Abstract: Background: The concept of intensive post-remission chemotherapy in acute myeloid leukemia (AML) is based on the observation that despite achievement of a first complete remission (CR) after intensive induction therapy virtually all patients relapse in the absence of further treatment. Moreover, randomized studies showed that intensive post-remission consolidation chemotherapy was superior to prolonged low-dose maintenance therapy in younger patients. With regard to consolidation therapy, the landmark study conducted by the Cancer and Leukemia Group B established the current standard for patients aged 60 years and younger with high-dose cytarabine (HDAC) 3g/m² bidaily on days days 1, 3, and 5. Aims: to compare a compressed schedule of high-dose cytarabine (HDAC) on days 1, 2, and 3 with the standard HDAC given on days 1, 3, and 5 as well as to evaluate the prophylactic use of pegfilgrastim after chemotherapy in patients in first CR receiving repetitive consolidation cycles for acute myeloid leukemia. Methods: Patients (18 to 60 years) were accrued between 2004 and 2009. They were randomized up-front 1:10 between the standard German intergroup-arm (Büchner et al. J Clin Oncol. 2012;30:3604-10) and the AMLSG 07-04 study (NCT00151242). Induction therapy in the AMLSG 07-04 study consisted of two cycles of idarubicin, cytarabine and etoposide +/- all-trans retionoic acid (ATRA) and +/- valproic acid (VPA) in a 2 by 2 factorial design. After recruitment of 392 patients the randomization for VPA was stopped due to toxicity. For consolidation therapy, patients with high-risk AML, defined either by high-risk cytogenetics or induction failure, were assigned to receive allogeneic hematopoietic cell transplantation from a matched related or unrelated donor. All other patients were assigned to 3 cycles of HDAC from 2004 to November 2006 with cytarabine 3g/m² bidaily, on days 1, 3, 5 and pegfilgrastim on day 10 (HDAC-135) and from December 2006 to 2009 patients were treated with a condensed schedule with cytarabine 3g/m², bidaily, on days 1,2,3 and pegfilgrastim on day 8 (HDAC-123). Patients randomized into the German AML intergroup arm were treated for consolidation therapy with cytarabine 3g/m² bid on days 1, 3, 5 (HDAC-135) without prophylactic growth-factor support. Results:Overall 568 patients receiving 1376 consolidation cycles were included into the study. According to up-front randomization 41 were treated with HDAC-135 without prophylactic growth factor support in the German AML Intergroup protocol, 135 with HDAC-135 and 392 with HDAC-123 with intended prophylactic pegfilgrastim at day 10 and 8, respectively, in the AMLSG 07-04 protocol. Time from start to chemotherapy until hematological recovery with leukocytes 〉 1.0G/l and neutrophils 〉 0.5G/l was significantly (p 〈 0.0001, each) and in median 4 days shorter in patients receiving HDAC-123 compared to HDAC-135, and further reduced by 2 days (p 〈 0.0001) by the addition of pegfilgrastim. Treatment with ATRA and VPA according to initial randomization had no impac on hematological recovery times. Rates of infections were significantly reduced by HDAC-123 compared to HDAC-135 (p 〈 0.0001) and pegfilgrastim yes versus no (p=0.002). Days in hospital and platelet transfusions were also significantly reduced in patients receiving HDAC-123 compared to HDAC-135. Relapse-free and overall survival were similar with HDAC-123 and HDAC-135 (p=0.48, p=0.90, respectively). Conclusion: Data from our study suggest that consolidation therapy with a condensed schedule of HDAC-123 is superior to that of standard HDAC-135 in terms of faster hematological recovery, lower infection rate and fever days in hospital. In addition, the administration of one dose of pegfilgrastim after chemotherapy further shortened hematological recovery and reduced infection rate. Importantly, similar efficacy in terms of relapse-free and overall survival rates after HDAC-123 and HDAC-135 were observed. Disclosures Lübbert: Ratiopharm: Other: Study drug valproic acid; Janssen-Cilag: Other: Travel Funding, Research Funding; Celgene: Other: Travel Funding. Fiedler:GSO: Other: Travel; Pfizer: Research Funding; Teva: Other: Travel; Gilead: Other: Travel; Novartis: Consultancy; Ariad/Incyte: Consultancy; Kolltan: Research Funding; Amgen: Consultancy, Other: Travel, Patents & Royalties, Research Funding. Schlenk:Amgen: Research Funding; Pfizer: Honoraria, 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.