Panobinostat as part of induction and maintenance for elderly patients with newly diagnosed acute myeloid leukemia: phase Ib/II panobidara study

Anticancer properties of histone deacetylase inhibitors - what is their potential?

INTRODUCTION

Histone modifications are crucial epigenetic mechanisms for regulating gene expression. Histone acetyltransferases and deacetylases (HDACs) catalyze histone acetylation, a process that mediates transcription. Over recent decades, studies have demonstrated that targeting histone acetylation can be effective in cancer treatment, leading to the development and approval of several HDAC inhibitors.

AREAS COVERED

A comprehensive literature review was conducted using the PubMed database to identify studies evaluating the anticancer efficacy of approved and novel HDAC inhibitors.

EXPERT OPINION

Accumulating evidence highlights the promising benefits of combining HDAC inhibitors with other anticancer agents. Additionally, HDAC-targeting therapeutics could enhance the sensitivity of cancer cells to chemotherapeutics or targeted tyrosine kinase inhibitors, thereby improving overall treatment outcomes. Future clinical studies must focus on optimizing combination therapies to ensure efficacy while maintaining manageable safety profiles.

Simultaneous inhibition of FLT3 and HDAC by novel 6-ethylpyrazine-2-Carboxamide derivatives provides therapeutic advantages in acute myelocytic leukemia

Synergetic inhibition of FMS-like tyrosine kinase 3 (FLT3) and histone deacetylase (HDAC) by small molecule chimera presents a promising therapeutic approach for acute myeloid leukemia (AML) with FLT3 mutations. In this study, we first observed that the combined use of FLT3 inhibitor gilteritinib and HDAC inhibitor vorinostat increased the survival rate of leukemia xenograft mouse model. Then, we employed a pharmacophore fusion strategy to develop a novel series of FLT3/HDAC dual inhibitors. Among them, compound 25h demonstrated superior inhibitory activity against both FLT3 and HDAC. In particular, compound 25h exhibited enhanced anti-proliferation activity against MOLM-13 cells in comparison to gilteritinib, vorinostat, and their combination, while maintaining reduced cytotoxicity towards normal cells. Mechanistically, the heightened anti-tumor effect of compound 25h was attributed to its more potent regulation of intracellular pathways, notably phosphorylation of ERK, compared to single drug and combination treatments. Furthermore, compound 25h demonstrated superior anti-tumor efficacy in the MOLM-13 xenograft model compared to combination therapy, along with reduced in vivo toxicity. To conclude, we have identified a novel FLT3/HDAC dual inhibitor that could serve as a potential candidate for the treatment of AML.

Guideline for treating relapsed or refractory myeloid leukemia in children with Down syndrome

Treatment of relapsed and refractory myeloid leukemia in Down syndrome (r/r ML-DS) poses significant challenges, as prognosis is dire and there is no established standard treatment. This guideline provides treatment recommendations based on a literature review and collection of expert opinions, aiming to improve overall and event-free survival of patients. Treatment options include fludarabine and cytarabine (FLA) ± gemtuzumab ozogamicin (GO), azacytidine (AZA) ± panobinostat, and hematopoietic stem cell transplantation (HSCT). Preferred approaches are AZA ± panobinostat for cases with low blast count or FLA ± GO for cases with high blast count, followed by HSCT after remission. Further research is crucial for the investigation of targeted therapies (e.g., BH3 mimetics, LSD1, JAK inhibitors).

Maintenance therapy in acute myeloid leukemia: advances and controversies

The last decade has seen steadfast progress in drug development in acute myeloid leukemia (AML) which has moved progressively towards genomic-based therapy. With these advances, outcomes in AML have improved but remains far from satisfactory. One approach towards preventing relapse in AML is to use maintenance therapy in patients, after attaining remission. Allogeneic hematopoietic stem cell transplantation (HSCT) is an effective post-remission therapy that has been proven to reduce the risk of relapse. However, in patients who are ineligible for HSCT or have a high risk of relapse, other effective measures to prevent relapse are needed. There is also a need for post-HSCT maintenance to reduce relapse in high-risk subsets. Over the last 3 decades maintenance therapy in AML has evolved from the use of chemotherapeutic agents to more targeted therapies and better modulation of the immune system. Unfortunately, improvements in survival outcomes as a result of using these agents have not been consistently demonstrated in clinical trials. To derive the optimum benefit from maintenance therapy the time points of therapy initiation need to be defined and therapy must be selected precisely with respect to the AML genetics and risk stratification, prior treatment exposure, transplant eligibility, expected toxicity and the patient's clinical profile and desires. The far-reaching goal is to facilitate patients with AML in remission to achieve a normal quality of life while improving remission duration and overall survival. The QUAZAR trial was a welcome step towards a safe maintenance drug that is easy to administer and showed survival benefit but leaves many open issues for discussion. In this review we will discuss these issues, highlighting the development of AML maintenance therapies over the last 3 decades.

Epigenetic Activation of Plasmacytoid DCs Drives IFNAR-Dependent Therapeutic Differentiation of AML

Pharmacologic inhibition of epigenetic enzymes can have therapeutic benefit against hematologic malignancies. In addition to affecting tumor cell growth and proliferation, these epigenetic agents may induce antitumor immunity. Here, we discovered a novel immunoregulatory mechanism through inhibition of histone deacetylases (HDAC). In models of acute myeloid leukemia (AML), leukemia cell differentiation and therapeutic benefit mediated by the HDAC inhibitor (HDACi) panobinostat required activation of the type I interferon (IFN) pathway. Plasmacytoid dendritic cells (pDC) produced type I IFN after panobinostat treatment, through transcriptional activation of IFN genes concomitant with increased H3K27 acetylation at these loci. Depletion of pDCs abrogated panobinostat-mediated induction of type I IFN signaling in leukemia cells and impaired therapeutic efficacy, whereas combined treatment with panobinostat and IFNα improved outcomes in preclinical models. These discoveries offer a new therapeutic approach for AML and demonstrate that epigenetic rewiring of pDCs enhances antitumor immunity, opening the possibility of exploiting this approach for immunotherapies.

SIGNIFICANCE

We demonstrate that HDACis induce terminal differentiation of AML through epigenetic remodeling of pDCs, resulting in production of type I IFN that is important for the therapeutic effects of HDACis. The study demonstrates the important functional interplay between the immune system and leukemias in response to HDAC inhibition. This article is highlighted in the In This Issue feature, p. 1397.

The contributory roles of histone deacetylases (HDACs) in hematopoiesis regulation and possibilities for pharmacologic interventions in hematologic malignancies

Although the definitive role of epigenetic modulations in a wide range of hematologic malignancies, spanning from leukemia to lymphoma and multiple myeloma, has been evidenced, few articles reviewed the task. Given the high accessibility of histone deacetylase (HDACs) to necessary transcription factors involved in hematopoiesis, this review aims to outline physiologic impacts of these enzymes in normal hematopoiesis, and also to outline the original data obtained from international research laboratories on their regulatory role in the differentiation and maturation of different hematopoietic lineages. Questions on how aberrant expression of HDACs contributes to the formation of hematologic malignancies are also responded, because these classes of enzymes have a respectable share in the development, progression, and recurrence of leukemia, lymphoma, and multiple myeloma. The last section provides a special focus on the therapeutic perspectiveof HDACs inhibitors, either as single agents or in a combined-modal strategy, in these neoplasms. In conclusion, optimizing the dose and the design of more patient-tailored inhibitors, while maintaining low toxicity against normal cells, will help improve clinical outcomes of HDAC inhibitors in hematologic malignancies.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

Recent Clinical Update of Acute Myeloid Leukemia: Focus on Epigenetic Therapies

Acute myeloid leukemia (AML) is a complicated disease characterized by genetic heterogeneity and simultaneous alterations in multiple genes. For decades, its only curative method has been intensive induction chemotherapy with or without allogeneic hematopoietic stem cell transplantation, and this approach cannot be applied to elderly patients, who make up more than 50% of AML patients. Recent advances in genomics facilitated the elucidation of various mutations related to AML, and the most frequent mutations were discovered in epigenetic regulators. Alterations to epigenetic modifications that are essential for normal cell biology, including DNA methylation and histone acetylation, have been identified. As epigenetic dysregulation is an important carcinogenic mechanism and some epigenetic changes are reversible, these epigenetic alterations have become targets for novel drug development against AML. This review summarizes the recent advances in epigenetic therapies for AML and discusses future research directions.

AML chemoresistance: The role of mutant TP53 subclonal expansion and therapy strategy

Acute myeloid leukemia (AML) is a heterogeneous clonal disease characterized by the proliferation and accumulation of myeloid blast cells in the bone marrow, which eventually lead to hematopoietic failure. Chemoresistance presents as a major burden for therapy of AML patients. p53 is the most important tumor suppressor protein that regulates cellular response to various stress. It is also important for hematopoietic stem cell development and hematopoiesis. Mutation or deletion of TP53 has been found to be linked to cancer progression, therapy-related resistance, and poor prognosis. TP53 mutation occurs in less than 10% of AML patients; however, it represents a subset of AML with therapy resistance and poor outcome. In addition, there is a subgroup of patients with low-frequency TP53 mutations. The percentage ranges from 1% to 3% of all AML patients. These patients have outcomes comparable to those of the high-frequency TP53 mutation patients. TP53-mutated clones isolated from the parental cells exhibit a survival advantage under drug treatment compared with cells with wild-type TP53, and have a higher population of leukemia stem cell (LSC) marker-positive cells, a characteristic of chemo-resistant cells. Therefore, low-frequency TP53 mutation, which is currently underappreciated, is an important prognosis factor for AML patients. Epigenetic drugs, such as hypomethylating agent and histone deacetylase inhibitors, have been found effective in targeting TP53-mutated AML. Histone deacetylase inhibitors can preferentially target the TP53-mutated subpopulation by reactivating p53-targeted genes and by eradicating LSC marker-positive cells. Therefore, combined treatment with epigenetic drugs may represent a new therapeutic strategy for treatments of TP53-mutated AML.

Epigenetic therapies in acute myeloid leukemia: the role of hypomethylating agents, histone deacetylase inhibitors and the combination of hypomethylating agents with histone deacetylase inhibitors

Epigenetic regulation includes changes of DNA methylation and modifications of histone proteins and is essential for normal physiologic functions, especially for controlling gene expression. Epigenetic dysregulation plays a key role in disease pathogenesis and progression of some malignancies, including acute myeloid leukemia (AML). Epigenetic therapies, including hypomethylating agents (HMAs) and histone deacetylase (HDAC) inhibitors, were developed to reprogram the epigenetic abnormalities in AML. However, the molecular mechanisms and therapeutic effects of the two agents alone or their combination remain unknown. An overview of these epigenetic therapies is given here. A literature search was conducted through PubMed database, looking for important biological or clinical studies related to the epigenetic regimens in the treatment of AML until October 15th, 2019. Various types of articles, including original research and reviews, were assessed, identified, and eventually summarized as a collection of data pertaining the mechanisms and clinical effects of HMAs and HDAC inhibitors in AML patients. We provided here an overview of the current understanding of the mechanisms and clinical therapeutic effects involved in the treatment with HMAs and HDAC inhibitors alone, the combination of epigenetic therapies with intensive chemotherapy, and the combination of both types of epigenetic therapies. Relevant clinical trials were also discussed. Generally speaking, the large number of studies and their varied outcomes demonstrate that effects of epigenetic therapies are heterogeneous, and that HMAs combination regimens probably contribute to significant response rates. However, more research is needed to explore therapeutic effects of HDAC inhibitors and various combinations of HMAs and HDAC inhibitors.

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.

Safety and efficacy of oral panobinostat plus chemotherapy in patients aged 65 years or younger with high-risk acute myeloid leukemia

The role of histone deacetylase inhibitors in the treatment of acute myeloid leukemia (AML) is not well characterized. The current study evaluated the safety and efficacy of panobinostat in combination with idarubicin and cytarabine in newly diagnosed patients aged ≤65 years with primary or secondary high-risk AML based on cytogenetic classification. Treatment included fixed dose idarubicin (12 mg/m²/d, IV; day 1-3) and cytarabine (100 mg/m²/d, continuous IV infusion; day 1-7) and escalating oral doses of panobinostat at 15 mg, 20 mg, and 25 mg, thrice weekly starting at week 2 of a 28-day cycle. Forty-six patients were enrolled (primary AML [n = 36], secondary AML [n = 10]). The median age was 55 years. The most common all-grade AEs were diarrhea (54.3%), nausea (39.1%), vomiting, and decreased appetite (each, 21.7%), stomatitis (19.6%), and fatigue (17.4%). The overall response rate was 60.9%, 43.5% achieved a complete remission (CR), and 17.4% achieved CR with incomplete count recovery. The event-free survival at 1-year was 78.3%. Panobinostat in combination with idarubicin and cytarabine demonstrated tolerable safety and efficacy in younger patients with high-risk AML. The recommended phase 2 dose of panobinostat in this combination was 20 mg. ClinicalTrials.gov registry no: NCT01242774, and European Trial Registry EudraCT no: 2009-016809-42.

Histone Deacetylase Inhibition with Panobinostat Combined with Intensive Induction Chemotherapy in Older Patients with Acute Myeloid Leukemia: Phase I Study Results

PURPOSE

The histone deacetylase (HDAC) inhibitor panobinostat potentiates anthracycline and cytarabine cytotoxicity in acute myeloid leukemia (AML) cells. We hypothesized that panobinostat prior to and during induction chemotherapy would be tolerable and augment response in patients showing increased histone acetylation.

PATIENTS AND METHODS

Patients received panobinostat 20-60 mg oral daily on days 1, 3, 5, and 8 with daunorubicin 60 mg/m²/day intravenously on days 3 to 5 and cytarabine 100 mg/m²/day intravenously by continuous infusion on days 3 to 9 ("7+3"). Peripheral blood mononuclear cells (PBMCs) were isolated for HDAC expression and histone acetylation changes.

RESULTS

Twenty-five patients ages 60-85 years (median age, 69) were treated. Fifteen patients had de novo AML, six AML with myelodysplasia-related changes, two AML with prior myeloproliferative neoplasm, one therapy-related myeloid neoplasm, and one myelodysplastic syndrome with excess blasts-2. No dose-limiting toxicities occurred in dose escalation cohorts. In dose expansion, six patients received panobinostat at 60 mg and nine patients at 50 mg due to recurrent grade 1 bradycardia at the 60-mg dose. The complete response (CR)/incomplete count recovery (Cri) rate was 32%. Median overall survival was 10 months: 23 months with CR/CRi versus 7.8 months without CR/CRi (log-rank P = 0.02). Median relapse-free survival was 8.2 months. Increased histone acetylation 4 and 24 hours after panobinostat was significantly associated with CR/CRi.

CONCLUSIONS

Panobinostat with "7+3" for older patients with AML was well tolerated. Panobinostat 50 mg on days 1, 3, 5, and 8 starting 2 days prior to "7+3" is recommended for future studies. Panobinostat-induced increases in histone acetylation in PBMCs predicted CR/CRi.

Myeloid cell leukemia-1 dependence in acute myeloid leukemia: a novel approach to patient therapy

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults, affecting approximately 21,000 people annually (nearly 11,000 deaths) in the United States. B-cell lymphoma 2 (BCL-2) family proteins, notably myeloid cell leukemia-1 (MCL-1), have been associated with both the development and persistence of AML. MCL-1 is one of the predominant BCL-2 family members expressed in samples from patients with untreated AML. MCL-1 is a critical cell survival factor for cancer and contributes to chemotherapy resistance by directly affecting cell death pathways. Here, we review the role of MCL-1 in AML and the mechanisms by which the potent cyclin-dependent kinase 9 inhibitor alvocidib, through regulation of MCL-1, may serve as a rational therapeutic approach against the disease.

Epigenetic therapy combinations in acute myeloid leukemia: what are the options?

Epigenetics refers to the regulation of gene expression mainly by changes in DNA methylation and modifications of histone proteins without altering the actual DNA sequence. While epigenetic modifications are essential for normal cell differentiation, several driver mutations in leukemic pathogenesis have been identified in genes that affect epigenetic processes, such as DNA methylation and histone acetylation. Several therapeutic options to target epigenetic alterations in acute myeloid leukemia (AML) have been successfully tested in preclinical studies and various drugs have already been approved for use in clinical practice. Among these already approved therapeutics are hypomethylating agents (azacitidine and decitabine) and isocitrate dehydrogenase inhibitors (ivosidenib, enasidenib). Other agents such as bromodomain-containing epigenetic reader proteins and histone methylation (e.g. DOT1L) inhibitors are currently in advanced clinical testing. As several epigenetic therapies have only limited efficacy when used as single agents, combination therapies that target AML pathogenesis at different levels and exploit synergistic mechanisms are also in clinical trials. Combinations of either epigenetic therapies with conventional chemotherapy, different forms of epigenetic therapies, or epigenetic therapies with immunotherapy are showing promising early results. In this review we summarize the underlying pathophysiology and rationale for epigenetically-based combination therapies, review current preclinical and clinical data and discuss the future directions of epigenetic therapy combinations in AML.

A machine learning approach to integrate big data for precision medicine in acute myeloid leukemia

Cancers that appear pathologically similar often respond differently to the same drug regimens. Methods to better match patients to drugs are in high demand. We demonstrate a promising approach to identify robust molecular markers for targeted treatment of acute myeloid leukemia (AML) by introducing: data from 30 AML patients including genome-wide gene expression profiles and in vitro sensitivity to 160 chemotherapy drugs, a computational method to identify reliable gene expression markers for drug sensitivity by incorporating multi-omic prior information relevant to each gene’s potential to drive cancer. We show that our method outperforms several state-of-the-art approaches in identifying molecular markers replicated in validation data and predicting drug sensitivity accurately. Finally, we identify SMARCA4 as a marker and driver of sensitivity to topoisomerase II inhibitors, mitoxantrone, and etoposide, in AML by showing that cell lines transduced to have high SMARCA4 expression reveal dramatically increased sensitivity to these agents.

Identification of markers of drug response is essential for precision therapy. Here the authors introduce an algorithm that uses prior information about each gene’s importance in AML to identify the most predictive gene-drug associations from transcriptome and drug response data from 30 AML samples.

Molecular targeting in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogenous disease associated with distinct genetic and molecular abnormalities. Somatic mutations result in dysregulation of intracellular signaling pathways, epigenetics, and apoptosis of the leukemia cells. Understanding the basis for the dysregulated processes provides the platform for the design of novel targeted therapy for AML patients. The effort to devise new targeted therapy has been helped by recent advances in methods for high-throughput genomic screening and the availability of computer-assisted techniques for the design of novel agents that are predicted to specifically inhibit the mutant molecules involved in these intracellular events. In this review, we will provide the scientific basis for targeting the dysregulated molecular mechanisms and discuss the agents currently being investigated, alone or in combination with chemotherapy, for treating patients with AML. Successes in molecular targeting will ultimately change the treatment paradigm for the disease.

Emerging therapies for acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by clinical and biological heterogeneity. Despite the advances in our understanding of its pathobiology, the chemotherapy-directed management has remained largely unchanged in the past 40 years. However, various novel agents have demonstrated clinical activity, either as single agents (e.g., isocitrate dehydrogenase (IDH) inhibitors, vadastuximab) or in combination with standard induction/consolidation at diagnosis and with salvage regimens at relapse. The classes of agents described in this review include novel cytotoxic chemotherapies (CPX-351 and vosaroxin), epigenetic modifiers (guadecitabine, IDH inhibitors, histone deacetylase (HDAC) inhibitors, bromodomain and extraterminal (BET) inhibitors), FMS-like tyrosine kinase receptor 3 (FLT3) inhibitors, and antibody-drug conjugates (vadastuximab), as well as cell cycle inhibitors (volasertib), B-cell lymphoma 2 (BCL-2) inhibitors, and aminopeptidase inhibitors. These agents are actively undergoing clinical investigation alone or in combination with available chemotherapy.

Hematologic Response to Vorinostat Treatment in Relapsed Myeloid Leukemia of Down Syndrome

Children with Down syndrome are at high risk to develop myeloid leukemia (ML-DS). Despite their excellent prognosis, children with ML-DS particularly suffer from severe therapy-related toxicities and for relapsed ML-DS the cure rates are very poor. Here we report the clinical course of one child with ML-DS treated with the histone deacetylase (HDAC) inhibitor vorinostat (suberoylanilide hydroxamic acid) after second relapse. The child had previously received conventional chemotherapy and stem cell transplantation, yet showed a remarkable clinical and hematologic response. Thus, HDAC inhibitor may represent an effective class of drugs for the treatment of ML-DS.

DNMT3A and TET2 in the Pre-Leukemic Phase of Hematopoietic Disorders

In recent years, advances in next-generation sequencing (NGS) technology have provided the opportunity to detect putative genetic drivers of disease, particularly cancers, with very high sensitivity. This knowledge has substantially improved our understanding of tumor pathogenesis. In hematological malignancies such as acute myeloid leukemia and myelodysplastic syndromes, pioneering work combining multi-parameter flow cytometry and targeted resequencing in leukemia have clearly shown that different classes of mutations appear to be acquired in particular sequences along the hematopoietic differentiation hierarchy. Moreover, as these mutations can be found in “normal” cells recovered during remission and can be detected at relapse, there is strong evidence for the existence of “pre-leukemic” stem cells (pre-LSC). These cells, while phenotypically normal by flow cytometry, morphology, and functional studies, are speculated to be molecularly poised to transform owing to a limited number of predisposing mutations. Identifying these “pre-leukemic” mutations and how they propagate a pre-malignant state has important implications for understanding the etiology of these disorders and for the development of novel therapeutics. NGS studies have found a substantial enrichment for mutations in epigenetic/chromatin remodeling regulators in pre-LSC, and elegant genetic models have confirmed that these mutations can predispose to a variety of hematological malignancies. In this review, we will discuss the current understanding of pre-leukemic biology in myeloid malignancies, and how mutations in two key epigenetic regulators, DNMT3A and TET2, may contribute to disease pathogenesis.

Panobinostat for the treatment of acute myelogenous leukemia

INTRODUCTION

Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi).

AREAS COVERED

The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML.

EXPERT OPINION

Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.