Abstract: Introduction: With the introduction of reduced-intensity conditioning (RIC), the age limit for allogeneic transplantation of AML patients has risen to 65 and above. In order to balance a low transplant-related mortality (TRM) with high anti-leukemic efficacy, Marks et al.1 introduced FBM conditioning consisting of 150mg/m2 Fludarabine, 300mg/m2 BCNU and 110mg/m2 Melphalan as RIC for elderly patients with encouraging results. However, no detailed analysis of factors predicting outcome in this subpopulation has been presented so far. Methods: In this two-center retrospective study, 51 patients (pts) with a median age of 64 y (range, 44-75y) diagnosed with AML were uniformly treated according to the FBM protocol. GvHD prophylaxis consisted of Ciclosporin A (CYA) and mycophenolate mofetil (MMF) in all patients. MMF was tapered after d50 and CYA after d90 in the absence of GvHD. Pts with matched unrelated donors (MUD) (n=33) or mismatched unrelated donors (MMUD) (n=9) received additional ATG or low dose alemtuzumab as GvHD and rejection prophylaxis. 9 pts with matched related donor (MRD) only received CYA and MMF as GvHD prophylaxis. Stem cell source was peripheral blood in 90% (n=46) and marrow in 10% (n=5) of the patients. The median number of transfused CD34+ cell was 7.1 million per kg body weight. The median follow-up at the time of analysis was 27 months. At the time of transplant 38 pts were in complete remission; the rest of the pts had active disease (partial remission or refractory disease). Molecular (NPM1, FLT3-ITD and CEBPA a) and cytogenetic characteristics (evaluable in 50 patients) were available for all patients. Results: Acute regimen-related toxicity was low, with a d30 mortality of 0 % in both centers. After 2 years, treatment failure was mainly due to relapse (CIR) with 36% (SE: 8%) in comparison to TRM (20%, SE: 7%). The resulting progression-free survival (PFS) and overall survival (OS) at 2 years was 50 % (SE: 5%) and 61% (SE: 7%), respectively. The median EBMT score was 4 (range 2-6). The EBMT score had no impact on different outcome variables (CIR (p=0.465), PFS (p=0.352) and OS (p=0.171)). Based on cytogenetic and molecular data patients were categorized according to the European LeukemiaNet (ELN) classification. 10% (n=5) of the patients belonged to the ELN favorable, 39% (n=20) to the ELN intermediate I, 29% (n=15) to the ELN intermediate II and 22% (n=11) to the ELN adverse risk group. Neither the ELN score itself nor stratification according to FLT3 -ITD or NPM1 mutation status or cytogenetic risk group impacted on outcome in our cohort. A trend for an improved OS in patients with NPM1 mutation (not stratified for FLT3-ITD or FLT3-TKD) was detected (p=0.255). By analyzing further risk factors such as remission status, donor type, age, CMV status, CD34+ cell number and acute or chronic GvHD we found the disease status at the time of transplant being the dominant predictor for OS. After 2 years patients transplanted not in remission had only an OS of 20% (SE: 8%) as compared to 75% (SE: 12%) in patients transplanted in CR (p 〈 0.001) (Figure 1). Conclusion: In this cohort of elderly patients with AML receiving allogeneic transplantation after FBM conditioning, disease status at the time of transplant was the dominant prognostic factor for outcome. At the present follow-up neither molecular status nor cytogenetics impacted OS, PFS or CIR, significantly. We conclude that alternative strategies have to be applied using FBM conditioning in refractory patients, i.e. the early tapering of immunosuppression and the use of donor lymphocytes or cytoreduction immediately before the start of conditioning. An additional focus should be on novel compounds, which might help to increase CR rates at time of transplant. References 1. Marks R, Potthoff K, et al. Reduced-toxicity conditioning with fludarabine, BCNU, and melphalan in allogeneic hematopoietic cell transplantation: particular activity against advanced hematologic malignancies. Blood. 2008;112(2):415-425. Figure 1. Overall survival dependent on disease status at transplant. Figure 1. Overall survival dependent on disease status at transplant. Disclosures No relevant conflicts of interest to declare.

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: Measurable residual disease (MRD), as determined by quantitation of Nucleophosmin 1-mutated (NPM1mut) transcript levels (TL), provides significant prognostic information independent of other risk factors in patients (pts) with acute myeloid leukemia (AML). This is also addressed by the 2017 European LeukemiaNet (ELN) risk stratification system, which recommends taking into account results from MRD monitoring when selecting the appropriate post-remission therapy. Furthermore, MRD monitoring provides a powerful tool to evaluate treatment effects within clinical trials investigating novel therapies. Aims: To determine the impact of the anti-CD33 immunotoxin Gemtuzumab-Ozogamicin (GO) on kinetics of NPM1mut TL in pts with newly diagnosed NPM1mut AML [18 to 82 years (yrs), median age 58 yrs] enrolled in our randomized Phase III AMLSG 09-09 study (NCT00893399). In this study GO was randomized (1:1) to standard chemotherapy plus ATRA. Patients and Methods: In total, 588 evaluable pts were enrolled in the clinical AMLSG 09-09 study. Standard treatment comprised two cycles of induction therapy with A-ICE (ATRA, idarubicin, cytarabine, etoposide; arm A) followed by three consolidation cycles of high-dose cytarabine (n=371, 63%) or allogeneic hematopoietic cell transplantation (n=42, 8%). In the investigational arm (arm B), GO (3 mg/m²) was given at d1 of each induction and in the first consolidation cycle. 296 pts were randomized to arm A and 292 pts to arm B. For this correlative study, outcome analysis was restricted to the clinical endpoint cumulative incidence of relapse (CIR) due to study protocol requirements allowing overall survival analysis to be performed only two years after the last pt had been enrolled. MRD monitoring was performed in a total 503 pts for whom at least one bone marrow (BM) sample was available using RQ-PCR technique; the median follow-up (FU) of the 503 pts was 2.8 yrs. NPM1mut TL (ratio of NPM1mut/ABL1 transcripts x 104) were determined by RQ-PCR (sensitivity 10-5 to 10-6). Results: In total, 3711 BM samples were analyzed (at diagnosis, n=415; during treatment, n=1765; during FU, n=1531). Both study arms were well balanced with regard to pts characteristics and pretreatment NPM1mut TL. First, we evaluated the impact of GO on kinetics of NPM1mut TL during treatment. After the first induction cycle, median NPM1mut TL were significantly lower in the investigational arm (p=.001) and this was true for all subsequent treatment cycles [after induction II (p=.008), consolidation I (p 〈 .001), consolidation II (p=.006), consolidation III (p=.009)]. Next, we evaluated treatment effects on NPM1mut TL after two cycles of induction therapy in pts in complete remission (CR, n=378). At this time point, there was no difference in the proportion of pts achieving RQ-PCR negativity (RQ-PCRneg) [arm A 15% (28/192), vs arm B 17% (32/186); p=.57] between the two treatment arms. However, treatment according to investigational arm B with GO was associated with a significantly lower CIR rate (CIR at 4 yrs: arm B 29% vs arm A 45%, p=.02). In multivariate analysis randomization to arm B revealed as an independent prognostic factor for remission duration (HR 0.63, p=.018). At the end of treatment (EOT, n=288 pts in CR) the proportion of pts achieving RQ-PCRneg was significantly higher (55% vs 41%; p=.02) in the investigational arm; pts treated in arm B had a significantly lower CIR rate compared to arm A (CIR at 4 yrs: arm B 29% vs arm A 45%, p=.04). Conclusion: In our randomized Phase III AMLSG 09-09 study, the addition of GO to intensive chemotherapy plus ATRA was associated with a significantly better reduction of NPM1mut TL after each treatment cycle. This better clearance translated into a significantly lower CIR in the investigational arm with GO. Disclosures Paschka: Otsuka: Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Other: Travel support, Speakers Bureau; Jazz: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees; Sunesis: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Travel support; Janssen: Other: Travel support; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Astex: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees, Travel support; Takeda: Other: Travel support. Krönke:Celgene: Honoraria. Fiedler:Amgen: Other: support for meetíng attendance; GSO: Other: support for meeting attendance; Teva: Other: support for meeting attendance; Gilead: Other: support for meeting attendance; JAZZ Pharmaceuticals: Other: support for meeting attendance; ARIAD/Incyte: Membership on an entity's Board of Directors or advisory committees, support for meeting attendance; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Pfizer: Research Funding; Amgen: Patents & Royalties; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi Sankyo: Other: support for meeting attendance. Schroeder:Celgene: Consultancy, Honoraria, Research Funding. Lübbert:Janssen: Honoraria, Research Funding; TEVA: Other: Study drug; Cheplapharm: Other: Study drug; Celgene: Other: Travel Support. Götze:JAZZ Pharmaceuticals: Honoraria; Novartis: Honoraria; Takeda: Honoraria, Other: Travel aid ASH 2017; Celgene: Honoraria, Research Funding. Schleicher:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Investigator; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Ipsen: Membership on an entity's Board of Directors or advisory committees; Eissai: Other: Investigator; Astra Zeneca: Other: Investigator; Pfizer: Speakers Bureau; Janssen: Speakers Bureau; Celgene: Speakers Bureau. Schlenk:Pfizer: Research Funding, Speakers Bureau. Ganser:Novartis: Membership on an entity's Board of Directors or advisory committees. Döhner:Amgen: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Pfizer: Research Funding; Agios: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Celator: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Seattle Genetics: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Bristol Myers Squibb: Research Funding; Bristol Myers Squibb: Research Funding; Astex Pharmaceuticals: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Pfizer: Research Funding; Seattle Genetics: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Celator: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Sunesis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, 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: In 2010 an international expert working group (European LeukemiaNet, ELN) has published recommendations for the diagnosis and management of acute myeloid leukemia (AML) including a risk stratification by cyto- and molecular genetics, subdividing AML into four risk groups. Emerging data on molecular markers in AML has led to an update of stratification criteria by ELN in 2017 including the recommendation for screening of the high-risk (HR) molecular markers ASXL1, RUNX1, and TP53 that have been shown to confer poor prognosis. The identification of HR markers results in a shift of the prognostic stratification towards adverse risk. Aim: To investigate the mutational landscape and to assess the prevalence of HR markers in patients (pts) with newly diagnosed AML classified as intermediate-I or -II risk (inter-I/-II) based on the 2010 ELN criteria in a prospective real-world application. Methods: Using a next-generation targeted sequencing approach [HaloPlex HS (Agilent) on a Miseq (Illumina)], we performed a prospective analysis of all coding regions of 42 tar get genes including the HR marker ASXL1, RUNX1, and TP53 in 329 newly diagnosed intermediate risk AML pts all enrolled in the AMLSG Biology and Outcome (BiO)-Registry [NCT01252485] of the German-Austrian AML Study Group (AMLSG). Pt genetic features obtained at diagnosis were as follows: inter-I: normal karyotype, n=198 (60%); inter-II: trisomy 8, n=28 (9%), nullisomy Y, n=12 (4%), t(9;11)(p21.3;q23.3), n=7 (2%), others, n=83 (25%); FLT3-internal tandem duplication (FLT3-ITD+), n=75 (23%), mutations (mut) in tyrosine kinase domain of FLT3 (FLT3-TKDmut), n=12 (3.6%), NPM1mut, n=59 (18%); median age was 67 years (range: 21-89 yrs); 60% of pts were male. Results: Overall, 1253 mut in 315 pts (96%) were identified. Mut in at least one of the HR markers were identified in 50% (n=166) of the pts. Mut in ASXL1 occurred in 32% (105/329), followed by RUNX1 in 26% (87/329), and TP53 in 4% (13/329) of the pts, respectively. Pts with mut in one of the three HR markers showed lower WBC (median 7.63 vs 24.25 109/L, P=.003), lower hemoglobin value (median 8.8 vs 9.3 g/dl, P=.01), lower LDH serum level (median 330 vs 559 U/l, P 〈 .0001) and were associated with older age at diagnosis (median 69.4 vs 66.8 yrs, P=.01). Furthermore, HR markers correlated with male gender (67% HR+ vs 51% HR-, P=.003). Mut in HR markers showed an inverse correlation with FLT3-ITD+ (6% vs 39%, P 〈 .0001), NPM1mut (1% vs 34%, P 〈 .0001), the genotype NPM1mut/FLT3-ITD+ (1% vs 37%, P 〈 .0001), normal karyotype (54% vs 66%, P=.025) and KMT2A rearrangement (0% vs 5%, P=.0035). Further, pts with HR markers exhibited more mut per case (mean 4.6 vs 2.8, P=.0001) and more frequently had co-mut in splicing genes such as SRSF2 (37% vs 14%, P 〈 0.0001) and SF3B1 (3% vs 0%, P=.029) and chromatin-cohesin genes such as EZH2 (9% vs 1%, P=.0009) and STAG2 (21% vs 4%, P 〈 0.0001); here, co-mut with SRSF2 and SF3B1 were mutually exclusive. Pts with HR wildtype showed a significant association with NPM1 (34% vs 1%, P 〈 .0001), DNMT3A (36% vs 20%, P=.0002), WT1 (8% vs 0.6 %, P=.0015) and GATA2 mut (7% vs 1.8%, P=.03) with significant co-mutational patterns such as WT1 with NPM1 (P=.03). Interestingly, we found BRAF mut in 3% (9/329) of the pt cohort with 5/9 pts harboring the p.V600E hotspot mut. Further analyses of survival data in these genotypes are currently ongoing. Conclusion: In this prospective study we could obtain real world mut data showing a high prevalence of HR marker mut in intermediate-I or -II risk AML pts as defined by 2010 ELN risk classification, thus revealing a significant proportion of pts (50%) harboring HR mut that confer an inferior survival. This high prevalence clearly demonstrates the clinical importance of HR marker screening as recommended by 2017 ELN criteria to identify pts, whose prognosis may be improved by more intensive therapy. Further, we could show that pts with HR marker mut differ significantly from HR wildtype pts with regard to clinical and molecular characteristics indicating a distinct biological subgroup which could potentially benefit from novel treatment approaches beyond conventional chemotherapy. Finally, novel genotypes such as NPM1mut/WT1mut will be further investigated with regard to their prognostic impact. Disclosures Bullinger: Bristol-Myers Squibb: Speakers Bureau; Pfizer: Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Research Funding, Speakers Bureau; Amgen: Honoraria, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer Oncology: Research Funding; Janssen: Speakers Bureau. Paschka:Sunesis: Membership on an entity's Board of Directors or advisory committees; Otsuka: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Astex: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Travel support; Jazz: Speakers Bureau; Bristol-Meyers Squibb: Other: Travel support, Speakers Bureau; Janssen: Other: Travel support; Agios: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees, Travel support; Takeda: Other: Travel support. Lubbert:Celgene: Other: Travel Grant; Janssen: Honoraria, Research Funding; Teva: Other: Study drug. Salih:Several patent applications: Patents & Royalties: e.g. EP3064507A1. Ganser:Novartis: Membership on an entity's Board of Directors or advisory committees. Döhner:Sunesis: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Research Funding; Janssen: Consultancy, Honoraria; Jazz: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Celator: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; Astellas: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Astex Pharmaceuticals: Consultancy, Honoraria; Pfizer: Research Funding; Celator: Consultancy, Honoraria; Sunesis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AROG Pharmaceuticals: Research Funding; AbbVie: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Pfizer: Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Jazz: Consultancy, Honoraria; Bristol Myers Squibb: Research Funding; Seattle Genetics: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding.

Abstract: Clinical trials with immune checkpoint inhibitors (ICI) in adrenocortical carcinoma (ACC) have yielded contradictory results. We aimed to evaluate treatment response and safety of ICI in ACC in a real-life setting. Design Retrospective cohort study of 54 patients with advanced ACC receiving ICI as compassionate use at 6 German reference centres between 2016 and 2022. Methods Objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and treatment-related adverse events (TRAE) were assessed. Results In 52 patients surviving at least 4 weeks after initiation of ICI, ORR was 13.5% (6-26) and DCR was 24% (16-41). PFS was 3.0 months (95% CI, 2.3-3.7). In all patients, median OS was 10.4 months (3.8-17). 17 TRAE occurred in 15 patients, which was associated with a longer PFS of 5.5 (1.9-9.2) vs 2.5 (2.0-3.0) months (HR 0.29, 95% CI, 0.13-0.66, P = 0.001) and OS of 28.2 (9.5-46.8) vs 7.0 (4.1-10.2) months (HR 0.34, 95% CI, 0.12-0.93). Positive tissue staining for programmed cell death ligand 1 (PD-L1) was associated with a longer PFS of 3.2 (2.6-3.8) vs 2.3 (1.6-3.0, P & lt; 0.05) months. Adjusted for concomitant mitotane use, treatment with nivolumab was associated with lower risk of progression (HR 0.36, 0.15-0.90) and death (HR 0.20, 0.06-0.72) compared to pembrolizumab. Conclusions In the real-life setting, we observe a response comparable to other second-line therapies and an acceptable safety profile in ACC patients receiving different ICI. The relevance of PD-L1 as a marker of response and the potentially more favourable outcome in nivolumab-treated patients require confirmation.

Abstract: Background: Mutations in the nucleophosmin (NPM1) gene represent one of the most common gene mutations in AML, and are considered a founder event in the pathogenesis of AML. Recently, we gained novel insights into clonal architecture and clonal evolution in 53 NPM1 mutated (NPM1mut) AML patients (pts). Here, we showed the highest stability for DNMT3A mutations (DNMT3Amut) suggesting that these mutations represent an early event in leukemogenesis as well as an increase in genomic complexity. Aims: To validate our previous results on clonal evolution in a larger cohort of NPM1mut AML pts and to define relapse specific mutation patterns. Methods: Paired samples at diagnosis and relapse from 129 NPM1mut AML pts were assessed for additional mutations by comprehensive mutation analysis (FLT3-ITD, FLT3-TKD, DNMT3A, IDH1/2, NRAS, ASXL1, TP53, MLL-PTD). In addition, 11 AML cases with loss of NPM1mut at the time of relapse and 12 cases with persisting NPM1mut were subjected to whole exome sequencing (WES). Results: At diagnosis, the incidence of concurrent gene mutations was as follows: FLT3-ITDmut 32% (40/126), FLT3-TKDmut 19% (22/118), DNMT3Amut 69% (78/113), NRASmut 19% (22/117), IDH1mut 21% (26/123) and IDH2mut 19% (22/118). None of the pts analyzed exhibited a TP53 (n=53), MLL-PTD (n=63) or ASXL1 (n=59) mutation. At relapse, a significant shift in the genetic pattern was found in 74 pts (57%). FLT3-ITDmut was lost in 10 pts and newly acquired in 24 pts,16 pts lost FLT3-TKDmut. DNMT3Amut was lost in 2 pts and gained in 1 pt. NRASmut was lost in 12 pts and gained in 4 pts. IDH1mut was lost in 3 pts and acquired in 4 pts, while IDH2mut was lost in 2 pts and gained in only one pt. ASXL1mut and TP53mut were gained in 2 and 1 pts, respectively; gain of MLL -PTDmut (n=4) was restricted to pts with loss of NPM1mut at the time of relapse. Based on these findings we calculated the following stabilities: FLT3-ITDmut 75%, FLT3-TKDmut 27%, DNMT3Amut 97%, NRASmut 45%, IDH1mut 88% and IDH2mut 91%, respectively. In total, 11 pts (9%) lost NPM1mut at relapse while DNMT3Amut was present in 9/11 pts at diagnosis and remained stable at relapse; 4/11 pts gained MLL-PTDmut, one pt ASXL1mut and 3 pts acquired RUNX1mut. By WES we observed a persistence of mutations known to be involved in clonal hematopoiesis, such as DNMT3A and TET2 mutations. These were usually seen during all analyzed time points (diagnosis, remission and relapse). In addition, we found distinct mutational patterns at the time of relapse compared to the time of diagnosis. For example, relapse- and diagnosis-specific mutations in NPM1mut loss cases were significantly enriched for different signaling pathways. Conclusions: 74 (57%) of 129 NPM1mut AML pts showed clonal evolution at the time of relapse. DNMT3Amut demonstrated the highest stability (97%) confirming our previous findings that DNMT3Amut constitutes an early event which persists in preleukemic hematopoietic stem cells. High-resolution sequencing of selected cases is ongoing and will further unravel the clonal hierarchy in NPM1mut AML. Those authors equally contributed to work: SKS, SC, LB and KD. Disclosures Heuser: Karyopharm: Research Funding.