The graft-versus-leukemia effect of prophylactic donor lymphocyte infusions after allogeneic stem cell transplantation is equally effective in relapse prevention but safer compared to spontaneous graft-versus-host disease.

Therapeutic donor lymphocyte infusions (tDLI) are used to reinforce the graft-versus-leukemia (GvL) effect in relapse after allogeneic stem cell transplantation (alloSCT). In contrast, the role of prophylactic DLI (proDLI) in preventing leukemia relapse has been less clearly established, although supported by retrospective, case-control, and registry analyses. We report a prospective, monocentric, ten year cohort of patients with high risk acute leukemias (AL) or myelodysplasia (MDS) in whom proDLI were applied beyond day +120 post alloSCT to compensate for lack of GvL.272 consecutive allotransplanted AL or MDS patients in complete remission and off immunosuppression at day +120 were stratified according to the prior appearance of relevant GvHD (acute GvHD °II-IV or extensive chronic GvHD) as a clinical indicator for GvL. Escalating doses of unmodified proDLI were applied to 72/272 patients without prior relevant GvHD. Conversely, 157/272 patients with prior spontaneous GvHD did not receive proDLI, nor did 43/272 patients with contraindications (uncontrolled infections, patient refusal, DLI unavailability).By day 160-landmark analysis (median day of first DLI application), proDLI recipients had significantly higher five-year overall (OS) and disease free survival (DFS) (77% and 67%) than patients with spontaneous GvHD (54% and 53%) or with contraindications (46% and 45%) (p=0.003). Relapse incidence for patients with proDLI (30%) or spontaneous GvHD (29%) was significantly lower than in patients with contraindications (39%; p=0.021). With similar GvHD incidence beyond day +160, non-relapse mortality (NRM) was less with proDLI (5%) than without proDLI (18%; p=0.036).In conclusion, proDLI may be able to compensate for lack of GvL in alloSCT recipients with high risk AL or MDS.

Impact of gemtuzumab ozogamicin on MRD and relapse risk in patients with NPM1-mutated AML: results from the AMLSG 09-09 trial.

Monitoring of measurable residual disease (MRD) provides prognostic information in patients with Nucleophosmin1-mutated (NPM1mut) acute myeloid leukemia (AML) and represents a powerful tool to evaluate treatment effects within clinical trials. We determined NPM1mut transcript levels (TLs) by quantitative reverse-transcription polymerase chain reaction and evaluated the prognostic impact of NPM1mut MRD and the effect of gemtuzumab ozogamicin (GO) on NPM1mut TLs and the cumulative incidence of relapse (CIR) in patients with NPM1mut AML enrolled in the randomized phase 3 AMLSG 09-09 trial. A total of 3733 bone marrow (BM) samples and 3793 peripheral blood (PB) samples from 469 patients were analyzed. NPM1mut TL log10 reduction ≥ 3 and achievement of MRD negativity in BM and PB were significantly associated with a lower CIR rate, after 2 treatment cycles and at end of treatment (EOT). In multivariate analyses, MRD positivity was consistently revealed to be a poor prognostic factor in BM and PB. With regard to treatment effect, the median NPM1mut TLs were significantly lower in the GO-Arm across all treatment cycles, resulting in a significantly greater proportion of patients achieving MRD negativity at EOT (56% vs 41%; P = .01). The better reduction in NPM1mut TLs after 2 treatment cycles in MRD positive patients by the addition of GO led to a significantly lower CIR rate (4-year CIR, 29.3% vs 45.7%, P = .009). In conclusion, the addition of GO to intensive chemotherapy in NPM1mut AML resulted in a significantly better reduction in NPM1mut TLs across all treatment cycles, leading to a significantly lower relapse rate.

Impact of NPM1/FLT3-ITD genotypes defined by the 2017 European LeukemiaNet in patients with acute myeloid leukemia.

Patients with acute myeloid leukemia (AML) harboring FLT3 internal tandem duplications (ITDs) have poor outcomes, in particular AML with a high (≥0.5) mutant/wild-type allelic ratio (AR). The 2017 European LeukemiaNet (ELN) recommendations defined 4 distinct FLT3-ITD genotypes based on the ITD AR and the NPM1 mutational status. In this retrospective exploratory study, we investigated the prognostic and predictive impact of the NPM1/FLT3-ITD genotypes categorized according to the 2017 ELN risk groups in patients randomized within the RATIFY trial, which evaluated the addition of midostaurin to standard chemotherapy. The 4 NPM1/FLT3-ITD genotypes differed significantly with regard to clinical and concurrent genetic features. Complete ELN risk categorization could be done in 318 of 549 trial patients with FLT3-ITD AML. Significant factors for response after 1 or 2 induction cycles were ELN risk group and white blood cell (WBC) counts; treatment with midostaurin had no influence. Overall survival (OS) differed significantly among ELN risk groups, with estimated 5-year OS probabilities of 0.63, 0.43, and 0.33 for favorable-, intermediate-, and adverse-risk groups, respectively (P < .001). A multivariate Cox model for OS using allogeneic hematopoietic cell transplantation (HCT) in first complete remission as a time-dependent variable revealed treatment with midostaurin, allogeneic HCT, ELN favorable-risk group, and lower WBC counts as significant favorable factors. In this model, there was a consistent beneficial effect of midostaurin across ELN risk groups.

A phase 1b study of glasdegib + azacitidine in patients with untreated acute myeloid leukemia and higher-risk myelodysplastic syndromes.

This phase 1b study evaluated glasdegib (100 mg once daily) + azacitidine in adults with newly diagnosed acute myeloid leukemia (AML), higher-risk myelodysplastic syndromes (MDS), or chronic myelomonocytic leukemia (CMML) who were ineligible for intensive chemotherapy. Of 72 patients enrolled, 12 were in a lead-in safety cohort (LIC) and 60 were in the AML and MDS (including CMML) expansion cohorts. In the LIC, the safety profile of glasdegib + azacitidine was determined to be consistent with those of glasdegib or azacitidine alone, with no evidence of drug-drug interaction. In the expansion cohort, the most frequently (≥ 10%) reported non-hematologic Grade ≥ 3 treatment-emergent adverse events were decreased appetite, electrocardiogram QT prolongation, and hypertension in the AML cohort and sepsis, diarrhea, hypotension, pneumonia, and hyperglycemia in the MDS cohort. Overall response rates in the AML and MDS cohorts were 30.0% and 33.3%, respectively; 47.4% and 46.7% of patients who were transfusion dependent at baseline achieved independence. Median overall survival (95% confidence interval) was 9.2 (6.2-14.0) months and 15.8 (9.3-21.9) months, respectively, and response was associated with molecular mutation clearance. Glasdegib + azacitidine in patients with newly diagnosed AML or MDS demonstrated an acceptable safety profile and preliminary evidence of clinical benefits.Trial registration: ClinicalTrials.gov NCT02367456.

Measurable residual disease monitoring in acute myeloid leukemia with t(8;21)(q22;q22.1): results from the AML Study Group.

We performed serial measurable residual disease (MRD) monitoring in bone marrow (BM) and peripheral blood (PB) samples of 155 intensively treated patients with RUNX1-RUNX1T1+ AML, using a qRT-PC-based assay with a sensitivity of up to 10-6. We assessed both reduction of RUNX1-RUNX1T1 transcript levels (TLs) and achievement of MRD negativity (MRD-) for impact on prognosis. Achievement of MR2.5 (>2.5 log reduction) after treatment cycle 1 and achievement of MR3.0 after treatment cycle 2 were significantly associated with a reduced risk of relapse (P = .034 and P = .028, respectively). After completion of therapy, achievement of MRD- in both BM and PB was an independent, favorable prognostic factor in cumulative incidence of relapse (4-year cumulative incidence relapse: BM, 17% vs 36%, P = .021; PB, 23% vs 55%, P = .001) and overall survival (4-year overall survival rate BM, 93% vs 70%, P = .007; PB, 87% vs 47%, P < .0001). Finally, during follow-up, serial qRT-PCR analyses allowed prediction of relapse in 77% of patients exceeding a cutoff value of 150 RUNX1-RUNX1T1 TLs in BM, and in 84% of patients exceeding a value of 50 RUNX1-RUNX1T1 TLs in PB. The KIT mutation was a significant factor predicting a lower CR rate and inferior outcome, but its prognostic impact was outweighed by RUNX1-RUNX1T1 TLs during treatment. Virtually all relapses occurred within 1 year after the end of treatment, with a very short latency from molecular to morphologic relapse, necessitating MRD assessment at short intervals during this time period. Based on our data, we propose a refined practical guideline for MRD assessment in RUNX1-RUNX1T1+ AML.

Midostaurin added to chemotherapy and continued single-agent maintenance therapy in acute myeloid leukemia with FLT3-ITD.

Patients with acute myeloid leukemia (AML) and a FLT3 internal tandem duplication (ITD) have poor outcomes to current treatment. A phase 2 hypothesis-generating trial was conducted to determine whether the addition of the multitargeted kinase inhibitor midostaurin to intensive chemotherapy followed by allogeneic hematopoietic cell transplantation (alloHCT) and single-agent maintenance therapy of 12 months is feasible and favorably influences event-free survival (EFS) compared with historical controls. Patients 18 to 70 years of age with newly diagnosed AML and centrally confirmed FLT3-ITD were eligible: 284 patients were treated, including 198 younger (18-60 years) and 86 older (61-70 years) patients. Complete remission (CR) rate, including CR with incomplete hematological recovery (CRi) after induction therapy, was 76.4% (younger, 75.8%; older, 77.9%). The majority of patients in CR/CRi proceeded to alloHCT (72.4%). Maintenance therapy was started in 97 patients (34%): 75 after alloHCT and 22 after consolidation with high-dose cytarabine (HiDAC). Median time receiving maintenance therapy was 9 months after alloHCT and 10.5 months after HiDAC; premature termination was mainly a result of nonrelapse causes (gastrointestinal toxicity and infections). EFS and overall survival at 2 years were 39% (95% confidence interval [CI], 33%-47%) and 34% (95% CI, 24%-47%) and 53% (95% CI, 46%-61%) and 46% (95% CI, 35%-59%) in younger and older patients, respectively. EFS was evaluated in comparison with 415 historical controls treated within 5 prospective trials. Propensity score-weighted analysis revealed a significant improvement of EFS by midostaurin (hazard ratio [HR], 0.58; 95% CI, 0.48-0.70; P < .001) overall and in older patients (HR, 0.42; 95% CI, 0.29-0.61). The study was registered at www.clinicaltrials.gov as #NCT01477606.

Midostaurin plus Chemotherapy for Acute Myeloid Leukemia with a FLT3 Mutation.

BACKGROUND: Patients with acute myeloid leukemia (AML) and a FLT3 mutation have poor outcomes. We conducted a phase 3 trial to determine whether the addition of midostaurin - an oral multitargeted kinase inhibitor that is active in patients with a FLT3 mutation - to standard chemotherapy would prolong overall survival in this population. METHODS: We screened 3277 patients, 18 to 59 years of age, who had newly diagnosed AML for FLT3 mutations. Patients were randomly assigned to receive standard chemotherapy (induction therapy with daunorubicin and cytarabine and consolidation therapy with high-dose cytarabine) plus either midostaurin or placebo; those who were in remission after consolidation therapy entered a maintenance phase in which they received either midostaurin or placebo. Randomization was stratified according to subtype of FLT3 mutation: point mutation in the tyrosine kinase domain (TKD) or internal tandem duplication (ITD) mutation with either a high ratio (>0.7) or a low ratio (0.05 to 0.7) of mutant to wild-type alleles (ITD [high] and ITD [low], respectively). Allogeneic transplantation was allowed. The primary end point was overall survival. RESULTS: A total of 717 patients underwent randomization; 360 were assigned to the midostaurin group, and 357 to the placebo group. The FLT3 subtype was ITD (high) in 214 patients, ITD (low) in 341 patients, and TKD in 162 patients. The treatment groups were well balanced with respect to age, race, FLT3 subtype, cytogenetic risk, and blood counts but not with respect to sex (51.7% in the midostaurin group vs. 59.4% in the placebo group were women, P=0.04). Overall survival was significantly longer in the midostaurin group than in the placebo group (hazard ratio for death, 0.78; one-sided P=0.009), as was event-free survival (hazard ratio for event or death, 0.78; one-sided P=0.002). In both the primary analysis and an analysis in which data for patients who underwent transplantation were censored, the benefit of midostaurin was consistent across all FLT3 subtypes. The rate of severe adverse events was similar in the two groups. CONCLUSIONS: The addition of the multitargeted kinase inhibitor midostaurin to standard chemotherapy significantly prolonged overall and event-free survival among patients with AML and a FLT3 mutation. (Funded by the National Cancer Institute and Novartis; ClinicalTrials.gov number, NCT00651261 .).

Measurable residual disease monitoring by NGS before allogeneic hematopoietic cell transplantation in AML.

Molecular measurable residual disease (MRD) assessment is not established in approximately 60% of acute myeloid leukemia (AML) patients because of the lack of suitable markers for quantitative real-time polymerase chain reaction. To overcome this limitation, we established an error-corrected next-generation sequencing (NGS) MRD approach that can be applied to any somatic gene mutation. The clinical significance of this approach was evaluated in 116 AML patients undergoing allogeneic hematopoietic cell transplantation (alloHCT) in complete morphologic remission (CR). Targeted resequencing at the time of diagnosis identified a suitable mutation in 93% of the patients, covering 24 different genes. MRD was measured in CR samples from peripheral blood or bone marrow before alloHCT and identified 12 patients with persistence of an ancestral clone (variant allele frequency [VAF] >5%). The remaining 96 patients formed the final cohort of which 45% were MRD+ (median VAF, 0.33%; range, 0.016%-4.91%). In competing risk analysis, cumulative incidence of relapse (CIR) was higher in MRD+ than in MRD- patients (hazard ratio [HR], 5.58; P < .001; 5-year CIR, 66% vs 17%), whereas nonrelapse mortality was not significantly different (HR, 0.60; P = .47). In multivariate analysis, MRD positivity was an independent negative predictor of CIR (HR, 5.68; P < .001), in addition to FLT3-ITD and NPM1 mutation status at the time of diagnosis, and of overall survival (HR, 3.0; P = .004), in addition to conditioning regimen and TP53 and KRAS mutation status. In conclusion, NGS-based MRD is widely applicable to AML patients, is highly predictive of relapse and survival, and may help refine transplantation and posttransplantation management in AML patients.

Phase I/II study on cytarabine and idarubicin combined with escalating doses of clofarabine in newly diagnosed patients with acute myeloid leukaemia and high risk for induction failure (AMLSG 17-10 CIARA trial).

This open-label, multicentre phase I/II study determined the maximum tolerated dose (MTD), safety and efficacy of clofarabine administered with cytarabine and idarubicin in newly diagnosed acute myeloid leukaemia (AML) patients lacking favourable genetic aberrations. The MTD was 30 mg/m2 clofarabine for patients below and above 60 years. The most frequently reported grade 3-4 non-haematological adverse events were infectious and gastrointestinal toxicities. Complete remission (CR)/CR with incomplete recovery rate was 67%. Allogeneic haematopoietic cell transplantation in first remission was feasible in a high proportion of younger AML patients and probably contributed to the favourable outcome compared to historical controls.

The hypomorphic TERT A1062T variant is associated with increased treatment-related toxicity in acute myeloid leukemia.

Hypomorphic germline variants in TERT, the gene encoding the reverse transcriptase component of the human telomerase complex, occur with a frequency of 3-5% in acute myeloid leukemia. We analyzed the clinical and prognostic impact of the most common TERT A1062T variant in younger patients with acute myeloid leukemia intensively treated within two prospective multicenter trials. Four hundred and twenty patients (age 17-60 years) were analyzed for the TERT A1062T variant by direct sequencing. Fifteen patients (3.6%) carried the TERT A1062T variant. Patients with the TERT A1062T variant had a trend towards less favorable and more intermediate 2/adverse karyotypes/genotypes according to the European Leukemia Net classification. In univariate and multivariate analysis, patients with the TERT A1062T variant had a significantly inferior overall survival compared to wild-type patients (6-year overall survival 20 vs. 41%, p = 0.005). Patients with the TERT A1062T variant showed a high rate of treatment-related mortality: 5/15 (33%) died during induction therapy or in complete remission as compared to 62/405 (15%) of the wild-type patients. In patients with the TERT variant, 14/15 (93%) suffered from non-hematological/non-infectious grade 3/4 adverse events (mostly hepatic and/or mucosal) as compared to 216/405 (53%) wild-type patients (p = 0.006). In multivariate analysis, the TERT A1062T variant was an independent risk factor predicting for adverse events during induction chemotherapy. In conclusion, the TERT A1062T variant is an independent negative prognostic factor in younger patients with acute myeloid leukemia and seems to predispose those patients to treatment-related toxicity.

Differential impact of allelic ratio and insertion site in FLT3-ITD-positive AML with respect to allogeneic transplantation.

The objective was to evaluate the prognostic and predictive impact of allelic ratio and insertion site (IS) of internal tandem duplications (ITDs), as well as concurrent gene mutations, with regard to postremission therapy in 323 patients with FLT3-ITD-positive acute myeloid leukemia (AML). Increasing FLT3-ITD allelic ratio (P = .004) and IS in the tyrosine kinase domain 1 (TKD1, P = .06) were associated with low complete remission (CR) rates. After postremission therapy including intensive chemotherapy (n = 121) or autologous hematopoietic stem cell transplantation (HSCT, n = 17), an allelic ratio ≥ 0.51 was associated with an unfavorable relapse-free (RFS, P = .0008) and overall survival (OS, P = .004); after allogeneic HSCT (n = 93), outcome was significantly improved in patients with a high allelic ratio (RFS, P = .02; OS, P = .03), whereas no benefit was seen in patients with a low allelic ratio (RFS, P = .38; OS, P = .64). Multivariable analyses revealed a high allelic ratio as a predictive factor for the beneficial effect of allogeneic HSCT; ITD IS in TKD1 remained an unfavorable factor, whereas no prognostic impact of concurrent gene mutations was observed. The clinical trials described herein were previously published or are registered as follows: AMLHD93 and AMLHD98A, previously published; AML SG 07-04, ClinicalTrials.gov identifier #NCT00151242.

Mutations in the cohesin complex in acute myeloid leukemia: clinical and prognostic implications.

Mutations in the cohesin complex are novel, genetic lesions in acute myeloid leukemia (AML) that are not well characterized. In this study, we analyzed the frequency, clinical, and prognostic implications of mutations in STAG1, STAG2, SMC1A, SMC3, and RAD21, all members of the cohesin complex, in a cohort of 389 uniformly treated AML patients by next generation sequencing. We identified a total of 23 patients (5.9%) with somatic mutations in 1 of the cohesin genes. All gene mutations were mutually exclusive, and STAG1 (1.8%), STAG2 (1.3%), and SMC3 (1.3%) were most frequently mutated. Patients with any cohesin complex mutation had lower BAALC expression levels. We found a strong association between mutations affecting the cohesin complex and NPM1. Mutated allele frequencies were similar between NPM1 and cohesin gene mutations. Overall survival (OS), relapse-free survival (RFS), and complete remission rates (CR) were not influenced by the presence of cohesin mutations (OS: hazard ratio [HR] 0.98; 95% confidence interval [CI], 0.56-1.72 [P = .94]; RFS: HR 0.7; 95% CI, 0.36-1.38 [P = .3]; CR: mutated 83% vs wild-type 76% [P = .45]). The cohesin complex presents a novel pathway affected by recurrent mutations in AML. This study is registered at www.clinicaltrials.gov as #NCT00209833.

Salvage therapy with high-dose cytarabine and mitoxantrone in combination with all-trans retinoic acid and gemtuzumab ozogamicin in acute myeloid leukemia refractory to first induction therapy.

Outcome of patients with primary refractory acute myeloid leukemia remains unsatisfactory. We conducted a prospective phase II clinical trial with gemtuzumab ozogamicin (3 mg/m(2) intravenously on day 1), all-trans retinoic acid (45 mg/m(2) orally on days 4-6 and 15 mg/m(2) orally on days 7-28), high-dose cytarabine (3 g/m(2)/12 h intravenously on days 1-3) and mitoxantrone (12 mg/m(2) intravenously on days 2-3) in 93 patients aged 18-60 years refractory to one cycle of induction therapy. Primary end point of the study was response to therapy; secondary end points included evaluation of toxicities, in particular, rate of sinusoidal obstruction syndrome after allogeneic hematopoietic cell transplantation. Complete remission or complete remission with incomplete blood count recovery was achieved in 47 (51%) and partial remission in 10 (11%) patients resulting in an overall response rate of 61.5%; 33 (35.5%) patients had refractory disease and 3 patients (3%) died. Allogeneic hematopoietic cell transplantation was performed in 71 (76%) patients; 6 of the 71 (8.5%) patients developed moderate or severe sinusoidal obstruction syndrome after transplantation. Four-year overall survival rate was 32% (95% confidence interval 24%-43%). Patients responding to salvage therapy and undergoing allogeneic hematopoietic cell transplantation (n=51) had a 4-year survival rate of 49% (95% confidence intervaI 37%-64%). Patients with fms-like tyrosine kinase internal tandem duplication positive acute myeloid leukemia had a poor outcome despite transplantation. In conclusion, the described regimen is an effective and tolerable salvage therapy for patients who are primary refractory to one cycle of conventional intensive induction therapy. (clinicaltrials.gov identifier: 00143975).

All-trans retinoic acid as adjunct to intensive treatment in younger adult patients with acute myeloid leukemia: results of the randomized AMLSG 07-04 study.

The aim of this clinical trial was to evaluate the impact of all-trans retinoic acid (ATRA) in combination with chemotherapy and to assess the NPM1 status as biomarker for ATRA therapy in younger adult patients (18-60 years) with acute myeloid leukemia (AML). Patients were randomized for intensive chemotherapy with or without open-label ATRA (45 mg/m2, days 6-8; 15 mg/m2, days 9-21). Two cycles of induction therapy were followed by risk-adapted consolidation with high-dose cytarabine or allogeneic hematopoietic cell transplantation. Due to the open label character of the study, analysis was performed on an intention-to-treat (ITT) and a per-protocol (PP) basis. One thousand one hundred patients were randomized (556, STANDARD; 544, ATRA) with 38 patients treated vice versa. Median follow-up for survival was 5.2 years. ITT analyses revealed no difference between ATRA and STANDARD for the total cohort and for the subset of NPM1-mutated AML with respect to event-free (EFS; p = 0.93, p = 0.17) and overall survival (OS; p = 0.24 and p = 0.32, respectively). Pre-specified PP analyses revealed better EFS in NPM1-mutated AML (p = 0.05) and better OS in the total cohort (p = 0.03). Explorative subgroup analyses on an ITT basis revealed better OS (p = 0.05) in ATRA for genetic low-risk patients according to ELN recommendations. The clinical trial is registered at clinicaltrialsregister.eu (EudraCT Number: 2004-004321-95).

A phase I/II study of sunitinib and intensive chemotherapy in patients over 60 years of age with acute myeloid leukaemia and activating FLT3 mutations.

Acute myeloid leukaemia (AML) with FLT3 mutation has a dismal prognosis in elderly patients. Treatment with a combination of FLT3 inhibitors and standard chemotherapy has not been extensively studied. Therefore, we instigated a phase I/II clinical trial of chemotherapy with cytosine arabinoside (Ara-C)/daunorubicin induction (7+3) followed by three cycles of intermediate-dose Ara-C consolidation in 22 AML patients with activating FLT3 mutations. Sunitinib was added at predefined dose levels and as maintenance therapy for 2 years. At dose level 1, sunitinib 25 mg daily continuously from day 1 onwards resulted in two cases with dose-limiting toxicity (DLT), prolonged haemotoxicity and hand-foot syndrome. At dose level -1, sunitinib 25 mg was restricted to days 1-7 of each chemotherapy cycle. One DLT was observed in six evaluable patients. Six additional patients were treated in an extension phase. Thirteen of 22 patients (59%; 8/14 with FLT3-internal tandem duplication and 5/8 with FLT3-tyrosine kinase domain) achieved a complete remission/complete remission with incomplete blood count recovery. For the 17 patients included at the lower dose level, median overall, relapse-free and event-free survival were 1·6, 1·0 and 0·4 years, respectively. Four out of five analysed patients with relapse during maintenance therapy lost their initial FLT3 mutation, suggesting outgrowth of FLT3 wild-type subclones.

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.

Mutant IDH1 promotes leukemogenesis in vivo and can be specifically targeted in human AML.

Mutations in the metabolic enzymes isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) are frequently found in glioma, acute myeloid leukemia (AML), melanoma, thyroid cancer, and chondrosarcoma patients. Mutant IDH produces 2-hydroxyglutarate (2HG), which induces histone- and DNA-hypermethylation through inhibition of epigenetic regulators. We investigated the role of mutant IDH1 using the mouse transplantation assay. Mutant IDH1 alone did not transform hematopoietic cells during 5 months of observation. However, mutant IDH1 greatly accelerated onset of myeloproliferative disease-like myeloid leukemia in mice in cooperation with HoxA9 with a mean latency of 83 days compared with cells expressing HoxA9 and wild-type IDH1 or a control vector (167 and 210 days, respectively, P = .001). Mutant IDH1 accelerated cell-cycle transition through repression of cyclin-dependent kinase inhibitors Cdkn2a and Cdkn2b, and activated mitogen-activated protein kinase signaling. By computational screening, we identified an inhibitor of mutant IDH1, which inhibited mutant IDH1 cells and lowered 2HG levels in vitro, and efficiently blocked colony formation of AML cells from IDH1-mutated patients but not of normal CD34(+) bone marrow cells. These data demonstrate that mutant IDH1 has oncogenic activity in vivo and suggest that it is a promising therapeutic target in human AML cells.

Axl, a prognostic and therapeutic target in acute myeloid leukemia mediates paracrine crosstalk of leukemia cells with bone marrow stroma.

Acute myeloid leukemia (AML) represents a clonal disease of hematopoietic progenitors characterized by acquired heterogenous genetic changes that alter normal mechanisms of proliferation, self-renewal, and differentiation.(1) Although 40% to 45% of patients younger than 65 years of age can be cured with current therapies, only 10% of older patients reach long-term survival.(1) Because only very few novel AML drugs were approved in the past 2 decades, there is an urgent need to identify novel targets and therapeutic strategies to treat underserved AML patients. We report here that Axl, a member of the Tyro3, Axl, Mer receptor tyrosine kinase family,(2-4) represents an independent prognostic marker and therapeutic target in AML. AML cells induce expression and secretion of the Axl ligand growth arrest-specific gene 6 (Gas6) by bone marrow-derived stromal cells (BMDSCs). Gas6 in turn mediates proliferation, survival, and chemoresistance of Axl-expressing AML cells. This Gas6-Axl paracrine axis between AML cells and BMDSCs establishes a chemoprotective tumor cell niche that can be abrogated by Axl-targeting approaches. Axl inhibition is active in FLT3-mutated and FLT3 wild-type AML, improves clinically relevant end points, and its efficacy depends on presence of Gas6 and Axl. Axl inhibition alone or in combination with chemotherapy might represent a novel therapeutic avenue for AML.