The Menin story in acute myeloid leukaemia-The road to success.

The treatment of acute myeloid leukaemia (AML) has changed fundamentally in the last decade with many new targeted therapies entering clinics. Some of the most interesting agents under development are Menin inhibitors which interfere with the interaction of Menin with wild-type (wt) KMT2A or a KMT2A-fusion protein and thereby downregulate the leukaemic gene expression (MEIS1, PBX3, HOX) in NPM1 mutant or KMT2A-rearranged leukaemia. Other HOX and MEIS1 expressing leukaemias may also be sensitive to Menin inhibition. Following the encouraging results as monotherapy in refractory and relapsed AML, the combination of Menin inhibitors with chemotherapeutic agents and other targeted drugs is being investigated clinically.

Immunoproteasome function maintains oncogenic gene expression in KMT2A-complex driven leukemia.

Pharmacologic targeting of chromatin-associated protein complexes has shown significant responses in KMT2A-rearranged (KMT2A-r) acute myeloid leukemia (AML) but resistance frequently develops to single agents. This points to a need for therapeutic combinations that target multiple mechanisms. To enhance our understanding of functional dependencies in KMT2A-r AML, we have used a proteomic approach to identify the catalytic immunoproteasome subunit PSMB8 as a specific vulnerability. Genetic and pharmacologic inactivation of PSMB8 results in impaired proliferation of murine and human leukemic cells while normal hematopoietic cells remain unaffected. Disruption of immunoproteasome function drives an increase in transcription factor BASP1 which in turn represses KMT2A-fusion protein target genes. Pharmacologic targeting of PSMB8 improves efficacy of Menin-inhibitors, synergistically reduces leukemia in human xenografts and shows preserved activity against Menin-inhibitor resistance mutations. This identifies and validates a cell-intrinsic mechanism whereby selective disruption of proteostasis results in altered transcription factor abundance and repression of oncogene-specific transcriptional networks. These data demonstrate that the immunoproteasome is a relevant therapeutic target in AML and that targeting the immunoproteasome in combination with Menin-inhibition could be a novel approach for treatment of KMT2A-r AML.

Synergistic targeting of FLT3 mutations in AML via combined menin-MLL and FLT3 inhibition.

The interaction of menin (MEN1) and MLL (MLL1, KMT2A) is a dependency and provides a potential opportunity for treatment of NPM1-mutant (NPM1mut) and MLL-rearranged (MLL-r) leukemias. Concomitant activating driver mutations in the gene encoding the tyrosine kinase FLT3 occur in both leukemias and are particularly common in the NPM1mut subtype. In this study, transcriptional profiling after pharmacological inhibition of the menin-MLL complex revealed specific changes in gene expression, with downregulation of the MEIS1 transcription factor and its transcriptional target gene FLT3 being the most pronounced. Combining menin-MLL inhibition with specific small-molecule kinase inhibitors of FLT3 phosphorylation resulted in a significantly superior reduction of phosphorylated FLT3 and transcriptional suppression of genes downstream of FLT3 signaling. The drug combination induced synergistic inhibition of proliferation, as well as enhanced apoptosis, compared with single-drug treatment in models of human and murine NPM1mut and MLL-r leukemias harboring an FLT3 mutation. Primary acute myeloid leukemia (AML) cells harvested from patients with NPM1mutFLT3mut AML showed significantly better responses to combined menin and FLT3 inhibition than to single-drug or vehicle control treatment, whereas AML cells with wild-type NPM1, MLL, and FLT3 were not affected by either of the 2 drugs. In vivo treatment of leukemic animals with MLL-r FLT3mut leukemia reduced leukemia burden significantly and prolonged survival compared with results in the single-drug and vehicle control groups. Our data suggest that combined menin-MLL and FLT3 inhibition represents a novel and promising therapeutic strategy for patients with NPM1mut or MLL-r leukemia and concurrent FLT3 mutation.

Next generation epigenetic modulators to target myeloid neoplasms.

PURPOSE OF REVIEW: Comprehensive sequencing studies aimed at determining the genetic landscape of myeloid neoplasms have identified epigenetic regulators to be among the most commonly mutated genes. Detailed studies have also revealed a number of epigenetic vulnerabilities. The purpose of this review is to outline these vulnerabilities and to discuss the new generation of drugs that exploit them. RECENT FINDINGS: In addition to deoxyribonucleic acid-methylation, novel epigenetic dependencies have recently been discovered in various myeloid neoplasms and many of them can be targeted pharmacologically. These include not only chromatin writers, readers, and erasers but also chromatin movers that shift nucleosomes to allow access for transcription. Inhibitors of protein-protein interactions represent a novel promising class of drugs that allow disassembly of oncogenic multiprotein complexes. SUMMARY: An improved understanding of disease-specific epigenetic vulnerabilities has led to the development of second-generation mechanism-based epigenetic drugs against myeloid neoplasms. Many of these drugs have been introduced into clinical trials and synergistic drug combination regimens have been shown to enhance efficacy and potentially prevent drug resistance.

Clonal evolution in relapsed NPM1-mutated acute myeloid leukemia.

Mutations in the nucleophosmin 1 (NPM1) gene are considered a founder event in the pathogenesis of acute myeloid leukemia (AML). To address the role of clonal evolution in relapsed NPM1-mutated (NPM1mut) AML, we applied high-resolution, genome-wide, single-nucleotide polymorphism array profiling to detect copy number alterations (CNAs) and uniparental disomies (UPDs) and performed comprehensive gene mutation screening in 53 paired bone marrow/peripheral blood samples obtained at diagnosis and relapse. At diagnosis, 15 aberrations (CNAs, n = 10; UPDs, n = 5) were identified in 13 patients (25%), whereas at relapse, 56 genomic alterations (CNAs, n = 46; UPDs, n = 10) were detected in 29 patients (55%) indicating an increase in genomic complexity. Recurrent aberrations acquired at relapse included deletions affecting tumor suppressor genes (ETV6 [n = 3], TP53 [n = 2], NF1 [n = 2], WT1 [n = 3], FHIT [n = 2]) and homozygous FLT3 mutations acquired via UPD13q (n = 7). DNMT3A mutations (DNMT3Amut) showed the highest stability (97%). Persistence of DNMT3Amut in 5 patients who lost NPM1mut at relapse suggests that DNMT3Amut may precede NPM1mut in AML pathogenesis. Of note, all relapse samples shared at least 1 genetic aberration with the matched primary AML sample, implying common ancestral clones. In conclusion, our study reveals novel insights into clonal evolution in NPM1mut AML.

High-resolution genomic profiling of chronic lymphocytic leukemia reveals new recurrent genomic alterations.

To identify genomic alterations in chronic lymphocytic leukemia (CLL), we performed single-nucleotide polymorphism-array analysis using Affymetrix Version 6.0 on 353 samples from untreated patients entered in the CLL8 treatment trial. Based on paired-sample analysis (n = 144), a mean of 1.8 copy number alterations per patient were identified; approximately 60% of patients carried no copy number alterations other than those detected by fluorescence in situ hybridization analysis. Copy-neutral loss-of-heterozygosity was detected in 6% of CLL patients and was found most frequently on 13q, 17p, and 11q. Minimally deleted regions were refined on 13q14 (deleted in 61% of patients) to the DLEU1 and DLEU2 genes, on 11q22.3 (27% of patients) to ATM, on 2p16.1-2p15 (gained in 7% of patients) to a 1.9-Mb fragment containing 9 genes, and on 8q24.21 (5% of patients) to a segment 486 kb proximal to the MYC locus. 13q deletions exhibited proximal and distal breakpoint cluster regions. Among the most common novel lesions were deletions at 15q15.1 (4% of patients), with the smallest deletion (70.48 kb) found in the MGA locus. Sequence analysis of MGA in 59 samples revealed a truncating mutation in one CLL patient lacking a 15q deletion. MNT at 17p13.3, which in addition to MGA and MYC encodes for the network of MAX-interacting proteins, was also deleted recurrently.

Commonly altered genomic regions in acute myeloid leukemia are enriched for somatic mutations involved in chromatin remodeling and splicing.

Acute myeloid leukemia (AML) is characterized by molecular heterogeneity. As commonly altered genomic regions point to candidate genes involved in leukemogenesis, we used microarray-based comparative genomic hybridization and single nucleotide polymorphism profiling data of 391 AML cases to further narrow down genomic regions of interest. Targeted resequencing of 1000 genes located in the critical regions was performed in a representative cohort of 50 AML samples comprising all major cytogenetic subgroups. We identified 120 missense/nonsense mutations as well as 60 insertions/deletions affecting 73 different genes (∼ 3.6 tumor-specific aberrations/AML). While most of the newly identified alterations were nonrecurrent, we observed an enrichment of mutations affecting genes involved in epigenetic regulation including known candidates like TET2, TET1, DNMT3A, and DNMT1, as well as mutations in the histone methyltransferases NSD1, EZH2, and MLL3. Furthermore, we found mutations in the splicing factor SFPQ and in the nonclassic regulators of mRNA processing CTCF and RAD21. These splicing-related mutations affected 10% of AML patients in a mutually exclusive manner. In conclusion, we could identify a large number of alterations in genes involved in aberrant splicing and epigenetic regulation in genomic regions commonly altered in AML, highlighting their important role in the molecular pathogenesis of AML.

High-resolution genomic profiling of adult and pediatric core-binding factor acute myeloid leukemia reveals new recurrent genomic alterations.

To identify cooperating lesions in core-binding factor acute myeloid leukemia, we performed single-nucleotide polymorphism-array analysis on 300 diagnostic and 41 relapse adult and pediatric leukemia samples. We identified a mean of 1.28 copy number alterations per case at diagnosis in both patient populations. Recurrent minimally deleted regions (MDRs) were identified at 7q36.1 (7.7%), 9q21.32 (5%), 11p13 (2.3%), and 17q11.2 (2%). Approximately one-half of the 7q deletions were detectable only by single-nucleotide polymorphism-array analysis because of their limited size. Sequence analysis of MLL3, contained within the 7q36.1 MDR, in 46 diagnostic samples revealed one truncating mutation in a leukemia lacking a 7q deletion. Recurrent focal gains were identified at 8q24.21 (4.7%) and 11q25 (1.7%), both containing a single noncoding RNA. Recurrent regions of copy-neutral loss-of-heterozygosity were identified at 1p (1%), 4q (0.7%), and 19p (0.7%), with known mutated cancer genes present in the minimally altered region of 1p (NRAS) and 4q (TET2). Analysis of relapse samples identified recurrent MDRs at 3q13.31 (12.2%), 5q (4.9%), and 17p (4.9%), with the 3q13.31 region containing only LSAMP, a putative tumor suppressor. Determining the role of these lesions in leukemogenesis and drug resistance should provide important insights into core-binding factor acute myeloid leukemia.

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.

Intensive chemotherapy with or without gemtuzumab ozogamicin in patients with NPM1-mutated acute myeloid leukaemia (AMLSG 09-09): a randomised, open-label, multicentre, phase 3 trial.

BACKGROUND: Acute myeloid leukaemia with mutated NPM1 is associated with high CD33 expression and intermediate-risk cytogenetics. The aim of this study was to evaluate intensive chemotherapy with or without the anti-CD33 antibody-drug conjugate gemtuzumab ozogamicin in participants with newly diagnosed, NPM1-mutated acute myeloid leukaemia. METHODS: This open-label, phase 3 trial was conducted at 56 hospitals in Germany and Austria. Eligible participants were 18 years or older and had newly diagnosed NPM1-mutated acute myeloid leukaemia and an Eastern Cooperative Oncology Group performance status of 0-2. Participants were randomly assigned, using age as a stratification factor (18-60 years vs >60 years), 1:1 to the two treatment groups using allocation concealment; there was no masking of participants and investigators to treatment groups. Participants received two cycles of induction therapy (idarubicin, cytarabine, and etoposide) plus all-trans retinoic acid (ATRA) followed by three consolidation cycles of high-dose cytarabine (or an intermediate dose for those older than 60 years) and ATRA, without or with gemtuzumab ozogamicin (3 mg/m2 administered intravenously on day 1 of induction cycles 1 and 2, and consolidation cycle 1). The primary endpoints were short-term event-free survival and overall survival in the intention-to-treat population (overall survival was added as a co-primary endpoint after amendment four of the protocol on Oct 13, 2013). The secondary endpoints were event-free survival with long-term follow-up, rates of complete remission, complete remission with partial haematological recovery (CRh), and complete remission with incomplete haematological recovery (CRi), cumulative incidences of relapse and death, and number of days in hospital. This trial is registered with ClinicalTrials.gov (NCT00893399) and has been completed. FINDINGS: Between May 12, 2010, and Sept 1, 2017, 600 participants were enrolled, of which 588 (315 women and 273 men) were randomly assigned (296 to the standard group and 292 to the gemtuzumab ozogamicin group). No difference was found in short-term event-free survival (short-term event-free survival at 6-month follow-up, 53% [95% CI 47-59] in the standard group and 58% [53-64] in the gemtuzumab ozogamicin group; hazard ratio [HR] 0·83; 95% CI 0·65-1·04; p=0·10) and overall survival between treatment groups (2-year overall survival, 69% [63-74] in the standard group and 73% [68-78] in the gemtuzumab ozogamicin group; 0·90; 0·70-1·16; p=0·43). There was no difference in complete remission or CRi rates (n=267 [90%] in the standard group vs n=251 [86%] in the gemtuzumab ozogamicin group; odds ratio [OR] 0·67; 95% CI 0·40-1·11; p=0·15) and complete remission or CRh rates (n=214 [72%] vs n=195 [67%]; OR 0·77; 0·54-1·10; p=0·18), whereas the complete remission rate was lower with gemtuzumab ozogamicin (n=172 [58%] vs n=136 [47%]; OR 0·63; 0·45-0·80; p=0·0068). Cumulative incidence of relapse was significantly reduced by gemtuzumab ozogamicin (2-year cumulative incidence of relapse, 37% [95% CI 31-43] in the standard group and 25% [20-30] in the gemtuzumab ozogamicin group; cause-specific HR 0·65; 0·49-0·86; p=0·0028), and there was no difference in the cumulative incidence of death (2-year cumulative incidence of death 6% [4-10] in the standard group and 7% [5-11] in the gemtuzumab ozogamicin group; HR 1·03; 0·59-1·81; p=0·91). There were no differences in the number of days in hospital across all cycles between treatment groups. The most common treatment-related grade 3-4 adverse events were febrile neutropenia (n=135 [47%] in the gemtuzumab ozogamicin group vs n=122 [41%] in the standard group), thrombocytopenia (n=261 [90%] vs n=265 [90%]), pneumonia (n=71 [25%] vs n=64 [22%]), sepsis (n=85 [29%] vs n=73 [25%]). Treatment-related deaths were documented in 25 participants (4%; n=8 [3%] in the standard group and n=17 [6%] in the gemtuzumab ozogamicin group), mostly due to sepsis and infections. INTERPRETATION: The primary endpoints of the trial of event-free survival and overall survival were not met. However, an anti-leukaemic efficacy of gemtuzumab ozogamicin in participants with NPM1-mutated acute myeloid leukaemia is shown by a significantly lower cumulative incidence of relapse rate, suggesting that the addition of gemtuzumab ozogamicin might reduce the need for salvage therapy in these participants. The results from this study provide further evidence that gemtuzumab ozogamicin should be added in the standard of care treatment in adults with NPM1-mutated acute myeloid leukaemia. FUNDING: Pfizer and Amgen.

Primary CD33-targeting CAR-NK cells for the treatment of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a malignant disorder derived from neoplastic myeloid progenitor cells characterized by abnormal proliferation and differentiation. Although novel therapeutics have recently been introduced, AML remains a therapeutic challenge with insufficient cure rates. In the last years, immune-directed therapies such as chimeric antigen receptor (CAR)-T cells were introduced, which showed outstanding clinical activity against B-cell malignancies including acute lymphoblastic leukemia (ALL). However, the application of CAR-T cells appears to be challenging due to the enormous molecular heterogeneity of the disease and potential long-term suppression of hematopoiesis. Here we report on the generation of CD33-targeted CAR-modified natural killer (NK) cells by transduction of blood-derived primary NK cells using baboon envelope pseudotyped lentiviral vectors (BaEV-LVs). Transduced cells displayed stable CAR-expression, unimpeded proliferation, and increased cytotoxic activity against CD33-positive OCI-AML2 and primary AML cells in vitro. Furthermore, CD33-CAR-NK cells strongly reduced leukemic burden and prevented bone marrow engraftment of leukemic cells in OCI-AML2 xenograft mouse models without observable side effects.

Midostaurin plus intensive chemotherapy for younger and older patients with AML and FLT3 internal tandem duplications.

We conducted a single-arm, phase 2 trial (German-Austrian Acute Myeloid Leukemia Study Group [AMLSG] 16-10) to evaluate midostaurin with intensive chemotherapy followed by allogeneic hematopoietic-cell transplantation (HCT) and a 1-year midosta urin maintenance therapy in adult patients with acute myeloid leukemia (AML) and fms-related tyrosine kinase 3 (FLT3) internal tandem duplication (ITD). Patients 18 to 70 years of age with newly diagnosed FLT3-ITD-positive AML were eligible. Primary and key secondary endpoints were event-free survival (EFS) and overall survival (OS). Results were compared with a historical cohort of 415 patients treated on 5 prior AMLSG trials; statistical analysis was performed using a double-robust adjustment with propensity score weighting and covariate adjustment. Results were also compared with patients (18-59 years) treated on the placebo arm of the Cancer and Leukemia Group B (CALGB) 10603/RATIFY trial. The trial accrued 440 patients (18-60 years, n = 312; 61-70 years, n = 128). In multivariate analysis, EFS was significantly in favor of patients treated within the AMLSG 16-10 trial compared with the AMLSG control (hazard ratio [HR], 0.55; P < .001); both in younger (HR, 0.59; P < .001) and older patients (HR, 0.42; P < .001). Multivariate analysis also showed a significant beneficial effect on OS compared with the AMLSG control (HR, 0.57; P < .001) as well as to the CALGB 10603/RATIFY trial (HR, 0.71; P = .005). The treatment effect of midostaurin remained significant in sensitivity analysis including allogeneic HCT as a time-dependent covariate. Addition of midostaurin to chemotherapy was safe in younger and older patients. In comparison with historical controls, the addition of midostaurin to intensive therapy led to a significant improvement in outcome in younger and older patients with AML and FLT3-ITD. This trial is registered at clinicaltrialsregistry.eu as Eudra-CT number 2011-003168-63 and at clinicaltrials.gov as NCT01477606.

Targeting Chromatin Regulators Inhibits Leukemogenic Gene Expression in NPM1 Mutant Leukemia.

Homeobox (HOX) proteins and the receptor tyrosine kinase FLT3 are frequently highly expressed and mutated in acute myeloid leukemia (AML). Aberrant HOX expression is found in nearly all AMLs that harbor a mutation in the Nucleophosmin (NPM1) gene, and FLT3 is concomitantly mutated in approximately 60% of these cases. Little is known about how mutant NPM1 (NPM1mut) cells maintain aberrant gene expression. Here, we demonstrate that the histone modifiers MLL1 and DOT1L control HOX and FLT3 expression and differentiation in NPM1mut AML. Using a CRISPR/Cas9 genome editing domain screen, we show NPM1mut AML to be exceptionally dependent on the menin binding site in MLL1. Pharmacologic small-molecule inhibition of the menin-MLL1 protein interaction had profound antileukemic activity in human and murine models of NPM1mut AML. Combined pharmacologic inhibition of menin-MLL1 and DOT1L resulted in dramatic suppression of HOX and FLT3 expression, induction of differentiation, and superior activity against NPM1mut leukemia. SIGNIFICANCE: MLL1 and DOT1L are chromatin regulators that control HOX, MEIS1, and FLT3 expression and are therapeutic targets in NPM1mut AML. Combinatorial small-molecule inhibition has synergistic on-target activity and constitutes a novel therapeutic concept for this common AML subtype. Cancer Discov; 6(10); 1166-81. ©2016 AACR.See related commentary by Hourigan and Aplan, p. 1087This article is highlighted in the In This Issue feature, p. 1069.

Designed to kill: novel menin-MLL inhibitors target MLL-rearranged leukemia.

The interaction between menin and oncogenic mixed lineage leukemia (MLL) fusion proteins is required for leukemic transformation and may represent a therapeutic opportunity. In this issue of Cancer Cell, Borkin and colleagues describe the development of highly potent small-molecule inhibitors of this interaction that reverse the leukemic phenotype and prolong survival in murine models of MLL-rearranged leukemia.

Deregulated expression of EVI1 defines a poor prognostic subset of MLL-rearranged acute myeloid leukemias: a study of the German-Austrian Acute Myeloid Leukemia Study Group and the Dutch-Belgian-Swiss HOVON/SAKK Cooperative Group.

PURPOSE: To evaluate the prognostic value of ecotropic viral integration 1 gene (EVI1) overexpression in acute myeloid leukemia (AML) with MLL gene rearrangements. PATIENTS AND METHODS: We identified 286 patients with AML with t(11q23) enrolled onto German-Austrian Acute Myeloid Leukemia Study Group and Dutch-Belgian-Swiss Hemato-Oncology Cooperative Group prospective treatment trials. Material was available from 177 AML patients for EVI1 expression analysis. RESULTS: We divided 286 MLL-rearranged AMLs into three subgroups: t(9;11)(p22;q23) (44.8%), t(6;11)(q27;q23) (14.7%), and t(v;11q23) (40.5%). EVI1 overexpression (EVI1(+)) was found in 45.8% of all patients with t(11q23), with t(6;11) showing the highest frequency (83.9%), followed by t(9;11) at 40.0%, and t(v;11q23) at 34.8%. Concurrent gene mutations were rare or absent in all three subgroups. Within all t(11q23) AMLs, EVI1(+) was the sole prognostic factor, predicting for inferior overall survival (OS; hazard ratio [HR], 2.06; P = .003), relapse-free survival (HR, 2.28; P = .002), and event-free survival (HR, 1.79; P = .009). EVI1(+) AMLs with t(11q23) in first complete remission (CR) had a significantly better outcome after allogeneic transplantation compared with other consolidation therapies (5-year OS, 54.7% v 0%; Mantel-Byar, P = .0006). EVI1(-) t(9;11) AMLs had lower WBC counts, more commonly FAB M5 morphology, and frequently had additional trisomy 8 (39.6%; P < .001). Among t(9;11) AMLs, EVI1(+) again was the sole independent adverse prognostic factor for survival. CONCLUSION: Deregulated EVI1 expression defines poor prognostic subsets among AML with t(11q23) and AML with t(9;11)(p22;q23). Patients with EVI1(+) MLL-rearranged AML seem to benefit from allogeneic transplantation in first CR.