Bloomfield, Clara D.

Abstract Overexpression of B-cell leukemia/lymphoma 2 (BCL2) renders acute myeloid leukemia (AML) cells resistant to chemotherapy and has been associated with unfavorable outcomes. Oblimersen (G3139) is a phosphorothioate 18-mer antisense oligonucleotide directed against the first 6 BCL2 codons. In a phase 1 study of AML patients treated with G3139, cytarabine, and daunorubicin induction with cytarabine consolidation, no antisense-related toxicity was reported, and BCL2 downregulation occurred in patients achieving complete remission. In this phase 3 trial, untreated older AML patients were randomized to cytarabine (100 mg/m2 per day on days 4-10) and daunorubicin (60 mg/m2 per day on days 4-6) followed by cytarabine consolidation (2000 mg/m2 per day on days 4-8) with (arm A) or without (arm B) G3139 (7 mg/m2 per day on days 1-10 [induction] or days 1-8 [consolidation]). A total of 506 patients were enrolled. No differences in toxicity were observed between arms. Estimated overall survival (OS) at 1 year was 43% for arm A and 40% for arm B (1-sided log rank P = .13), with no differences in disease-free (DFS; P = .26) or event-free survival (P = .80). Subgroup analyses showed patients age <70 years in arm A had improved OS by 1 month vs those in arm B (P = .04), and patients with secondary AML in arm A had better DFS vs those in arm B (P = .04). We conclude that addition of G3139 to chemotherapy failed to improve outcomes of older AML patients. However, more effective means of inhibiting BCL2 are showing promising results in combination with chemotherapy in AML. This trial was registered at www.clinicaltrials.gov as #NCT00085124.

Abstract Patients with core-binding factor (CBF) acute myeloid leukemia (AML), caused by either t(8;21)(q22;q22) or inv(16)(p13q22)/t(16;16)(p13;q22), have higher complete remission rates and longer survival than patients with other subtypes of AML. However, ∼40% of patients relapse, and the literature suggests that patients with inv(16) fare differently from those with t(8;21). We retrospectively analyzed 537 patients with CBF-AML, focusing on additional cytogenetic aberrations to examine their impact on clinical outcomes. Trisomies of chromosomes 8, 21, or 22 were significantly more common in patients with inv(16)/t(16;16): 16% vs 7%, 6% vs 0%, and 17% vs 0%, respectively. In contrast, del(9q) and loss of a sex chromosome were more frequent in patients with t(8;21): 15% vs 0.4% for del(9q), 37% vs 0% for loss of X in females, and 44% vs 5% for loss of Y in males. Hyperdiploidy was more frequent in patients with inv(16) (25% vs 9%, whereas hypodiploidy was more frequent in patients with t(8;21) (37% vs 3%. In multivariable analyses (adjusted for age, white blood counts at diagnosis, and KIT mutation status), trisomy 8 was associated with improved overall survival (OS) in inv(16), whereas the presence of other chromosomal abnormalities (not trisomy 8) was associated with decreased OS. In patients with t(8;21), hypodiploidy was associated with improved disease-free survival; hyperdiploidy and del(9q) were associated with improved OS. KIT mutation (either positive or not tested, compared with negative) conferred poor prognoses in univariate analysis only in patients with t(8;21).

Abstract The results from the RATIFY trial (ClinicalTrials.gov: NCT00651261; CALGB 10603) showed that midostaurin combined with standard chemotherapy significantly improved outcomes in patients with FMS-like tyrosine kinase 3 (FLT3)–mutated acute myeloid leukemia (AML), compared with placebo. In this post hoc subgroup analysis from the trial, we evaluated the impact of midostaurin in 163 patients with FLT3-tyrosine kinase domain (TKD) mutations. At a median follow-up of 60.7 months (95% CI, 55.0-70.8), the 5-year event-free survival (EFS) rate was significantly higher in patients treated with midostaurin than in those treated with placebo (45.2% vs 30.1%; P = .044). A trend toward improved disease-free survival was also observed with midostaurin (67.3% vs 53.4%; P = .089), whereas overall survival (OS) was similar in the 2 groups. Patients with AML and NPM1mut/FLT3-TKDmut or core binding factor (CBF)–rearranged/FLT3-TKDmut genotypes had significantly prolonged OS with or without censoring at hematopoietic cell transplantation (HCT), compared with NPM1WT/CBF-negative AMLs. The multivariable model for OS and EFS adjusted for allogeneic HCT in first complete remission as a time-dependent covariable, revealed NPM1 mutations and CBF rearrangements as significant favorable factors. These data show that NPM1 mutations or CBF rearrangements identify favorable prognostic groups in patients with FLT3-TKD AMLs, independent of other factors, also in the context of midostaurin treatment.

Abstract 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.

Abstract Introduction: Mutations localized in the tyrosine kinase domain activation loop of FLT3 (FLT3-TKD), representing point mutations in codon D835/I836 and rarely deletions of codon I836, induce constitutive tyrosine phosphorylation and activation of the receptor tyrosine kinase similarly to FLT3 internal tandem duplication (ITD) mutations. However, the prognostic role of FLT3-TKD in AML, particularly in the presence of NPM1 mutations, is not well established. The phase 3 RATIFY trial [NCT00651261; Stone et al. N Engl J Med. 2017] showed that in combination with standard chemotherapy, midostaurin (PKC412) improved survival outcomes across all 3 FLT3 stratification subgroups (ITD high allelic ratio [≥ 0.7], ITD low allelic ratio [< 0.7], and TKD) vs placebo in patients with newly diagnosed FLT3-mutated AML. Here, we evaluated the prognostic impact of FLT3-TKD and NPM1 mutations in a post hoc analysis from the RATIFY trial. Methods: In RATIFY, newly diagnosed patients with AML 18-60 years old were randomly assigned to receive midostaurin or placebo together with standard induction and consolidation therapy followed by 12 28-day cycles of maintenance therapy with midostaurin or placebo. FLT3-TKD mutation was detected by PCR and capillary electrophoresis at 9 reference laboratories. Patients were categorized as NPM1 mutated (mut) or NPM1 wild-type (WT) using PCR. Efficacy outcomes included complete remission (CR), overall survival (OS), event-free survival (EFS) and disease-free survival (DFS). EFS and DFS analyses were performed considering CR within a 60-day window. P values presented have not been adjusted for multiplicity. Results: Of the total randomized 162 FLT3-TKD patients, 134 with available NPM1 data had consented for exploratory analysis and thus were included in this study (see Table for subgroup distribution). Overall, 47.8% of patients were male, and the median age was 49 years (95% CI, 45.5-51.1 years). The median white blood cell (WBC) count was higher in patients with NPM1-mut than in patients with NPM1-WT (34.1 vs 15.5 × 109/L, P = .0011). CR rates (during the first 60 days) were higher in patients with FLT3-TKD/NPM1-mut vs FLT3-TKD/NPM1-WT (66% vs 53%); however, this was driven by the higher rate of CR in the midostaurin arm (76% NPM1-mut vs 44% NPM1-WT) rather than the placebo arm (53% NPM1-mut vs 60% NPM1-WT). The overall CR rate (regardless of NPM1 genotype) was 64% for midostaurin and 56% for placebo in FLT3-TKD patients. The prognostic effect of the NPM1 mutation concurrent with FLT3-TKD was seen for all endpoints consistently with hazard ratios (HRs) around 0.50 or lower (Figures 1 and 2 and Table). Overall (regardless of treatment) OS, EFS, and DFS estimates at 3 years were 73% vs 52%, 48% vs 25%, and 74% vs 47%, respectively, in patients with FLT3-TKD/NPM1-mut vs FLT3-TKD/NPM1-WT. Whereas the HRs for midostaurin vs placebo were 0.73 for both OS and EFS, the impact of treatment on outcomes varied between the individual NPM1/TKD subgroups and was not consistently observed when endpoints were censored at stem cell transplant (SCT) (Table). It should be noted that the number of patients in each subgroup was small and therefore the HRs with 95% CIs should be interpreted with caution. Multivariate analyses in these FLT3-TKD patients revealed that NPM1 genotype was an independent prognostic factor for OS, EFS and DFS (2-sided P < .05), whereas study drug, age, sex, WBC at baseline and SCT (no/yes) did not reach this level of significance in the Cox model. Conclusions: This post hoc analysis of the FLT3-TKD patient subset in the RATIFY trial showed the high prognostic value of NPM1 mutational status. Whereas midostaurin showed an overall benefit in the FLT3-TKD patients for OS, EFS, CR and DFS, the impact of treatment on outcome varied between the individual NPM1 subgroups within these FLT3-TKD patients and was not consistently observed.Further analyses using additional endpoints and additional multivariate analyses are planned. Support: U10CA180821, U10CA180882, U10CA180820, U10CA180791, U10CA180888, U10CA180863, (CCSRI) #704970, U24CA196171; ClinicalTrials.gov Identifier: NCT00651261 Disclosures Voso: Celgene: Research Funding, Speakers Bureau. Larson:Ariad/Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BristolMyers Squibb: Consultancy, Research Funding. Heuser:Janssen: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; StemLine Therapeutics: Consultancy; Astellas: Research Funding; BergenBio: Research Funding; Karyopharm: Research Funding; Bayer Pharma AG: Consultancy, Research Funding; Tetralogic: Research Funding; Sunesis: Research Funding; Daiichi Sankyo: Research Funding. Wei:Novartis: Honoraria, Other: Advisory committee, Research Funding, Speakers Bureau; Pfizer: Honoraria, Other: Advisory committee; Amgen: Honoraria, Other: Advisory committee, Research Funding; Abbvie: Honoraria, Other: Advisory board, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Other: Advisory committee, Research Funding; Celgene: Honoraria, Other: Advisory committee, Research Funding. Brandwein:Lundbeck: Consultancy; Celgene: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Boehringer Ingelheim: Consultancy, Research Funding. de Witte:Novartis: Research Funding; Amgen: Consultancy, Research Funding; Celgene: Honoraria, Research Funding. Medeiros:Celgene: Consultancy, Research Funding; Genentech: Employment. Tallman:Cellerant: Research Funding; Orsenix: Other: Advisory board; BioSight: Other: Advisory board; ADC Therapeutics: Research Funding; AROG: Research Funding; AbbVie: Research Funding; Daiichi-Sankyo: Other: Advisory board. Schlenk:Pfizer: Research Funding, Speakers Bureau. Ganser:Novartis: Membership on an entity's Board of Directors or advisory committees. Cheng:Novartis: Employment. Gathmann:Novartis: Employment. Tiecke:Novartis: Employment. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding. Döhner:AbbVie: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; Celator: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Seattle Genetics: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Sunesis: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Celator: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Bristol Myers Squibb: Research Funding; Agios: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Jazz: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Pfizer: Research Funding; Pfizer: Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Stone:Otsuka: Consultancy; Argenx: Other: Data and Safety Monitoring Board; Amgen: Consultancy; Agios: Consultancy, Research Funding; Orsenix: Consultancy; Ono: Consultancy; Novartis: Consultancy, Research Funding; Astellas: Consultancy; Arog: Consultancy, Research Funding; Merck: Consultancy; Cornerstone: Consultancy; Fujifilm: Consultancy; Jazz: Consultancy; Celgene: Consultancy, Other: Data and Safety Monitoring Board, Steering Committee; Pfizer: Consultancy; Sumitomo: Consultancy; AbbVie: Consultancy.

Abstract Introduction: The preferred post-remission therapy for older patients (pts) with AML remains uncertain. We compared outcomes for older AML pts in CR1 receiving HCT reported to the CIBMTR to older AML pts achieving CR1 on National Clinical Trials Network induction and non-HCT consolidation therapy (CT) trials. Methods: This study focused on pts 60-75 years of age treated between 2004 to 2013. CT pts (n=211) underwent induction and consolidation on Alliance for Clinical Trials in Oncology, ECOG-ACRIN or SWOG clinical trials for initial therapy for newly diagnosed AML; the CIBMTR provided data for HCT pts (n=431). CT patients received at least one cycle of CT on study and were excluded if HCT occurred at any time. Time to event started at CR1 and pts entered at CT or HCT, respectively, using left-truncation to account for differential entry times. Results: For the CT cohort, first consolidation included standard therapy (e.g., cytarabine or a hypomethylating agent) and additional study drug (e.g., bortezomib, dasatinib, sorafenib, and Zosuquidar, gemtuzumab) or tipifarnib alone. Among HCT pts, the donor was a HLA-matched sibling or unrelated donor (URD) in 66% and the others were partially HLA-matched/mismatched URD (10%) or cord blood (24%). HCT pts were younger and more frequently had high-risk AML (high WBC, secondary AML and unfavorable cytogenetics) (Table). The median time from CR1 to HCT and CT was 3.2 and 0.5 months, respectively. Allogeneic HCT showed worse overall survival (OS) (HR=1.52, p=0.02) prior to 9 months and better OS thereafter (HR= 0.53, p <0.0001) relative to CT (figure 1A). Treatment-related mortality (TRM) was worse after HCT in the first 9 months (HR=2.8, CI: 1.5 -5.2, p=.0009), while relapse was less frequent beyond 9 months after treatment (HR = 0.42, CI: 0.29 to 0.61, p<.0001). Despite higher early TRM, HCT recipients went on to manifest superior OS [5 year OS: HCT 29% (24-34%), CT 13.8% (9 -22%)] (Figure 1A). The benefit of HCT for survival after 9 months was more prominent in those with unfavorable cytogenetics (Figure 1B). Multivariate analysis for OS showed no statistically significant effect of age or performance status, while unfavorable cytogenetics were detrimental (HR=1.74, p<.0001). Conclusions. Allogeneic HCT led to heightened early risks from TRM, but resulted in superior long-term survival in older AML pts receiving HCT relative to CT by reducing relapse. Efforts to attenuate early TRM after allogeneic HCT may further improve HCT outcomes for older pts. Disclosures Ustun: novartis: Speakers Bureau. Attar:Agios: Employment, Equity Ownership. Larson:Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BristolMyers Squibb: Consultancy, Research Funding; Ariad/Takeda: Consultancy, Research Funding. Roboz:Roche/Genentech: Consultancy; Eisai: Consultancy; Cellectis: Research Funding; Aphivena Therapeutics: Consultancy; Sandoz: Consultancy; Janssen Pharmaceuticals: Consultancy; Otsuka: Consultancy; Jazz Pharmaceuticals: Consultancy; Sandoz: Consultancy; AbbVie: Consultancy; Celltrion: Consultancy; Cellectis: Research Funding; Eisai: Consultancy; Astex Pharmaceuticals: Consultancy; Argenx: Consultancy; Pfizer: Consultancy; Celgene Corporation: Consultancy; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy; Bayer: Consultancy; Bayer: Consultancy; Roche/Genentech: Consultancy; Orsenix: Consultancy; Astex Pharmaceuticals: Consultancy; Celgene Corporation: Consultancy; Daiichi Sankyo: Consultancy; Pfizer: Consultancy; Janssen Pharmaceuticals: Consultancy; Otsuka: Consultancy; Orsenix: Consultancy; Daiichi Sankyo: Consultancy; Celltrion: Consultancy; Novartis: Consultancy; Aphivena Therapeutics: Consultancy; Argenx: Consultancy; AbbVie: Consultancy. Uy:GlycoMimetics: Consultancy; Curis: Consultancy. Stone:Fujifilm: Consultancy; Ono: Consultancy; Orsenix: Consultancy; Otsuka: Consultancy; Agios: Consultancy, Research Funding; AbbVie: Consultancy; Argenx: Other: Data and Safety Monitoring Board; Celgene: Consultancy, Other: Data and Safety Monitoring Board, Steering Committee; Arog: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Jazz: Consultancy; Astellas: Consultancy; Merck: Consultancy; Pfizer: Consultancy; Sumitomo: Consultancy; Amgen: Consultancy; Cornerstone: Consultancy. Foran:Agios: Research Funding; Xencor, Inc.: Research Funding. Weisdorf:Seattle Genetics: Consultancy; Equillium: Consultancy; FATE: Consultancy; SL Behring: Consultancy; Pharmacyclics: Consultancy.

Abstract Introduction B progenitor acute lymphoblastic leukemia (B-ALL) is a leading cause of childhood cancer death. Many chimeric genes have been identified and led to a refined classification of B-ALL and tailored therapies. Still, up to 30% of B-ALL cannot be classified into established subtypes, and the outcome for many is poor. Methods To identify novel subtypes of B-ALL, we performed integrative genomic analysis including transcriptome sequencing (RNA-seq) of 1,988 cases from St. Jude, Children's Oncology Group and adult cooperative group studies and analyzed chromosomal rearrangements, gene-expression profiles (GEP), somatic mutations and chromosome-level copy-number alterations. Cases lacking known or putative subtype-defining alterations underwent whole genome sequencing. Effects on proliferation and transformation of novel lesions were assessed by retroviral expression in cell lines and point-mutation knock-in mice using CRISPR/Cas9 genome editing. Results Using integrated genetic alterations and gene expression profiling, we classified 23 B-ALL subtypes (Table and Figure). Three groups included cases with similar GEP as canonical subtypes (ETV6-RUNX1, KMT2A-rearranged, and ZNF384-rearranged), but lacking the expected drivers (e.g., ETV6-RUNX1-like, n=42). Eighteen cases (0.9%) had rearrangements of BCL2, MYC and/or BCL6 showing a distinct GEP; they were mostly adults (n=16) with very poor outcome. These alterations, rarely seen in ALL, are identical to those observed in "double/triple hit" lymphoma, and are of pre-B immunophenotype. Eight cases with tightly clustered GEP comprised a novel subtype defined by IKZF1 N159Y missense mutation. N159Y is in the DNA-binding domain of IKZF1, and is known to perturb IKZF1 function, with distinct nuclear mislocalization and induction of aberrant intercellular adhesion. We identified two subtypes with distinct GEP characterized by PAX5 alterations. One, herein termed PAX5 altered (PAX5alt), comprised 148 (7.4%) cases, was characterized by diverse PAX5 alterations including rearrangements (n=57), sequence mutations (n=46) and/or focal intragenic amplifications (n=8). These PAX5 alterations were found in 73.6% of PAX5alt cases and different alteration types were mutually exclusive. Other PAX5 alterations, including deletions and large-scale amplifications were also assessed using SNP array, but were not enriched in the PAX5alt group. Clinically, PAX5alt pediatric and adult patients had favorable (96.8±3.2%) and intermediate (42.1±10.2%) 5-year overall survival (OS), respectively. The other GEP distinct subtype comprised 44 cases, all with PAX5 P80R missense mutations. In 30 of these cases, PAX5 P80R was homozygous due to deletion of the wild-type (WT) PAX5 allele or copy-neutral loss of heterozygosity. Of the other 14 cases with heterozygous PAX5 P80R mutations, 13 had a second frameshift (n=7), nonsense (n=2) or deleterious missense (n=4) PAX5 mutation. Four of the remaining 1,944 cases also had the PAX5 P80R mutation, but all were heterozygous with preservation of a WT PAX5 allele, consistent with the notion that homozygous or compound heterozygous PAX5 P80R mutation is the hallmark of this subtype. Adult PAX5 P80R cases (n=14) showed better 5-year OS (61.9±13.4%) than those in PAX5alt subtype (42.1±10.2%). To examine the effects of PAX5 P80R on B-cell maturation, WT PAX5, PAX5 P80R, V26G and P34Q were expressed in Pax5-/- lineage-depleted bone marrow cells. Expression of WT PAX5, PAX5 V26G and P34Q resulted in near complete rescue of B cell differentiation; however, expression of PAX5 P80R blocked the differentiation at the pre-pro-B stage of B-cell maturation. Further, Pax5 P80R heterozygous or homozygous mice developed pre-B-ALL with a median latency of 166 and 87 days, respectively, with heterozygous mice acquiring alterations on the second allele. In contrast, Pax5+/- mice, and those harboring G183S mutation observed in familial leukemia, do not spontaneously develop B-ALL. Conclusions These results show the utility of transcriptome sequencing in defining subtypes and founding genetic alterations in B-ALL, provide a revised taxonomy of the disease across the age spectrum, and reinforce the central role of PAX5 as a checkpoint in B lymphoid maturation and leukemogenesis. Disclosures McKay: ImmunoGen Inc.: Employment. Tallman:Orsenix: Other: Advisory board; AROG: Research Funding; BioSight: Other: Advisory board; Cellerant: Research Funding; AbbVie: Research Funding; Daiichi-Sankyo: Other: Advisory board; ADC Therapeutics: Research Funding. Stock:Jazz Pharmaceuticals: Consultancy. Konopleva:Stemline Therapeutics: Research Funding. Relling:Shire Pharmaceuticals: Research Funding. Mullighan:Cancer Prevention and Research Institute of Texas: Consultancy; Amgen: Honoraria, Speakers Bureau; Abbvie: Research Funding; Loxo Oncology: Research Funding; Pfizer: Honoraria, Research Funding, Speakers Bureau.

Abstract In CN-AML, mutations of specific genes have prognostic significance and are used for treatment guidance. However, these mutations are in general not mutually exclusive and CN-AML patients (pts) frequently harbor mutational combinations with unclear prognostic significance because of the concurrent presence of mutations with favorable (CEBPA, NPM1) and unfavorable (ASXL1, DNMT3A, IDH1, IDH2, FLT3-ITD, MLL-PTD, RUNX1, TET2, WT1) impact on outcome. Here, we report the frequency and clinical significance of isolated mutations and their combinations in 364 CN-AML pts. Younger [<60 years (y); n=163] and older (≥60 y; n=201) pts were intensively treated on frontline CALGB/Alliance protocols and, per protocol, did not undergo allogeneic stem cell transplantation in first complete remission (CR). Median follow-up for pts alive was 8.7 y. Pts were analyzed centrally for mutations in the ASXL1, CEBPA, DNMT3A, IDH1, IDH2, NPM1, RUNX1, TET2, and WT1 genes and the presence of FLT3-ITD, FLT3-TKD and MLL-PTD. We found that 99% of pts had ≥1 and 88% ≥2 of the 12 mutations. Specifically, 11% of pts had 1 gene mutated (n1), 40% had 2 (n2), 31% 3 (n3), and 18% harbored ≥4 mutated genes (n4). The distribution of the different n groups in younger and older pts was similar (Fig 1). The expected frequency of each mutated gene in every numerical (n) group was calculated as follows: [no. of pts with the mutated gene] x [total no. of mutations in the n group] / [total no. of mutations in all pts], and compared with the observed frequency. CEBPA, IDH2, NPM1, and RUNX1 mutations were overrepresented in the n1 and n2 groups (P<.001, P<.001, P=.002, P=.02, respectively) and thus likely represent “early” events in leukemogenesis. In contrast, DNMT3A, FLT3-ITD, and TET2 mutations were more frequent in the n3 and n4 groups (P=.008, P<.001, P=.02, respectively) suggesting that they are likely “late” events. The distribution among age groups and clinical impact of the “early” mutations (i.e., CEBPA, NPM1, IDH2) presenting as isolated mutations or in combination with other mutations were then investigated. Isolated RUNX1 mutations could not be evaluated due to small sample size. Younger pts were more likely to harbor an isolated “early” mutated gene than older pts (21% v 12%, P=.03). Specifically, isolated CEBPA and NPM1 mutations were more frequent in younger pts compared with the older (7% v 2%, P=.007; 7% v 3%, P=.07, respectively). In pts with isolated CEBPA mutations, these were always bi-allelic. Single “early” mutated genes varied in their impact on CR achievement (CEBPA: 100%, NPM1: 94%, IDH2: 67%), and overall survival (OS; 3-y OS: CEBPA: 87%, NPM1: 69%, IDH2: 22%). Acquisition of additional mutations adversely modified the prognostic significance of favorable “early” mutations in the CEBPA (Fig 2A) and NPM1 (Fig 2B) genes, but left unchanged the unfavorable effect of IDH2 mutations (Fig 2C). Two mutational combinations were exceptions to this: younger pts with both NPM1 and DNMT3A mutations (8 pts) had an excellent prognosis with 3-y OS of 100%; and older pts with concurrent NPM1 and IDH2 mutations (9 pts; all IDH2 mutations were in codon R140) had a high 3-y OS rate of 67%. We conclude that CEBPA and NPM1 mutations mainly define pts with favorable prognosis when they present as single markers, whereas mutated IDH2 predominantly associates with adverse outcome. The NPM1+DNMT3A and NPM1+IDH2 mutational patterns may define novel favorable molecular subtypes in younger and older CN-AML pts, respectively, but these results require corroboration in larger pt cohorts. Disclosures: Mrózek: AMERICAN SOCIETY OF HEMATOLOGY: I will review abstracls submitted for presentation at the 55th ASH Annual Meeting in the 611 category Other. Eisfeld:AMERICAN SOCIETY OF HEMATOLOGY: I will review abstracls submitted for presentation at the 55th ASH Annual Meeting in the 608 category Other.

Abstract Background: The few therapies available to treat higher-risk MDS and CMML have limited impact on outcome. We previously reported initial results of S1117, which compared overall response rates (ORRs) of azacitidine (AZA) monotherapy to AZA combined with the histone deacetylase inhibitor vorinostat (VOR), or the immunomodulator lenalidomide (LEN)( ASH 2014 LBA-5). We now report updated response data and overall survival (OS), subgroup analyses, impact of cytogenetics, and effect of treatment center volume/centers of excellence on outcome. Methods: This randomized, Phase II study (ClinTrials.gov # NCT01522976) enrolled higher-risk MDS (International Prognostic Scoring System (IPSS) Int-2 or High and/or bone marrow blasts ≥5%) and CMML adult patients (pts) with <20% blasts from 3/12-6/14 to receive AZA (75 mg/m2/d on d1-7 of a 28d cycle), AZA + LEN (10 mg/d on d1-21), or AZA + VOR (300 mg BID on d3-9). Pts continued treatment until treatment failure, defined as disease progression, relapse, significant or unresolved toxicity, or lack of response. Dose reductions occurred for grade ≥3 adverse events (per NCI CTCAE) or delayed count recovery. Cytogenetic risk groups were defined per IPSS-R. The primary endpoint was improvement in ORR, by intention to treat and reviewed centrally, of one of the combination arms vs. AZA per 2006 International Working Group MDS response criteria (complete response (CR) + partial response (PR) + hematologic improvement (HI)). OS was from study entry. MDS Centers of Excellence (MCE) were defined per MDS Foundation; center volume was defined as low (1-4 pts enrolled) or high (5-17 pts). Results: Of 277 pts, 92 received AZA, 93 AZA+LEN, and 92 AZA+VOR. Baseline characteristics, previously reported, were similar across arms. Pts received a median of 22 weeks of therapy and were followed for a median of 10 months (range: 0-30). Non-protocol defined dose modification and protocol discontinuation due to toxicity occurred more frequently in combination arms vs. AZA (p=.0014 and p=.018, respectively). Responses are now assessable in all pts (Table 1). ORR was statistically similar for combination arms vs. AZA, with a trend for longer response duration (p=.083) for combinations. Within HI, AZA+LEN pts had higher HI-n than AZA pts (16% vs. 5%, p=.031). ORR for CMML pts was significantly higher for LEN+AZA vs. AZA (63% vs. 29%, p=.04), with a trend for longer response duration for combinations (p=.06); no differences in ORR were seen for therapy-related MDS, IPSS subgroups, or transfusion-dependent pts. Allogeneic transplantation rates were similar. Median OS (Figure) for AZA:AZA+LEN:AZA+VOR was 15:18 (p=.38):17 (p=.17) months; p=.19 for combination arms vs. AZA. Median OS after failure was 7:9 (p=.6):9 (p=.05) months; p=.15 for combination arms after failure vs. AZA. For pts on therapy >6 months, there was a trend (p=.08) for higher ORR for AZA+LEN vs. AZA, though response duration was similar; median OS was 18:21 (p=.44 vs. AZA):21 months (p=.45 vs. AZA). Cytogenetic risk category distribution and ORR was similar across arms. OS (compared to Very Good/Good) was worse for Poor (HR 2.07, p=.022) and Very poor (HR 4.41, p<.001), without significant modification by treatment arm (Table 2). Compared to pts without identified cytogenetic abnormalities (abn), ORR across arms was better for pts with Chr 5 abn (OR 2.38, p=.004); OS was better for normal (HR .42, p<.001) and worse for Chr 5 abn (HR 3.1, p<.001), -7 (HR 2.69, p<.001), and 17p (HR 2.61, p<.001). While small numbers prevented definitive conclusions for treatment arm effect, combinations trended towards improving OS in Normal and Chr 5 abn only. The outcome of all pts and pts on discrete study arms treated at MCE (n=75) or high volume (n=138) sites were similar to non-MCE or low-volume sites for ORR, non-protocol defined dose modifications, dose adjustment in first 4 cycles, time to off-protocol (HR 1.2, p=.21 and HR .94, p=.64), and OS (HR .81, p=.3 and HR .77, p=.12). Conclusions: In higher-risk MDS pts, ORR and OS was similar for AZA monotherapy compared to combination arms, while for CMML pts, ORR was significantly higher with AZA+LEN. For cytogenetic subgroups, OS was worse for Chr 5 abn, -7, and 17p, and may be improved by combinations in normal or Chr 5 abn. MCE or treatment at a high volume site did not impact these effects or outcomes. Figure 1. Responses Figure 1. Responses Figure 2. Cytogenetics Figure 2. Cytogenetics Figure 3. Figure 3. Disclosures Sekeres: Celgene Corporation: Membership on an entity's Board of Directors or advisory committees. List:Celgene Corporation: Honoraria, Research Funding. Odenike:Sunesis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Stone:Merck: Consultancy; Celgene: Consultancy. Gore:Celgene: Consultancy, Honoraria, Research Funding. Buckstein:Celgene: Honoraria, Research Funding. Fang:Affymetrix: Research Funding. Attar:Agios Pharmaceuticals: Employment. Erba:Ariad: Consultancy; Daiichi Sankyo: Consultancy; Sunesis: Consultancy; Pfizer: Consultancy; Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy; Incyte: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Jannsen (J&J): Other: Data Safety and Monitoring Committees ; Ariad: Consultancy; Celgene: Consultancy, Speakers Bureau; GlycoMimetics: Other: Data Safety and Monitoring Committees; Seattle Genetics: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Millennium/Takeda: Research Funding; Millennium/Takeda: Research Funding; Celator: Research Funding; Celator: Research Funding; Astellas: Research Funding; Astellas: Research Funding; Sunesis: Consultancy; Daiichi Sankyo: Consultancy; GlycoMimetics: Other: Data Safety and Monitoring Committees; Jannsen (J&J): Other: Data Safety and Monitoring Committees.