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: Bosutinib (BOS), an oral dual Src/Abl tyrosine kinase inhibitor (TKI), showed clinical activity and manageable toxicity in an open-label, phase 1/2 trial in patients (pts) with chronic phase (CP) chronic myeloid leukemia (CML) following resistance (R)/intolerance (I) to imatinib (IM) only (2nd line; CP2L) or to IM plus dasatinib (D) and/or nilotinib (N) (3rd/4th line; CP3L). In this retrospective analysis, a major cytogenetic response (MCyR) by 3 or by 6 mo (but not by 3 mo) was assessed as a predictor of long-term outcomes in CP2L or CP3L pts receiving BOS. CP-CML pts aged ≥18 y received BOS starting at 500 mg/d. MCyR and complete cytogenetic response (CCyR) rates and maintenance of MCyR were assessed in CP2L pts at 4 y and CP3L pts at 3 y. Pts with MCyR newly attained or maintained from baseline by 3 mo, by 〉 3 to ≤6 mo (but not by 3 mo), or no MCyR by 6 mo were assessed for overall survival (OS) at 2 y (all pts) and cumulative incidence of progression (including lack of efficacy)/death at 4 y (CP2L) or 3 y (CP3L), adjusted for competing risks (see Table). OS rates were limited to 2 y (pts were followed for only 2 y from BOS discontinuation). P values were based on Gray's test for comparison of cumulative incidence distributions and log-rank test for OS distributions (no adjustment for multiple comparisons).Table.MCyR by 3 moMCyR by 〉 3 to ≤6 moNo MCyRby ≤6 moCP2L ptsOSEvaluable pts,* n9628151KM rate at 2 y (95% CI), %98 (91.8–99.5)†96 (77.2–99.5)89 (82.1–92.7)Cumulative incidence of progression (including lack of efficacy)/death,‡ %Evaluable pts,µ n9026100Rate at 4 y (95% CI), %13 (7.9–22.7)†23 (11.4–46.6)40 (31.5–50.9)CP3L ptsOSEvaluable pts,* n281271KM rate at 2 y (95% CI), %89 (68.9–96.2)100 (Not estimable–100)84 (73.1–90.9)Cumulative incidence of progression (including lack of efficacy)/death,‡ %Evaluable pts,µ n241237Rate at 3 y (95% CI), %33 (18.9–58.7)25 (9.4–66.6)51 (37.5–70.3)*Pts known to be alive as of the 6-mo response landmark.†P≤0.0004 vs no MCyR by ≤6 mo (comparison of OS and cumulative incidence distributions, unadjusted [P≤0.0002] and adjusted [P≤0.0004] for pre-existing neutropenia and/or thrombocytopenia and presence of a baseline mutation).‡Adjusted for the competing risk of treatment discontinuation without progression/death.µPts known to be alive with no disease progression as of the 6-mo response landmark. CP2L pts (n=286 [IM-R, n=196; IM-I, n=90]) had a median (range) age of 53 (18–91) y. CP3L pts (n=118 with prior IM failure [D-R, n=38; D-I, n=50; N-R, n=26; N-I or D-R/I + N-R/I, n=4] ) had a median (range) age of 56 (20–79) y. Median time from CML diagnosis was 3.7 (0.1–15.1) and 6.6 (0.6–18.3) y for CP2L and CP3L pts, respectively; BOS treatment duration was 24.8 (0.2–83.4) and 8.5 (0.2–78.1) mo; follow-up duration was 47.3 (0.6–90.6) and 33.1 (0.3–84.8) mo. Time from last enrolled pt's first dose to database snapshot was ≥48 mo for CP2L and ≥36 mo for CP3L. Of 264 CP2L pts with a valid baseline assessment, 107/183 (58%) IM-R and 49/81 (60%) IM-I pts attained/maintained a MCyR; 88/183 (48%) and 42/81 (52%) pts had CCyR. The Kaplan-Meier (KM) probability of maintaining MCyR at 4 y was 69% for IM-R and 86% for IM-I pts. Of 110 CP3L pts with valid assessment, overall MCyR and CCyR rates were 40% and 32%; the KM probability of maintaining MCyR at 3 y was 65%. There was no significant difference in OS or cumulative incidence of progression/death distribution between CP2L pts with MCyR by 3 mo vs by 〉 3 to ≤6 mo; however, OS (P=0.0004) and cumulative incidence of progression/death (P=0.0002) distributions were significantly better for CP2L pts with MCyR by 3 mo vs no MCyR by 6 mo (Table). For CP3L pts, there was no significant difference in long-term outcomes between early response groups. In conclusion, in CP-CML pts receiving BOS as 2nd-line therapy following IM failure (CP2L), pts who attained/maintained a MCyR by 3 mo had better OS and a lower progression/death distribution vs pts without MCyR by 6 mo; no significant differences were observed between pts achieving MCyR by 3 mo vs by 〉 3 to ≤6 mo, although pt number was low for late responders. There were no significant differences in outcomes for CP-CML pts receiving BOS as 3rd/4th-line therapy, regardless of when or if MCyR was achieved, although the number of pts with MCyR was low. These results suggest that pts not achieving a MCyR by 6 mo, particularly in the 2nd-line setting, may require alternative therapies if options with better likelihood of response are available. Disclosures: Cortes: Pfizer, Ariad, Teva: Consultancy; Novartis, Bristol Myers Squibb, Pfizer, Ariad, Teva: Research Funding. Hochhaus:Pfizer: Research Funding. Apperley:Novartis: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Pfizer, Ariad: Honoraria (not direct from company), Honoraria (not direct from company) Other. O'Brien:BMS: Consultancy, Honoraria, Research Funding; Ariad, Novartis, Pfizer: Research Funding. Leip:Pfizer Inc: Employment. Turnbull:Pfizer Inc: Employment. Conlan:Pfizer Inc: Employment. Kantarjian:Pfizer Inc: Research Funding. Brümmendorf:Patent on the use of imatinib and hypusination inhibitors: Patents & Royalties; Ariad: Consultancy; Novartis: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb, Pfizer: Consultancy, Honoraria.

Abstract: Introduction: Mutations (muts) in JAK2, MPL, and CALR are genetic hallmarks in myeloproliferative neoplasms such as myelofibrosis (MF). Prognostication in MF is predominantly based on clinical parameters according to the Dynamic International Prognostic Scoring System (DIPSS). However, gene mutations become increasingly important allowing for a more precised assessment of prognosis. For instance, CALR mutated MF is associated with favorable prognosis, while mutations in distinct high molecular-risk (HMR) genes are considered adverse. Our multicenter phase-Ib/II MPNSG-0212 trial (NCT01644110) investigating ruxolitinib plus pomalidomide in a total cohort of 92 patients with advanced MF and anemia provides an ideal basis for investigating the genomic landscape and molecular risk in a well-defined study population. Aims & Methods: To assess the genomic landscape in MF patients treated within the MPNSG-0212 trial and to correlate the results with clinical parameters and overall survival (OS). So far, targeted next generation sequencing (NGS) of 269 candidate genes was performed in peripheral blood or bone marrow from 81/92 patients using libraries prepared with SureSelectXT HS (Agilent, Santa Clara, USA). NGS was carried out on a NextSeq550 (Illumina, San Diego, USA). Results: At study entry, median age of the 81 patients was 71 years (range 52-86), median Hb 8.6 g/dL (range 5.4-11.7 g/dl); 30% of patients were RBC transfusion-dependent; 67% had primary MF (PMF) and 33% secondary MF (SMF), respectively. According to DIPSS, the vast majority of the patients were categorized as intermediate-2 (63%) or high-risk (26%) MF; 11% were low- and intermediate-1 risk patients. Overall, 315 muts were identified in 80/81 (99%) patients with a median of 3 muts/patient (range 0-9). Recurrent muts (≥5%) were identified in JAK2 (60%), ASXL1 (30%), SRSF2 (21%), CALR (20%; type-1: 75% [n=12], type-2 and non-type-1/2: 12.5% [n=2] each), MPL (19%), SF3B1 (19%), TET2 (16%), U2AF1 (15%), CBL and EZH2 (10% each), IDH2 and DNMT3A (7% each), PHF6, ZRSR2, and CUX1 (5% each). The majority of the patients (95%) was characterized by the presence of a driver mut in JAK2, CALR, or MPL; 4/81 patients (5%) were triple negative (Figure 1). JAK2mut was associated with TET2mut (p=.047), whereas muts in CALR and TET2 were mutually exclusive (p=.05). CALRmut patients had less co-muts than patients with JAK2/MPL muts (mean 2.5 vs. 4.1, p=.007) and were mutually exclusive with muts in the spliceosome regulating genes SRSF2, SF3B1, U2AF1, and ZRSR2 (p=.009). Compared to MF with mutated JAK2 or MPL, MF patients with mutated CALR had a longer median OS (not reached vs. 3.1 years; p=.04). With regard to high molecular risk (HMR) muts, n=56 were detected in 38 patients (47%), with 40% (15/38) of the patients harboring ≥2 HMR muts. The most commonly mutated HMR genes were ASXL1 (43%; 24/56), followed by SRSF2 (30%), EZH2 (14%), IDH2 (11%), and IDH1 (2%). MPLmut but not JAK2mut or CALRmut were significantly associated with HMR mut (p=.023). HMR mut patients harbored more co-muts than HMR wt patients (median 5 vs. 3; p & lt;.0001). There were no significant differences in the variables age, sex, WBC, Hb, PLT, or LDH level between patients with HMR mut and HMR wt MF. In univariate analysis, patients with HMR mut MF had shorter median OS (2.3 vs 3.7 years, p=.007). In multivariate analysis (HMR mut, age, DIPSS-category, SMF vs. PMF) a higher DIPSS-score (HR, 3.2; 95% CI, 1.5-7.0; p=.004) and muts in HMR genes (HR, 3.5; 95% CI, 1.5-8.1; p=.003) were significant adverse prognostic factors for OS. Conclusions: Our NGS data underline the genomic complexity of advanced MF. CALR mutations were only found in 20% of the patients that were characterized by less co-mutations, mutual exclusivity with spliceosome mutations, and with more favorable outcome suggesting a distinct disease biology. Almost 50% of patients showed mutations in HMR genes which were associated with an inferior OS in univariate and multivariate analyses. §Frank Stegelmann and Konstanze Döhner contributed equally to this work. Figure 1 Figure 1. Disclosures Koschmieder: Shire: Honoraria, Other; Alexion: Other: Travel support; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Geron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; AOP Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Baxalta: Membership on an entity's Board of Directors or advisory committees, Other; Abbvie: Other: Travel support; CTI: Membership on an entity's Board of Directors or advisory committees, Other; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Image Biosciences: Other: Travel support; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Karthos: Other: Travel support. Heidel: Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; CTI: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene/BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AOP: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Hochhaus: Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Incyte: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hebart: AbbVie: Honoraria; AstraZeneca: Honoraria; BMS: Honoraria; Janssen: Honoraria; Roche: Honoraria. Isfort: Alexion: Other: Travel reimbursement; Roche: Other: Travel reimbursement; Amgen: Other: Travel reimbursement; Mundipharma: Other: Travel reimbursement; Hexal: Other: Travel reimbursement; BMS: Honoraria; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Ariad: 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, Other: Travel reimbursement; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement. Reiter: AOP Orphan Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support; Deciphera: Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; Blueprint Medicines: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses, Research Funding. Waller: Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Mylan: Consultancy; Alvotech: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Lilly: Membership on an entity's Board of Directors or advisory committees, Other: travel support; Chugai: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees, Other: travel support; Amgen: Membership on an entity's Board of Directors or advisory committees; IPSEN: Other: travel grant. Scheid: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Goethert: Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel support; Incyte: Consultancy, Honoraria, Other: Travel support; zr pharma & : Honoraria; BMS: Consultancy, Honoraria, Other: Travel support; AOP Orphan Pharmaceuticals: Honoraria, Other: travel support; Proteros Biostructures: Consultancy. Schafhausen: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Swedish Orphan Biovitrum AB: 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, Speakers Bureau; MSD: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees. Radsak: Otsuka: Consultancy, Honoraria; Abbvie: Other: e.g. travel support; Astellas: Other: e.g. travel support; TEVA: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: e.g. travel support; Daiichi Sankyo: Consultancy, Honoraria, Other: e.g. travel support; Celgene/BMS: Consultancy, Honoraria, Other: e.g. travel support; Amgen: Other: e.g. travel support; Takeda: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Corat: Consultancy, Honoraria; Cogent Biosciences: Consultancy, Honoraria; JAZZ: Other: e.g. travel support. Gattermann: Takeda: Research Funding; Novartis: Honoraria; Celgene: Honoraria. von Bubnoff: Novartis: Honoraria; Takeda: Honoraria. Brümmendorf: Bristol Myers: Research Funding; Janssen: Honoraria; Novartis: Honoraria, Patents & Royalties, Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Repeat Diagnostics: Research Funding; Takepart Media: Honoraria. Döhner: Celgene: Honoraria, Research Funding; Agios: Honoraria, Research Funding; GEMoaB: Honoraria; Astex Pharmaceuticals: Honoraria; Astellas: Honoraria, Research Funding; Oxford Biomedica: Honoraria; Novartis: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Janssen: Honoraria; Helsinn: Honoraria; Gilead: Honoraria; AstraZeneca: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Berlin-Chemie: Honoraria; Roche: Honoraria; Pfizer: Research Funding. Griesshammer: Amgen: Consultancy, Honoraria; AOP Orphan: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; CTI: Consultancy, Honoraria; Shire: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Astra Zeneca: Consultancy, Honoraria. Stegelmann: BMS: 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; Novartis: 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. Döhner: Abbvie: Consultancy, Honoraria; Janssen: Honoraria, Other: Advisory Board; Jazz Roche: Consultancy, Honoraria; Daiichi Sankyo: Honoraria, Other: Advisory Board; Astellas: Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Agios and Astex: Research Funding. OffLabel Disclosure: Pomalidomide was shown to be active in patients with myelofibrosis in particular in the treatment of anemia (Tefferi et al 2009, Begna et al 2011, Mesa et al 2010)

Abstract: Introduction: BOS is approved for patients (pts) with Philadelphia chromosome-positive (Ph+) CML resistant/intolerant to prior therapy and pts with newly diagnosed Ph+ CP CML. Approval of first-line BOS was based on the primary results from the phase 3 BFORE trial, which showed superior efficacy vs imatinib (IMA) in the modified intent-to-treat (ITT) population (pop; Ph+ with e13a2/e14a2 transcripts) after ≥12 mo of follow-up. We report the final efficacy and safety results from the BFORE trial after 5 y of follow-up. Methods: In the open-label BFORE trial (NCT02130557), 536 pts with newly diagnosed CP CML were randomized 1:1 to receive BOS (n=268) or IMA (n=268; 3 untreated), both at 400 mg once daily. Efficacy was assessed in the ITT pop (all randomized pts). Long-term secondary endpoints included duration of response (DOR), on-treatment event-free survival (EFS) and overall survival (OS). Safety was assessed in the safety pop (all treated pts). This final analysis was based on an April 17, 2020 last pt last visit (June 12, 2020 database lock), 5 y (240 weeks) after the last enrolled pt. Results: At study completion in BOS and IMA arms, respectively, 59.7% and 57.4% were still on treatment, 86.6% and 86.2% completed 5 y on study. Median duration of treatment and time on study was 55.2 mo for pts receiving BOS or IMA; respective median (range) dose intensity was 394 (39-583) vs 400 (189-765) mg/d. Cumulative major molecular response (MMR) rate by 60 mo was higher with BOS vs IMA (73.9% vs 64.6%), as was cumulative molecular response (MR)4 (58.2% vs 48.1%) and MR4.5 rate (47.4% vs 36.6%; Table). Among evaluable pts, more pts in the BOS arm achieved BCR-ABL1 ≤10% at 3 months (Table); cumulative MMR by 60 mo was higher in pts with transcripts ≤10% vs & gt;10% in both treatment arms (BOS, HR 2.67 [95% CI, 1.90-3.75]; IMA, HR 3.12 [2.19-4.45] ). Pts in the BOS arm achieved responses earlier than pts in the IMA arm; cumulative incidence function for MMR, MR4 and MR4.5 was higher with BOS vs IMA (HR [95% CI]: MMR 1.34 [1.10-1.64] , MR4 1.34 [1.07-1.69], MR4.5 1.41 [1.09-1.83] ). Among responders, duration of MMR was similar for BOS and IMA (Table). Superior MRs with BOS vs IMA were consistent across Sokal risk groups, with the greatest difference seen in pts with high Sokal risk (Table). On-treatment transformations to accelerated/blast phase (AP/BP) occurred in 6 (AP 3; BP 3) BOS- and 7 (AP 6; BP 1) IMA-treated pts. No transformation occurred after the 24-mo follow-up. In all, 18 BOS- vs 25 IMA-treated pts had EFS events. There were no differences in EFS between treatment arms; cumulative incidence of on treatment progression/death at 60 mo was 6.7% for BOS vs 9.3% for IMA (Table). The 60-mo OS rates were similar (94.5% and 94.6%; Table); 14 BOS- and 14 IMA-treated pts died during the study period: 3 and 4 were CML-related, 0 and 1 were due to adverse events (AEs) related to study treatment. The most common reasons for permanent discontinuation were AEs (25.0% vs 12.5%) and lack of efficacy (4.9% vs 16.2%). Treatment-emergent AEs (TEAEs) occurred in 98.9% of pts in each arm; most common ( & gt;30%) were diarrhea (75.0%), nausea (37.3%), thrombocytopenia (35.8%) and increased alanine aminotransferase (ALT; 33.6%) with BOS, and diarrhea (40.4%), nausea (42.3%) and muscle spasms (30.6%) with IMA. Most TEAEs occurred during the first year of treatment. Grade 3/4 TEAEs occurred in 73.5% of BOS- vs 57.0% of IMA-treated pts; most common ( & gt;5%) were increased ALT (20.9%) and lipase (13.4%), thrombocytopenia (14.2%), increased aspartate aminotransferase (10.4%), diarrhea (9.0%) and neutropenia (7.5%) with BOS, and neutropenia (13.6%), thrombocytopenia (6.0%), anemia (5.7%) and increased lipase (5.7%) with IMA. No individual AE led to discontinuation in & gt;5% of pts. The most frequent AEs leading to permanent treatment discontinuation were increased ALT (4.9%) with BOS vs thrombocytopenia (1.5%) with IMA; 1.5% vs 1.1% of pts discontinued due to diarrhea. Conclusions: At 5 y, first-line BOS continued to show superior efficacy vs IMA; BOS-treated pts achieved earlier and deeper molecular response. An improvement in MR with BOS was demonstrated across Sokal risk groups, with the greatest benefit vs IMA observed in Sokal high-risk pts. Long-term AEs were generally manageable, and consistent with previous reports and the known safety profiles of both drugs. These results confirm the use of BOS as a standard of care in pts with newly diagnosed CP CML. Disclosures Brümmendorf: Takeda: Consultancy; Janssen: Consultancy; Pfizer: Consultancy, Honoraria, Other: Travel, Accommodation, Expenses, Research Funding; Merck: Consultancy; Novartis: Consultancy, Other: travel, accommodation, expenses, Research Funding. Cortes:Astellas: Research Funding; Arog: Research Funding; Merus: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; BioPath Holdings: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Amphivena Therapeutics: Research Funding; Immunogen: Research Funding; Telios: Research Funding; BiolineRx: Consultancy, Research Funding; Bristol-Myers Squibb: Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Sun Pharma: Research Funding; Novartis: Consultancy, Research Funding. Milojkovic:Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria. Gambacorti-Passerini:Pfizer: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy. Clark:Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Ariad/Incyte: Honoraria; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees. le Coutre:Incyte: Honoraria; Pfizer: Honoraria; Novartis: Honoraria. Garcia-Gutiérrez:Novartis: Consultancy, Other: Travel, Accommodation, Expenses, Research Funding; Bristol-Myers Squibb: Consultancy, Other: Travel, Accommodation, Expenses, Research Funding; Pfizer: Consultancy, Other: Travel, Accommodation, Expenses, Research Funding; Incyte: Consultancy, Other: Travel, Accommodation, Expenses, Research Funding. Chuah:Novartis: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Other: Travel, Research Funding; Korea Otsuka Pharmaceutical: Honoraria. Kota:Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical, Company Ltd, Cambridge, MA, USA: Honoraria; Ariad: Honoraria; Incyte: Honoraria; Xcenda: Honoraria. Lipton:BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Bristol-Myers Squibb: Honoraria; Takeda: Consultancy, Honoraria, Research Funding; Ariad: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding. Rousselot:Incyte: Consultancy, Research Funding; Takeda: Consultancy; Pfizer: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy. Mauro:Sun Pharma/SPARC: Research Funding; Novartis: Consultancy, Honoraria, Other: Travel, Accommodation, Expenses, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel, Accommodation, Expenses, Research Funding; Takeda: Consultancy, Honoraria, Other: Travel, Accommodation, Expenses, Research Funding; Pfizer: Consultancy, Honoraria, Other: Travel, Accommodation, Expenses, Research Funding. Hochhaus:MSD: Research Funding; Takeda: Honoraria; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding. Hurtado Monroy:Incyte: Consultancy; Pfizer: Consultancy. Leip:Pfizer: Current Employment, Current equity holder in publicly-traded company. Purcell:Pfizer: Current Employment, Current equity holder in publicly-traded company. Yver:Pfizer: Current Employment, Current equity holder in publicly-traded company. Viqueira:Pfizer: Current Employment, Current equity holder in publicly-traded company. Deininger:Gilead Sciences: Research Funding; Celgene: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy, Honoraria, Other; SPARC: Research Funding; DisperSol: Consultancy; Pfizer: Honoraria, Other, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Other, Research Funding; Fusion Pharma: Consultancy; Blueprint Medicines Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: part of a study management committee, Research Funding; Leukemia & Lymphoma Society: Research Funding; Incyte: Consultancy, Honoraria, Other, Research Funding; Novartis: Consultancy, Other, Research Funding; Medscape: Consultancy; Sangamo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Galena: Consultancy, Honoraria, Other.

Abstract: Mutations of the isocitrate dehydrogenase-1 (IDH1) and IDH2 genes are among the most frequent alterations in acute myeloid leukemia (AML) and can be found in ∼20% of patients at diagnosis. Among 4930 patients (median age, 56 years; interquartile range, 45-66) with newly diagnosed, intensively treated AML, we identified IDH1 mutations in 423 (8.6%) and IDH2 mutations in 575 (11.7%). Overall, there were no differences in response rates or survival for patients with mutations in IDH1 or IDH2 compared with patients without mutated IDH1/2. However, distinct clinical and comutational phenotypes of the most common subtypes of IDH1/2 mutations could be associated with differences in outcome. IDH1-R132C was associated with increased age, lower white blood cell (WBC) count, less frequent comutation of NPM1 and FLT3 internal tandem mutation (ITD) as well as with lower rate of complete remission and a trend toward reduced overall survival (OS) compared with other IDH1 mutation variants and wild-type (WT) IDH1/2. In our analysis, IDH2-R172K was associated with significantly lower WBC count, more karyotype abnormalities, and less frequent comutations of NPM1 and/or FLT3-ITD. Among patients within the European LeukemiaNet 2017 intermediate- and adverse-risk groups, relapse-free survival and OS were significantly better for those with IDH2-R172K compared with WT IDH, providing evidence that AML with IDH2-R172K could be a distinct entity with a specific comutation pattern and favorable outcome. In summary, the presented data from a large cohort of patients with IDH1/2 mutated AML indicate novel and clinically relevant findings for the most common IDH mutation subtypes.

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.

Abstract: Introduction: The TIGER (CML V)-study (NCT01657604) is a multicenter, randomized phase III trial to evaluate efficacy and tolerability of nilotinib (NIL) 2*300mg/d monotherapy vs NIL 2*300mg/d + pegylated interferon alpha2b (Peg-IFN) and the option to discontinue therapy after Peg-IFN maintenance as first line therapy for chronic myeloid leukemia (CML) patients in chronic phase. Methods: Recruitment started in August 2012 with a pilot phase, aiming to validate the recommended dose of PEG-IFN. 25 pilot phase patients (pts) were treated with the combination of NIL 2*300 mg daily and PEG-IFN (30-50μg/week according to tolerability and commenced after 〉 6 weeks NIL monotherapy). During the main phase of the study, newly diagnosed pts were randomized between NIL 2*300 mg/d and NIL/PEG-IFN combination in accordance with the approach which was confirmed to be feasible during the pilot phase. After at least 2 years NIL based induction therapy and achievement of major molecular remission (MMR, BCR-ABL transcript level ≤0.1% according to the international scale, IS), maintenance therapy (NIL vs PEG-IFN) started. Requirements for treatment discontinuation were treatment duration of at least 3 years with stable MR4 (BCR-ABL ≤0.01%) for at least one year. NIL therapy was reinitiated in case of molecular recurrence, defined as loss of MMR. The major co-endpoints of the study are (i) rate of MMR at 18 months (NIL vs NIL+PEG-IFN), and (ii) rate of continuous MMR 12 and 24 months after discontinuation of NIL vs PEG-IFN. Efficacy and safety data are presented without specification of the randomized therapy during the ongoing study. Results: Within 5 years, a total of 717 pts (429 male; median age 51, range 18-85 years; 13.3% EUTOS high risk) were recruited from 111 sites in Germany, Switzerland, and the Czech Republic. Median observation time since recruitment was 30.3 months. 396 pts concluded the induction phase and reached the maintenance phase of the study. 138 pts achieved and maintained MR4 (BCR-ABL ≤0.01% IS) for at least one year during the maintenance phase and discontinued all therapy. With regard to efficacy in the two treatment arms, 79.5% reached MMR at 12 mo. (95% confidence interval (CI): [76.1-82.7%]), 84.9% at 18 mo. (95% CI: [81.4-88.0%] ), and 89.4% at 24 mo. (95% CI: [86.0-92.2%]) after randomization. Probabilities of adverse events of grade 1-5 after 12 mo. of therapy were 83.7 (95% CI: [79.2-87.3%] ) and 90.0% (95% CI: [85.8-93.0%]), and of grade 3-5 after 3 years 39.6 (95% CI: [33.4-45.7%] ) and 49.5% (95% CI: [42.7-56.0%]) for the two treatment arms. Twelve pts progressed to accelerated phase or blast crisis; four of them died from blast crisis. A total of 13 patients received 14 allogeneic stem cell transplantations in chronic phase (n=7) or blast crisis (n=7). In total, 19 pts died, five related to CML, three from vascular complications. Conclusions: This interim analysis demonstrates feasibility of 1st-line treatment with NIL 2*300 mg/d combined with PEG-IFN 30-50 μg/week. Molecular response during the first 24 mo. favourably compares with data from recent NIL based studies (ENESTnd, NCT00471497; ENEST1st, NCT01061177) and permits access to the maintenance phase (NIL vs PEG-IFN monotherapies) for the majority of patients - with the potential of treatment-free remission. The study was conducted by the German CML Study Group in cooperation with the Schweizerische Arbeitsgemeinschaft für Klinische Krebsforschung (SAKK) and the Ostdeutsche Studiengruppe Hämatologie und Onkologie (OSHO). Figure. Figure. Disclosures Hochhaus: Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Incyte: Research Funding; Novartis: Research Funding. Saussele:Novartis: Research Funding; BMS: Research Funding; MSD: Research Funding. Baerlocher:Novartis: Research Funding. Brümmendorf:Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Takeda: Consultancy; Merck: Consultancy; Janssen: Consultancy. Burchert:AOP Orphan: Honoraria, Research Funding; Bayer: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Pfizer: Honoraria; Novartis: Research Funding. La Rosée:Novartis: Research Funding. Hasford:Novartis: Research Funding. Heim:Novartis: Research Funding. Krause:Novartis: Research Funding. le Coutre:Incyte: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; BMS: Honoraria. Niederwieser:Miltenyi: Speakers Bureau; Novartis: Research Funding. Mayer:Novartis: Research Funding; Amgen: Research Funding. Lange:Novartis: Research Funding. Haenel:Amgen: Honoraria; Roche: Honoraria; Takeda: Honoraria; Novartis: Honoraria. Stegelmann:Novartis: Consultancy, Honoraria. Gil:Novartis: Research Funding. Ernst:Novartis: Research Funding. Fabisch:Novartis: Research Funding. Pfirrmann:Novartis: Research Funding.

Abstract: BCR-ABL1 inhibitors have revolutionized treatment of CML patients. However several drawbacks remain, including therapy resistance of T315I-mutated CML and incapability of current drugs to eliminate quiescent CML stem cells warranting development of novel therapies. In addition, drugs with the potential to enhance efficacy of BCR-ABL1 targeting agents could improve treatment of CML patients. Members of the Tyro3, Axl, Mer receptor (TAMR) tyrosine kinase family are abundantly expressed in physiological and malignant hematopoiesis and their ligand Gas6 can support hematopoietic (progenitor) cells. Evidence in the literature indicates that Axl is upregulated upon treatment with imatinib (IM). In this study, we investigated the relevance of the Gas6-Axl axis in CML patients and the therapeutic potential of the clinically applicable small molecule Axl inhibitor BGB324 (former designation R428) in primary CML (stem cell) samples, cell lines and preclinical models. In a first step we quantified Axl-expressing cells by flow cytometry in chronic phase (CP) CML bone marrow at primary diagnosis and healthy bone marrow donors. Here, we found higher numbers of Axl-positive cells in CML bone marrow compared to controls (11.42±0.42% (n=5) vs. 0.65±0.10% (n=6), respectively; p=0.0015). In addition, we determined Gas6 plasma levels by ELISA in healthy controls and CML patients in CP and blast crisis (BC). These analyses revealed that Gas6 plasma levels were upregulated in a stage specific manner (plasma levels of Gas6: healthy controls 1290±684 pg/ml (n=14), CP 3465±405 pg/ml (n=50), BC 10940±3868 pg/ml (n=7); p=0.0001). Thus, the Gas6-Axl axis represents a potential therapeutic target in CML patients. Based on this finding we analyzed efficacy of BGB324 in Axl-expressing BV173, KCL22, K562, BaF3_BCR-ABL1-wt and BaF3_BCR-ABL1-T315I cell lines in vitro. We found inhibition of proliferation in all analyzed cell lines with IC50 values ranging from 500-3000 nM. Combination experiments with the IC50 dose of BGB324 and IM revealed additive effects of both treatments in all cell lines. Dose finding experiments with BGB324 in sorted CD34+ primary CML cells grown in the presence of physiological growth factors yielded a mean IC50 of 1.1 ± 0.3 mM (n=3), which was similar to nilotinib. BGB324 did not accumulate CD34+CFSEmax (undivided) cells any more than nilotinib but enhanced apoptosis of CD34+ cells in combination with nilotinib. Notably, there was a consistent inhibitory effect of 3 mM BGB324 alone or in combination with nilotinib against colony forming cells (CFC) with the more primitive BFU-E and GEMM being most sensitive to inhibition (n=4). Interestingly, the Ph- lymphocytes (confirmed by FISH) sorted simultaneously with Ph+ CD34+ cells from the same CML patient were unaffected in terms of viability when treated with Axl inhibitor; thus the BGB324’s activity is cell context specific. Encouraged by these data we analyzed efficacy of BGB324 in an aggressive preclinical CML model in which bone marrow cells were retrovirally transduced with constructs containing T315I-mutated BCR-ABL1. Transduced cells were subsequently i.v. transplanted into sublethally irradiated recipient mice, who rapidly developed blast crisis CML. Mice were treated with 25 mg BGB324 or vehicle BID by oral gavage starting from day 3 after transplantation when homing of transduced cells to the bone marrow is completed. In this model we found a significant prolongation of survival upon treatment with BGB324 (Figure 1). Analyses of the leukemia phenotype by differential blood counts and flow cytometry revealed that BGB324 reduced leukemia cell burden (WBC 138±20x103/µl (n=14) vs. 60x103±21 k/µl WBC in the BGB324 treated group (n=13); p=0.0078). Taken together, these data suggest that the Gas6-Axl axis represents a therapeutic target and that BGB324 is a potent molecule effective against T315I-mutated and wt CML alone and in combination with TKI. Furthermore, BGB324 induces apoptosis of quiescent Ph+ CML stem/progenitor cells. Thus BGB324 might open up novel therapeutic avenues in CML patients. Disclosures: Loges: BerGenBio: research support Other.