Litzow, Mark R.

PURPOSE Calcineurin inhibitors (CNI) are standard components of graft-versus-host disease (GVHD) prophylaxis after hematopoietic cell transplantation (HCT). Prior data suggested that CNI-free approaches using donor T-cell depletion, either by ex vivo CD34 selection or in vivo post-transplant cyclophosphamide (PTCy) as a single agent, are associated with lower rates of chronic GVHD (cGVHD). METHODS This multicenter phase III trial randomly assigned patients with acute leukemia or myelodysplasia and an HLA-matched donor to receive CD34-selected peripheral blood stem cell, PTCy after a bone marrow (BM) graft, or tacrolimus and methotrexate after BM graft (control). The primary end point was cGVHD (moderate or severe) or relapse-free survival (CRFS). RESULTS Among 346 patients enrolled, 327 received HCT, 300 per protocol. Intent-to-treat rates of 2-year CRFS were 50.6% for CD34 selection (hazard ratio [HR] compared with control, 0.80; 95% CI, 0.56 to 1.15; P = .24), 48.1% for PTCy (HR, 0.86; 0.61 to 1.23; P = .41), and 41.0% for control. Corresponding rates of overall survival were 60.1% (HR, 1.74; 1.09 to 2.80; P = .02), 76.2% (HR, 1.02; 0.60 to 1.72; P = .95), and 76.1%. CD34 selection was associated with lower moderate to severe cGVHD (HR, 0.25; 0.12 to 0.52; P = .02) but higher transplant-related mortality (HR, 2.76; 1.26 to 6.06; P = .01). PTCy was associated with comparable cGVHD and survival outcomes to control, and a trend toward lower disease relapse (HR, 0.52; 0.28 to 0.96; P = .037). CONCLUSION CNI-free interventions as performed herein did not result in superior CRFS compared with tacrolimus and methotrexate with BM. Lower rates of moderate and severe cGVHD did not translate into improved survival.

Abstract Introduction According to population-based Surveillance, Epidemiology and End Results (SEER) cancer registry data, approximately 40% of adolescents and young adults (AYA) with acute lymphoblastic leukemia (ALL) in the United States (U.S.) are Hispanic and 7% are Black and both Hispanic and Black patients have significantly inferior outcomes relative to non-Hispanic Whites (NHW). CALGB 10403, a prospective Phase II clinical trial conducted by the U.S. Intergroup, demonstrated the feasibility of delivering a pediatric-inspired ALL regimen to newly diagnosed AYA ALL patients and found this approach to be superior to historical adult regimens (Stock et al. Blood 2019). In the current analysis, we evaluate enrollment patterns of Hispanic and Black AYAs on CALGB 10403 and compare survival relative to SEER estimates. Methods Demographics on AYAs (18-40 yrs) enrolled on CALGB 10403 (N=295 from 2007-2012) were supplemented with patient-reported education and socioeconomic status (SES) information. Data from the North American Association of Cancer Registries (NAACCR; 2013-2017) were used to evaluate U.S. country-wide ALL incidence (20-49 yrs) overall and among Hispanics, reported per U.S. state. SEER registries (2008-2012) provided racial/ethnic distribution and overall survival (OS) of AYA ALL (15-39 yrs). The distribution of OS was estimated using the Kaplan-Meier method and compared across racial/ethnic groups using log-rank tests. Results Relative to the U.S. AYA ALL population, CALGB 10403 included proportionally fewer Hispanics (41.7% vs. 16.3%, P < 0.001); the distribution of blacks was similar (6.4% vs. 8.5%, P = 0.174). Demographics and ALL characteristics among CALGB 10403 enrollees demonstrated no significant differences in age, sex, cytogenetics, or BMI by race/ethnicity; however, Black AYAs were more likely to have T-ALL, and Hispanic patients were more likely to have Ph-like B-ALL and rearrangements in CRLF2. Hispanic and Black patients reported lower household yearly income, and Black patients had less educational attainment. In order to explore reasons for disproportionately low Hispanic enrollment on CALGB 10403, we calculated the proportion of Hispanic AYAs with ALL relative to the AYA ALL incidence across U.S. states using NAACCR data and compared this with the geographical distribution of CALGB 10403 enrollments. The incidence of AYA ALL across U.S. states is represented in Fig 1A and the proportion of Hispanic AYA ALL patients in Fig 1B. The states with highest proportion of Hispanic patients included CA, TX, and NM, followed by AZ, CO, FL, and NJ. Although CALGB 10403 enrolled patients in 31 U.S. states, the trial did not open in TX or FL. The enrollments numbers were highest across the Mid-Western U.S., with only 47/295 (15.9%) of enrollments coming from the seven states with a high proportion of Hispanic AYA ALL patients (Fig 1C). The 3-yr event-free survival (EFS) and OS for the total CALGB 10403 cohort were 59.1% (53.1%, 65.75%) and 73.5% (68.1%, 79.4%), respectively. Per protocol completion of therapy was highest in Hispanics (75%), relative to Black (64%) and NHW patients (56%), P=0.049. Overall survival among CALGB 10403 participants differed significantly across race/ethnicity (Fig 2), with superior OS experienced by Hispanic patients and inferior OS by Black patients (P= 0.021). These clinical trial results differ from SEER estimates, where both Hispanic and Black patients experience worse OS relative to NHW (Fig 2). Conclusions This in-depth analysis of racial/ethnic enrollments and outcomes on CALGB 10403 uncovered findings that may translate across clinical trials beyond AYA ALL. Importantly, our data suggest that closer matching of trial site selection to geographical racial/ethnic disease incidence may improve minority enrollments on multi-center clinical trials. Relative to NHW, Hispanic patients had superior survival despite having higher rates of Ph-like ALL, indicating that clinical trial participation may mitigate racial/ethnic survival disparities seen in population-based data. Finally, we saw no improvement in trial outcomes among Black AYAs; a deeper understanding of the biological leukemia underpinnings and barriers to successful outcomes would aid future efforts at improving survival across racial/ethnic groups. Figure 1 Figure 1. Disclosures Muffly: Pfizer, Amgen, Jazz, Medexus, Pfizer: Consultancy; Astellas, Jasper, Adaptive, Baxalta: Research Funding; Adaptive: Honoraria, Other: fees for non-CME/CE services: , Research Funding. Advani: Abbvie: Research Funding; Macrogenics: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Glycomimetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Immunogen: Research Funding; Pfizer: Honoraria, Research Funding; OBI: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Tallman: NYU Grand Rounds: Honoraria; Syros: Membership on an entity's Board of Directors or advisory committees; Kura: Membership on an entity's Board of Directors or advisory committees; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Biosight: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Orsenix: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Rafael Pharmaceuticals: Research Funding; Glycomimetics: Research Funding; Biosight: Research Funding; Orsenix: Research Funding; Abbvie: Research Funding; Mayo Clinic: Honoraria; UC DAVIS: Honoraria; Northwell Grand Rounds: Honoraria; NYU Grand Rounds: Honoraria; Danbury Hospital Tumor Board: Honoraria; Acute Leukemia Forum: Honoraria; Miami Leukemia Symposium: Honoraria; New Orleans Cancer Symposium: Honoraria; ASH: Honoraria; NCCN: Honoraria. Litzow: Omeros: Other: Advisory Board; Jazz: Other: Advisory Board; Pluristem: Research Funding; Actinium: Research Funding; Amgen: Research Funding; AbbVie: Research Funding; Astellas: Research Funding; Biosight: Other: Data monitoring committee. Foster: Macrogenics: Research Funding; Rafael Pharmaceuticals: Research Funding; Macrogenics: Consultancy; Daiichi Sankyo: Consultancy; Agios: Consultancy; Bellicum Pharmaceuticals: Research Funding. Larson: Gilead: Research Funding; Epizyme: Consultancy; Astellas: Consultancy, Research Funding; Rafael Pharmaceuticals: Research Funding; CVS/Caremark: Consultancy; Takeda: Research Funding; Novartis: Research Funding; Cellectis: Research Funding.

Abstract Background: Venetoclax, a small-molecule inhibitor of B cell leukemia/lymphoma-2, in combination with hypomethylating agents (HMA) has shown improved efficacy and survival benefit compared to HMA alone (DiNardo et al, 2020) in elderly/unfit patients with acute myeloid leukemia (AML). Since FDA-approval of this regimen for elderly/unfit AML patients, it is frequently utilized both in the upfront and relapsed/refractory setting. Cardiac events with venetoclax are not well described. In the VIALE-E trial, which included patients ineligible for standard induction chemotherapy due to congestive heart failure or stable angina, 15% of patients receiving azacitidine plus venetoclax experienced atrial fibrillation as a serious adverse event, vs. 1% in the azacitidine plus placebo group (DiNardo et al, 2020). Our objective was to provide an estimate of the prevalence of and a description of all cardiac events that occurred in AML patients undergoing treatment with venetoclax + HMA. Methods: 170 consecutive patients with AML who received venetoclax +HMA (azacitidine or decitabine) outside the context of a clinical trial between 1/2017-11/2020 at the Mayo Clinic were included. Patients received venetoclax + HMA either as upfront treatment or for relapsed/refractory disease. Patients with relapse following allogeneic stem cell transplant were excluded. We evaluated all cardiac events that occurred while treatment with venetoclax + HMA was ongoing. Baseline patient and treatment characteristics were compared using the Mann-Whitney U-test and the Fisher's exact test. All statistics were computed using EZR (Version 1.53). Results: 1. Patient characteristics A total of 170 patients who received venetoclax + HMA (median age 69 years [range 17-91], 63% males) were included. ELN risk category was either adverse risk (48%, 82/170) or intermediate risk (48%, 82/170) in the majority of patients. 64% (109/170) of patients received venetoclax + HMA as upfront treatment. Characteristics including age, ELN cytogenetic risk, cardiovascular risk factors, and upfront vs relapsed therapy were similar among patients with or without cardiac events. The only exception was a higher incidence of CEBPA mutation amongst those with cardiac events (12% vs 2%, p=0.03). The majority (83%, 141/170) of patients underwent an echocardiogram prior to initiation of therapy. 2. Cardiac events Of 170 patients treated with venetoclax + HMA during the study period, 34 (20%) patients experienced a total of 48 cardiac events. Of patients experiencing cardiac events, 32% (11/34) had no pre-existing cardiac disease and 12% (4/34) had no cardiovascular risk factors (Table 1). The majority of events occurred early in treatment course: 41% during cycle 1, 26% during cycle 2 and 15% during cycle 3 (Table 1). The most frequently occurring cardiac event (21%, 10/48 events) was a decrease in left ventricular ejection fraction on echocardiography, which was associated with symptoms in all ten patients. Second most frequent was atrial fibrillation with rapid ventricular response at 17% (8/48 events), followed by troponin elevation without electrocardiogram changes at 15% (7/46 events). Of patients with troponin elevation, 57% (4/7 events) occurred in the setting of another inciting factor such as severe anemia, while 43% represented a troponin elevation without explanation (Table 1). Other cardiac events included heart failure with preserved ejection fraction (n=4), other symptomatic arrhythmia (n=4), and symptomatic pericardial effusion or pericarditis (n=3). In addition, 2 of 34 (6%) patients experienced fatal cardiopulmonary arrest. The majority (88%) of cardiac events required either inpatient admission (62%, 21/34 patients) or intensive care unit (ICU) care (26%, 9/34 patients). 77% of patients required new cardiac medications or procedural intervention (n=4). In 27% of cases (9/34 patients), the cardiac event directly contributed to death (Table 1). Conclusions: Cardiac complications were observed in one-fifth (20%) of AML patients treated with venetoclax + HMA, despite the absence of preexisting cardiac disease in a third of cases; moreover 27% of events were fatal. Further comparative studies are required to identify salient clinical features predictive of cardiac complications in these patients. Figure 1 Figure 1. Disclosures Al-Kali: Novartis: Research Funding; Astex: Other: Research support to institution. Litzow: Astellas: Research Funding; Amgen: Research Funding; Omeros: Other: Advisory Board; AbbVie: Research Funding; Actinium: Research Funding; Pluristem: Research Funding; Jazz: Other: Advisory Board; Biosight: Other: Data monitoring committee. Patnaik: Kura Oncology: Research Funding; StemLine: Research Funding.

Abstract Leukemia relapse and treatment related mortality (TRM) remain major obstacles for successful allogeneic hematopoietic cell transplantation (allo-HCT). The number of induction cycles using intensive chemotherapy at AML diagnosis to achieve complete remission (CR) and the number of consolidation cycles and disease status at the time of allo-HCT for patients with acute myeloid leukemia (AML) may each affect TRM and relapse rates. We investigated the impact of the number of induction/consolidation cycles and disease status on the success of allo-HCT in 3113 AML patients reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) (2008-2019). They received allo-HCT in first CR or with persistent leukemia (primary induction failure-PIF) receiving myeloablative (MA) or reduced-intensity (RIC) conditioning. 1473 AML patients (median age, 47 years) in CR received MAC; 862 (58%) achieved CR after 1 cycle of intensive induction chemotherapy and 74% of these had no evidence of measurable residual disease (MRD). 454 (31%) patients required 2 cycles to CR (72 % MRD negative) and 157 (11%) patients (69% MRD negative) after ≥ 3 cycles. The overall survival (OS), relapse and TRM by induction cycle number is shown in Table 1. Multivariate analysis demonstrated that CR after 1 cycle led to higher OS vs. 2 cycles (HR 1.32 95%CI 1.11-1.56, p< 0.01) or ≥ 3 cycles (HR 1.47 95%CI 1.16-1.87, p< 0.01), while OS after 2 cycles or ≥ 3 cycles were similar (HR 1.2 95%CI 0.87-1.4, p=0.38). Higher TRM was observed in patients receiving 2 or ≥ 3 cycles vs. only 1 induction cycles (HR 1.34 95%CI 1.05-1.72, p< 0.02). Relapse risk was greater in those needing ≥ 3 cycles to achieve CR. Consolidation therapy after CR was associated with improved OS vs. no consolidation therapy (HR 1.57 95%CI 1.24-1.99, p< 0.01). The need for ≥2 induction cycles plus consolidation therapy was associated with higher TRM (HR 1.34 95%CI 1.05-1.72, p< 0.02). 1162 AML patients (median age, 63 years) in CR received allo-HCT after RIC; 714 (61%) achieved CR after 1 cycle of induction chemotherapy (72% MRD negative); 310 (27%) patients after 2 cycles (67% MRD negative) and 138 (12%) patients (58% MRD negative) after ≥ 3 cycles (Table 1). Multivariate analysis demonstrated that the number of induction cycles did not affect the OS or TRM. Relapse risk was greater in patients requiring ≥2 cycles to achieve CR. The use of consolidation therapy did not affect OS or TRM. MRD status at the time of allo-HCT did not have a significant impact on OS, TRM and relapse rates after either MA or RIC conditioning. 478 AML patients received allo-HCT after PIF (328 patients with MAC [median age, 51 years], 150 patients RIC [median age, 61 years], Table 1). After MAC, OS and relapse were significantly worse in PIF patients compared to any CR patients (p<0.01). After RIC, relapse was significantly more frequent in PIF patients vs. CR patients after 1 or more induction cycles (p<0.01). TRM was similar for PIF vs CR patients after MAC or RIC allo-HCT. These data demonstrate that among patients eligible for allo-HCT, the need for only one induction cycle to achieve CR, particularly when combined with consolidation therapy is associated with better outcomes after MA conditioning. Achieving CR prior to allo-HCT needing one or more induction cycles is associated with lower relapse rates and improved OS compared to patients with PIF that receive allo-HCT. Figure 1 Figure 1. Disclosures de Lima: BMS: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Miltenyi Biotec: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Hourigan: Govt. COI: Other. Litzow: Omeros: Other: Advisory Board; Pluristem: Research Funding; Jazz: Other: Advisory Board; AbbVie: Research Funding; Amgen: Research Funding; Actinium: Research Funding; Astellas: Research Funding; Biosight: Other: Data monitoring committee. Saber: Govt. COI: Other. Weisdorf: Incyte: Research Funding; Fate Therapeutics: Research Funding.

Abstract Introduction: Allogeneic stem cell transplantation (alloSCT) is the most effective post remission anti-leukemia strategy. However, the associated toxicity is a barrier for its routine adoption as standard of care in older adults. Studies of AML patients who underwent alloSCT are mainly retrospective as randomized controlled trials comparing transplantation to non-transplantation are very difficult to conduct. We herein present prospective data from a randomized controlled phase III study, E2906, designed to compare two intensive chemotherapy arms. Patients who achieved remission and had a donor were to proceed to alloSCT after induction or first consolidation, at investigator discretion. Non-transplanted patients received 2 cycles of consolidation and then underwent a second randomization between observation and decitabine maintenance. Herein are reported all patients who received alloSCT either on protocol during first remission (CR1) or at other post induction time-points. Patients and Methods: Enrolled to E2906 study were 727 AML patients age 60 years and over. AlloSCT was performed in 166 patients, of whom 71 received alloSCT as part of the study and 95 received alloSCT off protocol. 105 patients (66/71 on protocol, 39/95 off protocol) received alloSCT at CR1/CRi1/LFS1 (CR: 92, CRi: 9 LFS: 4). Patients were followed for a median of 33.6 months from diagnosis and 29.1 months from transplant. No patients received decitabine maintenance prior to alloSCT. Overall survival (OS) is defined as the time from allo transplant to death from any cause, with follow-up censored at the date of last contact. Disease free survival (DFS) is defined as the time from alloSCT transplant to relapse or death of any cause. The censored follow-up time for patients without relapse or death information is the date of last contact. Kaplan-Meier estimates were used to estimate OS and DFS. DFS and OS were compared between subgroups using log rank tests. A cumulative incidence analysis, with death without prior relapse as competing events, was performed to evaluate the subgroup effect on time to relapse after transplant. Results: Patient characteristics of those who received alloSCT at CR1/CRi1/LFS1 are similar to the general distribution of AML patients eligible for intensive chemotherapy. Median age was 66 years, 52% were male and 88% with ECOG PS of 0-1. Cytogenetic data were available for 85 patients of whom 26% presented with unfavorable cytogenetics. Minimal residual disease (MRD) status prior to alloSCT was available for 44 patients of whom 19 (43%) achieved a MRD negative state. Long-term OS and DFS rates for all 105 patients who underwent alloSCT at CR1/CRi1/LFS1 are encouraging (Figure 1). OS and DFS at two years were 56.4% and 53.6% and 49.4%, 45.6% and 42.9%, 39% at 3 and 4 years, respectively. Age above or below 65 years, gender, induction regimen (3+7 or clofarabine) and MRD status prior to transplantation had no impact on outcome. Survival curves by intermediate or adverse cytogenetic risk are not significantly different. The numbers of patients with CRi1 or LFS1 are too small to compare with patients in CR1. Nevertheless, 36/38 patients that were alive and remain in first remission at the time of data cutoff, are patients who achieved CR1 and only 2/38 are patients transplanted at CRi1 or LFS1. Notably, the non-relapse mortality (NRM) was not significantly different for patients less or over 65 years. NRM at 6 months and 2 years for patients over and under 65 years of age were 4.4%, 8.4% and 15.6%, 24.0% respectively. Relapse during the first year post alloSCT is the main barrier for longer survival, particularly in patients with adverse cytogenetics and MRD positivity prior to transplantation (Figure 2). Conclusions: Fit older patients, including those over age 65, who undergo an alloSCT in CR1, can expect a 4-year survival of 43% with an acceptable NRM rate. The NRM was, surprisingly, not higher than for a typically younger cohort of AML. Relapse within one year after transplant is the major limitation to prolonged survival and this finding reflects the biology of the leukemia in these patients. In this patient population, novel post remission strategies should either be complimentary to alloSCT or competitive with updated outcome of alloSCT. Figure 1 Figure 1. Disclosures Ofran: Medison Israel: Consultancy; Janssen: Consultancy; Pfizer: Consultancy; Astellas: Consultancy; AbbVie: Consultancy. Claxton: Astellas: Other: Clinical Trial; Novartis: Research Funding; Astex: Research Funding; Cyclacel: Research Funding; Daiichi Sankyo: Research Funding; Incyte: Research Funding. Tallman: Syros: Membership on an entity's Board of Directors or advisory committees; Kura: Membership on an entity's Board of Directors or advisory committees; NYU Grand Rounds: Honoraria; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Biosight: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Orsenix: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Rafael Pharmaceuticals: Research Funding; Glycomimetics: Research Funding; Biosight: Research Funding; Orsenix: Research Funding; Abbvie: Research Funding; Mayo Clinic: Honoraria; UC DAVIS: Honoraria; Northwell Grand Rounds: Honoraria; NYU Grand Rounds: Honoraria; Danbury Hospital Tumor Board: Honoraria; Acute Leukemia Forum: Honoraria; Miami Leukemia Symposium: Honoraria; New Orleans Cancer Symposium: Honoraria; ASH: Honoraria; NCCN: Honoraria. Melnick: Constellation: Consultancy; Epizyme: Consultancy; Daiichi Sankyo: Research Funding; Sanofi: Research Funding; Janssen Pharmaceuticals: Research Funding; KDAC Pharma: Membership on an entity's Board of Directors or advisory committees. Levine: Prelude: Membership on an entity's Board of Directors or advisory committees; Ajax: Membership on an entity's Board of Directors or advisory committees; Zentalis: Membership on an entity's Board of Directors or advisory committees; Mission Bio: Membership on an entity's Board of Directors or advisory committees; QIAGEN: Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria; Lilly: Honoraria; Morphosys: Consultancy; Janssen: Consultancy; Incyte: Consultancy; Astellas: Consultancy; Imago: Membership on an entity's Board of Directors or advisory committees; Auron: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Celgene: Research Funding; Roche: Honoraria, Research Funding; C4 Therapeutics: Membership on an entity's Board of Directors or advisory committees; Isoplexis: Membership on an entity's Board of Directors or advisory committees. Lazarus: Bristol Myer Squibb: Membership on an entity's Board of Directors or advisory committees. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Foran: gamida: Honoraria; aptose: Research Funding; syros: Honoraria; boehringer ingelheim: Research Funding; kura: Research Funding; takeda: Research Funding; abbvie: Research Funding; trillium: Research Funding; revolution medicine: Honoraria; certara: Honoraria; actinium: Research Funding; OncLive: Honoraria; pfizer: Honoraria; servier: Honoraria; bms: Honoraria; novartis: Honoraria; taiho: Honoraria; sanofi aventis: Honoraria; h3bioscience: Research Funding; aprea: Research Funding; sellas: Research Funding; stemline: Research Funding. Litzow: Jazz: Other: Advisory Board; AbbVie: Research Funding; Omeros: Other: Advisory Board; Amgen: Research Funding; Actinium: Research Funding; Astellas: Research Funding; Pluristem: Research Funding; Biosight: Other: Data monitoring committee.

Abstract Background: trALL is an important secondary primary malignancy (SPM) that has recently been appreciated. While patients (pts) with MM have an 8%-17% risk of developing an SPM while on lenalidomide (R) maintenance following autologous stem cell transplant (ASCT), trALL has been rarely observed. Little is known about the characteristics of trALL in pts with MM compared to pts who had other malignancies prior to the development of trALL. We define tALL as any prior exposure to cytotoxic chemotherapy and/or radiation for another malignancy, and herein, we report a comparative analysis of characteristics and outcomes of pts with trALL with and without MM from the Mayo Clinic Cancer Center (MCCC). Methods: We performed a systematic search in the 3-site MCCC registry and included all pts diagnosed and received at least 1 cycle of ALL-directed therapy and/or underwent allogeneic transplantation (AlloHCT) for ALL between 2007-2020. All cases of trALL in this series are B-ALL. Comparisons of characteristics between trALL patients with and without MM were made using a Wilcoxon rank sum test (continuous variables) or Fisher's exact test (categorical variables). Time-to-event variables were compared using unadjusted Cox proportional hazards regression models. Results: 70 trALL pts (14 MM [20%], 56 non-MM [80%]) were identified during the study period. The median age at trALL diagnosis was 63.9 (range 47-71) for MM pts and 63.1 (range 18.2-84) for non-MM pts. Median follow-up from trALL diagnosis was 1.42 years (range 0.02-10.6 years). The most common prior non-MM malignancies among tALL pts were breast (28.6%), lymphoma (17.9%), myeloid (17.9%), and GU/GYN (14.3%). Amongst the 14 MM pts, 100% (n=10) had ISS-I disease, 8 (57%) had IgG K MM, 1 (n=10) had high risk cytogenetics, 8 (57.1%) received R-based induction , 4 (28.6%) received CyBorD induction, 4(28.6%) received VRD induction, 3 (21.4%) received RD induction. 10 (71.4%) pts were actively on R when they developed trALL, 8 (57.1%) pts received prior ASCT. The median time to develop trALL following ASCT for MM was 46.3 months (m), (95% CI 20.4-67.6), 12 (85.7%) pts received R maintenance with a median duration of 53m (95% CI 16.9-121). The median time to develop trALL after initiation of R maintenance was 61.2m (95% CI 16.9-123.4). The most common trALL induction regimen received was HyperCVAD which was used in 71.4% of MM pts and 51.8% of non-MM pts. In comparison to non-MM pts, MM patients had a significantly lower WBC at diagnosis (Median: 2.0 vs. 5.8, P=0.005),no t(9;22) BCR/ABL1 cytogenetics (0.0% vs. 35.7%, P=0.008), a higher frequency of hypodiploid/near-triploid (Ho-Tri) cytogenetics (42.9% vs. 12.5%, P=0.009), and a lower frequency of prior radiation therapy (7.1% vs. 44.6%, P=0.012). MM pts had a higher frequency of AlloHCT for trALL (71.4% vs. 42.9%, P=0.075) and were more commonly in complete response (CR) at transplant (100.0% vs. 70.8%, P=0.078). No trALL in MM pts were Ph-like ALL. There was a statistically significant difference in time to development of trALL between previous malignancy locations (P=0.018), with GU/GYN (Median: 9 years) having the longest time and myeloid (Median: 3 years) having the shortest time; MM was 6 years. In the overall pt cohort, 56 (80%) pts achieved a complete response after induction and 60% (n=25) were minimal residual disease (MRD)+ after induction. Pts with MM had a significantly lower likelihood of being MRD+ after induction (OR=0.09, P=0.015). Overall, 24.3% of pts relapsed after induction therapy for trALL; 39 (55.5%) died after trALL diagnosis including 43% (n=35) who died after AlloHCT. Although pts with MM tended to have better outcomes compared to non-MM trALL pts in terms of overall survival after trALL diagnosis (Figure 1A), survival after AlloHCT (Figure 1B), relapse rate after trALL diagnosis and non-relapse mortality after AlloHCT, none of these findings were statistically significant in this small cohort (Figure 1C). Conclusion: trALL is a unique SPM that can occur in pts with MM. It is associated with Ho-Tri cytogenetics and is BCR/ABL1 negative. The majority of MM pts that developed trALL had undergone prior ASCT and were on R maintenance when they developed trALL. Despite being more likely to have adverse cytogenetics features, MM-associated trALL has similar survival compared to non-MM-associated trALL which speaks to the poor survival outcomes of this SPM. Further research on trALL in MM pts is merited. Figure 1 Figure 1. Disclosures Litzow: Amgen: Research Funding; Pluristem: Research Funding; AbbVie: Research Funding; Actinium: Research Funding; Astellas: Research Funding; Omeros: Other: Advisory Board; Jazz: Other: Advisory Board; Biosight: Other: Data monitoring committee. Bergsagel: Janssen: Consultancy. Fonseca: Scientific Advisory Board: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Caris Life Sciences: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy; Patent: Prognosticaton of myeloma via FISH: Patents & Royalties; Bayer: Consultancy; Takeda: Consultancy; Celgene: Consultancy; Amgen: Consultancy; BMS: Consultancy; Mayo Clinic in Arizona: Current Employment; Juno: Consultancy; Kite: Consultancy; Aduro: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Novartis: Consultancy; Merck: Consultancy; Sanofi: Consultancy; Pharmacyclics: Consultancy; Janssen: Consultancy. Dispenzieri: Takeda: Research Funding; Alnylam: Research Funding; Pfizer: Research Funding; Oncopeptides: Consultancy; Sorrento Therapeutics: Consultancy; Janssen: Consultancy, Research Funding. Murthy: CRISPR Therapeutics: Research Funding. Ailawadhi: GSK: Consultancy, Research Funding; Sanofi: Consultancy; Pharmacyclics: Consultancy, Research Funding; Takeda: Consultancy; Medimmune: Research Funding; Xencor: Research Funding; Genentech: Consultancy; Janssen: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Cellectar: Research Funding; Beigene: Consultancy; BMS: Consultancy, Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Ascentage: Research Funding. Foran: actinium: Research Funding; taiho: Honoraria; bms: Honoraria; servier: Honoraria; pfizer: Honoraria; novartis: Honoraria; OncLive: Honoraria; abbvie: Research Funding; boehringer ingelheim: Research Funding; takeda: Research Funding; trillium: Research Funding; aptose: Research Funding; revolution medicine: Honoraria; syros: Honoraria; sanofi aventis: Honoraria; certara: Honoraria; gamida: Honoraria; kura: Research Funding; h3bioscience: Research Funding; aprea: Research Funding; sellas: Research Funding; stemline: Research Funding.

Abstract Background: Outcomes of patients with relapsed/refractory AML (RR-AML) have remained poor. Therapy with venetoclax based combinations in this setting leads to CR/CRi rates of 21-49% (DiNardo CD et al. Am J Hematol 2018, Aldoss I et al. Haematologica 2018, Stahl M et al. Blood Adv 2020). Preclinical studies with BCL-2 inhibitors indicate potential mechanisms of drug resistance including overexpression of the anti-apoptotic protein MCL-1 (Konopleva et al. Cancer Cell. 2006). Pevonedistat is a first in class inhibitor of Nedd8 activating enzyme that induces the pro-apoptotic protein NOXA leading to neutralization of MCL-1 and apoptosis. Preclinical studies evaluating the combination of pevonedistat and venetoclax against AML cell lines have demonstrated a synergistic effect (Knorr KL et al. Cell Death Differ. 2015). Hence, we designed a phase I study to assess the safety and tolerability of adding pevonedistat to the combination of azacitidine and venetoclax in patients with RR-AML. Study design and methods: We conducted a phase I study with the combination of pevonedistat, venetoclax and azacitidine in patients with RR-AML. Patients aged 18 years or above with morphologically documented RR-AML, ECOG performance status 0-2 and adequate organ function were eligible. Major exclusion criteria were isolated extramedullary relapse, hematopoietic cell transplantation (HCT) within 100 days of enrollment, and active acute GVHD. Previous therapy with hypomethylating agents (HMA) or venetoclax was not an exclusion criterion. The dose escalation phase was conducted using 3+3 design. Treatment included azacitidine (75 mg/m 2 daily x 7 days), venetoclax (400 mg daily x 28 days), and pevonedistat in escalating doses (10-20 mg/m 2 IV days 1,3,5 of each cycle) with a cycle length of 28 days. Pevonedistat was given at 10 mg/m 2 dose in cohort 1, 15 mg/m 2 dose in cohort 2 and 20 mg/m 2 dose in cohort 3. The primary endpoint is to determine the recommended phase 2 dose (RP2D) and toxicity profile of pevonedistat, azacitidine and venetoclax. Other endpoints included determination of response rates, duration of response, survival, pharmacokinetics, correlation of response rates with AML genomic profile, correlation of pretreatment levels of BCL2, BCLXL, MCL1, BAX or BAK with response, determination of changes in NOXA (PMAIP1) mRNA and protein expression pre-and post-pevonedistat treatment, evaluation of BH3 mimetic profiling on bone marrow samples by flow cytometry and assessing the sensitivity of leukemia and leukemic stem/progenitor cells to pevonedistat ex vivo. Results: Thirteen patients participated in the dose escalation phase, 12 of whom were evaluable. Median age was 69 years (61-91), 30.8% had secondary/therapy related AML, 69.2% with adverse risk disease, 53.8% previously received venetoclax/HMA and 23.1% had relapse after prior allogeneic hematopoietic cell transplantation (HCT) (Table 1). Seven patients were enrolled into cohort 1 (pevonedistat 10 mg/m 2 dose) of which one was not evaluable, three patients enrolled into cohort 2 (pevonedistat 15 mg/m 2 dose), and three patients enrolled into cohort 3 (pevonedistat 20 mg/m 2 dose). Grade 3 or higher AEs included febrile neutropenia (23%), infection (15%), anemia (38%), neutropenia (54%), thrombocytopenia (38%). There was 1 dose limiting toxicity (DLT) in cohort 1 (atrial fibrillation) that triggered cohort expansion. However, subsequent patients did not experience DLT despite planned dose escalation. Of the 12 evaluable total patients, CR/CRi was observed in 5 (41.6%) patients. Notably, patients with RR-AML who were venetoclax/HMA naïve had a CR/CRi 83.3% (5/6 patients). The response rates for each cohort are summarized in Table 2. Three of the five patients with CR/CRi (60%) achieved MRD negativity by flow cytometry. Four patients who achieved CR/CRi proceeded to allogeneic HCT after therapy. Median OS of the cohort was 5.4 months (1.8-14) and median OS was not reached in patients with CR/CRi. Conclusions: The addition of pevonedistat to venetoclax and azacitidine backbone is safe and well tolerated in patients with RR-AML. Dose escalation yielded encouraging efficacy in venetoclax/HMA naïve RR-AML patients. The study is currently in the dose expansion phase. Details on correlative studies examining mechanisms of therapeutic efficacy and resistance will be reported in the main meeting. Figure 1 Figure 1. Disclosures Guru Murthy: Cardinal health: Honoraria; TG Therapeutics: Other: Advisory board meeting; DAVA Oncology: Honoraria; CancerExpertNow: Honoraria; Qessential: Honoraria; Techspert: Consultancy; Curio Sciences: Honoraria; Guidepoint: Consultancy. Abedin: AltruBio: Research Funding; Helsinn: Research Funding; Amgen: Honoraria; Pfizer: Research Funding; Agios: Honoraria; Actinium: Research Funding; Astellas Pharma Inc.: Research Funding. Litzow: Jazz: Other: Advisory Board; Pluristem: Research Funding; Actinium: Research Funding; Amgen: Research Funding; Astellas: Research Funding; AbbVie: Research Funding; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. Atallah: Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Research Funding; BMS: Honoraria, Speakers Bureau; Takeda: Consultancy, Research Funding; Abbvie: Consultancy, Speakers Bureau; Amgen: Consultancy.

Abstract Introduction: Clonal hematopoiesis of indeterminate potential (CHIP) is defined by the presence and subsequent expansion of leukemia-associated driver mutations (MT). These MT predominantly involve epigenetic regulators such as DNMT3A, ASXL1, and TET2 (DAT, 75%). CHIP is a disease of aging and is associated with increased all-cause mortality. Clonal Hematopoiesis (CH), when present in the context of unexplained cytopenias and MT variant allele fractions (VAF) >20%, is termed as clonal cytopenias of undetermined significance (CCUS). Chronic myelomonocytic leukemia (CMML) is a hematological malignancy characterized by TET2, ASXL1, and SRSF2MT as well as sustained monocytosis. It usually arises in the setting of existing CH and clonal monocytosis. Here, we assessed the clonal compositions involving DAT genes in patients (pts) with CHIP, CCUS, and CMML. Methods: We included 1008 pts: 54 (5%) with CHIP, 334 (33%) with CCUS, and 620 (62%) with CMML. Demographics, laboratory parameters, and mutational spectrum at diagnosis were collected. We characterized and compared DAT MT in all three cohorts and assessed correlations with clinical parameters. MT locus and type along with protein sequences were analyzed using ProteinPaint. All statistical analyses were performed using R. Results: Of the 1008 pts, 427 (42%) had DAT MT; 36 had CHIP (67%); 96 had CCUS (29%), and 296 had CMML (48%). The median age was 71 years (IQR 65-76), and 68% were male. CMML pts had higher white blood cell counts, absolute neutrophil counts, absolute monocyte counts, and lower hemoglobin and platelet counts in comparison to CCUS and CHIP pts. The distribution of age and sex were similar among the three groups. After a median follow-up of 11 months (IQR 9.5-12.8), there were no myeloid progressions in the CHIP group and 17 (18%) in the CCUS group (8 of which developed CMML, Table 1). There were 738 protein-altering or splice-site DATMT in 495 unique MT hotspots. Pts with TET2MT were older (71 years, compared to DNMT3AMT: 69 years and ASXL1MT: 69 years , p<0.022). ASXL1MT were more common in males (75%, compared to DNMT3AMT: 52% and TET2MT: 66%, p=0.005). The mean VAF (mVAF) were 15.5% for DNMT3AMT, 35% for ASXL1MT and 39.2% TET2MT, respectively (p<0.001). We then compared DATMT characteristics in CHIP, CCUS, and CMML groups: DNMT3AMT were most common in CHIP, followed by CCUS, and were very rare in CMML (35% vs. 15% vs. 3%, p<0.001), with mVAF of DNMT3AMT increasing across this spectrum (CHIP: 6.5% vs. CCUS: 17.1% vs. CMML: 43.4%, p<0.0001). While DNMT3A missense MTs were most common (n=62, 67.4%), the AML-associated R882 hotspot MT was seen in 26 (28%) pts (CHIP: n=3, 5%, CCUS: n=10, 16%, and CMML n=13, 21%, Figure 1a). None of the DNMT3AMT CHIP and CCUS pts progressed to CMML.ASXL1MT were most frequently seen in CMML (n=178, 28.6%), followed by CHIP (n=4, 7.4%), and CCUS (n=17, 5%, p<0.001). The mVAF of ASXL1MT was significantly lower in CHIP, followed by CCUS, and CMML (11% vs. 34% vs. 36%, p<0.0001). Truncating ASXL1 MTs were most common (n=205, 53%). Mutational hotspots included G646W (n=81, CCUS: n=6, 3%, CMML: n=75, 37%) and E635 (n=27, CHIP: n=1, 0.5%, CCUS: n=1, 0.5%, CMML: n=27, 13%, Figure 1b). Four ASXL1MT CCUS pts transformed to CMML (R965, E635, G646W, Q910*, and Q925*); of which 2 co-mutated with TET2MT, one with SRSF2MT, and one with an additional ASXL1MT.TET2MT were frequently encountered in CMML, followed by CCUS and CHIP pts (CMML: n=205, 33% vs. CCUS: n=88, 26.3% vs. CHIP: n=15, 27.8%, p=0.02). The mVAF of TET2MT progressively increased across the 3 groups (CHIP: 14.1%, CCUS: 31.9%, CMML: 45.5%, p<0.001). TET2MT occurred across the span of the gene, with no clear hotspots identified, with nonsense MT being most frequent (n=150, 37.3%, Figure 1c). Among the nonsense and frameshift TET2MT (n=209), 131 (63%) involved the N terminal region, and 78 (37%) involved the catalytic domain. Among 8 CCUS pts that transformed to CMML, 6 had TET2MT, including 4 with spliceosome co-MT. Conclusion: While CMML, a disease of aging, arises in the background of CH, the most common CH MT, DNMT3AMT, plays a minor role in this process, and in fact, DNMT3AMT tend to occur at younger ages. While DNMT3A MT and ASXL1MT are preferentially observed in hotspots, TET2MT span the entire gene. Clonal compositions largely involving truncating TET2MT and frameshift ASXL1MT, in conjunction with splicing MT, shape the CMML genotype. Figure 1 Figure 1. Disclosures Komrokji: Geron: Honoraria; Novartis: Honoraria; Agios: Honoraria, Speakers Bureau; Abbvie: Honoraria, Speakers Bureau; JAZZ: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Acceleron: Honoraria. Zeidan: Genentech: Consultancy; BeyondSpring: Consultancy; Kura: Consultancy, Other: Clinical Trial Committees; Amgen: Consultancy, Research Funding; Cardiff Oncology: Consultancy, Other: Travel support, Research Funding; Astex: Research Funding; Epizyme: Consultancy; Geron: Other: Clinical Trial Committees; Boehringer Ingelheim: Consultancy, Research Funding; AstraZeneca: Consultancy; Acceleron: Consultancy, Research Funding; Astellas: Consultancy; Novartis: Consultancy, Other: Clinical Trial Committees, Travel support, Research Funding; Agios: Consultancy; Aprea: Consultancy, Research Funding; AbbVie: Consultancy, Other: Clinical Trial Committees, Research Funding; Loxo Oncology: Consultancy, Other: Clinical Trial Committees; Pfizer: Other: Travel support, Research Funding; ADC Therapeutics: Research Funding; Gilead: Consultancy, Other: Clinical Trial Committees; BMS: Consultancy, Other: Clinical Trial Committees, Research Funding; Jazz: Consultancy; Incyte: Consultancy, Research Funding; Ionis: Consultancy; Jasper: Consultancy; Daiichi Sankyo: Consultancy; Janssen: Consultancy; BioCryst: Other: Clinical Trial Committees. Coombs: LOXO: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; AstraZeneca: Honoraria; AbbVie: Honoraria; Genentech: Honoraria; MEI Pharma: Honoraria. Madanat: Blue Print Pharmaceutical: Honoraria; Stem line pharmaceutical: Honoraria; Onc Live: Honoraria; Geron Pharmaceutical: Consultancy. Griffiths: Takeda Oncology: Consultancy, Honoraria; Novartis: Honoraria; Taiho Oncology: Consultancy, Honoraria; Apellis Pharmaceuticals: Research Funding; Alexion Pharmaceuticals: Consultancy, Research Funding; Boston Biomedical: Consultancy; Astex Pharmaceuticals: Honoraria, Research Funding; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Genentech: Research Funding; Abbvie: Consultancy, Honoraria. Lai: Jazz Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Speakers Bureau; Jazz Pharma: Speakers Bureau; Macrogenics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees. Savona: CTI: Consultancy, Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; BMS-Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; NOVARTIS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Ryvu: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; ALX Oncology: Research Funding; Astex: Research Funding; Incyte: Research Funding. Litzow: AbbVie: Research Funding; Actinium: Research Funding; Pluristem: Research Funding; Amgen: Research Funding; Astellas: Research Funding; Jazz: Other: Advisory Board; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. Al-Kali: Novartis: Research Funding; Astex: Other: Research support to institution. Patnaik: StemLine: Research Funding; Kura Oncology: Research Funding.

Abstract Background: Therapy-related acute myeloid leukemia (AML) is a well-described entity and known to carry a worse prognosis, compared to de novo AML. In the current study, we sought to describe the presenting features and outcome of patients with AML, in the setting of previous history of cancer with or without exposure to chemotherapy or radiotherapy. Methods: A Mayo Clinic database of patients with AML was queried to identify patients with a previous history of cancer, both hematologic and solid tumors. A comparative analysis of presenting features, treatment details and survival were performed between patients with therapy-related AML (Group A) and those with AML and a history of cancer that had been managed with surgery alone (Group B). Results: A total of 250 patients (median age 68 years, range 19-90; 60% males) with AML and a previous history of cancer (both hematologic and solid) were identified; 182 (73%) cases were determined to be therapy-related AML (Group A) while the remaining 68 (27%) did not receive chemotherapy or radiotherapy for their antecedent cancer (Group B) (Table). Among group A patients 106 (58%) were exposed to chemotherapy, 37 (20%) to radiotherapy and 39 (22%) to combination chemotherapy and radiotherapy for their cancer. At the time of AML diagnosis, adverse karyotype was noted in 91 (51%) group A and 12 (19%) group B patients (p<0.0001); the incidence of adverse karyotype in patients exposed to chemotherapy vs radiotherapy alone vs combined chemoradiotherapy was 54% (57/106), 30% (11/37), and 59% (23/39) respectively (p=0.04). Group A patients, compared to those in group B, included more females (46% vs 24%; p=0.001), and more preceding hematologic malignancies (p=<0.0001). Next generation sequencing was performed in 74 patients and the results showed no significant difference between groups A and B (Table). Treatment and outcome in Groups A and B: Intensive and less intensive AML-directed chemotherapy were given to 100 (55%) and 44 (24%) patients in group A and 38 (56%) and 14 (21%) patients in group B (P=0.8). 79 (65%) remissions (complete remission (CR) 42 (29%) and CR with incomplete count recovery (CRi) 37 (26%) were documented in Group A and 37 (71%) remissions (CR: 21 (40%) and CRi=16 (31%) in Group B (P=0.2). After a median follow-up of 8.4 months (range: 0.9-217), 184 deaths were documented: 132 (72.5%) in Group A and 52 (76.5%) in Group B (P=0.5). 52 (36%) patients from Group A and 25 (48%) from Group B relapsed (P=0.1). The median (range) overall survival (OS) rates of patients from Group A was 13 (9-17) months and that of Group B was 14 (10-35) months (P=0.6). The 1-, 3- and 5-year OS rates were 52%, 28%, and 24% in Group A; and 62%, 33%, and 24% in Group B patients (Fig 1). Multivariable analysis identified relapse (HR 2.8, 95% CI 1.7-4.7) and failure to achieve CR/CRi (HR 2.8 95% CI 1.9-4.7) as risk factors for inferior survival (Fig 2a and 2b). The median (range) relapse free survival of patients in Group A was 28 (17 -81) and that of Group B was 27 (14 - 76) months (P=0.9) (Fig 2c). 28 patients underwent allogenic stem-cell transplant (25 in CR1 and 3 in CR2), 23 in Group A and 5 in Group B; the 1-, 3-, and 5-year OS of patients who underwent allogenic stem cell transplant were 88%, 72%, and 72% regardless of the group (Fig 2d). Conclusion: The current study did not find significant differences between AML patients with previous history of cancer with or without exposure to chemo/radiotherapy, in terms of either response to AML-directed therapy or overall or relapse-free survival, despite a higher prevalence of adverse karyotype in therapy-related AML. Figure 1 Figure 1. Disclosures Patnaik: Kura Oncology: Research Funding; Stemline Therapeutics: Membership on an entity's Board of Directors or advisory committees; Stemline Therapeutics: Membership on an entity's Board of Directors or advisory committees. Al-Kali: Astex: Other: Research support to institution; Novartis: Research Funding. Litzow: Pluristem: Research Funding; Actinium: Research Funding; AbbVie: Research Funding; Astellas: Research Funding; Amgen: Research Funding; Jazz: Other: Advisory Board; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee.

Abstract Background: Relapsed or refractory (R/R) acute lymphoblastic leukemia (ALL) or lymphoblastic lymphoma (LL) remain a therapeutic challenge, especially in elderly patients(pts) or those with T-cell immunophenotype. Inhibition of apoptosis is an increasingly recognized mechanism for resistance to conventional chemotherapy. Recently, the oral bcl-2 inhibitor venetoclax (VEN) has shown remarkable activity in a variety of hematologic malignancies. Preclinical data in both B- and T-ALL suggests synergy of VEN with vincristine(VCR). Liposomal VCR (L-VCR) is FDA approved for relapsed ALL having progressed following 2 or more antileukemia therapies. We designed a phase I/II trial (EA9152) of the combination of L-VCR and VEN for pts with r/r B-or T-cell ALL or LL. Here, we report for the first time the safety and efficacy outcomes of the phase I portion of this trial (NCT03504644). Methods: This open-label phase I/II study enrolled pts age>=18 with ALL or LL who were R/R to multiagent chemotherapy. Subjects could have received prior VCR or VEN . In a standard 3 + 3 dose escalation design, subjects were given a two week lead-in phase of single agent VEN in the following schedule: dose level 1 - 20, 50, 100, 200 mg on days 1, 2, 3, 4 and 400 mg on days 5 ‒ 42; dose level 2 - 50, 100, 200, 400 mg on days 1, 2, 3, 4 and 600 mg on days 5 ‒ 42; and dose level 3 ‒ 100, 200, 400, 600 mg on days 1, 2, 3, 4 and 800 mg on days 5 ‒ 42. Weekly L-VCR 2.25mg/m 2 IV was started on D15 of cycle 1, and starting day 1 for subsequent cycles (cycle 2+ = 28 days). For cycle 2 and beyond, VEN 400mg, 600mg, or 800mg based on dose level was given starting on day 1 of the cycle. Primary objective of the phase I portion was to determine the maximum tolerated dose (MTD) of VEN in combination with L-VCR. Secondary objectives included determining preliminary response rates. Results: EA9152 was activated on April 26, 2018 and the phase I portion closed to accrual on March 2, 2021. Among the 18 pts in dose escalation (Table 1), the median age was 42 years (22-77). The majority of pts were male (56%), white (80%), and with a performance status (PS) of 1 (78%). Among 13 pts with disease diagnosis reported, 9 had ALL and 4 had LL. Seventeen of 18 (94%) reported previous chemotherapy, two of which had previous stem cell transplant. Median treatment cycles received is 1 (range 1-11). One patient, having received 11 cycles, remains on study at the time of data analysis. Grade >=3 treatment-related adverse events were reported in 89% of treated pts, with neutrophil count decreased (67%), white blood cell decreased (56%), and anemia (50%) as the most common. One pt experienced grade 3 tumor lysis syndrome. Twelve pts were considered evaluable for MTD determination. Six pts were considered not evaluable for toxicity analysis on account of withdraw of consent for treatment (n=4) or rapid disease progression (n=2). Two pts (2 of 3) at dose level 3 experienced DLTs, one each of hypokalemia and heart failure. Therefore, the MTD of the combination was determined to be dose level 2 - VEN 50, 100, 200, 400 mg on days 1, 2, 3, 4 and 600 mg on days 5 ‒ 42 and for subsequent cycles, with L-VCR 2.25mg/m2 IV weekly. In regards to best overall responses observed (Table 2) 4 of 18 pts (22%) achieved complete response (CR), 4 patients (22%) had stable disease, and 7 (39%) had progressive disease. Two patients in CR were found to be measurable residual disease (MRD) negative as well. Conclusions: In the phase 1 portion of this study, the combination of VEN and L-VCR was found to be safe for patients with ALL and LL. The MTD of the combination was found to be VEN 600mg daily with encouraging preliminary efficacy seen including MRD negative responses. The phase 2 portion of this trial is actively enrolling with VEN 600mg daily starting C1D1. Figure 1 Figure 1. Disclosures Palmisiano: Takeda: Consultancy; Genentech: Research Funding; Foundation One: Consultancy; AbbVie: Consultancy, Research Funding. Claxton: Astellas: Other: Clinical Trial; Novartis: Research Funding; Astex: Research Funding; Cyclacel: Research Funding; Daiichi Sankyo: Research Funding; Incyte: Research Funding. Park: BMS: Consultancy; Amgen: Consultancy; Autolus: Consultancy; Novartis: Consultancy; Minerva: Consultancy; PrecisionBio: Consultancy; Curocel: Consultancy; Artiva: Consultancy; Kite Pharma: Consultancy; Kura Oncology: Consultancy; Affyimmune: Consultancy; Servier: Consultancy; Innate Pharma: Consultancy; Intellia: Consultancy. Podoltsev: Novartis: Honoraria; Incyte: Honoraria; Celgene: Honoraria; Pfizer: Honoraria; Blueprint Medicines: Honoraria; Bristol-Myers Squib: Honoraria; PharmaEssentia: Honoraria; CTI BioPharma: Honoraria. Atallah: Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Research Funding; BMS: Honoraria, Speakers Bureau; Takeda: Consultancy, Research Funding; Abbvie: Consultancy, Speakers Bureau; Amgen: Consultancy. Dinner: Kite/Gilead: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Webster: AmGen: Consultancy; Pfizer: Consultancy. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Litzow: AbbVie: Research Funding; Astellas: Research Funding; Amgen: Research Funding; Actinium: Research Funding; Pluristem: Research Funding; Jazz: Other: Advisory Board; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. OffLabel Disclosure: Venetoclax, a BCL-2 inihibitor, is not FDA-approved for use in ALL.