances of different therapies in development based on the biological characteristics of LSCs, with particular attention on natural products, synthetic compounds, antibody therapies, and adoptive cell therapies that promote the LSC eradication. We also explore the causes of AML recurrence and proposed potential strategies with new dimensions for targeting LSCs in the future.

Emerging pharmacotherapies for elderly acute myeloid leukemia patients

INTRODUCTION

Acute myeloid leukemia (AML) is a disease mainly seen in the elderly, for which treatment is undergoing rapid changes. Although recent studies have supported the survival benefit of induction chemotherapy in fit patients and that of hypomethylating agents (HMAs) in non-induction candidates, treatment of this patient age population remains a significant challenge for the treating oncologist.

AREAS COVERED

In this review, we will examine effectiveness and safety outcomes of upcoming novel treatment strategies in elderly (≥60 years old) patients with AML, highlight the current literature and ongoing trials able to maximize therapeutic options in this heterogeneous patient population.

EXPERT OPINION

Current developments including new chemotherapeutic strategies and combinations of HMAs with novel drugs targeting epigenetic or immunomodulatory pathways are underway to improve patient survival and quality of life.

Pracinostat plus azacitidine in older patients with newly diagnosed acute myeloid leukemia: results of a phase 2 study

Pracinostat, a potent oral pan-histone deacetylase inhibitor with modest single-agent activity in acute myeloid leukemia (AML), has shown synergistic antitumor activity when combined with azacitidine. This single-group, multicenter phase 2 study assessed the safety and efficacy of pracinostat combined with azacitidine in patients who were at least 65 years old with newly diagnosed AML and who were ineligible for standard induction chemotherapy. Patients received pracinostat 60 mg/d, 3 d/wk, for 3 consecutive weeks, plus azacitidine 75 mg/m² daily for 7 days in a 28-day cycle. Primary endpoints were complete remission (CR), CR with incomplete count recovery (CRi), and morphologic leukemia-free state (MLFS) rates of the combination. Secondary endpoints included safety, progression-free survival (PFS), and overall survival (OS) of the regimen. Fifty patients (33 de novo, 12 secondary, and 5 therapy-related AML) were enrolled. Twenty-six patients (52%) achieved the primary endpoint of CR (42%), CRi (4%), and MLFS (6%). Median OS and PFS were 19.1 months (95% confidence interval [CI], 10-26.5 months) and 12.6 months (95% CI, 10-17.7 months), respectively, with a 1-year OS rate of 62%. Forty-three patients (86%) experienced at least 1 grade 3 or worse treatment-emergent adverse event with the combination, with infections (52%), thrombocytopenia (46%), and febrile neutropenia (44%) reported as the most common toxicities. The 30- and 60-day all-cause mortality rates were 2% and 10%, respectively. DNA sequencing revealed somatic mutations at baseline, and clearance rates correlated with response to treatment. Pracinostat plus azacitidine is a well-tolerated and active regimen in the frontline treatment of older patients with AML unfit for intensive therapy. A larger controlled trial is ongoing. This trial was registered at www.clinicaltrials.gov as #NCT01912274.

Evaluation of the bioequivalence and food effect on the bioavailability of CC-486 (oral azacitidine) tablets in adult patients with cancer

Purpose

CC-486 is an oral formulation of azacitidine that allows for extended dosing schedules to prolong azacitidine exposure to malignant cells and maximize clinical activity. CC-486 300 mg daily, administered for 14 or 21 days of 28-day treatment cycles, is currently under investigation in two ongoing phase III trials. The 300-mg daily dose in these studies is administered as two 150-mg tablets (Formulation A).

Methods

We evaluated the bioequivalence of one 300-mg CC-486 tablet (Formulation B) with Formulation A and food effect on Formulation B, in adult patients with cancer in a 2-stage crossover design study.

Results

The ratios of the geometric means of the maximum azacitidine plasma concentration (C_max) and of the area under the plasma concentration–time curve from time 0 extrapolated to infinity (AUC_∞) were 101.5% and 105.7%, demonstrating the bioequivalence of Formulations A and B. Formulation B was rapidly absorbed under fasted and fed conditions. The geometric mean of C_max was significantly decreased by ~ 21% in the fed state. Median T_max was reached at 2 h and 1 h post-dose in fed and fasted states, respectively (P < 0.001). Nevertheless, systemic drug exposure (AUC) in fed and fasted states was within the 80–125% boundaries of bioequivalence and differences in C_max and T_max are not expected to have a clinical impact.

Conclusion

The single 300-mg CC-486 tablet was bioequivalent to two 150-mg tablets, which have shown to be efficacious and generally well-tolerated in clinical trials, and can be taken with or without food.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04037-9) contains supplementary material, which is available to authorized users.

HDAC Inhibitors in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a hematological malignancy characterized by uncontrolled proliferation, differentiation arrest, and accumulation of immature myeloid progenitors. Although clinical advances in AML have been made, especially in young patients, long-term disease-free survival remains poor, making this disease an unmet therapeutic challenge. Epigenetic alterations and mutations in epigenetic regulators contribute to the pathogenesis of AML, supporting the rationale for the use of epigenetic drugs in patients with AML. While hypomethylating agents have already been approved in AML, the use of other epigenetic inhibitors, such as histone deacetylases (HDAC) inhibitors (HDACi), is under clinical development. HDACi such as Panobinostat, Vorinostat, and Tricostatin A have been shown to promote cell death, autophagy, apoptosis, or growth arrest in preclinical AML models, yet these inhibitors do not seem to be effective as monotherapies, but rather in combination with other drugs. In this review, we discuss the rationale for the use of different HDACi in patients with AML, the results of preclinical studies, and the results obtained in clinical trials. Although so far the results with HDACi in clinical trials in AML have been modest, there are some encouraging data from treatment with the HDACi Pracinostat in combination with DNA demethylating agents.

A phase II study of addition of pracinostat to a hypomethylating agent in patients with myelodysplastic syndromes who have not responded to previous hypomethylating agent therapy

Hypomethylating agents (HMAs) are standard of care for higher-risk myelodysplastic syndromes (MDS). However, less than half of patients achieve objective responses and most eventually lose their response. Pracinostat is a pan-histone deacetylase inhibitor with demonstrated activity in advanced myeloid malignancies. This phase II study explored the benefit of adding pracinostat to HMAs in MDS patients who did not respond to single-agent HMA treatment. The goal was to estimate the clinical improvement rate [complete remission (CR), marrow CR, partial response (PR) and haematological improvement]. Group 1 included patients with primary/secondary HMA failures; Group 2 included those who did not achieve response but had stable disease (SD) after single-agent HMAs. Forty-five patients (39 Group 1, 6 Group 2) received a median of 3 cycles. Among all patients, 1 (2%) had CR, 7 (16%) had marrow CR and 18 (40%) had SD; disease progression occurred in 3 (7%). Median overall survival was 5·7/5·6 months for Group 1/2. Grade ≥3 adverse events occurred in 38 patients (84%) leading to treatment discontinuation in 12 (33%). Adding pracinostat to HMAs did not improve outcomes in patients previously treated with HMAs. Frequent dose modifications/early discontinuation resulted in suboptimal drug exposure. A reduced pracinostat dose may improve tolerability and efficacy.

Novel therapies in low- and high-risk myelodysplastic syndrome

Introduction: Myelodysplastic syndromes (MDS) comprise a heterogeneous group of myeloid neoplasms with diverse clinical courses. The revised version of the international prognostic scoring system (IPSS-R) provides risk stratification into 5 different groups. Areas covered: For lower-risk patients, red blood cell transfusions and iron chelation are the backbone of supportive care. In addition, erythropoiesis-stimulating agents (ESA) are used to ameliorate anemia. Lenalidomide is approved for the treatment of lower-risk patients with del(5q) who are transfusion-dependent. Patients with higher-risk disease should be offered allogeneic stem cell transplantation whenever possible. If they are unfit for transplantation or an appropriate donor cannot be found, hypomethylating agents may be used. Expert opinion: New therapeutic options for lower-risk patients include thrombopoietin analogues, the TGF-beta family ligand trapping drug Luspatercept, and the telomerase inhibitor Imetelstat. Combinations of hypomethylating agents (HMA) with other compounds, and inhibitors of bcl2, such as venetoclax are being developed for higher-risk patients. Finally, hypomethylating agents in combination with donor lymphocytes may lead to long-term remission following molecular or hematological relapse after allogeneic SCT.

Safety and Tolerability of Histone Deacetylase (HDAC) Inhibitors in Oncology

Histone deacetylases (HDACs) are expressed at increased levels in cells of various malignancies, and the use of HDAC inhibitors has improved outcomes in patients with haematological malignancies (T-cell lymphomas and multiple myeloma). However, they are not as effective in solid tumours. Five agents are currently approved under various jurisdictions, namely belinostat, chidamide, panobinostat, romidepsin and vorinostat. These agents are associated with a range of class-related and agent-specific serious and/or severe adverse effects, notably myelosuppression, diarrhoea and various cardiac effects. Among the cardiac effects are ST-T segment abnormalities and QTc interval prolongation of the electrocardiogram, isolated cases of atrial fibrillation and, in rare instances, ventricular tachyarrhythmias. In order to improve the safety profile of this class of drugs as well as their efficacy in indications already approved and to further widen their indications, a large number of newer HDAC inhibitors with varying degrees of HDAC isoform selectivity have been synthesised and are currently under clinical development. Preliminary evidence from early studies suggests that they may be effective in non-haematological cancers as well when used in combination with other therapeutic modalities, but that they too appear to be associated with the above class-related adverse effects. As the database accumulates, the safety, efficacy and risk/benefit of the newer agents and their indications will become clearer.

Minor structural modifications to Pracinostat produce big changes in its biological responses

A series of compounds similar to Pracinostat that contained benzimidazole ring and N-hydroxyacrylamide attached at 5- or 6-position were designed, synthesized, and evaluated as HDAC inhibitors. It was interesting to find that the corresponding derivative 1 with N-hydroxyacrylamide attached at 5-position was a potent HDAC inhibitor while the others at 6-position were not. This is the first time to demonstrate the position difference plays important role in the HDAC inhibitory activities of the cinnamic hydroxamates.

Precision medicine in the treatment stratification of AML patients: challenges and progress

Recent advances in high throughput technologies have led to the generation of vast amounts of clinical data and the development of personalized medicine approaches in acute myeloid leukemia (AML). The ability to treat cancer patients based upon their individual molecular characteristics or drug sensitivity profiles is expected to significantly advance cancer treatment and improve the long-term survival of patients with refractory AML, for whom current treatment options are restricted to palliative approaches. The clinical development of omics-based and phenotypic screens, however, is limited by a number of bottlenecks including the generation of cost-effective high-throughput data, data interpretation and integration of multiple approaches, sample availability, clinically relevant timelines, and the development and education of multidisciplinary teams. Recently, a number of small clinical trials have shown survival benefits in patients treated based on personalized medicine approaches. While these preliminary studies are encouraging, larger trials are needed to evaluate the utility of these technologies in routine clinical settings.

Novel Agents for Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a complex hematological disease characterized by genetic and clinical heterogeneity. Recent advances in the understanding of AML pathogenesis have paved the way for the development of new agents targeting specific molecules or mechanisms that contribute to finally move beyond the current standard of care, which is "3 + 7" regimen. In particular, new therapeutic options such as targeted therapies (midostaurin and enasidenib), monoclonal antibodies (gemtuzumab ozogamicin), and a novel liposomal formulation of cytarabine and daunorubicin (CPX-351) have been recently approved, and will be soon available for the treatment of adult patients with AML. In this review, we will present and describe these recently approved drugs as well as selected novel agents against AML that are currently under investigation, and show the most promising results as monotherapy or in combination with chemotherapy. The selection of these emerging treatments is based on the authors' opinion.

Leveraging Hypomethylating Agents for Better MDS Therapy

PURPOSE OF REVIEW

Myelodysplastic syndrome (MDS) is a clinically and molecularly heterogeneous disease, which primarily occurs in older adults. Although hypomethylating agents have survival benefit and are the current standard of care, many MDS patients will not garner a response from therapy. For those who do respond, most responses are not durable, and the only hope for a cure is allogeneic stem cell transplant. New therapies to improve outcomes are urgently needed.

RECENT FINDINGS

Clinical trials combining standard hypomethylating agents with novel experimental agents are underway in an effort to improve clinical outcomes in MDS patients. Several of these small molecules have demonstrated the ability to augment the response rates of hypomethylating agents alone, including complete remission rates, in both the front line and refractory settings. Combination approaches utilizing hypomethylating agents and novel-targeted therapies have demonstrated the ability to improve response rates in MDS patients in both the front line and salvage settings, and thus may change the standard of care.

Targeting cancer stem cells and their niche: perspectives for future therapeutic targets and strategies

A small subpopulation of cells within the bulk of tumors share features with somatic stem cells, in that, they are capable of self-renewal, they differentiate, and are highly resistant to conventional therapy. These cells have been referred to as cancer stem cells (CSCs). Recent reports support the central importance of a cancer stem cell-like niche that appears to help foster the generation and maintenance of CSCs. In response to signals provided by this microenvironment, CSCs express the tumorigenic characteristics that can drive tumor metastasis by the induction of epithelial-mesenchymal-transition (EMT) that in turn fosters the migration and recolonization of the cells as secondary tumors within metastatic niches. We summarize here recent advances in cancer stem cell research including the characterization of their genetic and epigenetic features, metabolic specialities, and crosstalk with aging-associated processes. Potential strategies for targeting CSCs, and their niche, by regulating CSCs plasticity, or therapeutic sensitivity is discussed. Finally, it is hoped that new strategies and related therapeutic approaches as outlined here may help prevent the formation of the metastatic niche, as well as counter tumor progression and metastatic growth.

A phase 1 trial of vadastuximab talirine combined with hypomethylating agents in patients with CD33-positive AML

Treatment of acute myeloid leukemia (AML) among the elderly is challenging because of intolerance of intensive therapy and therapy-resistant biology. Hypomethylating agents (HMAs) are commonly used, with suboptimal outcomes. Vadastuximab talirine is a CD33-directed antibody conjugated to pyrrolobenzodiazepine (PBD) dimers. Preclinically, HMAs followed by vadastuximab talirine produced upregulated CD33 expression, increased DNA incorporation by PBD, and enhanced cytotoxicity. A combination cohort in a phase 1 study (NCT01902329) assessed safety, tolerability, and activity of vadastuximab talirine with HMAs. Those eligible had Eastern Cooperative Oncology Group status 0 to 1 and previously untreated CD33-positive AML, and declined intensive therapy. Vadastuximab talirine was administered intravenously at 10 μg/kg on last day of HMA (azacitidine or decitabine) infusion in 4-week cycles. Among 53 patients treated, the median age was 75 years. Patients had adverse (38%) or intermediate (62%) cytogenetic risk. Median treatment duration was 19.3 weeks. No dose-limiting toxicities were reported. The majority of adverse events were a result of myelosuppression, with some causing therapy delays. Thirty- and 60-day mortality rates were 2% and 8%, respectively. The composite remission rate (complete remission [CR] and CR with incomplete blood count recovery) was 70%. Fifty-one percent of remissions were minimal residual disease-negative by flow cytometry. Similarly high remission rates were observed in patients with secondary AML, aged at least 75 years, and with adverse cytogenetic risk. Median relapse-free survival and overall survival were 7.7 and 11.3 months, respectively. Compared with historical data for HMA monotherapy, the combination of vadastuximab talirine with HMAs produced a high remission rate, but was accompanied by increased hematologic toxicity.