Prevalence and Prognostic Role of IDH Mutations in Acute Myeloid Leukemia: Results of the GIMEMA AML1516 Protocol

IDH1/2 mutations are common in acute myeloid leukemia (AML) and represent a therapeutic target. The GIMEMA AML1516 observational protocol was designed to study the prevalence of IDH1/2 mutations and associations with clinico-biological parameters in a cohort of Italian AML patients. We analyzed a cohort of 284 AML consecutive patients at diagnosis, 139 females and 145 males, of a median age of 65 years (range: 19−86). Of these, 38 (14%) harbored IDH1 and 51 (18%) IDH2 mutations. IDH1/2 mutations were significantly associated with WHO PS >2 (p < 0.001) and non-complex karyotype (p = 0.021) when compared to IDH1/2-WT. Furthermore, patients with IDH1 mutations were more frequently NPM1-mutated (p = 0.007) and had a higher platelet count (p = 0.036). At relapse, IDH1/2 mutations were detected in 6 (25%) patients. As per the outcome, 60.5% of IDH1/2-mutated patients achieved complete remission; overall survival and event-free survival at 2 years were 44.5% and 36.1%, respectively: these rates were similar to IDH1/2-WT. In IDH1/2-mutated patients, high WBC proved to be an independent prognostic factor for survival. In conclusion, the GIMEMA AML1516 confirms that IDH1/2 mutations are frequently detected at diagnosis and underlines the importance of recognizing IDH1/2-mutated cases up-front to offer the most appropriate therapeutic strategy, given the availability of IDH1/2 inhibitors.

2-Hydroxyglutarate in Acute Myeloid Leukemia: A Journey from Pathogenesis to Therapies

The oncometabolite 2-hydroxyglutarate (2-HG) plays a key role in differentiation blockade and metabolic reprogramming of cancer cells. Approximatively 20–30% of acute myeloid leukemia (AML) cases carry mutations in the isocitrate dehydrogenase (IDH) enzymes, leading to a reduction in the Krebs cycle intermediate α-ketoglutarate (α-KG) to 2-HG. Relapse and chemoresistance of AML blasts following initial good response to standard therapy account for the very poor outcome of this pathology, which represents a great challenge for hematologists. The decrease of 2-HG levels through pharmacological inhibition of mutated IDH enzymes induces the differentiation of AML blasts and sensitizes leukemic cells to several anticancer drugs. In this review, we provide an overview of the main genetic mutations in AML, with a focus on IDH mutants and the role of 2-HG in AML pathogenesis. Moreover, we discuss the impact of high levels of 2-HG on the response of AML cells to antileukemic therapies and recent evidence for highly efficient combinations of mutant IDH inhibitors with other drugs for the management of relapsed/refractory (R/R) AML.

Venetoclax resistance: mechanistic insights and future strategies

Acute myeloid leukemia (AML) is historically associated with poor prognosis, especially in older AML patients unfit for intensive chemotherapy. The development of Venetoclax, a potent oral BH3 (BCL-2 homology domain 3) mimetic, has transformed the AML treatment. However, the short duration of response and development of resistance remain major concerns. Understanding mechanisms of resistance is pivotal to devising new strategies and designing rational drug combination regimens. In this review, we will provide a comprehensive summary of the known mechanisms of resistance to Venetoclax and discuss Venetoclax-based combination therapies. Key contributing factors to Venetoclax resistance include dependencies on alternative anti-apoptotic BCL-2 family proteins and selection of the activating kinase mutations. Mutational landscape governing response to Venetoclax and strategic approaches developed considering current knowledge of mechanisms of resistance will be addressed.

Translating recent advances in the pathogenesis of acute myeloid leukemia to the clinic

Despite FDA approval of nine new drugs for patients with acute myeloid leukemia (AML) in the United States over the last 4 years, AML remains a major area of unmet medical need among hematologic malignancies. In this review, we discuss the development of promising new molecular targeted approaches for AML, including menin inhibition, novel IDH1/2 inhibitors, and preclinical means to target TET2, ASXL1, and RNA splicing factor mutations. In addition, we review progress in immune targeting of AML through anti-CD47, anti-SIRPα, and anti-TIM-3 antibodies; bispecific and trispecific antibodies; and new cellular therapies in development for AML.

Venetoclax combination therapy in acute myeloid leukemia and myelodysplastic syndromes

PURPOSE OF REVIEW

Venetoclax is a BCL-2 inhibitor that was approved in combination therapy with hypomethylating agents or low dose cytarabine for newly diagnosed acute myeloid leukemia (AML). The purpose of this review is to outline the most recent venetoclax-based combination therapies in newly diagnosed or relapsed myelodysplastic syndrome (MDS) and AML patients.

RECENT FINDING

Venetoclax has been incorporated in various therapeutic regimens - either with chemotherapy, immunotherapy or targeted therapies. These combinations achieve high remission rates with deep molecular responses, as suggested by measurable residual disease measurements. There are concerns regarding the incomplete count recovery, prolonged cytopenia and infection rates, especially when combined with chemotherapy. There is also limited data concerning durability of these remissions, and the effectiveness in high-risk population (i.e. p53-mutated AML patients).

SUMMARY

Venetoclax-based combination therapies encompass novel therapeutic possibilities in MDS and AML with encouraging initial results. However, the exact role of each combination therapy and the long-term effects on patients' outcome are yet to be defined.

Clinical development of IDH1 inhibitors for cancer therapy

Isocitrate dehydrogenase 1 (IDH1) has been investigated as a promising therapeutic target in select cancers with a mutated version of the enzyme (mtIDH1). With only one phase III trial published to date and two indications approved for routine clinical use by the FDA, we reviewed the entire clinical trial portfolio to broadly understand mtIDH1 inhibitor activity in patients. We queried PubMed.gov and ClinicalTrials.gov to identify published and ongoing clinical trials related to IDH1 and cancer. Progression-free survival (PFS), overall survival (OS), 2-hydroxyglutarate levels, and adverse events were summarized. To date, ten clinical trials investigating mtIDH1 inhibitors among patients with diverse malignancies (cholangiocarcinoma, acute myeloid leukemia, chondrosarcoma, glioma) have been published. Almost every trial (80%) has investigated ivosidenib. In multiple phase I trials, ivosidenib treatment resulted in promising radiographic and biochemical responses with improved survival outcomes (relative to historic data) among patients with both solid and hematologic mtIDH1 malignancies. Among patients enrolled in a phase III trial with advanced cholangiocarcinoma, ivosidenib resulted in a PFS rate of 32% at 6 months, as compared to 0% with placebo. There was a 5.2 month increase in OS with ivosidenib relative to placebo, after considering crossover. The treatment-specific grade ≥3 adverse event rate of ivosidenib was 2%-26% among all patients, and was just 3.6% among 284 patients who had a solid tumor across four trials. Although <1% of malignancies harbor IDH1 mutations, small molecule mtIDH1 inhibitors, namely ivosidenib, appear to be biologically active and well tolerated in patients with solid and hematologic mtIDH1 malignancies.

Have we reached a molecular era in myelodysplastic syndromes?

Myelodysplastic syndromes (MDS) are characterized by heterogeneous biological and clinical characteristics, leading to variable outcomes. The availability of sophisticated platforms of genome sequencing allowed the discovery of recurrently mutated genes, which have led to a new era in MDS. This is reflected by the 2016 update of the World Health Organization classification, in which the criteria to define MDS with ringed sideroblasts include the presence of SF3B1 mutations. Further, the detection of somatic mutations in myeloid genes at high variant allele frequency guides the diagnostic algorithm in cases with cytopenias, unclear dysplastic changes, and normal karyotypes, supporting MDS over alternative diagnoses. SF3B1 mutations have been shown to play a positive prognostic role, while mutations in ASXL1, EZH2, RUNX1, and TP53 have been associated with a dismal prognosis. This is particularly relevant in lower- and intermediate-risk disease, in which a higher number of mutations and/or the presence of "unfavorable" somatic mutations may support the use of disease-modifying treatments. In the near future, the incorporation of mutation profiles in currently used prognostication systems, also taking into consideration the classical patient clinical variables (including age and comorbidities), will support a more precise disease stratification, eg, the assignment to targeted treatment approaches or to allogeneic stem cell transplantation in younger patients.

How do molecular aberrations guide therapy in MDS?

Myelodysplastic syndromes (MDS) represent a cluster of genetically and phenotypically heterogeneous hematological disorders. While molecularly targeted therapies have entered the standard of care for other hematological malignancies like acute myeloid leukemia, this approach has been elusive in MDS. This review has summarized recent evidence to determine how molecular aberrations can be used to guide therapy in MDS and improve outcomes among patients.

Molecular determinants of therapy response of venetoclax-based combinations in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous, highly malignant disease of the bone marrow. After decades of slow progress, recent years saw a surge of novel agents for its treatment. The most recent advancement is the registration of the Bcl-2 inhibitor ventoclax in combination with a hypomethylating agent (HMA) in the US and Europe for AML patients not eligible for intensive chemotherapy. Treatment of newly diagnosed AML patients with this combination results in remission rates that so far could only be achieved with intensive treatment. However, not all AML patients respond equally well, and some patients relapse early, while other patients experience longer periods of complete remission. A hallmark of AML is its remarkable genetic, molecular and clinical heterogeneity. Here, we review the current knowledge about molecular features of AML that help estimate the probability of response to venetoclax-containing therapies. In contrast to other newly developed AML therapies that target specific recurrent molecular alterations, it seems so far that responses are not specific for a certain subgroup. One exception is spliceosome mutations, where good response has been observed in clinical trials with venetoclax/azacitidine. These mutations are rather associated with a more unfavorable outcome with chemotherapy. In summary, venetoclax in combination with hypomethylating agents represents a significant novel option for AML patients with various molecular aberrations. Mechanisms of primary and secondary resistance seem to overlap with those towards chemotherapy.

Differential impact of IDH1/2 mutational subclasses on outcome in adult AML: Results from a large multicenter study

Patients with IDH1-R132C have a lower complete remission rate and a trend toward reduced OS.

Patients with IDH2-R172K in the European LeukemiaNet intermediate/adverse-risk group have significantly better relapse-free survival and OS.

Mutations of the isocitrate dehydrogenase-1 (IDH1) and IDH2 genes are among the most frequent alterations in acute myeloid leukemia (AML) and can be found in ∼20% of patients at diagnosis. Among 4930 patients (median age, 56 years; interquartile range, 45-66) with newly diagnosed, intensively treated AML, we identified IDH1 mutations in 423 (8.6%) and IDH2 mutations in 575 (11.7%). Overall, there were no differences in response rates or survival for patients with mutations in IDH1 or IDH2 compared with patients without mutated IDH1/2. However, distinct clinical and comutational phenotypes of the most common subtypes of IDH1/2 mutations could be associated with differences in outcome. IDH1-R132C was associated with increased age, lower white blood cell (WBC) count, less frequent comutation of NPM1 and FLT3 internal tandem mutation (ITD) as well as with lower rate of complete remission and a trend toward reduced overall survival (OS) compared with other IDH1 mutation variants and wild-type (WT) IDH1/2. In our analysis, IDH2-R172K was associated with significantly lower WBC count, more karyotype abnormalities, and less frequent comutations of NPM1 and/or FLT3-ITD. Among patients within the European LeukemiaNet 2017 intermediate- and adverse-risk groups, relapse-free survival and OS were significantly better for those with IDH2-R172K compared with WT IDH, providing evidence that AML with IDH2-R172K could be a distinct entity with a specific comutation pattern and favorable outcome. In summary, the presented data from a large cohort of patients with IDH1/2 mutated AML indicate novel and clinically relevant findings for the most common IDH mutation subtypes.

Keeping up with venetoclax for leukemic malignancies: key findings, optimal regimens and clinical considerations

INTRODUCTION

Venetoclax has transformed the treatment landscape in hematologic malignancies, especially in elderly population. With high rates of remission, deep and durable responses, and safe toxicity profile, venetoclax in combination therapy has been extremely effective, garnering accelerated approval and becoming standard of care in lymphoid and myeloid malignancies.

AREAS COVERED

The role of venetoclax in the intrinsic apoptotic pathway is covered. This includes preclinical and clinical experience of venetoclax monotherapy and combination therapy in relapsed/refractory and frontline CLL, AML, ALL and high-risk MDS, with an emphasis on key clinical trials and efficacy of combination regimens in distinct mutational landscapes. Strategies to mitigate myelosuppression, manage dose adjustments and infectious complications are addressed.

EXPERT OPINION

Targeting BCL-2 offers a safe and highly effective adjunct to available therapies in hematologic malignancies. Despite success and frequent utilization of venetoclax, several resistance mechanisms have been elucidated, prompting development of novel combinatorial strategies. Further, on-target myelosuppression of venetoclax is a key obstacle in clinical practice, requiring diligent monitoring and practice-based knowledge of dose modifications. Despite these limitations, venetoclax has gained tremendous popularity in hematologic-oncology, becoming an integral component of numerous combination regimes, with ongoing plethora of clinical trials encompassing standard chemotherapy, targeted agents and immune-based approaches.

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.

SOHO State of the Art Updates and Next Questions: IDH Inhibition

There has been extraordinary progress in the field of targeted therapy for myeloid malignancies in the last few years, especially due to the approval of various agents that can be used as monotherapy or in combination as first-line treatment or when facing a refractory or relapsed disease. Many successful trials have been conducted recently, and a consistent body of work about the efficacy of novel molecules is now available. In this review, we sought to explain how enasidenib and ivosidenib have changed the face of myeloid neoplasm treatment through isocitrate dehydrogenase inhibition and to summarize the trials results that have led to the current commercial indications for the two molecules.

Hypomethylating agents (HMA) for the treatment of acute myeloid leukemia and myelodysplastic syndromes: mechanisms of resistance and novel HMA-based therapies

Aberrant DNA methylation plays a pivotal role in tumor development and progression. DNA hypomethylating agents (HMA) constitute a class of drugs which are able to reverse DNA methylation, thereby triggering the re-programming of tumor cells. The first-generation HMA azacitidine and decitabine have now been in standard clinical use for some time, offering a valuable alternative to previous treatments in acute myeloid leukemia and myelodysplastic syndromes, so far particularly in older, medically non-fit patients. However, the longer we use these drugs, the more we are confronted with the (almost inevitable) development of resistance. This review provides insights into the mode of action of HMA, mechanisms of resistance to this treatment, and strategies to overcome HMA resistance including next-generation HMA and HMA-based combination therapies.

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.

Efficacy and Safety Profile of Ivosidenib in the Management of Patients with Acute Myeloid Leukemia (AML): An Update on the Emerging Evidence

The isocitrate dehydrogenase enzyme, catalyzing isocitrate conversion to α-ketoglutarate (αKG) in both the cell cytoplasm and mitochondria, contributes to the production of dihydronicotinamide-adenine dinucleotide phosphate (NADPH) as a reductive potential in various cellular processes. IDH1 gene mutations are revealed in up to 20% of the patients with acute myeloid leukemia (AML). A mutant IDH enzyme, existing in the cell cytoplasm and possessing neomorphic activity, converts αKG into oncometabolite R-2-hydroxyglutarate (R-2-HG) that accumulates in high amounts in the cell and inhibits αKG-dependent enzymes, including epigenetic regulators. The resultant alteration in gene expression and blockade of differentiation ultimately lead to leukemia development. Myeloid differentiation capacity can be restored by obstruction of the mutant enzyme, inducing substantial reduction in R-2-HG levels. Ivosidenib, a potent selective inhibitor of mutant IDH1, is a differentiating agent shown to be clinically effective in newly diagnosed AML (ND-AML) and relapsed/refractory (R/R) AML harboring this mutation. The drug is approved by the Food and Drug Administration (FDA) as a single-agent treatment for R/R AML. Significance of mutated IDH1 targeting and a potential role of ivosidenib in AML management, when used either as a single agent or as part of combination therapies, will be reviewed herein.

An evaluation of venetoclax in combination with azacitidine, decitabine, or low-dose cytarabine as therapy for acute myeloid leukemia

INTRODUCTION

Older patients with acute myeloid leukemia (AML) ineligible for conventional chemotherapy have historically received low-intensity treatments, if any, and have had dismal outcomes. Recent phase III data have demonstrated significant efficacy of venetoclax-based combinations and have begun to address the unmet need in this patient population. As venetoclax-based combinations become increasingly used in the clinical setting, it is important to understand their development, current use, and future directions.

AREAS COVERED

This review covers the clinical development of venetoclax-based combinations for the management of AML, and their current and future use. A search of PubMed and ashpublications.org using the keywords 'venetoclax', 'AML', and 'hypomethylating agents' as the search terms was undertaken to identify the most pertinent publications.

EXPERT OPINION

While venetoclax-based combinations have shown excellent responses and improved survival in patients with untreated AML, further studies are required to understand how to expand on their frontline use, manage patients who fail venetoclax-based combinations, and their true efficacy in the relapsed/refractory setting. Management of AML with venetoclax-based combinations is expected to evolve over the next few years.

The implications of IDH mutations for cancer development and therapy

Mutations in the genes encoding the cytoplasmic and mitochondrial forms of isocitrate dehydrogenase (IDH1 and IDH2, respectively; collectively referred to as IDH) are frequently detected in cancers of various origins, including but not limited to acute myeloid leukaemia (20%), cholangiocarcinoma (20%), chondrosarcoma (80%) and glioma (80%). In all cases, neomorphic activity of the mutated enzyme leads to production of the oncometabolite D-2-hydroxyglutarate, which has profound cell-autonomous and non-cell-autonomous effects. The broad effects of IDH mutations on epigenetic, differentiation and metabolic programmes, together with their high prevalence across a variety of cancer types, early presence in tumorigenesis and uniform expression in tumour cells, make mutant IDH an ideal therapeutic target. Herein, we describe the current biological understanding of IDH mutations and the roles of mutant IDH in the various associated cancers. We also present the available preclinical and clinical data on various methods of targeting IDH-mutant cancers and discuss, based on the underlying pathogenesis of different IDH-mutated cancer types, whether the treatment approaches will converge or be context dependent.

Acute myeloid leukemia with IDH1 and IDH2 mutations: 2021 treatment algorithm

Acute myeloid leukemia is a genetically heterogeneous hematologic malignancy; approximately 20% of AML harbors a mutation in the isocitrate dehydrogenase (IDH) genes, IDH1 or IDH2. These recurrent mutations in key metabolic enzymes lead to the production of the oncometabolite 2-hydroxyglutarate, which promotes leukemogenesis through a block in normal myeloid differentiation. Since this discovery, selective oral inhibitors of mutant IDH1 and IDH2 have subsequently been developed and are now approved as single agent therapy, based on clinical efficacy observed within the original first-in-human trials. The investigation of IDH inhibitors in combination with standard therapies such as azacytidine, with intensive chemotherapy, and with other small molecule targeted therapies in rational combinations are currently under evaluation to further improve upon clinical efficacy.

Venetoclax-based combinations for the treatment of newly diagnosed acute myeloid leukemia

Elderly and/or unfit patients with acute myeloid leukemia have historically been challenging to manage as they were ineligible for what was considered standard of care treatment with induction chemotherapy. The emergence of venetoclax with hypomethylating agents or low-dose cytarabine has substantially improved outcomes in the frontline setting with manageable toxicity. However, this regimen can be challenging to deliver given its differences from standard intensive chemotherapy. In this review, we summarize the landmark trials that established venetoclax-based combinations as a new standard of care for patients with acute myeloid leukemia not suitable for intense chemotherapy, provide practical clinical pearls for managing patients on these therapies, and offer a brief overview of modifications to these regimens under development to improve their efficacy and/or applicability.

Advances in therapeutic options for newly diagnosed, high-risk AML patients

Acute myeloid leukemia (AML) is an aggressive malignancy characterized by clonal proliferation of neoplastic immature precursor cells. AML impacts older adults and has a poor prognosis. Despite recent advances in treatment, AML is complex, with both genetic and epigenetic aberrations in the malignant clone and elaborate interactions with its microenvironment. We are now able to stratify patients on the basis of specific clinical and molecular features in order to optimize individual treatment strategies. However, our understanding of the complex nature of these molecular abnormalities continues to expand the defining characteristics of high-risk mutations. In this review, we focus on genetic and microenvironmental factors in adverse risk AML that play critical roles in leukemogenesis, including those not described in an European LeukemiaNet adverse risk group, and describe therapies that are currently in the clinical arena, either approved or under development.

Targeting epigenetic mechanisms to overcome venetoclax resistance

The BH-3 mimetic venetoclax overcomes apoptosis and therapy resistance caused by high expression of BCL2 or loss of BH3-only protein function. Although a promising therapy for hematologic malignancies, increased expression of anti-apoptotic MCL-1 or BCL-XL, as well as other resistance mechanisms prevent a durable response to venetoclax. Recent studies demonstrate that agents targeting epigenetic mechanisms such as DNA methyltransferase inhibitors, histone deacetylase (HDAC) inhibitors, histone methyltransferase EZH2 inhibitors, or bromodomain reader protein inhibitors may disable oncogenic gene expression signatures responsible for venetoclax resistance. Combination therapies including venetoclax and epigenetic therapies are effective in preclinical models and the subject of many current clinical trials. Here we review epigenetic strategies to overcome venetoclax resistance mechanisms in hematologic malignancies.

Accelerated Phase of Myeloproliferative Neoplasms

BACKGROUND

Myeloproliferative neoplasms (MPNs) can transform into blast phase MPN (leukemic transformation; MPN-BP), typically via accelerated phase MPN (MPN-AP), in ∼20-25% of the cases. MPN-AP and MPN-BP are characterized by 10-19% and ≥20% blasts, respectively. MPN-AP/BP portend a dismal prognosis with no established conventional treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole modality associated with long-term survival.

SUMMARY

MPN-AP/BP has a markedly different mutational profile from de novo acute myeloid leukemia (AML). In MPN-AP/BP, TP53 and IDH1/2 are more frequent, whereas FLT3 and DNMT3A are rare. Higher incidence of leukemic transformation has been associated with the most aggressive MPN subtype, myelofibrosis (MF); other risk factors for leukemic transformation include rising blast counts above 3-5%, advanced age, severe anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, lack of driver mutations (negative for JAK2, CALR, or MPL genes), adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157). The aforementioned factors have been incorporated in several novel prognostic scoring systems for MF. Currently, elderly/unfit patients with MPN-AP/BP are treated with hypomethylating agents with/without ruxolitinib; these regimens appear to confer comparable benefit to intensive chemotherapy but with lower toxicity. Retrospective studies in patients who acquired actionable mutations during MPN-AP/BP showed positive outcomes with targeted AML treatments, such as IDH1/2 inhibitors, and require further evaluation in clinical trials. Key Messages: Therapy for MPN-AP patients represents an unmet medical need. MF patients, in particular, should be appropriately stratified regarding their prognosis and the risk for transformation. Higher-risk patients should be monitored regularly and treated prior to progression to MPN-BP. MPN-AP patients may be treated with hypomethylating agents alone or in combination with ruxolitinib; also, patients can be provided with the option to enroll in rationally designed clinical trials exploring combination regimens, including novel targeted drugs, with an ultimate goal to transition to transplant.

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.

IDH1/IDH2 Inhibition in Acute Myeloid Leukemia

Recently, the discovery of biological and clinical properties of mutated isoforms 1 and 2 mutations of isocitrate dehydrogenases (IDH) 1 and 2, affecting approximately 20% of patients with acute myeloid leukemia (AML), lead to the development of an individualized treatment strategy. Promoting differentiation and maturation of the malignant clone targeting IDH is an emerging strategy to promote clinical responses in AML. Phase I/II trials have shown evidence of safety, tolerability, and encouraging evidence of efficacy of two small molecule inhibitors targeting IDH2 and IDH1 gene mutations, respectively enasidenib and ivosidenib. In this review, the contribution of IDH1/IDH2 mutations in leukemogenesis and progress of targeted therapeutics in AML will be highlighted.

Which novel agents will have a clinically meaningful impact in AML at diagnosis?

New drug approvals now afford AML physicians a wider choice of initial treatment options than ever before. Although chemotherapy for AML is by no means ready to be replaced entirely by novel agents, the role of traditional cytotoxics in AML therapy is rapidly changing. In particular, biologically targeted agents such as the BCL2 inhibitor venetoclax and inhibitors of FLT3 and IDH mutations stand out as drugs likely to take AML therapy in important new directions. Maximum response and survival benefits likely require combinations of novel agents and chemotherapy or multiple novel agents together. The recently-published phase 3 VIALE-A study demonstrates a very successful example of a new combination approach, which led to venetoclax plus azacitidine establishing itself as the new standard of care for patients unfit for intensive chemotherapy. One could reasonably expect other subsets of AML to benefit from this regimen or other applications of venetoclax combinations. Building on this experience, venetoclax-based regimens also have the potential to replace standard intensive cytarabine/anthracycline "7&3" induction approach for some if not many patients who are fit for induction. This review will describe novel agents with the greatest potential for impactful frontline applications that will change the AML treatment paradigm.

Emerging agents and regimens for AML

Until recently, acute myeloid leukemia (AML) patients used to have limited treatment options, depending solely on cytarabine + anthracycline (7 + 3) intensive chemotherapy and hypomethylating agents. Allogeneic stem cell transplantation (Allo-SCT) played an important role to improve the survival of eligible AML patients in the past several decades. The exploration of the genomic and molecular landscape of AML, identification of mutations associated with the pathogenesis of AML, and the understanding of the mechanisms of resistance to treatment from excellent translational research helped to expand the treatment options of AML quickly in the past few years, resulting in noteworthy breakthroughs and FDA approvals of new therapeutic treatments in AML patients. Targeted therapies and combinations of different classes of therapeutic agents to overcome treatment resistance further expanded the treatment options and improved survival. Immunotherapy, including antibody-based treatment, inhibition of immune negative regulators, and possible CAR T cells might further expand the therapeutic armamentarium for AML. This review is intended to summarize the recent developments in the treatment of AML.

Targeting BCL-2 in Cancer: Advances, Challenges, and Perspectives

Simple Summary

Apoptosis, a programmed form of cell death, represents the main mechanism by which cells die. Such phenomenon is highly regulated by the BCL-2 family of proteins, which includes both pro-apoptotic and pro-survival proteins. The decision whether cells live or die is tightly controlled by a balance between these two classes of proteins. Notably, the pro-survival Bcl-2 proteins are frequently overexpressed in cancer cells dysregulating this balance in favor of survival and also rendering cells more resistant to therapeutic interventions. In this review, we outlined the most important steps in the development of targeting the BCL-2 survival proteins, which laid the ground for the discovery and the development of the selective BCL-2 inhibitor venetoclax as a therapeutic drug in hematological malignancies. The limitations and future directions are also discussed.

Abstract

The major form of cell death in normal as well as malignant cells is apoptosis, which is a programmed process highly regulated by the BCL-2 family of proteins. This includes the antiapoptotic proteins (BCL-2, BCL-XL, MCL-1, BCLW, and BFL-1) and the proapoptotic proteins, which can be divided into two groups: the effectors (BAX, BAK, and BOK) and the BH3-only proteins (BIM, BAD, NOXA, PUMA, BID, BIK, HRK). Notably, the BCL-2 antiapoptotic proteins are often overexpressed in malignant cells. While this offers survival advantages to malignant cells and strengthens their drug resistance capacity, it also offers opportunities for novel targeted therapies that selectively kill such cells. This review provides a comprehensive overview of the extensive preclinical and clinical studies targeting BCL-2 proteins with various BCL-2 proteins inhibitors with emphasis on venetoclax as a single agent, as well as in combination with other therapeutic agents. This review also discusses recent advances, challenges focusing on drug resistance, and future perspectives for effective targeting the Bcl-2 family of proteins in cancer.

Venetoclax-containing regimens in acute myeloid leukemia

Venetoclax in combination with hypomethylating agents (HMAs) or low-dose cytarabine (LDAC) has demonstrated exceptional activity in elderly and unfit patients with newly diagnosed acute myeloid leukemia (AML). Notably, the safety profile of venetoclax-based induction regimens was favorable, with a low rate of early treatment-related mortality, even in frail study participants. Thus, the introduction of venetoclax has transformed the landscape of AML therapy in elderly patients. Given these promising results, venetoclax in combination with other agents is now being studied as a frontline therapy in younger patients with AML, as well as in relapsed/refractory AML patients. Here, we review clinical data for venetoclax-based therapy in AML, both from prospective as well as retrospective studies, and highlight ongoing novel studies of venetoclax-containing regimens and discuss future research directions.

Venetoclax for the treatment of elderly or chemotherapy-ineligible patients with acute myeloid leukemia: a step in the right direction or a game changer?

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive malignancy with poor prognosis and high rates of relapse, especially in elderly patients who are ineligible to receive intensive chemotherapy. Venetoclax, an oral BCL-2 inhibitor, is approved by the Food and Drug Administration in combination with hypomethylating agents or low-dose cytarabine in newly-diagnosed AML patients who are ineligible to receive intensive chemotherapy. Confirmatory phase III VIALE-A and VIALE-C trials showed a composite complete remission rate of 66.4% and 48%, respectively. Thus, further validating venetoclax as an attractive therapeutic option in the AML treatment landscape.

AREAS COVERED

A review of venetoclax in AML, focusing on preclinical and clinical data, toxicity profile, and mechanisms of resistance; and its strengths and weaknesses in regards to its current and future role in AML treatment is discussed. To find relevant studies, authors searched PubMed/Medline and ClinicalTrials.gov.

EXPERT OPINION

The introduction of venetoclax-based combination therapies has greatly expanded the therapeutic options for elderly and chemotherapy-ineligible AML patients. Additional studies with extended follow-up are necessary to address remaining open questions such as (I) durability of responses, (II) head-to-head comparisons with intensive chemotherapy in selected patients (e.g. TP53 mutations), and (III) novel triplet combinations using an HMA-venetoclax backbone.

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.

Apoptosis targeted therapies in acute myeloid leukemia: an update

Introduction: Management of acute myeloid leukemia (AML) continues to be a therapeutic challenge despite significant recent advancements. Dysregulation of several components of apoptotic pathways has been identified as potential driver in AML. Areas covered: Overexpression of anti-apoptotic proteins, B-cell lymphoma 2 (BCL2), BCL-XL, and myeloid cell leukemia-1 (MCL1), has been associated with worse outcome in AML. Dysfunction of p53 pathway (often through mouse double minute 2 homolog (MDM2)) and high expression of inhibitor of apoptosis proteins (IAP) constitute other disruptions of apoptotic machinery. Significant antileukemic activity of BCL2 inhibitors (particularly venetoclax) in preclinical models has translated into improved objective response and overall survival in combination with hypomethylating agents in AML. Addition of MCL1, BCL-XL, or MDM2 inhibitors could potentially overcome resistance to BCL2 inhibition. Authors conducted a thorough review of available literature on therapeutic options targeting apoptosis in AML, using PubMed, MEDLINE, meeting abstracts, and ClinicalTrials.gov. Expert opinion: While venetoclax remains the core component of targeting apoptosis, ongoing clinical trials should help find ideal combination regimens in different AML subgroups. Future research should focus on overcoming resistance to BCL2 inhibition, optimal management of adverse events, and development of biomarkers to identify patients most likely to benefit from apoptosis-targeted therapies.

Does patient fitness play a role in determining first-line treatment of acute myeloid leukemia?

The treatment choice for newly diagnosed patients with acute myeloid leukemia (AML) is no longer straightforward. Historically, patient fitness has been a major driver of the initial therapy decision based on the belief that intensive chemotherapy would be the optimal choice if a patient were "fit" enough to receive it. Tools based on chronological age, performance status, and comorbidities have been developed to help estimate patient fitness. With newer approved therapies that include nonintensive options such as IDH1 inhibition or less intensive options such as hypomethylating agent (HMA)- or low-dose cytarabine (LDAC)-based combinations with venetoclax, the choice of frontline AML therapy places more emphasis on disease-specific features, including cytogenetics and mutational profile. Moreover, newer treatments have higher response rates than what has been expected with older nonintensive options such as LDAC or HMA monotherapy. We present cases of three patients with AML with varying cytogenetic and molecular risks to demonstrate the important but changing role of patient fitness in the current era of expanding therapeutic options.

Venetoclax-based chemotherapy in acute and chronic myeloid neoplasms: literature survey and practice points

Venetoclax (VEN), a small-molecule inhibitor of B cell leukemia/lymphoma-2, is now FDA approved (November 2018) for use in acute myeloid leukemia (AML), specific to newly diagnosed elderly or unfit patients, in combination with a hypomethylating agent (HMA; including azacitidine or decitabine) or low-dose cytarabine. A recent phase-3 study compared VEN combined with either azacitidine or placebo, in the aforementioned study population; the complete remission (CR) and CR with incomplete count recovery (CRi) rates were 28.3% and 66.4%, respectively, and an improvement in overall survival was also demonstrated. VEN-based chemotherapy has also shown activity in relapsed/refractory AML (CR/CRi rates of 33-46%), high-risk myelodysplastic syndromes (CR 39% in treatment naïve, 5-14% in HMA failure), and blast-phase myeloproliferative neoplasm (CR 25%); in all instances, an additional fraction of patients met less stringent criteria for overall response. Regardless, venetoclax-induced remissions were often short-lived (less than a year) but long enough to allow some patients transition to allogeneic stem cell transplant. Herein, we review the current literature on the use of VEN-based combination therapy in both acute and chronic myeloid malignancies and also provide an outline of procedures we follow at our institution for drug administration, monitoring of adverse events and dose adjustments.

Venetoclax-Based Combinations in Acute Myeloid Leukemia: Current Evidence and Future Directions

The past decade has witnessed major advances in our understanding of molecular biology, which led to breakthrough novel therapies, importantly including the B-cell lymphoma-2 (BCL-2) inhibitor venetoclax. Notably, venetoclax-based combinations have improved outcomes, including both remission rates and overall survival, of older patients with acute myeloid leukemia (AML) deemed "unfit" for intensive chemotherapy due to age or comorbidities. This has translated into a rapid and widespread use of venetoclax-based combinations in both academic and community-based settings. Other venetoclax-based combinations are being investigated in AML with the ultimate goal of improving cure rates across many subgroups; frontline and relapsed/refractory, in combination with intensive chemotherapy, in the post-transplant setting, or as maintenance strategy. In this article, we summarize the current available data on venetoclax-based combinations. We also highlight areas of unmet medical need, and we offer practical clinical pearls for management of patients receiving such therapy.

Advances in Acute Myeloid Leukemia: Recently Approved Therapies and Drugs in Development

Acute myeloid leukemia (AML) is a genetically heterogeneous malignancy comprised of various cytogenetic and molecular abnormalities that has notoriously been difficult to treat with an overall poor prognosis. For decades, treatment options were limited to either intensive chemotherapy with anthracycline and cytarabine-based regimens (7 + 3) or lower intensity regimens including hypomethylating agents or low dose cytarabine, followed by either allogeneic stem cell transplant or consolidation chemotherapy. Fortunately, with the influx of rapidly evolving molecular technologies and new genetic understanding, the treatment landscape for AML has dramatically changed. Advances in the formulation and delivery of 7 + 3 with liposomal cytarabine and daunorubicin (Vyxeos) have improved overall survival in secondary AML. Increased understanding of the genetic underpinnings of AML has led to targeting actionable mutations such as FLT3, IDH1/2 and TP53, and BCL2 or hedgehog pathways in more frail populations. Antibody drug conjugates have resurfaced in the AML landscape and there have been numerous advances utilizing immunotherapies including immune checkpoint inhibitors, antibody-drug conjugates, bispecific T cell engager antibodies, chimeric antigen receptor (CAR)-T therapy and the development of AML vaccines. While there are dozens of ongoing studies and new drugs in the pipeline, this paper serves as a review of the advances achieved in the treatment of AML in the last several years and the most promising future avenues of advancement.

Enasidenib and ivosidenib in AML

The isocitrate dehydrogenases enzymes, IDH1 and IDH2, catalyze the conversion of isocitrate to α-ketoglutarate (αKG) in the cell cytoplasm and mitochondria, respectively, and contribute to generating the dihydronicotinamide-adenine dinucleotide phosphate (NADPH) as reductive potential in different cellular processes. Mutations in IDH1 and IDH2 genes are found collectively in about 20-25% of acute myeloid leukemia (AML) patients. Mutant IDH enzymes have neomorphic activity and convert αKG to the oncometabolite R-2-hydroxyglutarate (R-2-HG) which accumulates at high levels in the cell and hampers the function of αKG-dependent enzymes, including epigenetic regulators, thus leading to altered gene expression and block of differentiation and contributing to leukemia development. Inhibition of the neomorphic mutants induces marked decrease in R-2-HG levels and restores myeloid differentiation. Enasidenib and ivosidenib are potent and selective inhibitors of mutant IDH2 and IDH1, respectively, act as differentiating agents and showed clinical activity in relapsed/refractory (R/R) AML harboring the specific mutation. As single agents, both drugs have been approved by the Food and Drug Administration (FDA) for the treatment of R/R AML. The relevance of IDH targeting within either single agent approach or, most importantly, combinatorial treatments in AML will be discussed.