Abstract: 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 & lt; .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.

Abstract: Background: Internal tandem duplications (ITD) in the receptor tyrosine kinase FLT3 occur in roughly 25% of younger adult patients (pts) with acute myeloid leukemia (AML). The multi-targeted kinase inhibitor midostaurin combined with intensive chemotherapy has shown activity against AML with FLT3 mutations. However, toxicity and potential drug-drug interactions with strong CYP3A4 inhibitors such as posaconazole may necessitate dose reduction. Aims: To evaluate the impact of age and midostaurin dose-adaptation after intensive induction chemotherapy on response and outcome in AML with FLT3-ITD within the AMLSG 16-10 trial (NCT01477606). Methods: The study included adult pts (age 18-70 years (yrs)) with newly diagnosed FLT3-ITD positive AML enrolled in the ongoing single-arm phase-II AMLSG 16-10 trial. Pts with acute promyelocytic leukemia were not eligible. The presence of FLT3-ITD was analyzed within our diagnostic study AMLSG-BiO (NCT01252485) by Genescan-based DNA fragment-length analysis. Induction therapy consisted of daunorubicin (60 mg/m², d1-3) and cytarabine (200 mg/m², continuously, d1-7); midostaurin 50 mg bid was applied from day 8 until 48h before start of the next treatment cycle. A second cycle was allowed in case of partial remission (PR). For consolidation therapy, pts proceeded to allogeneic hematopoietic-cell transplantation (HCT) as first priority; if alloHCT was not feasible, pts received three cycles of age-adapted high-dose cytarabine (HDAC) in combination with midostaurin starting on day 6. In all pts one-year maintenance therapy with midostaurin was intended. The first patient entered the study in June 2012 and in April 2014, after recruitment of n=147 pts, the study was amended including a sample size increase to 284 pts and a dose reduction to 12.5% of the initial dose of midostaurin in case of co-medication with strong CYP3A4 inhibitors (e.g. posaconazole). This report focuses on age and the comparison between the first (n=147) and the second cohort (n=137) of the study in terms midostaurin dose-adaptation. Results: Patient characteristics were as follows: median age 54 yrs (range, 18-70; younger, 68% 〈 60 yrs; older, 32% ≥ 60 yrs); median white cell count 44.7G/l (range 1.1-1543 G/l); karyotype, n=161 normal, n=16 high-risk according to ELN recommendations; mutated NPM1 n=174 (59%). Data on response to first induction therapy were available in 277 pts; complete remission (CR) including CR with incomplete hematological recovery (CRi) 60%, PR 20%, refractory disease (RD) 15%, and death 5%. A second induction cycle was given in 54 pts. Overall response (CR/CRi) after induction therapy was 76% (76%, younger; 76%, older) and death 6% (4%, younger; 10% older). The dose of midostaurin during first induction therapy was reduced in 53% and 71% of patients in cohort-1 and cohort-2, respectively. Reasons for dose reduction were in 58% and 49% toxicity, and in 9% and 23% co-medication in cohort-1 and cohort-2, respectively. No difference in response to induction therapy was noted between cohorts (p=0.81). Median follow-up was 18 months. Overall 146 pts received an alloHCT, 128 in first CR (n=94 younger, n=34 older; n=92 from a matched unrelated and n=36 from a matched related donor). In pts receiving an alloHCT within the protocol in median two chemotherapy cycles were applied before transplant (range 1-4). The cumulative incidence of relapse (CIR) and death after transplant were 13% (SE 3.2%) and 16% (SE 3.5%) without differences (p=0.97, p=0.41, respectively) between younger and older patients. So far maintenance therapy was started in 86 pts, 61 pts after alloHCT and 25 pts after HDAC. Fifty-five adverse events 3°/4° were reported being attributed to midostaurin; cytopenias after alloHCT were the most frequent (29%). CIR in patients starting maintenance therapy was 20% one year after start of maintenance without difference between alloHCT and HiDAC (p=0.99). In addition, no difference in CIR was identified in patients after consolidation with alloHCT or HDAC according to dose reduction of midostaurin during first induction therapy (p=0.43, p=0.98, respectively). Median overall survival was 25 months (younger, 26 months; older 23 months; p=0.15). Conclusions: The addition of midostaurin to intensive induction therapy and as maintenance after alloHCT or HDAC is feasible and effective without an impact of age and dose adaptation on outcome. Disclosures Schlenk: Amgen: Research Funding; Pfizer: Honoraria, Research Funding. Fiedler:GSO: Other: Travel; Pfizer: Research Funding; Kolltan: Research Funding; Amgen: Consultancy, Other: Travel, Patents & Royalties, Research Funding; Gilead: Other: Travel; Ariad/Incyte: Consultancy; Novartis: Consultancy; Teva: Other: Travel. Lübbert:Celgene: Other: Travel Funding; Janssen-Cilag: Other: Travel Funding, Research Funding; Ratiopharm: Other: Study drug valproic acid. Greil:Janssen-Cilag: Honoraria; Genentech: Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Merck: Honoraria; AstraZeneca: Honoraria; Boehringer-Ingelheim: Honoraria; GSK: Research Funding; Ratiopharm: Research Funding; Cephalon: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Honoraria; Bristol-Myers-Squibb: Consultancy, Honoraria; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Sanofi Aventis: Honoraria; Eisai: Honoraria; Amgen: Honoraria, Research Funding. Greiner:BMS: Research Funding. Paschka:ASTEX Pharmaceuticals: Consultancy; Novartis: Consultancy; Medupdate GmbH: Honoraria; Bristol-Myers Squibb: Honoraria; Pfizer Pharma GmbH: Honoraria; Celgene: Honoraria. Heuser:Bayer Pharma AG: Research Funding; Karyopharm Therapeutics Inc: Research Funding; Novartis: Consultancy, Research Funding; Celgene: Honoraria; Pfizer: Research Funding; BerGenBio: Research Funding; Tetralogic: Research Funding.

Abstract: Background: Clonal hematopoiesis of indeterminate potential (CHIP) is defined by the detection of mutations in genes like DNA methyltransferase 3A (DNMT3A) and has recently been described to occur in healthy people and to predispose them to myeloid malignancies. DNMT3A is frequently mutated in acute myeloid leukemia (AML) and mutations have been detected in CD3 positive T-cells of some AML patients. In these patients DNMT3A mutations are early events that are likely to arise from CHIP. It is unknown how a history (hx) of CHIP influences the characteristics of AML patients and their response to therapy. We studied this question on the basis of a large cohort of DNMT3A mutated AML patients. Patients and Methods: 171 DNMT3A mutated AML patients (aged 18-87 years) were included in our study. 127 patients were treated intensively in trials of the AMLSHG and AMLSG. 34 patients received non-intensive therapy and for 10 patients the therapy is unknown. 148 patients carried a mutation at arginine R882. At the time of diagnosis and relapse samples were further sequenced for 54 genes involved in leukemia with next generation sequencing (NGS) on the Illumina platform. Library preparation of diagnostic samples was performed with the TruSight Myeloid sequencing panel (Illumina). T-cells (CD3+ CD11b- CD14- CD33-) were purified by flow cytometry from AML samples at the time of diagnosis. DNMT3A mutational analysis of T-cell samples and of mononuclear cells during remission or at relapse was performed also with ultra-deep sequencing using customized DNMT3A NGS primers. Presence of a DNMT3A mutation in sorted T cell populations was used as an indicator of a hx of CHIP. Results: A total of 40 patients (23%) were found to have the DNMT3A mutation in mononuclear cells and T-cells (hx of CHIP), while 131 patients (77%) had a DNMT3A mutation in mononuclear cells, but not T-cells (control cohort). Comparing these two patient cohorts revealed that significantly more patients in the hx of CHIP cohort had secondary AML (p=0.009), were older (p=0.005) and less likely to receive intensive treatment (p=0.047) while other clinical parameters did not significantly differ. Analysing the mutational profile of 54 genes revealed that the number of mutations per patient between these 2 groups was similar (median 5 vs 4 mutations, p=0.39). Patients with a hx of CHIP were significantly more likely to harbour mutations in TET2 (p=0.006), RUNX1 (p=0.004), SF3B1 (p=0.049), U2AF1 (p=0.015) but less likely to be NPM1 mutated (p=0.005). There was no significant difference in the allelic burden of DNMT3A in the CHIP hx (mean 43.6) vs control group (mean 44.5). The mean variant allele frequencies of DNMT3A, RUNX1 and NPM1 were highest (44, 45 and 43 respectively) as compared to other mutated genes like IDH1, IDH2 and FLT3 (32, 37 and 34). In relapse samples (n=11), the identical DNMT3A mutation could always be identified. However, patients with a hx of CHIP (n=2) had comparable allelic frequencies compared to diagnosis of mutated DNMT3A ( 〈 10% difference), but not NPM1 ( 〉 10% difference), while 7 out of 9 patients in the control group had a change in the allelic frequency at the time of relapse (mostly reduction). In all remission samples DNMT3A mutations could be identified with ultra-deep NGS but with variable allelic frequencies (0.13-50.01% in the control group, 0.25-70.14% in the hx of CHIP group). In the cohort of patients with intensive therapy there was no difference in CR rates between hx of CHIP and control groups (82 vs 90%, p=0.31). Overall survival (OS) was not influenced by a hx of CHIP (whole cohort: HR 1.09; 95%CI 0.67-1.79; P=.73; intensively treated cohort: HR 0.72; 95%CI 0.34-1.51; P=.38). Relapse-free survival (RFS) was also not different in the hx of CHIP vs the control group (HR 1.06; 95%CI 0.58-1.93; P=.85; intensively treated cohort only HR 0.91; 95%CI 0.46-1.78; P=.78). However, when looking at the influence of allogeneic stem cell transplantations (HSCT) on outcome in intensively treated patients, patients with a hx of CHIP showed abenefit from HSCT (HR 0.082; 95%CI 0.009-0.75; P= 0.027 Figure 1A) as compared to the control group (HR 0.68; 95%CI 0.39-1.21; P= 0.19, Figure 1B). Conclusion: AML patients with a hx of CHIP, as defined by mutated DNMT3A in T-cells, show a distinct clinical and molecular profile and may benefit from HSCT. Figure 1A. Figure 1A. Figure 1B. Figure 1B. Disclosures Bug: TEVA Oncology, Astellas: Other: Travel Grant; NordMedica, Boehringer Ingelheim, Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene, Novartis: Research Funding. Fiedler:Pfizer, Amgen, Kolltan: Research Funding; Teva, Amgen, Astellas: Other: Travel Grant; Karyopharm: Research Funding. Schlenk:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Research Funding; Arog: Honoraria, Research Funding; Teva: Honoraria, Research Funding; Boehringer-Ingelheim: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Research Funding.

Abstract: Background: Activating mutations in receptor tyrosine kinases like FLT3 (FLT3mut) lead to an aberrant signal transduction thereby causing an increased proliferation of hematopoietic cells. Internal tandem duplications (FLT3-ITD) or mutations in the tyrosine kinase domain (FLT3-TKD) occur in about 25% of younger adult patients (pts) with acute myeloid leukemia (AML), with FLT3 -ITD being associated with an unfavourable outcome. FLT3mut present an excellent target for small molecule tyrosine kinase inhibitors (TKI). The multi-targeted kinase inhibitor midostaurin (PKC412) is currently under investigation as a FLT3-inhibitor in combination with intensive chemotherapy. Monitoring of the efficacy of such a targeted therapy and correlation of the results with clinical outcome will be of major importance. The plasma inhibitor activity (PIA) assay allows the visualization of the level of dephosphorylation of the target under TKI therapy. Preliminary data suggest a correlation between the grade of dephosphorylation, as a marker for the activity of the TKI, and clinical outcome. Aims: To individually measure the level of FLT3 dephosphorylation by PIA analysis in a large cohort of FLT3-ITD AML pts treated within our AMLSG16-10 trial (NCT: NCT01477606) which combines midostaurin with intensive chemotherapy, and to correlate the results with clinical outcome. Methods: Plasma samples from pts (age 18-70 years) with newly diagnosed FLT3-ITD AML were obtained at different time points for PIA analysis. All pts were enrolled on the ongoing AMLSG 16-10 trial applying intensive therapy in combination with midostaurin (50mg twice a day). For consolidation therapy, pts proceeded to allogeneic hematopoietic stem cell transplantation (alloHSCT) as first priority; pts not eligible for alloHSCT were intended to receive 3 cycles of age-adapted high-dose cytarabine (HiDAC) in combination with midostaurin from day 6 onwards. In all pts one year of maintenance therapy with midostaurin was intended. PIA analyses were performed at defined time points (day 15 of induction, each consolidation cycle, at the end of each treatment cycle, every 3 months during maintenance therapy) as previously described (Levis MJ, et al. Blood 2006; 108:3477-83). Results: So far, PIA analyses were performed in 63 pts (median age, 51.6 years; range, 20-70 years) during (n=63) and after (n=73) first and second induction cycle, during (n=40) and after (n=53) consolidation therapy with HiDAC as well as during maintenance therapy (n=82). During and after induction therapy median levels of phosphorylated FLT3 (p-FLT3) were 46.6% (4.5-100%, 〈 20% in 7.9%) and 39.4% (0.3-100%, 〈 20% in 20.5%), respectively. Co-medication with azoles had no impact on p-FLT3 levels. In pts with a FLT3-ITD mutant to wildtype ratio above our recently defined cut-off value of 0.5, levels of p-FLT3 〈 20% were associated with a complete remission (CR)-rate of 100%, whereas in those pts with p-FLT3 levels ≥20%, 4 out of 22 pts (18%) had resistant disease. In contrast, response in pts with a mutant to wildtype ratio below 0.5 was independent of the p-FLT3 level. During and at the end of consolidation cycles as well as during maintenance therapy p-FLT3 levels in pts treated with midostaurin were 52% (14.8-100%, 〈 20% in 5%), 63% (7.6-100%, 〈 20% in 7.4%) and 60.2% (11.5-100%, 〈 20% in 3.7%), respectively. In pts concomitantly treated with azoles levels of p-FLT3 were lower without reaching significance. 39 of 63 pts received alloHSCT in first CR; those pts with p-FLT3 levels 〈 20% after induction therapy had an in trend better survival, whereas no impact of phosphorylation levels was evident in pts receiving chemotherapy alone. Conclusion: In our study of FLT3-ITD AML pts treated with midostaurin in combination with intensive chemotherapy we could show that the lowest levels of p-FLT3 were reached during and after induction therapy. In pts with a FLT3-ITD mutant to wildtype ratio 〉 0.5, levels of p-FLT3 〈 20% during and after induction therapy were associated with a high CR-rate. When receiving alloHSCT these pts had an in trend better survival compared to those with p-FLT3 levels 〉 20%. An update of the data will be presented at the meeting. Disclosures Salwender: Celgene: Honoraria; Janssen Cilag: Honoraria; Bristol Meyer Sqibb: Honoraria; Amgen: Honoraria; Novartis: Honoraria. Horst:Amgen: Honoraria, Research Funding; Pfizer: Research Funding; Ingleheim: Research Funding; Boehringer: Research Funding; MSD: Research Funding; Gilead: Honoraria, Research Funding. Schlenk:Novartis: Honoraria, Research Funding; Boehringer-Ingelheim: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Research Funding; Teva: Honoraria, Research Funding; Arog: Honoraria, Research Funding.

Abstract: Background: The ASXL2 (Additional Sex comb-like 2) gene on chromosome 2p23.3 encodes an epigenetic regulator that is thought to act through histone modification and thereby regulating gene transcription in a context-dependent manner. Recently, ASXL2 mutations (ASXL2mut) were found with a high incidence (~23%) in a cohort of 110 pediatric or adult AML patients (pts) with t(8;21)(q22;q22) (Micol et al., Blood 2014). Aim: We assessed the frequency and prognostic impact of ASXL2mut in the context of other clinical and genetic factors in a large clinically well-defined cohort of intensively treated adults with t(8;21) AML. In addition, the stability of ASXL2 mutation status was analysed in a subset of pts at the time of relapse. Methods: Diagnostic samples from 204 adults with t(8;21);RUNX1/RUNX1T1 -positive AML [median age: 49 years, range: 18-82] were analysed for ASXL2mut in exon 11 and 12 using a combination of PCR-based amplification and subsequent direct DNA-sequencing. Paired samples at diagnosis and relapse were evaluated for the ASXL2 mutation status in a subset of 22 pts. Additional mutation analyses were performed for KIT, FLT3 (ITD and TKD), NRAS, and ASXL1 genes. All pts received intensive treatment either within AMLSG trials (n=155) or according to standard chemotherapy regimens. Results: Thirty four ASXL2mut were identified in 33 (16.2%) of the 204 pts. All mutations (frame-shifts, n=32; non-sense, n=2) created stop codons leading to premature protein truncation with loss of the terminal PHD domain; 27% of the mutations affected codon T740 in exon 12. At diagnosis, there was no significant difference between pts with ASXL2mut and ASXL2 wildtype (ASXL2wt) with respect to sex, WBC, haemoglobin, platelets, LDH serum levels, and circulating or bone marrow blasts. Of note, ASXL2mut were not associated with increasing age, a finding which is commonly observed for ASXL1 mutations in AML. In terms of secondary chromosome aberrations ASXL2mut were frequently associated with del(9q) (P=.006), whereas they never co-occurred with trisomy 8. There was no significant association between ASXL2mut and all other gene mutations analysed. Analysis for ASXL2 mutation status in 22 paired samples obtained at diagnosis and relapse showed a high stability since the mutation was still present in two pts at relapse whereas none of the remaining 20 ASXL2 wildtype cases acquired ASXL2mut. There was no difference in complete remission (CR) rate after double induction between pts with ASXL2mut (88%) and those with ASXL2wt (92%); the same was true when comparing pts with ASXL1 or ASXL2 mutations (ASXL1/2mut) as one group (93%) versus those with ASXL1/2 wildtype. Neither ASXL2mut nor ASXL1/2mut did impact the endpoints event-free-survival, cumulative incidence of relapse, relapse-free and overall survival. Conclusions: Beside KIT and NRAS, ASXL2 is among the most frequently mutated genes in t(8;21) AML. ASXL2mut did not impact achievement of CR or any survival endpoint. Nevertheless, the high incidence (16.2%) of ASXL2mut in t(8;21) AML and the exclusivity to this subgroup of core-binding factor AML implies a peculiar role of ASXL2 in the leukemogenesis of t(8;21) AML providing a basis for further studies. Disclosures Horst: MSD: Research Funding; Pfizer: Research Funding; Amgen: Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Boehringer Ingleheim: Research Funding. Schlenk:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Boehringer-Ingelheim: Honoraria; Arog: Honoraria, Research Funding; Teva: Honoraria, Research Funding.

Abstract: Background: Internal tandem duplications (ITD) in the receptor tyrosine kinase FLT3 occur in roughly 25% of younger adult patients (pts) with acute myeloid leukemia (AML), implicating FLT3 as a potential target for kinase inhibitor therapy. The multi-targeted kinase inhibitor midostaurin shows potent activity against FLT3 as a single agent but also in combination with intensive chemotherapy. Aims: To evaluate the feasibility and efficacy of midostaurin in combination with intensive induction therapy and as single agent maintenance therapy after allogeneic hematopoietic stem cell transplantation (alloHSCT) or high-dose cytarabine (HIDAC). Methods: The study includes adult pts (age 18-70 years (yrs)) with newly diagnosed FLT3-ITD positive AML enrolled in the ongoing single-arm phase-II AMLSG 16-10 trial (NCT: NCT01477606). Pts with acute promyelocytic leukemia are not eligible. The presence of FLT3-ITD is analyzed within our diagnostic study AMLSG-BiO (NCT01252485) by Genescan-based fragment-length analysis (allelic ratio & gt;0.05 required to be FLT3-ITD positive). Induction therapy consists of daunorubicin (60 mg/m², d1-3) and cytarabine (200 mg/m², continuously, d1-7); midostaurin 50 mg bid is applied from day 8 onwards until 48h before start of the next treatment cycle. A second cycle is optional. For consolidation therapy, pts proceed to alloHSCT as first priority; if alloHSCT is not feasible, pts receive three cycles of age-adapted HIDAC in combination with midostaurin from day 6 onwards. In all pts maintenance therapy for one year is intended. This report focuses on the first cohort of the study (n=149) recruited between June 2012 and April 2014 prior to the amendment increasing the sample size; the amendment to the study is active since October 2014. Results: At study entry patient characteristics were median age 54 years (range, 20-70, 34% ≥ 60 yrs); median white cell count (WBC) 48.4G/l (range 1.1-178G/l); karyotype, n=103 normal, n=3 t(6;9), n=2 t(9;11), n=20 intermediate-2 and n=7 high-risk according to ELN recommendations, n=14 missing; mutated NPM1 n=92 (62%). Data on response to first induction therapy were available in 147 pts; complete remission (CR) 58.5%, partial remission (PR) 20.4%, refractory disease (RD) 15% and death 6.1%. A second induction cycle was given in 34 pts. Overall response after induction therapy was CR 75% and death 7.5%. Adverse events 3°/4° reported during the first induction cycle were most frequently gastrointestinal (n=34) and infections (n=81). During induction therapy midostaurin was interrupted, dose-reduced or stopped in 55% of the pts. Overall 94 pts received an alloHSCT, 85 in first CR (n=65 age & lt;60 yrs, n=20 age ≥60 yrs) and 9 pts after salvage outside the protocol or after relapse (n=70 from a matched unrelated and n=24 from a matched related donor). In pts receiving an alloHSCT within the protocol in median 2 chemotherapy cycles were applied before transplant (range 1-4) and the cumulative incidence of relapse and death at 12 months were 9.2% (SE 3.3%) and 19.5% (SE 4.8%). Maintenance therapy was started in 52 pts, 40 pts after alloHSCT and 12 pts after HIDAC. Only 4 adverse events 3°/4° were attributed to midostaurin. First analyses revealed a low cumulative incidence of relapse irrespective of the FLT3-ITD mutant to wildtype ratio ( & lt;0.5 versus ≥0.5) in patients proceeding to alloHSCT with 12% and 5% as well as for those after HIDAC consolidation with 28% and 29%, respectively. Conclusions: The addition of midostaurin to intensive induction therapy and as maintenance after alloHSCT or HIDAC is feasible and compared to historical data may be most effective in those patients with a high FLT3-ITD mutant to wildtype ratio. Disclosures Schlenk: Novartis: Honoraria, Research Funding. Salwender:Celgene: Honoraria; Janssen Cilag: Honoraria; Bristol Meyer Sqibb: Honoraria; Amgen: Honoraria; Novartis: Honoraria. Götze:Celgene Corp.: Honoraria; Novartis: Honoraria.

Abstract: To evaluate the prognostic impact of gene expression levels ( EL s) of two tumor suppressor genes, sprouty 4 ( SPRY 4, located on 5q) and lysine methyltransferase 2C ( KMT 2C, located on 7q) in correlation with clinical characteristics and genetic abnormalities assessed at initial diagnosis in acute myeloid leukemia ( AML ). Method Gene expression levels were measured on cDNA by RT ‐ qPCR from diagnostic bone marrow samples of 275 intensively treated adult AML patients (median age, 48 years). Results KMT 2C EL s were significantly lower in abn7q/‐7 ( P  = .001), whereas SPRY 4 EL s were not associated with abn5q/‐5. Higher KMT 2C and SPRY 4 EL s were significantly associated with lower genetic risk groups as defined by the European LeukemiaNet classification. Additionally, KMT 2C EL s were lower in cytogenetically normal patients with DNMT 3A ( P  = .01) or FLT 3 ‐ ITD mutations ( P  = .05). KMT 2C EL s were not associated with prognosis, whereas higher SPRY 4 EL s showed a favorable impact on event‐free ( EFS , P  = .01), relapse‐free ( RFS , P  = .01) and in‐trend on overall survival ( P  = .06) for cytogenetically abnormal patients, which was confirmed in multivariable analysis for EFS ( HR , 0.84; 95%‐ CI , 0.73‐0.97; P  = .02) and RFS ( HR , 0.85; 95%‐ CI , 0.73‐0.98; P  = .02). Conclusion Our data indicate that KMT 2C EL s are associated with specific genetic features and that SPRY 4 EL s may add prognostic information.

Abstract: Background:Recent publications suggest important roles of lysine methyltransferase 2C (KMT2C, located on 7q) and sprouty 4 (SPRY4, located on 5q) as candidate genes in leukemogenesis of acute myeloid leukemia (AML). The prognostic impact of the gene expression levels (ELs) of both genes on outcome in AML patients (pts) is currently unclear. Aim:To evaluate the prognostic impact of KMT2C and SPRY4 expression in correlation to clinical characteristics and genetic abnormalities assessed at diagnosis in a cohort of intensively treated adult AML pts. Methods: We retrospectively studied 268 AML pts (median age, 48 years; range, 17-60 years) who had been enrolled on 2 AML SHG trials (0295 and 0199, n=148; only normal cytogenetics pts (CN)) and the SAL-AML2003 trial (n=120; only abnormal cytogenetics pts (CA)). Acute promyelocytic and core-binding factor leukemia pts were excluded. Type of AML was de novo in 235 (88%), secondary in 19 (7%) and therapy-related in 14 (5%) of the 268 pts. Regarding baseline characteristics, CN pts had significantly higher white blood counts (WBC; p=0.001) and blast cells in peripheral blood (p=0.02) as compared to CA pts; all other factors were comparable. Cytogenetic analyses could be performed in 263 (98%) of the 268 pts. Cytogenetic risk classification according to ELN guidelines was intermediate-II in 55 (47%) and adverse in 63 (53%) of the CA pts, respectively. Abnormalities (abn) of 5q were present in 21 (18%) and abn of 7q in 16 (14%) of the CA pts. NPM1 and FLT3-ITD were analyzed in 145 (98%) of the CN pts. Of those, 59 (41%) were only NPM1 positive (pos), 12 (8%) were only FLT3-ITD pos, 34 (23%) were double pos and 40 (28%) were double negative (neg). KMT2C and SPRY4 ELs, normalized to ABL1and log2-transformed for analysis, were measured in triplets on cDNA obtained at diagnosis by RT-qPCR. Based on cDNA availability, KMT2C ELs could be analyzed in 143 (97%) of the CN and in all of the 120 CA pts, respectively. SPRY4 ELs could be measured in 30 (21%) of the CN and 107 (89%) of the CA pts, respectively. Results: KMT2C ELs were significantly lower in CN pts with de novo as compared to secondary AML (p= 0.02), whereas there was no difference in CA pts. No significant association was found for SPRY4 and type of AML. KMT2C ELs were significantly lower in FLT3-ITD pos as compared to FLT3-ITD neg CN pts (p=0.046), whereas there was no difference for SPRY4 ELs between the two groups (p=0.57). In addition, there was a significantly lower KMT2C expression in CN pts with intermediate-I risk as compared to NPM1 pos / FLT3-ITD neg pts (p=0.01). Regarding CA pts, there was no difference of KMT2C or SPRY4 ELs in adverse as compared to intermediate-II risk pts (p=0.08; p=0.20, respectively). When focusing on specific subgroups, KMT2C ELs were significantly lower in abn7q CA pts as compared to those without abn7q (p=0.002), whereas there was no difference of SPRY4 ELs in CA pts with or without abn5q (p=0.27). In univariate analysis higher SPRY4 ELs showed a significant favorable impact on relapse-free (RFS, p=0.03) and a trend towards a beneficial impact on overall survival (OS, p=0.06) for CA patients. A similar effect for KMT2C was not observed (RFS, p=0.96; OS, p=0.92). In subgroup analyses of pts with adverse risk cytogenetics, there was no impact of KMT2C or SPRY4 ELs on RFS (p=0.73; p=0.39) or OS (p=0.49; p=0.46), respectively. The same was true for FLT3-ITD pos CN pts (RFS, p=0.73; p=0.37; OS, p=0.91; p=0.36, respectively). In multivariate analyses on RFS and OS in CA pts including age, gender, KMT2C and SPRY4 ELs, logarithm of WBC, blast cells in bone marrow and cytogenetic risk group as variables, only higher age (OS, Hazard ratio (HR),1.28 per 10 years; 95%-confidence interval (CI): 1.02-1.59; p=0.03) and complex karyotype as compared to intermediate-II risk cytogenetics (RFS, HR: 2.25; 95%-CI: 1.20-4.22; p=0.01; OS, HR: 2.97; 95%-CI: 1.65-5.35; p 〈 0.001) had an adverse impact. An effect of KMT2C or SPRY4 on RFS (p=0.84; p=0.16) or OS (p=0.85; p=0.45) was not found in the multivariate setting. In addition, in a multivariate model on CN pts (risk class according to NPM1 and FLT3-ITD mutational status instead of cytogenetic risk class) neither KMT2C nor SPRY4 had an impact on RFS (p=0.13; p=0.39, respectively) or OS (p=0.36; p=0.56, respectively). Conclusions:Lower KMT2C and SPRY4 ELs are associated with distinct genetic risk groups. An impact on prognosis was evident in univariable analyses for SPRY4 but not for KMT2C ELs in CA pts. Disclosures Kayser: Novartis: Consultancy. Platzbecker:Amgen: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; TEVA Pharmaceutical Industries: Honoraria, Research Funding; Janssen-Cilag: Honoraria, Research Funding; Celgene Corporation: Honoraria, Research Funding. Heuser:Tetralogic: Research Funding; Novartis: Consultancy, Research Funding; Celgene: Honoraria; Bayer Pharma AG: Research Funding; Pfizer: Research Funding; Karyopharm Therapeutics Inc: Research Funding; BerGenBio: Research Funding. Thiede:AgenDix: Employment, Other: Ownership.

Abstract: Background: Mutations in the metabolic enzyme isocitrate dehydrogenase 1 (IDH1) are frequently found in patients with acute myeloid leukemia (AML) and several other tumors. Mutant IDH1 produces R-2-hydroxyglutarate (R-2HG), which induces histone and DNA hypermethylation through inhibition of epigenetic regulators, and leads to a block in differentiation to promote tumorigenesis. Methods: We developed a novel, highly active oral pan-IDH1 inhibitor, BAY-1436032, for clinical evaluation. Its inhibitory potency was evaluated in primary human AML cells in vitro for the five major IDH1R132 mutation types and in two patient derived AML xenograft (PDX) models in vivo, in which BAY-1436032 cleared leukemic blasts in peripheral blood and prolonged survival by induction of differentiation and inhibition of leukemia stem cell self-renewal. Results: R-2HG production by mutant IDH1 was effectively inhibited in patient derived AML cells with all reported IDH1R132 mutations ex vivo by BAY-1436032 with an IC50 between 3 to 16 nM. AML cells cultured ex vivo showed morphologic differentiation and marked upregulation of the myeloid differentiation markers CD14 and CD15. For in vivo experiments, human AML cells from two patients were transplanted into sublethally irradiated NSG mice. After stable engraftment at 17 (PDX1) or 90 (PDX2) days post transplantation, mice were treated with BAY-1436032 orally every day at a dose of 150 mg/kg or vehicle for 100-150 days (n=10 per group). The R/S-2HG ratio in serum was reduced to near normal levels by BAY-1436032. Leukemic cell counts in peripheral blood constantly increased in control mice, while leukemic cells declined from day 30 of BAY-1436032 treatment onwards with morphologic and immunophenotypic evidence of differentiation (Figure). Importantly, all BAY-1436032 treated PDX1 mice survived until the end of treatment at 150 days. In contrast, vehicle-treated mice died with a median latency of 91 days (range 70-95, P 〈 .001). In an independent second model (PDX2) 6 of 10 BAY-1436032 treated mice survived until the end of treatment at day 100 with a median of 15% leukemic cells in peripheral blood, while all vehicle-treated mice suffered from high leukemic burden and died from leukemia with a median survival of 62 days (P=.014). Early mortality was increased with 4 mice dying in the BAY-1436032 group reminiscent of clinical differentiation syndrome in AML patients treated with the IDH1 inhibitor AG-120. To assess the effect of BAY-1436032 on leukemic stem cell self-renewal we treated PDX1 mice with 150 mg/kg BAY-1436032 or vehicle for 4 weeks and performed a limiting dilution transplantation experiment in secondary recipient mice. LSC frequency was 100-fold lower in BAY-1436032 treated compared to control mice. Gene expression profiling showed that stemness associated genes were downregulated, while genes associated with myeloid differentiation like PU.1 and CEBPA were upregulated upon treatment with BAY-1436032. In addition, cell cycle progression was slowed and E2F transcription factors concomitantly inhibited. In accordance with gene expression profiling results, methylation of the PU.1 promoter decreased, while E2F1 promoter methylation increased upon treatment with BAY-1436032. Finally, histone trimethylation levels at residues H3K4, H3K9, H3K27, and H3K36 decreased in both IDH1R132C and IDH1R132H mutant AML cells but not in IDH1 wildtype cells upon BAY-1436032 treatment. Conclusion: In summary, the novel oral pan-mutant IDH1 inhibitor BAY-1436032 is active against all IDH1R132 mutation types and shows strong anti-leukemic activity in two independent AML PDX mouse models. Clinical development is ongoing with a first in man study with BAY-1436032 in IDH1 mutant solid tumors. * M. Heuser and L. Herbst contributed equally to this article #A. Krämer and A. Chaturvedi share senior authorship Figure Human leukemic cells in peripheral blood of mice treated with BAY-1436032. ** P 〈 .001, ns, not significant. Figure. Human leukemic cells in peripheral blood of mice treated with BAY-1436032. ** P 〈 .001, ns, not significant. Disclosures Heuser: Tetralogic: Research Funding; BerGenBio: Research Funding; Karyopharm Therapeutics Inc: Research Funding; Bayer Pharma AG: Research Funding; Celgene: Honoraria; Novartis: Consultancy, Research Funding; Pfizer: Research Funding. Pusch:German Cancer Research Center: Patents & Royalties: WO2013/127997A1. Kaulfuss:Bayer Pharma AG: Employment. Panknin:Bayer Pharma AG: Employment. Zimmermann:Bayer Pharma AG: Employment, Patents & Royalties: WO2015/121210 . Toschi:Bayer Pharma AG: Employment. Neuhaus:Bayer Pharma AG: Employment, Patents & Royalties: WO2015/121210. Haegebarth:Bayer Pharma AG: Employment, Equity Ownership. Rehwinkel:Bayer Pharma AG: Employment, Equity Ownership, Patents & Royalties: WO2015/121210. Hess-Stumpp:Bayer Pharma AG: Employment. Bauser:Bayer Pharma AG: Employment. Ho:Sanofi-Aventis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. von Deimling:German Cancer Research Center: Patents & Royalties: IDH1R132H mutant specific antibody H09; BRAF V600E mutant specific antibody VE1; BAY-1436032 patent.