ALBERT

Description: Abstract 2371 PNH is a clonal stem cell disease. While nonmalignant, PNH shows certain similarities to MDS and other neoplasms affecting hematopoietic stem and progenitor cells, including persistence of an aberrant clone, clonal expansion, and phenotypic abnormalities. In a small proportion of patients, subtle chromosomal abnormalities can be found and cases of otherwise classical PNH due to microdeletions involving the PIG-A locus have been described, illustrating similarities to other malignant conditions. PIG-A gene mutations lead to defective biosynthesis of GPI anchors and are responsible for the PNH phenotype. Similarly, phenotypic features of stem cells affected by PIG-A mutations are believed to be responsible for the extrinsic growth advantage and clonal expansion in the context of immune mediated suppression of hematopoiesis. While this scenario is plausible, there are also observations suggesting that intrinsic factors may be also involved. For instance, PNH persists after successful immunosuppression, often for many years, suggesting activation of stem cell maintenance genes. Furthermore, PNH clones can also be encountered (albeit at a very low frequency) in healthy individuals, and PNH can present in a pure form without aplastic anemia. Such extrinsic factors may include additional, secondary genetic events such as somatic mutations. Supporting this theory, clonal rearrangement of chromosome 12, which leads to overexpression of the transcription factor HMGA2 gene, were found in cells with the PIG-A mutation from 2 PNH cases. Also, we recently reported 3 PNH cases with JAK2 V617F mutation, who presented with a MPN phenotype and thrombosis. We theorized that study of clonal architecture in PNH will reveal clues as to the pathogenesis of clonal evolution of the PNH stem cell. We applied next generation whole exome sequencing to detect somatic mutations in PNH cases (N=6). The subsequent validation set included 45 PNH cases. PNH and non-PNH cells were sorted using magnetic beads. DNA from both fractions was analyzed by whole exome sequencing and results of the non-PNH cells were subtracted from the results of the PNH clone. We found biallelic PIG-A mutations in 2 female cases and a single mutation in each male case. In an index female case with thrombosis, a novel somatic heterozygous mutation of NTNG1 (P24S) was detected, while the patient was negative for the JAK2 mutation. Allelic frequency with the NTNG1 mutation (53/160 sequence reads (33%)) was larger than that with a concomitant heterozygous PIG-A mutation (intron 5 splice donor site G

Description: NPM1 and DNMT3A mutations are highly recurrent (∼30% of cases) in de novo acute myeloid leukemia (AML). Besides aberrant cytoplasmic localization of mutated NPM1, and decreased DNA methyltransferase activity of mutated DNMT3A, the molecular mechanisms of pathogenesis are mysterious. Here, novel specific molecular mechanisms are demonstrated. These results build on and are separate from data presented (poster) at ASH 2012. LC-MSMS analysis of murine hematopoietic cells was used to analyze the protein interaction network of the key monocyte/macrophage differentiation-driving transcription factor Pu.1. Npm1 was noted to interact with Pu.1 in these analyses, confirmed by bidirectional co-immunoprecipitation-Western blot assays. This interaction suggested that PU.1 might be dragged into the cytoplasm by mutated NPM1 in AML. Accordingly, in the OCI-AML3 cell line that contains an NPM1 mutation, but not in OCI-AML2 cells with wild-type NPM1, PU.1 was co-dislocated into the cytoplasm together with NPM1, obvious by Western analysis of cellular fractions, and by immunofluorescence (IF) assays. IF analysis of primary AML cells from patients with NPM1 mutated AML confirmed this cytoplasmic dislocation of both NPM1 and PU.1 (n=3), with strong cytoplasmic instead of nuclear staining of both proteins. In contrast, primary AML cells with wild-type NPM1demonstrated the expected strong staining of these proteins in the nucleus but not in the cytoplasm (n=3). NPM1 movement into the cytoplasm is mediated by CRM1 (exportin). Thus, we hypothesized that antagonizing mutated NPM1 interaction with CRM1 would retain mutated NPM1 and PU.1 in the nucleus. Decoy peptides based on NPM1 C-terminal sequences, to hopefully minimize disruption to CRM1 interactions with other proteins, were designed to antagonize NPM1 binding to CRM1. These decoy peptides were combined with different nuclear delivery sequences including the TAT peptide, and with fluorescent tags for tracking. All six peptides entered AML-OCI3 cells (shown by IF), with the strongest signals observed for peptides fused to TAT and TAT-NES (nuclear export signal). The decoy peptides significantly and substantially inhibited cell growth of AML-OCI3 cells (〉3-fold reduction), accompanied by an increase in expression of the monocyte differentiation marker CD14 (quantified by flow-cytometry). In contrast, TAT peptide alone, as a control, did not inhibit cell growth or induce monocytic differentiation. Western and IF analyses was used to study PU.1 and NPM1 localization: decoy peptide treatment clearly increased nuclear presence of both PU.1 and NPM1, although these proteins remained detectable in cytoplasmic fractions also. At ASH 2012, we showed that OCI-AML3 cells have high nuclear CEBPA and retain granulocytic differentiation potential, readily induced by ATRA. Thus, we hypothesized that the NPM1-induced differentiation block, that is specific for the monocytic lineage, creates selective pressure for cooperative mutations that derepress monocyte-commitment. DNMT3A interacts with polycomb proteins that repress lineage-programs, and in NPM1/DNMT3A double mutant versus NPM1 mutant AML, double mutation was significantly associated with M4/M5 (14/23 [61%]) versus M1 morphology (4/13 [30%], p40-fold, p

Description: Aplastic Anemia (AA) is a rare bone marrow failure disorder characterized by pancytopenia, and an empty bone marrow. The disease can develop from unknown causes (idiopathic) or can be secondary to drugs, toxins, chemotherapy (acquired). Hematopoietic bone marrow transplant is a potential cure for idiopathic AA patients. Pharmacologic therapies remain the foremost therapy for patients who lack suitable donors or ineligible for bone marrow transplant. Antithymocyte globulin (ATG) is a first line treatment for these patients. However, relapsed and refractory cases of AA can occur even after ATG treatment. Patients with relapsed/ refractory AA may benefit from alternative immunosuppressive therapies. Alefacept is a novel immunosuppressive agent that targets the CD2-LFA3 pathway important in various T cell functions especially T cell activation. The occurrence of relapsed/ refractory cases of AA coupled with the side effect profile of ATG prompted us to test alefacept in refractory AA. This Phase I/II study was fully approved by the Institutional Review Board of the Cleveland Clinic and conducted in patients with relapsed/ refractory AA. This trial was registered under ClinicalTrial.Gov Identifier Number: NCT01267643. A total of four patients were successfully enrolled in this trial. All four patients had refractory AA. Antecedent treatment for three patients was immunosuppressive therapy: ATG in one case, cyclosporine in one, and both plus daclizumab in one case. All patients are female. Patient ages at the beginning of the study were 39, 57, 83, and 90 years. Three of the four patients were ECOG performance status 1 and one patient was ECOG 2. Three patients received dose level 1 (7.5 mg/ week) while one patient was treated at dose level 2 (10 mg/week). All patients received once weekly treatments for a total of 12 weeks. All 4 patients have been followed for 15, 13, 12, and 11 months, respectively. None of the patients had a PNH clone at presentation. Blood parameters at the beginning of the alefacept treatment indicated that two patients had three cytopenias (Hgb

Description: Despite documented success of immunosuppressive therapy (IST) in the treatment of aplastic anemia (AA), a significant minority of patients remain refractory, most responses are incomplete, and allogeneic stem cell transplantation is not available for older patients or those with significant comorbidities. Until introduction of the cMpl agonist eltrombopag, anabolic steroids were the most commonly used salvage drugs. At least theoretically, engaging growth factor receptors with eltrombopag has the potential to promote the evolution or expansion of mutant clones and thereby increase the rate of progression to secondary MDS, a feared complication of AA occurring in 10-20% of patients. Recently we and others reported detection of clonogenic somatic mutations typical of MDS in patients with AA and PNH. Subsequent study demonstrated that mutations characteristic of sMDS can be found in some patients at presentation of AA and may constitute risk for subsequent progression to MDS. As the risk of MDS evolution was a prominent concern when filgrastim was more widely used in management of AA, now similar questions have been raised regarding use of eltrombopag, be it as salvage therapy or to complement IST. Recently, one of our primary refractory patients receiving eltrombopag progressed to AML. This clinical observation led to investigation of the impact of eltrombopag on evolution and clonal expansion using deep sequencing of a cohort of patients with AA. DNA from bone marrow cells was sequenced before and after initiation of eltrombopag to evaluate clonal expansion or evolution using a targeted multi-amplicon deep sequencing panel of the top 60 most commonly mutated genes in MDS. Among 208 AA patients treated at Cleveland Clinic, we identified 13 patients (median age 68 yrs.) who were treated with eltrombopag for IST-refractory AA; median duration of treatment was 85 wks. The overall response rate, defined as sustained improvement in blood counts and transfusion independence after 12 weeks of therapy, was 46% (6/13), while 38% (5/13) of patients showed stable disease with intermittent transfusions (one of whom underwent HSCT). Among the two non-responders, one patient developed a PNH clone and another progressed to AML (see below). Expansion of PNH granulocytes after eltrombopag treatment was observed in 2 patients. Two patients had chromosomal abnormalities at initial diagnosis, one with t (10; 18) in 2 metaphases, and one with an extranumeral Y chromosome. Use of next generation sequencing (NGS) allows for the quantitative detection of clonal events. We hypothesized that serial analysis by NGS before and after eltrombopag therapy may provide clues as to potential effects of this drug on clonal evolution. Sequencing analysis before eltrombopag treatment revealed the presence of a sole clonal mutational event in 3/13 cases, including CEBPA, EZH2, and BCOR. In the patient with a CEBPA mutation, the mutation persisted during treatment with minimal clonal expansion evidenced by a change in VAF from 53% to 65%. In the second patient, NGS results revealed the initial presence of an EZH2 mutation. A post eltrombopag sample clearly identified acquisition of additional clonal events in genes highly associated with advanced disease and clonal evolution (RUNX1 and U2AF1), as well as slight expansion of a persistent EZH2 clone from 2 to 8%. The third patient harbored a BCOR mutation which expanded markedly, increasing from 8% to 21%, and was accompanied by a hematological response. Sequencing results after eltrombopag treatment revealed the acquisition of new somatic mutations in 5/13 (38%) cases: 2 new CEBPA mutations, 1 new BCOR mutation, and, as discussed, one case with an initial EZH2 mutation in which RUNX1 and U2AF1 mutations were later discovered. In the 5th patient, evolution to AML was observed and accompanied by a large DNMT3A and U2AF1 clone that was absent on initial evaluation. In conclusion, we did observe occasional expansion of clones with potentially leukemogenic mutations during treatment with eltrombopag. At our institution a case control study of patients with refractory aplastic anemia without treatment with eltrombopag is ongoing; ideally a prospective trial would be needed to confirm results. Our results suggest that the initial detection of certain somatic mutations (CBL, SETBP1 and RUNX1) associated with post-AA MDS may contraindicate use of eltrombopag in AA. Disclosures Sekeres: Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; TetraLogic: Membership on an entity's Board of Directors or advisory committees.

Description: Background Several recurrent somatic mutations have been identified in MDS and these mutations play an important role in disease pathophysiology and outcome. BCOR and BCORL1 are located on chromosome X and interact with histone deacetylases and other cell functions. The BCOR gene is mutated (BCORMUT) in 4-6% of MDS patients (pts) and is associated with poor outcome. BCORL1 mutations (BCORL1MUT ) are present in

Description: Recurrent somatic nonsense PHF6 mutations have been reported in patients with T-acute lymphocytic leukemia, AML and chronic myeloid leukemia in blast crisis. Germ line (GL) PHF6 mutations are responsible for Borjeson−Forssman−Lehmann syndrome (BFLS), a hereditary X-linked disorder characterized by mental retardation and dysmorphic features. PHF6 is a highly conserved 41kDa protein with ubiquitous expression in hematopoietic cells, including CD34+ cells. We screened patients (N=1166) with myeloid neoplasms by targeted multi-amplicon deep NGS targeting all ORFs of PHF6 to determine the prevalence and distribution and molecular context of PHF6 gene alterations. In total, we identified and verified 52 cases with somatic PHF6 mutations, 32 of which were frameshift or nonsense mutations and with a strong male predominance (76%). Mutations were distributed almost equally between 2 DNA binding domains. Previously, PHF6 has been included in other screening panels (Haferlach et al. 2014 and Papaemmanuil 2013) with somatic mutations found in 24/944 and 21/738 MDS cases, respectively. SNP-array karyotyping showed that microdeletions involving the PHF6 locus were present in about 1.2% of myeloid neoplasms, but affected only female patients. The most frequent chromosomal aberration observed in conjunction with PHF6 mutations was trisomy-8 (P=.018). The most commonly associated somatic mutations included RUNX1 (P=.001) and IDH1 (P=.008) but not IDH2 (P〉.1). There was no impact on overall survival with respect to PHF6 mutant status in total or within individual risk groups (low risk (RA,RARS) vs. high-risk (RAEB1/2). Concomitant PHF6 and RUNX1 mutations were associated with particularly poor prognosis. RUNX1 mutational status correlated with PHF6 expression levels and PHF6 expression inversely correlated with RUNX1 mRNA levels. Subsequent analysis of clonal architecture using VAF calculations and serial samples for these cases suggested that PHF6 may function as a founder driver gene in 18% of cases. PHF6 variant allelic frequency (VAF) varied between disease subtypes, with the highest clonal burden found in AML patients (P

Description: Acute undifferentiated leukemia (AUL) and mixed phenotype acute leukemia (MPAL) are acute leukemias of ambiguous lineage representing less than 5% of all adult leukemias. Ontogenetically, they are thought to be caused by precursor lesions in early pluripotent hematopoietic progenitor cells having the ability to differentiate into both lymphoid and myeloid lineages. In contrast, common lymphoid and myeloid leukemias are likely derived from precursor lesions in committed progenitor cells. The molecular characteristics of the cell of origin of these leukemias have not been fully characterized. Given the ambiguous classification of these disorders, we used NGS to evaluate the molecular profiles of this unique subset of leukemias. Our panel tested for the 60 most commonly mutated genes in myeloid malignancies (MM), which can be used to further elucidate driver mutations that play a role in the pathogenesis of this unique entity. Molecular data was available for 18 of 35 patients (pts) (51%), of whom 8 were T/myeloid, 7 were B/myeloid, and 3 were AUL. 14 pts out of the 18 had samples at the time of initial diagnosis, 3 AUL cases harbored mutations commonly seen in MM, including one patient with DNMT3A and a germ line JAK3 mutation, another with U2AF1 and PHF6 mutations, and one pt with SF3B1 and MECOM mutations. Of the 5 B/myeloid cases, 4 had only one mutation detected by the sequencing panel, including TET2, PTPN11, KDM6A, and PHF6, and one had no mutations, but did have complex cytogenetics. Of interest, we identified four patients with T/myeloid MPAL that harbored a FLT3-ITD mutation. Notably, one of these cases had additional DNMT3A and TET2 mutations while another case had a WT1 mutation. We assert that the mutational data for MPAL supports that T-myeloid MPAL encompasses a borderland between early T precursor (ETP)-ALL/AML in addition to more typical cases of T-ALL/AML given its similar immunophenotype to ETP ALL (CD117, CD13 and CD33 positive). The overlap between these two entities is illustrated in the figure below. With this immunophenotyping and molecular profiling we propose a new provisional entity, ETP-myeloid MPAL in addition to already existing ETP ALL. Of 1250 pts with acute leukemia diagnosed from 1997-2016 at Cleveland Clinic, 35 had immunophenotypic characteristics of ambiguous leukemia based on WHO criteria. The median age at diagnosis was 50 years, and 22 (63%) were male. There were 31 MPAL (16 T/myeloid, 15 B/myeloid) and 4 AUL cases. Among the 31 MPAL patients, 2 were mixed lineage chimera (subclones), and 29 had true biphenotypic features. 48% of the cohort had normal cytogenetics at diagnosis, 23% had other cytogenetic abnormalities, 14% had complex karyotype, 9% had MLL gene rearrangement, and 6% had t(9;22). 62% of pts were treated with acute lymphoblastic leukemia (ALL) directed induction chemotherapy (IC), while 38% were treated with acute myelogenous leukemia (AML) directed IC. Rates of complete remission (CR) were significantly higher in pats treated with ALL-IC regimen (82%) versus AML-IC regimen (23%) (p=.003). In our study, two cases with the recurrent lymphoid mutations WT1 and KDM6A, that achieved CR with upfront ALL-IC, while one case with FLT3-ITD, DNMT3A, and TET2 mutations achieved CR with AML-IC treatment. Pts

Description: Recently, rare somatic nonsense PHF6 mutations and deletions have been reported in patients with T-ALL, AML and blast crisis CML. Germ line PHF6 mutations have been described in Borjeson−Forssman−Lehmann syndrome (BFLS), a hereditary X-linked disorder characterized by mental retardation and somatic deformities. Patients with BFLS have been also reported to develop leukemia, suggesting PHF6 mutations may predispose to cancer. PHF6 is a highly conserved 41kDa protein showing ubiquitous expression in a variety of tissues, including bone marrow, CD34+ cells and leukocytes. The function and molecular pathogenesis in hematological disorders is unknown. PHF6 has been suggested to be a tumor suppressor gene (TSG) involved in the control of rRNA synthesis. Recent CHIPseq experiments showed that PHF6 binds upstream of the regulatory sequence of RUNX1. In an index case of a young adult female patient with proliferative CMML with dysmorphic features, we have identified remarkable GL mosaicism for PHF6 mutation (p.K44fs), confirmed by deep sequencing of bone marrow, CD3+ cells, spleen and skin tissue. Subsequently, we screened patients with myeloid neoplasms by targeted multi-amplicon sequencing to determine the prevalence and distribution of PHF6 gene alterations. Sequencing results from 1122 cases were analyzed (778 by targeted deep sequencing and 344 by whole exome sequencing). In total, we identified 45 cases with PHF6 mutations, 32 of which were frameshift or nonsense mutations. Previously, PHF6 have been included in screening panels by Haferlach et al., (Leukemia 2014) and Papaemmanuil et al., (Blood 2013) and somatic mutations were found in 24/944 and 21/738 cases of MDS, respectively. The somatic nature of these defects was confirmed by analysis of non-clonal CD3+ lymphocytes, Thus the incidence of PHF6 mutations ranges from 4.3% in current study to 2.8% and 2.5% reported by others and are most frequently observed among patients with secondary AML (33%), suggesting that PHF6 mutations are not uncommon driver events in myeloid neoplasia. Gender distribution showed a strong male predominance (76%), indicating that retention of a single copy of PHF6 may be protective. There was no significant sex difference in the transcriptional expression of PHF6 itself. The most frequent chromosomal aberration observed in conjunction with PHF6 mutations was trisomy-8 (p=.08). The most commonly associated somatic mutations were in RUNX1 (p=.001) and IDH2 (p=.008). Concomitant PHF6 and RUNX1 mutations are associated with a poor prognosis in AML, and occur predominantly in males. There was no association observed between low expressors of PHF6 and RUNX1 mutations or RUNX1 expression levels. Conversely, RUNX1 mutant cases without somatic PHF6 mutations were not observed to have low transcriptional PHF6 levels. Subsequent analysis of clonal architecture using variant allelic frequency calculations and serial sampling suggested that mutated PHF6 may function as a founder driver gene in proportion of cases, while RUNX1 mutations are acquired as secondary events. Recent studies proposed that PHF6 deficiency leads to impaired cell proliferation, cell cycle arrest at the G2/M phase and an increase in DNA damage. To delineate a possible pathophysiological pathway involving PHF6 we compared transcriptional expression profiles of low expressors to those with normal levels of PHF6. The most notably deregulated group of genes were clustered to a functionally related group of ribosomal RNA proteins (p

Description: Acute myeloid leukemia (AML) is self-renewal by immature myeloid precursors that fail to differentiate. An influential 'leukemia stem cell' model thus proposes that leukemogenic proteins augment or introduce a stem cell-like self-renewal program into cells, e.g., by upregulating signaling or transcription factors (TF) emblematic of stem cells (e.g., HOX). We investigated how the most recurrently mutated protein in AML, mutant nucleophosmin (mNPM1), causes leukemic cell expansion. The results challenge this model, but most importantly, open the door to rational targeted therapy for mNPM1 AML. One way of examining for stem cell programs in AML cells is to look at expression patterns of master TF that regulate expression of hundreds of genes and dictate cell fates. Of these select TF, the master TF that create hematopoietic stem cells (HLF etc.) are minimally or not expressed. Instead, there are very high levels of the master TF that drive monocyte and granulocyte lineage fates, PU.1 (SPI1) and CEBPA. Clearly, however, the lineage-programs intended by PU.1/CEBPA are inefficiently executed if at all - mNPM1 AML patient bone marrows had 85-97% cells with a granulocyte-monocyte progenitor phenotype, accumulated at the expense of downstream mature cells (Quek et al, JEM 2016). This aggregation at a lineage-committed, intermediate, naturally proliferative level of the hematopoietic hierarchy suggests an alternative model - instead of introducing a poorly-defined stem cell self-renewal program, mutant proteins disable differentiation programs which usually quench MYC-driven proliferation intrinsic to lineage-progenitors. To better understand how mNPM1 interacts with cellular machinery, we used mass-spectrometry to comprehensively document the protein interactions of endogenous NPM1 in AML cell nuclear and cytoplasmic fractions, the first analysis of this kind. Notably, the NPM1 protein interactome was enriched for PU.1. Critically, wild-type (wt) NPM1/PU.1 was in the nucleus of wtNPM1 AML cells, but mNPM1/PU.1 was in the cytoplasm of mNPM1 AML cells. This was evident clearly also by Western blot of cell fractions and by IF microscopy of primary AML cells and cell lines. Is cytoplasmic dis-location of PU.1 sufficient to explain persistent hematopoietic precursor proliferation? We used murine Pu.1 knock-out hematopoietic precursors transduced to express Pu.1 fused with the estrogen receptor (Pu.1-ER) to answer this question - Pu.1 relocation from the cytoplasm to the nucleus by tamoxifen triggered monocytic differentiation that terminated proliferation. Moreover, Pu.1-ER cells, like mNPM1 AML cells, highly express Hox genes, rapidly suppressed upon Pu.1 relocation to the nucleus. Thus, Pu.1 dominantly controls Hox and proliferation, as befitting of a master TF, and persistent HOX expression, like persistent progenitor proliferation, can be caused by Pu.1 loss-of-function. Protein macromolecules like NPM1 require transport factors to exit (exportins) the nucleus. A specific exportin, XPO1, was the major exportin found in the NPM1 interactome. XPO1 interactions with transported cargo can be inhibited by the small molecule drug KPT330. KPT330 10-20 nM rapidly re-located mNPM1 and PU.1 to the nucleus, downregulated MYC, upregulated p27/CDKN1B, upregulated monocyte but not granulocyte differentiation markers, induced morphologic changes of monocyte differentiation, and terminated proliferation of mNPM1 AML cells. The same low nanomolar treatment did not induce differentiation of wtNPM1 AML cells (THP1). Moreover, these KPT330 levels are not toxic to normal hematopoiesis (also shown by others). Thus, rather than gain-of-function of elusive stem cell-like self-renewal, the most frequently mutated protein in AML creates self-renewal by disabling a differentiation program that quenches intrinsic MYC-driven proliferation of lineage-progenitors. These observations are a mechanistic rationale to select refractory/relapsed mNPM1 AML patients for treatment with low well-tolerated doses of KPT330, with a defined molecular pharmacodynamic objective of returning PU.1 to the nucleus, to produce cell cycle exits by differentiation rather than p53-mediated apoptosis (to address chemotherapy resistance), to spare precious normal HSC (good therapeutic index), and directly reverse the basis for leukemic self-renewal (proliferation without differentiation). Figure. Figure. Disclosures Landesman: Karyopharm Therapeutics Inc: Employment, Other: stockholder. Saunthararajah:EpiDestiny: Consultancy, Other: patents around decitabine and tetrahydrouridine.

Description: Background Achieving a complete remission (CR) in patients with newly diagnosed acute myeloid leukemia (AML) after induction chemotherapy with cytarabine and an anthracycline (7+3) remains an important treatment goal associated with better overall survival (OS). Approximately 25-30% of younger, and up to 50% of older patients (pts) fail to achieve CR. AML pts with residual leukemia at day 14 receive a second cycle of the same regimen; whether these pts have worse survival than pts not requiring re-induction is unclear. Information on pts with primary refractory AML and the best treatment strategy in this setting are limited. Methods Pts with newly diagnosed AML treated at our institution between 1/2000 and 1/2015 were included. Pts received standard induction chemotherapy with cytarabine for 7 days and an anthracycline for 3 days (7+3). Bone marrow biopsies were obtained at day 14 and a second cycle of the same regimen (7+3 for younger adults, 5+2 for older adults) was given to pts with residual leukemia (blasts 〉 5%). All responses were assessed at day 30 +/- 5 days post induction. Response was defined as CR and CR with incomplete hematologic recovery (CRi) or platelet recovery (CRp) per International Working Group (IWG) 2003 response criteria. Cytogenetic risk stratifications were based on CALGB/Alliance criteria. OS was calculated from the time of diagnosis to time of death or last follow up. A panel of 62 gene mutations that have been described as recurrent mutations in myeloid malignancies was used to evaluate whether genomic data can be used to predict response. Results: Among 227 pts with AML, 123 received 7+3 and had clinical and mutational data available. Median age was 60 years (range, 23-82). Median baseline WBC was 8.2 X 109/L (range, 0.3-227), hemoglobin 8.9 g/L (range, 4.7-13.8), platelets 47 X 109/L (range, 9-326), and BM blasts 46% (range, 20-95). Cytogenetic risk groups were: favorable in 12 (10%), intermediate in 68 (56%) [normal karyotype in 44 (36%)], and unfavorable in 42 (34%). A total of 93 pts (76%) responded, 69 (74%) received 1 cycle of induction and 24 (26%) required re-induction at day 14 due to residual leukemia. A total of 39 pts (32%) received allogeneic stem cell transplant (ASCT): 18 (46%) from a matched sibling donor, 16 (41%) from a matched unrelated donor and 5 (13%) had an umbilical cord transplant. With a median follow up of 13.5 months, the median OS for the entire group was 13 months (m, range, 0.1-120). The median OS for pts who failed 1-2 cycles of 7+3 was significantly worse than pts who responded (median 2.6 vs 16.9 m, p = 0.002). When pts undergoing ASCT were censored, the median OS was 2.3 vs 9.9 m, p= 0.003, respectively. Overall, 33 pts (27%) had residual leukemia at day 14 and received re-induction, 24 (72%) achieved a response at day 30+/- 5 days. The median OS for pts who received re-induction was inferior compared to pts who did not (10.1 vs. 16.1 months, p= 0.02). When pts who received ASCT were censored, the OS was similar (8.5 vs. 7.4 months, p = 0.49, respectively). Among the 30 pts with persistent disease following induction therapy at day 30, 11 (37%) died from induction complications, 6 (20%) received salvage therapy with mitoxantrone/etoposide/cytarabine, 3 (10%) received high dose cytarabine, 2 (7%) received azacitidine, and 8 (27%) received best supportive care. Among pts who received salvage chemotherapy 56% achieved CR and proceeded with ASCT. Two pts had ASCT with residual leukemia and relapsed within 3 m of ASCT. Pts who received ASCT after induction failure had a significantly better OS compared to non-transplant pts (median OS 22.0 vs. 1.4 months, p 〈 0.001, respectively); however, this benefit was only seen in pts who had ASCT in CR. We then investigated if genomic mutations can predict response or resistance to chemotherapy. Out of the 62 genes tested, only a TP53 mutation was associated with resistance, p = 0.02. Further, pts with TP53 mutations had significantly inferior OS compared to TP53 wild type regardless of ASCT status (1.4 vs 14.8 m, p〈 0.001) Conclusion: Pts with newly diagnosed AML who fail induction chemotherapy with a 7+3 regimen have a poor outcome. Re-induction with the same regimen at day 14 for residual leukemia converted most non-responders to responders, but was associated with worse OS. ASCT improves outcome only in pts who achieve CR with salvage therapy. TP53 mutations predicted resistance to chemotherapy with 7+3. Disclosures Carew: Boehringer Ingelheim: Research Funding. Sekeres:TetraLogic: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees.