Abstract: Abstract 1637 Blinatumomab (MT103) is a single-chain bispecific antibody construct with specificity for CD19 and CD3 belonging to the class of bispecific T cell engager (BiTE®). A phase I trial with indolent and mantle cell lymphoma patients established a maximal tolerable dose (MTD) at 60 μg/m2/d. The trial was subsequently amended to evaluate blinatumomab in patients with diffuse large B cell lymphoma (DLBCL). Patients were treated by 4–8-week continuous i.v. administration with the following dosing regimen: first week at 5 μg/m2/d, second week at 15 μg/m2/d and for the remaining treatment period at 60 μg/m2/d. Two cohorts each with 6 DLBCL patients were enrolled. The two cohorts solely differed by the dose and schedule of corticosteroid medication administered at the beginning of blinatumomab infusion for mitigation of adverse events. In the first cohort 100 mg prednisolone was applied 1 hour prior to start; and in the second cohort patients received dexamethasone on days 1, 2, and 3. Three sequential patients received dexamethasone also 6–12 hours prior to start of infusion. Out of the twelve patients, 5 were male and 7 female. The median age was 57 years (range from 26 to 78 years). Patients had received a median of 4 prior regimens (range from 2–6). All patients had been exposed to rituximab. Eight of the 12 patients had undergone autologous stem cell transplantation (ASCT). International prognostic index (IPI) at screening ranged from 1 to 3 with a median of 2. The most common clinical adverse events (AEs) regardless of causality ( 〉 30%) were pyrexia (81.8%), fatigue (54.5%), constipation (36.4%), headache (36.4%), tremor (36.4%) and weight increase (36.4%). The most frequent laboratory AEs regardless of causality ( 〉 30%) were hyperglycemia (63.6%), lymphopenia (54.5%), C-reactive protein increase (45.5%), gamma-glutamyltransferase increase (45.5%) and thrombocytopenia (36.4%). Most AEs occurred early and were reversible. Four of 12 patients discontinued infusion due to fully reversible CNS events, 2 of which qualified as dose limiting toxicities (DLTs). Although just one DLT (reversible CNS event grade 3) occurred in the prednisolone cohort, a further cohort applying prophylactic dexamethasone was opened to optimize management of CNS events. A further refinement of the dexamethasone schedule, starting longer time prior to start of blinatumomab, was introduced after one early patient in the cohort receiving dexamethasone had experienced a reversible CNS event leading to discontinuation. All three patients treated in this manner completed the first blinatumomab cycle without discontinuations. Only one showed a grade 1 tremor, and no other CNS AEs were reported in these three patients. Two of 12 patients were not exposed to 60 μg/m2/d due to early discontinuations and 1 patient is too early in treatment for response evaluation. Five out of the remaining 9 evaluable patients (56%) showed objective clinical responses (4 CR/CRu; 1 PR). Three out of the 5 patients with CR/CRu or PR had prior ASCT. Two patients achieved objective responses (1 CR, 1 PR) despite of discontinuation at 60 μg/m2/d. The median response duration is +182 days (longest current duration +428 days), with 4 out of 5 responses still ongoing. Further evaluation of the last cohort will refine the recommended phase II dose, and the intensity and timing of dexamethasone comedication. The observation of lasting CRs after blinatumomab monotherapy in DLBCL patients is promising and warrants further exploration in a phase II study. Disclosures: Krause: Micromet: Research Funding. Mackensen:Micromet Inc.: Research Funding. Topp:Micromet: Consultancy, Honoraria. Scheele:Micromet Inc.: Employment, Equity Ownership, Patents & Royalties. Nagorsen:Micromet Inc.: Employment, Equity Ownership, Patents & Royalties. Zugmaier:Micromet: Employment. Degenhard:Micromet Inc: Employment. Schmidt:Micromet AG: Employment. Kufer:Micromet Inc: Employment, Equity Ownership. Libicher:Micromet Inc.: Consultancy, Honoraria. Bargou:Micromet: Consultancy, Honoraria.

Abstract: Background: Trisomy 4 is a recurrent but rare cytogenetic abnormality reported in patients with acute myeloid leukemia (AML). The prognostic significance of this abnormality in AML patients is not clear. Prognosis of AML patients with trisomy 4 seems to be poor as compared to that of patients with intermediate-risk cytogenetics. Allogeneic hematopoietic stem cell transplantation (allo-HCT) may improve survival if applied early in first complete remission (CR). However, neither prospective clinical nor larger retrospective cohort studies are available to support these results from small series. Aims: To characterize AML patients with trisomy 4 and compare outcomes according to different treatment strategies. Methods: We retrospectively studied 123 AML patients with trisomy 4 (median age at diagnosis, 58 years; range, 16-76 years) treated between 2000 and 2019 within 2 large study groups. Standard statistical methods were applied. Results: Median white blood cell count at diagnosis was 4.8/nl (range, 0.4-255/nl) and platelets 46/nl (range, 2-330/nl). Type of AML was de novo in 97 (79%), secondary after myelodysplastic syndrome/myeloproliferative neoplasm in 18 (15%), and therapy-related in 8 (6%) patients. Sixty-two (50%) patients were female. Cytogenetic analysis revealed trisomy 4 as the sole abnormality in 28 (23%), additional abnormalities in 95 (77%) patients, most frequently ≥3 (n=66) abnormalities, trisomy 8 (n=41), karyotypes characterized by trisomies only (n=21) and t(8;21) or inv(16) (CBF; n=10). A total of 98 patients (80%) had NPM1 and FLT3-ITD mutation testing. Of those, 21 (21%) and 15 (15%) harbored NPM1 and FLT3-ITD mutations. Only 2 (3%) of 72 patients were CEBPA double mutated. Data on response to intensive anthracycline-based induction therapy were available in 117 patients. Early death rate was 5% (n=6). CR was achieved in 68% (n=79) with 22 (19%) requiring an intensive salvage treatment cycle. Notably, patients with trisomy 4 as sole abnormality had a CR rate of 89% (n=25/28). There was no difference in the CR rate in FLT3-ITD positive (n=10/15) as compared to FLT3 wild type (n=56/83) patients (67% each, P=0.99). Univariable analysis revealed trisomy 4 as sole abnormality (OR, 5.76; P=0.007) and NPM1 (OR, 12.08; P=0.02) as favorable factors. An allo-HCT was performed in 40 (34%) patients, of whom 19 patients were transplanted in first CR after induction therapy. Nine patients achieved CR after salvage chemotherapy and went on to allo-HCT; another 12 patients received allo-HCT with active disease. Type of donor was matched-related in 8, matched-unrelated in 30, and unknown in 2 of the 40 patients, respectively. Median follow-up of the intensively treated cohort was 73 months (95%-CI, 36-91 months). Five-year overall survival (OS) and relapse-free survival (RFS) were 31% (95%-CI, 23-42%) and 27% (95%-CI, 18-42%). OS rates were significantly higher in patients with CBF leukemia or patients with trisomy 4 as compared to all other abnormalities (Figure 1; P & lt;0.001). Cox regression analysis on OS revealed CBF/CEBPA (HR, 0.75; P=0.02) and trisomy 4 as sole abnormality (HR, 0.63; P=0.04) as favorable factors; age with a difference of ten years was an in trend adverse factor (HR, 1.15; P=0.06; not significant: NPM1, FLT3-ITD, complex karyotype with ≥3 abnormalities). There was no difference on OS if patients proceeded to allo-HCT in CR1 or with active disease (P=0.8). Five-year RFS was 26% (95%-CI, 14-50%) in patients proceeding to allo-HCT after induction therapy (n=40), as compared to 28% (95%-CI, 17-46%; P=0.99) in those who received consolidation chemotherapy (n=49). Conclusions: Clinically, patients with trisomy 4 are very heterogeneous in particular with respect to cytogenetic and molecular abnormalities. In our cohort, patients with trisomy 4 as a sole abnormality had a high CR rate and favorable clinical outcome. In the total cohort, allo-HCT did not improve RFS. Figure 1 Figure 1. Disclosures Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Haenel: Takeda: Consultancy, Honoraria; Bayer Vital: Honoraria; Jazz: Consultancy, Honoraria; GSK: Consultancy; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Crysandt: Incyte: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees. Fransecky: Medac: Honoraria; Amgen: Honoraria; Abbvie: Honoraria, Research Funding; Novartis: Honoraria; Takeda: Honoraria. Martinez-Lopez: Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Platzbecker: AbbVie: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Geron: Honoraria; Takeda: Honoraria. Baldus: Novartis: Honoraria; Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria. Müller-Tidow: Pfizer: Research Funding; Janssen: Consultancy, Research Funding; Bioline: Research Funding. Levis: Astellas and FujiFilm: Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Honoraria; Amgen, Astellas Pharma, Daiichi-Sankyo, FujiFilm, and Menarini: Honoraria; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria; Takeda: Honoraria. Montesinos: Stemline/Menarini: Consultancy; Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Forma Therapeutics: Consultancy; Glycomimetics: Consultancy; Tolero Pharmaceutical: Consultancy; Agios: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau. Röllig: Roche: Honoraria, Research Funding; Bristol-Meyer-Squibb: Honoraria, Research Funding; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Amgen: Honoraria; AbbVie: Honoraria, Research Funding. Schlenk: Novartis: Honoraria; Pfizer: Honoraria, Research Funding, Speakers Bureau; Hexal: Honoraria; Neovio Biotech: Honoraria; Daiichi Sankyo: Honoraria, Research Funding; Celgene: Honoraria; Astellas: Honoraria, Research Funding, Speakers Bureau; Abbvie: Honoraria; Agios: Honoraria; Roche: Honoraria, Research Funding; AstraZeneca: Research Funding; Boehringer Ingelheim: Research Funding.

Abstract: Background In newly diagnosed acute myeloid leukemia (AML), the general recommendation is to start treatment immediately after the diagnosis has been made. This paradigm is based both on the observation that untreated acute leukemia has a poor prognosis and on retrospective analyses demonstrating a shorter survival in younger AML patients (pts) in whom treatment was delayed by more than 5 days (Sekeres et al., 2009). A more recent single-center analysis came to a different conclusion, showing no prognostic effect for the time from diagnosis to treatment (TDT; Bertoli et al., 2013). We explored the relationship between TDT and prognosis on a large set of real-world data from the AML registry of the Study Alliance Leukemia (SAL) and compared it to the published cohorts. Methods The SAL runs a transregional AML registry in 46 treatment centers across Germany (NCT03188874). All registered patients with an intensive induction treatment, a minimum follow-up time of 12 months and no acute promyelocytic leukemia were selected (n=2,200). Treatment start was defined by the first day of cytarabine, whereas single agent hydroxyurea (HU) was labeled as pretreatment. We analyzed the influence of TDT on complete remission (CR), early death (ED) and overall survival (OS) in univariable analyses for each day of treatment delay, in groups of 0-5, 6-10, 11-15 and & gt;15 days of TDT, and by using the restricted cubic spline (RCS) method for data modelling. In order to adjust for the influence of established prognostic variables on the outcomes, we used multivariable regression models and propensity score weighting. The influence of HU pretreatment on outcomes was investigated by introducing an interaction term between TDT and the presence of HU pretreatment. Results The median age was 59 years (y) (IQR 50-68), the proportion of pts with favorable, intermediate and adverse genetic risk according to ELN was 27%, 53%, and 20%; & gt;95% of pts received induction treatment with standard 7+3. HU pretreatment was administered in 4% of pts. The median TDT was 3 days (IQR 2-6). Descriptive statistics after grouping of pts showed the highest median age and the lowest proportion of NPM1 mutated and favorable risk in the TDT group 11-15. Of all pts, 79% achieved a CR/CRi; unadjusted CR rates for the patient groups with TDT of 0-5, 6-10, 11-15 and & gt;15 days were 80%, 77%, 74% and 76%, respectively (p=0.317). In multivariable analysis accounting for the influence of ELN risk, age, WBC, LDH, de novo versus secondary AML and ECOG, the OR for each additional day of TDT was 0.99 (95%-CI, 0.97-1.00; p=0.124). Four percent of pts died within the first 30 days from treatment start. The respective rates in the four TDT categories were 4.0%, 3.8%, 5.1% and 4.1% (p=0.960). In multivariable analysis, the OR for TDT was 1.01 (95%-CI, 0.98-1.05; p=0.549). After a median follow-up of 40 months, the 2-y OS of all pts was 51%. The unadjusted 2-y OS rates stratified by TDT of 0-5, 6-10, 11-15, & gt;15 days were 52, 49, 46, and 51% (see Table 1 and Figure 1). The hazard ratio (HR) for each day of treatment delay was 1.00 (95%-CI; 0.99-1.01; p=0.317). In multivariable Cox regression analysis, the HR for TDT as continuous variable was 1.00 (95%-CI, 0.99-1.01; p=0.689). When OS was analyzed separately stratified for age ≤60 and & gt;60 ys and for high versus lower initial WBC defined by a threshold of 50 x 109/L, no significant differences between TDT groups were observed. Multivariable models using TDT as a grouped variable or with RCS did not provide evidence for a significant influence of TDT on outcomes. Propensity score matching of pts in the four TDT groups did not reveal an influence on outcomes. The use of HU was not associated with CR, ED nor OS. Conclusion Our study on 2,200 newly diagnosed registry pts receiving consistent intensive induction with standard-dose cytarabine plus daunorubicin (7+3) suggests that TDT is not related to response or survival, neither in younger nor in older pts. Despite multivariable analyses, a bias towards longer TDT intervals in pts judged to be clinically stable by the treating physician cannot be excluded entirely. As treatment stratification in intensive first-line treatment of AML evolves, the TDT data suggests that it may be a safe and reasonable approach to wait for genetic and other laboratory test results in order to assign clinically stable pts to the best available treatment option before the start of intensive treatment. Disclosures Krämer: Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Hänel:Roche: Honoraria; Amgen: Honoraria; Celgene: Other: advisory board; Novartis: Honoraria; Takeda: Other: advisory board. Jost:Daiichi: Honoraria; Sanofi: Honoraria; Gilead: Other: travel grants; Jazz Pharmaceuticals: Honoraria. Brümmendorf:Merck: Consultancy; Janssen: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; University Hospital of the RWTH Aachen: Employment; Ariad: Consultancy. Krause:Siemens: Research Funding; Takeda: Honoraria; MSD: Honoraria; Gilead: Other: travel; Celgene Corporation: Other: Travel. Scholl:Novartis: Other: Project funding; Pfizer: Other: Advisory boards; Gilead: Other: Project funding; Daiichi Sankyo: Other: Advisory boards; AbbVie: Other: Advisory boards. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding. Kiani:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Middeke:Sanofi: Research Funding, Speakers Bureau; Roche: Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Gilead: Consultancy; Janssen: Consultancy, Speakers Bureau; MSD: Consultancy. Thiede:AgenDix GmbH: Employment, Equity Ownership; Novartis: Research Funding, Speakers Bureau; Bayer: Research Funding; Daiichi-Sankyo: Speakers Bureau. Stoelzel:JAZZ Pharmaceuticals: Consultancy; Neovii: Other: Travel funding; Shire: Consultancy, Other: Travel funding. Platzbecker:Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding.

Abstract: Background Venetoclax (VEN)-based combination therapy with hypomethylating agents (HMA) has been approved for first-line treatment in patients ineligible for intensive treatment based on two randomized trials. There is some evidence for efficacy also in the in relapsed/ refractory setting (R/R), but comparative controlled data is lacking. Here, we report our experience of VEN-Azacitidine (AZA) in R/R AML salvage treatment and bridge to allogeneic cell transplantation (allo-HCT) in fit patients compared to historical data from the Study Alliance Leukemia (SAL) registry (ClinicalTrials.gov Identifier: NCT03188874). Design/Methods We analyzed all patients with R/R AML after initial intensive therapy, who started VEN-AZA salvage treatment at the University Hospital Heidelberg, between October 2018 and October 2020. Patients, who were bridged to allo-HCT were compared in a multivariable analysis to data of R/R AML patients from the SAL registry receiving an allo-HCT. Results: A total of 26 patients (median age 60 years, range 23 to 79) were included. All patients initially received intensive therapy, 16 patients (62%) had been refractory to intensive induction therapy with DA (daunorubicin, cytarabine) (11 patients)/ CPX-351 (2 patients) or to an intensive salvage therapy regime with HAM (2 patients)/ Cytarabin-Bortezomib (1 patient). Ten patients (38%) had morphologic (7 patients) or molecular relapse (3 patients) after intensive first line therapy. The distribution of AML according to WHO-2016 classification was n=10 recurrent genetic abnormalities (n= 7, mutated NPM1; n=1, biallelic CEBPA mutations; n=1, mutated RUNX1; n=1, CBFB-MYH11), n=10 AML with MRC, n=6 AML NOS. According to the 2017 ELN classification, 9 patients (34,5%) had low risk, 8 (31%) intermediate risk and 9 (34,5%) adverse risk disease. All patients received AZA 75mg/m² for 7 days combined with VEN 400mg/day after initial ramp up or a reduced dose of 100mg/day in case of co-medication with azoles in 28 days cycles. Best response was CR/CRi in 58% (n=15), PR in 23% (n=6) patients. Day 30-mortality was 0%, day 60-mortality was 4% (n=1). Allo-HCT was performed in 20 patients (77%). Pre-Allo-HCT remission status was CR/CRi in 11 (55%), PR in 4 (20%) patients and MLFS in 1 patient and 4 patients had active disease (n=3, relapse after achieving CR/CRi on VEN-AZA, n=1 refractory to VEN-AZA.). At the time of analysis 15 (75%) of the 20 bridged patients were alive and 11 (55%) are still in CR resulting in a median relapse-free survival in bridged patients of 406 days, whereas all patients not proceeding to allo-HCT died after a median of 139 days. In total, 63 patients with R/R AML were identified in the SAL-registry proceeding to allo-HCT with non VEN-based salvage attempt. Pre-Allo-HCT remission status was CR/CRi in 18 (28%), PR in 15 (24%), unknown in 13 patients (21%) and 17 (27%) patients had active disease (n=9 relapsed, n=8 refractory). Patients of the SAL registry were younger (median, 55 years; range, 22-75 years) and more patients were ELN-int (low risk, 32%, n=20; int, 52%, n=33, adv, 16%, n=10). Median follow-up in the VEN-AZA and the SAL cohorts were 1.4 years and 4.6 years, respectively. Cox-regression modeling of survival measured from the date of being refractory/relapsed revealed a non-significant effect of the cohorts favoring the VEN-AZA salvage therapy (HR, 0.87, p=0.73). However, stratified univariable survival analysis revealed in trend better survival (p=0.10) in the VEN-AZA compared to the SAL cohort with 77% (95%-CI, 62-95%) and 74% (95%-CI, 57-97%) as well as 84% (95%-CI, 76-94%) and 52% (95-CI, 41-68%) 1- and 2-years survival, respectively. Conclusion: Our data confirms the efficacy of VEN-AZA in patients with R/R AML and underlines its potential as an effective strategy for bridging to successful allo-HCT. Disclosures Unglaub: JazzPharma: Consultancy, Other: travel costs/ conference fee; Novartis: Consultancy, Other: travel costs/ conference fee. Schlenk: Boehringer Ingelheim: Research Funding; AstraZeneca: Research Funding; Roche: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria; Neovio Biotech: Honoraria; Hexal: Honoraria; Daiichi Sankyo: Honoraria, Research Funding; Celgene: Honoraria; Astellas: Honoraria, Research Funding, Speakers Bureau; Abbvie: Honoraria; Agios: Honoraria. Middeke: Janssen: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria; Gilead: Consultancy; Abbvie: Consultancy, Honoraria; Jazz: Consultancy; Pfizer: Consultancy, Honoraria; Sanofi: Honoraria, Research Funding; Astellas: Consultancy, Honoraria; Novartis: Consultancy; Glycostem: Consultancy; UCB: Honoraria. Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Haenel: GSK: Consultancy; Jazz: Consultancy, Honoraria; Bayer Vital: Honoraria; Takeda: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy; Celgene: Consultancy, Honoraria. Crysandt: Pfizer: Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria. Fransecky: Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Seggewiss-Bernhardt: Astra-Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; ipsen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; EusaPharma: Honoraria, Membership on an entity's Board of Directors or advisory committees. Platzbecker: AbbVie: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Novartis: Honoraria; Geron: Honoraria; Takeda: Honoraria. Baldus: Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria; Novartis: Honoraria. Dreger: Bluebird Bio: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; BMS: Consultancy; AbbVie: Consultancy, Speakers Bureau; Janssen: Consultancy; Gilead Sciences: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Müller-Tidow: Pfizer: Research Funding; Janssen: Consultancy, Research Funding; Bioline: Research Funding. Sauer: Takeda: Consultancy, Other: DSMB/SAB Member; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Abbvie: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau. OffLabel Disclosure: off-label use of Venetoclax-based combination therapy in relapsed or refractory AML

Abstract: Abstract 3281 Poster Board III-1 Introduction: In the two consecutive German CML studies III and IIIA (recruitment periods from 1995 to 2001 and 1997 to 2004), eligible patients were assigned to early HSCT by genetic randomization according to availability of a matched related donor. After randomization, 113 patients of study III (84% of 135) and 144 of study IIIA (87% of 166) were eventually transplanted in first chronic phase (CP) using a related donor. Despite comparable transplantation protocols and most centers participating in both studies, survival probabilities in study IIIA were significantly better, even when adjusted for the established EBMT risk score (Gratwohl et al., Lancet 1998 [1]), p + 0.0097. For further explanation, the German Registry for Stem Cell Transplantation (DRST) and the Swiss Transplant Working Group for Blood and Marrow Transplantation (STABMT) were asked for data support. Patients and Methods: The main sample characteristics of the 257 transplanted CML study patients were also applied to the registry patients: diagnosis of CML between 1994 and 2004, first HSCT with a related donor performed in first CP between 1995 and 2004 at an age between 12 and 65 years, and blood or bone marrow as stem cell sources. Thus, additional data of 582 HSCT patients were retrieved from the two registries. Age, recipient sex, donor sex, time between diagnosis and HSCT, calendar year of HSCT, stem cell source, and HLA matching were investigated as potential predictive factors for survival. Then, a sample of patients with the same risk distribution as the 113 patients of study III was randomly drawn from the registry patients. By application of repeated resampling to this new patient group, bootstrap confidence intervals for survival probabilities at various times after HSCT were extractable. This provided the basis to judge whether the survival in study III could be seen as a typical random representation of a sample with an equivalent risk structure or not. The same method was applied to the 144 patients of study IIIA. Results: The 5-year survival probability of all 839 patients resulted in 73% (229 died). Median follow-up time of living patients was 6.7 years. Due to the characteristic plateau of post-transplant survival probabilities, the predictive influence was judged by the Kaplan-Meier method and the log rank statistic. Also consideration of age and time between diagnosis and HSCT as continuous variables seemed less appropriate than working with categorizations. Furthermore, the previously published cut-points “1 year” for time from diagnosis to HSCT ([1] ) and “44 years” for age at HSCT (Maywald et al., Leukemia 2006) were independently confirmed to be the best. Cox model and logistic regression with survival status after 3 years both indicated that age at HSCT, HLA matching, time between diagnosis and HSCT, and calendar year of HSCT had independent statistically significant predictive influence on survival (p 〈 0.05). The first two factors had the strongest effects. Calendar year was only influential when distinction was made between HSCT until and after 1999. All possible combinations of the 4 factors could be summarized in 4 risk groups with significantly different survival probabilities (at 5 years: 87%, 76%, 63%, and 24%). Matched for the risk group distribution of study III [study IIIA], a maximum of 290 [428] registry patients could be drawn. For the 290 [428] patients, 5-year survival was 69% [77%] with a 95% bootstrap confidence interval from 63% to 74% [72% to 81%]. Thus, as for all yearly intervals within the first 5 years, the 5-year survival probabilities of studies III: 65% and IIIA: 79% lied within the corresponding confidence intervals. Conclusions: Along with the registry patients, the study data enabled the identification of age at HSCT, HLA matching, time between diagnosis and HSCT, and calendar year of HSCT as factors with independent predictive impact on survival which led to 4 risk groups with statistically significantly different survival probabilities. More favorable-risk patients in study IIIA stood for a better transplantation strategy. In consideration of these different risks, the survival probabilities in both studies did not significantly vary from those of registry samples with matched risk structures. Accordingly, an improved transplantation strategy along with random variation could be considered as an explanation of the significantly different survival probabilities between the two studies. Disclosures: Haferlach: MLL Munich Leukemia Laboratory: Equity Ownership. Hochhaus:Novartis, Bristol-Myers Squibb: Research Funding. Hasford:Novartis: Research Funding. Gratwohl:AMGEN, Roche, Bristol-Myers Squibb, Novartis, Pfizer: Research Funding; Novartis: Consultancy. German CML Study Group:Kompetenznetz Leukämie, European Leukemia Net, Roche, Essex, AMGEN: Research Funding.

Abstract: Background In a recent phase-III trial CPX-351 (Jazz Pharmaceuticals, Palo Alto, CA), a liposomal encapsulation of cytarabine and daunorubicin, has shown higher remission rates and longer overall survival (OS) in patients aged 60 to 75 years with AML with myelodysplasia-related changes (AML-MRC) or therapy-related AML (t-AML) in comparison to conventional 7+3 regimen. Based on this CPX-351 has been approved in the USA 2017 and in Europe 2018 for adult patients with newly-diagnosed AML-MRC or t-AML. Still, several issues such as age ( & lt;60 years), measurable residual disease (MRD), molecular subgroups and outcome after allo-HCT were not addressed in the phase-III trial. Aiming to investigate these open aspects and to provide more clinical experience with CPX-351, we performed a real-world analysis of patients with AML treated with CPX-351 as first-line therapy. Design/Methods: For this retrospective analysis, we collected data on baseline characteristics, treatment details including allo-HCT and outcome from patients with newly-diagnosed AML-MRC or t-AML, who were treated with CPX-351 according to the EMA label between 2018 and 2020 in 25 German centers participating in the Study Alliance Leukemia (SAL), German Cooperative Transplant Study Group and the AML Study Group (AMLSG). Results: A total of 188 patients (median age 65 years, range 26 to 80) with t-AML (29%) or AML-MRC (70%) including 46 patients (24%) & lt;60 years could be analyzed. Eigthy-six percent received one, 14% two induction cycles and 10% received consolidation with CPX-351. Following induction, CR/CRi rate was 47% including 64% of patients with available information achieving measurable residual disease (MRD) negativity ( & lt;10-3) as measured by flow cytometry at local laboratories. Additionally, 35 patients were categorized as MLFS at first remission control, which achieved CRi (n=16) or CR (n=10) in the further course without additional therapy. After median follow-up of 9.3 months, median overall survival (OS) was 21 months and 1-year OS rate was 64%. In multivariate analysis, complex karyotype predicted lower response (p=.0001), and pretreatment with hypomethylating agents (p=.02) and adverse European LeukemiaNet 2017 genetic risk (p & lt;.0001) were associated with lower OS. Allo-HCT was performed in 116 patients (62%) including 101 of these patients with CR prior transplant and resulted in 1-year OS of 73% (median survival not reached), especially in MRD negative patients (p=.048). With 69% of patients developing grade III/IV non-hematologic toxicity following induction and a day 30-mortality of 8% the safety profile was consistent with previous findings. Conclusion: The results from this real-world analysis confirm CPX-351 as an efficient treatment for these high-risk AML patients bridging to facilitating allo-HCT in many patients with encouraging outcome after transplantation. Disclosures Röllig: AbbVie: Honoraria, Research Funding; Amgen: Honoraria; Bristol-Meyer-Squibb: Honoraria, Research Funding; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Gaidzik: Janssen: Speakers Bureau; Pfizer: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Unglaub: Novartis: Consultancy, Other: travel costs/ conference fee; JazzPharma: Consultancy, Other: travel costs/ conference fee. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Haenel: Celgene: Consultancy, Honoraria; Amgen: Consultancy; Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Bayer Vital: Honoraria; Jazz: Consultancy, Honoraria; GSK: Consultancy. Vucinic: Novartis: Honoraria; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Fransecky: Novartis: Honoraria; Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Kobbe: Celgene: Research Funding. Holderried: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Speakers Bureau; Gilead Sciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; MSD: Speakers Bureau; Daiichi Sankyo: Other: travel support; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Therakos: Other: Travel support; Janssen: Other: Travel support; Abbvie: Other: Travel support; Eurocept Pharmaceuticals: Other: Travel support; Medac: Other: Travel support. Heuser: Astellas: Research Funding; Bayer AG: Honoraria, Research Funding; BMS/Celgene: Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; BergenBio: Research Funding; Daichi Sankyo: Honoraria, Research Funding; Karyopharm: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Research Funding; Tolremo: Honoraria; AbbVie: Honoraria; Janssen: Honoraria. Sauer: Pfizer: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Takeda: Consultancy, Other: DSMB/SAB Member. Goetze: Abbvie: Other: Advisory Board; BMS/Celgene: Other: Advisory Board, Research Funding. Döhner: Jazz Roche: Consultancy, Honoraria; Agios and Astex: Research Funding; Astellas: Research Funding; Abbvie: Consultancy, Honoraria; Janssen: Honoraria, Other: Advisory Board; Daiichi Sankyo: Honoraria, Other: Advisory Board; Novartis: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding. Döhner: Jazz Pharmaceuticals: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria; Helsinn: Honoraria; GEMoaB: Honoraria; Amgen: Honoraria, Research Funding; Astellas: Honoraria, Research Funding; Astex Pharmaceuticals: Honoraria; AstraZeneca: Honoraria; Berlin-Chemie: Honoraria; Oxford Biomedica: Honoraria; Roche: Honoraria. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Schetelig: Roche: Honoraria, Other: lecture fees; Novartis: Honoraria, Other: lecture fees; BMS: Honoraria, Other: lecture fees; Abbvie: Honoraria, Other: lecture fees; AstraZeneca: Honoraria, Other: lecture fees; Gilead: Honoraria, Other: lecture fees; Janssen: Honoraria, Other: lecture fees . Germing: Novartis: Honoraria, Research Funding; Janssen: Honoraria; Bristol-Myers Squibb: Honoraria, Other: advisory activity, Research Funding; Celgene: Honoraria; Jazz Pharmaceuticals: Honoraria. Schroeder: JAZZ: Honoraria, Research Funding.

Abstract: Background Chronic myeloid leukemia (CML)-study IV was designed to explore whether treatment with imatinib (IM) at 400mg/day (n=400) could be optimized by doubling the dose (n=420), adding IFN (n=430) or cytarabine (n=158) or using IM after IFN-failure (n=128). Methods From July 2002 to March 2012, 1551 newly diagnosed patients in chronic phase were randomized into a 5-arm study. The study was powered to detect a survival difference of 5% at 5 years. The impact of patients' and disease factors on survival was prospectively analyzed. At the time of evaluation, at least 62% of patients still received imatinib, 26.2% were switched to 2nd generation tyrosine kinase inhibitors. Results After a median observation time of 9.5 years, 10-year overall survival was 82%, 10-year progression-free survival 80% and 10-year relative survival 92%. In spite of a faster response with IM800mg, the survival difference between IM400mg and IM800mg was only 3% at 5 years. In a multivariate analysis, the influence on survival of risk-group, major-route chromosomal aberrations, comorbidities, smoking and treatment center (academic vs. other) was significant in contrast to any form of initial treatment optimization. Patients that reached the response milestones 3, 6 and 12 months, had a significant survival advantage of about 6% after 10 years regardless of therapy. The progression probability to blast crisis was 5.8%. Blast crisis was proceeded by high-risk additional chromosomal aberrations. Conclusions For responders, monotherapy with IM400mg provides a close to normal life expectancy independent of the time to response. Survival is more determined by patients' and disease factors than by initial treatment selection. Although improvements are also needed for refractory disease and blast crisis, more life-time can currently be gained by carefully addressing non-CML determinants of survival. Disclosures Hehlmann: Novartis: Research Funding; BMS: Consultancy. Saussele: Pfizer: Honoraria; Incyte: Honoraria; Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding. Pfirrmann: BMS: Honoraria; Novartis: Honoraria. Krause: Novartis: Honoraria. Baerlocher: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria. Bruemmendorf: Novartis: Research Funding. Müller: Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Ariad: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding. Jeromin: MLL Munich Leukemia Laboratory: Employment. Hänel: Roche: Honoraria; Novartis: Honoraria. Burchert: BMS: Honoraria. Waller: Mylan: Consultancy, Honoraria. Mayer: Eisai: Research Funding; Novartis: Research Funding. Link: Novartis: Honoraria. Scheid: Novartis: Honoraria. Schafhausen: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Ariad: Honoraria. Hochhaus: Incyte: Research Funding; MSD: Research Funding; Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; ARIAD: Research Funding.

Abstract: Biallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis; however, the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adults with acute myeloid leukemia (AML) who had been recruited into the Study Alliance Leukemia trials, to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%): 131 CEBPAbi and 109 CEBPAsm (60 affecting the N-terminal transactivation domains [CEBPAsmTAD] and 49 the C-terminal DNA-binding or basic leucine zipper region [CEBPAsmbZIP] ). Interestingly, patients carrying CEBPAbi or CEBPAsmbZIP shared several clinical factors: they were significantly younger (median, 46 and 50 years, respectively) and had higher white blood cell (WBC) counts at diagnosis (median, 23.7 × 109/L and 35.7 × 109/L) than patients with CEBPAsmTAD (median age, 63 years, median WBC 13.1 × 109/L; P & lt; .001). Co-mutations were similar in both groups: GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs 6.7% CEBPAsmTAD; P & lt; .001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs 38.3% CEBPAsmTAD; P & lt; .001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (OS; median 103 and 63 vs 13 months) and event-free survival (EFS; median, 20.7 and 17.1 months vs 5.7 months), in univariate and multivariable analyses. Additional analyses revealed that the clinical and molecular features as well as the favorable survival were confined to patients with in-frame mutations in bZIP (CEBPAbZIP-inf). When patients were classified according to CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and non-CEBPAbZIP-inf), only patients bearing CEBPAbZIP-inf showed superior complete remission rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutation.