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Introduction: Health disparities for underrepresented U.S. minority populations with hematologic cancers contribute to differential treatment and higher death rates. The Hispanic population (including people of Mexican, South/Central American, Cuban, Puerto Rican, or other Spanish-speaking cultures, regardless of race) collectively constitutes the largest minority group in the United States. Hispanic patients have been reported to have an increased incidence of B-cell acute lymphoblastic lymphoma (B-ALL) and acute promyelocytic leukemia (APL). While APL is associated with favorable outcomes compared to other acute leukemias, registry data suggest poorer outcomes in Hispanic patients with both acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML). The Hispanic paradox is an epidemiological paradox that refers to the finding that Hispanic patients have paradoxically comparable, or better, health outcomes compared to their U.S. non-Hispanic White counterparts despite barriers to care such as lower socioeconomic status. This paradox has also been reported in hematologic malignancies. Definitive data regarding differences in outcome between Hispanic and non-Hispanic patients with acute leukemias (AL) are lacking. We sought to compare outcomes of Hispanic patients and non- Hispanic patients with acute leukemia with access to care, and examine whether the Hispanic paradox reported in hematologic malignancies is attributable to enrichment of patients with highly curable disease such as APL. Methods: Using data from a Vizient Clinical Data Base, a healthcare claims database, we identified patients with leukemia using ICD 10 codes for acute leukemia. Adult patients with AL, ages 18-89 who were treated between January 2020 and June 2021 were evaluated. Data from 121 academic centers was included. We focused on academic centers to limit the impact of access to care . Demographic information was obtained from the registry, to which ethnicity was self-reported. Patients were stratified by age, and we compared complication rates, number of complications, number of deaths, percent deaths and mortality index between Hispanic and non-Hispanic patients. The key metric used to compare outcomes of Hispanic patients with non-Hispanic patients was the severity adjusted mortality index, which is the ratio of observed mortality over expected mortality for patients with the same diagnosis in this registry. Chi-squared test is used for to determine the statistical significance of differences in mortality (by age group) in Hispanics v. non-Hispanic patients. Initial analysis included all patients with acute leukemias, and the data was subsequently reanalyzed excluding patients with APL, as APL is known to portend a favorable prognosis. Results: A total of 29,967 patients were with acute leukemia were evaluated; of these patients, 2903 identified as Hispanic and 27,064 were non- Hispanic. As seen in table 1, patients of Hispanic origin generally had lower treatment related complication rates in all age groups compared to their age matched non-Hispanic counterparts. Except for the 51-64 and 80-84 age groups the mortality index was lower in Hispanic patients compared to non-Hispanic peers. Differences in mortality between Hispanic and non-Hispanic patients in all age groups were not statistically significant. Trends to a lower mortality index in Hispanic patients are highlighted in green in table 1. When patients with APL were excluded from the analysis, the trend lower mortality in Hispanic patients in most age groups persisted. Again, the mortality index was comparatively higher in hispanic patients in the 51-64 and 80-84 age groups, but differences in mortality between Hispanic and non- Hispanic patients were not statistically significant. Exclusion of APL patients did not have a significant impact on the complication rate or mortality supporting that the Hispanic paradox is independent of higher rates of very favorable risk myeloid malignacies in this population. Conclusions: Hispanic patients with access to academic cancer centers have the potential for non-inferior outcomes compared to non-Hispanic patients. Equivalent outcomes as assessed by mortality index were not attributable solely to the higher incidence of very favorable risk disease such as APL in the Hispanic population. Figure 1 Figure 1. Disclosures Watts: Takeda: Consultancy, Research Funding; Genentech: Consultancy; Rafael Pharma: Consultancy; Celgene/BMS: Consultancy. Bradley: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Sekeres: Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

Background: Clonal cytopenia of undetermined significance (CCUS) is defined as persistent unexplained cytopenia with evidence of clonality [myeloid-associated somatic mutations (MTs) or cytogenetic [CG] abnormalities] but without definitive evidence of myeloid neoplasms (MN). The outcomes in CCUS patients (pts) are not well understood. Methods: The CCUS International Study database includes pts from 17 institutions who meet the criteria of CCUS and do not have other causes of cytopenia. Pts with MDS defining CG abnormalities were excluded. We collected baseline clinical data, laboratory parameters, CGs, molecular genetics, treatment, and disease course. Diverse gene panels from different institutions were collated to include a total of 70 myeloid-related somatic genes (30 genes in common). 2018 IWG MDS response criteria were used to determine response rate (RR). Disease progression (DP) is defined by progression to MN. The relationship between independent variables and DP and death was assessed using Cox proportional hazards models. Progression-free survival (PFS) and overall survival (OS) were estimated using Kaplan-Meier method. All statistical analysis was performed using SAS. Results: A total of 258 pts were captured by July 2021. The median age was 71 (IQR 63-77) years, and 66% were male. Among 73 (28%) pts with known malignancy history, 27 (37%) pts received previous chemo- or radiation therapy. 27 (10%) pts had non-malignant hematology comorbidities. 91 (35%) had cardiovascular disease, and 33 (13%) had inflammatory disease. (Table 1) The red blood cell and platelet transfusion-dependent rates were 7.3% and 2.3%, respectively. The median number of MTs was 2 (IQR 1-3), with 221 (86%) pts had ≥1 MT, of which 116 (53%) had ≥ 2 MTs. The most common 5 MTs were TET2 (n=78, 30%), SRSF2 (n=50, 19%), DNMT3A (n=47, 18%), ASXL1 (n=40, 16%), and U2AF1 (n=22, 9%) (Figure 1). The median VAF (mVAF) was 28% (IQR: 9.2%, 43%) with VAF < 10% in 47 (18%) and VAF ≥40% in 78 (30.2%) of the MTs. mVAF of the all genes are shown in Figure 2. Among pts with CG abnormalities (n=62, 24%), trisomy 8 and -Y are the most common karyotypes (n=15 for each, 24%) (Table 2). Eighty one (31%) patients received various treatments for CCUS with modest RR, including growth factors (n=47, 18.2%, RR: 25.5%), supportive care (n=23, 9%, RR: 26%), immunoglobulin/immunosuppressive therapy (n=15, 6%, RR: 40%), and DNMTi (n=8, 3%, RR=13%). The median length of follow-up was 15.6 (IQR 6.9-30.6) months. 24 pts progressed to MN, 14 (58.3%) of which were MDS, 8 (33.3%) CMML, and 2 (8.3%) AML. The 2-year PFS was 86.1% (95% CI: 80-93%) with a median PFS of 16.3 (IQR: 3.7, 21) months. In the multivariable model, positive MT of KRAS (HR: 8.4, 95% CI: 1.9-36.9, p=0.005) and CBL (HR: 16.5, 95% CI: 3.7-73.8, p=0.003) were significantly associated with DP. In the functional pathway analysis, having at least 1 splicing factor MT was significantly associated with DP (HR: 2.6, 95% CI:1.2-5.9, p=0.02). TP53 was not significantly associated with DP (HR: 1.2, 95% CI: 0.2-8.7, p=0.88). Having >1 MT (HR: 3.57, 95% CI: 1.19-10.7, p=0.02) compared to a single MT was significantly associated with DP (Figure 3). Over the follow-up period, 35 pts died. The 2-year OS was 81% (95% CI: 74.9-87.9%). In the multivariable model, MT of KRAS (HR: 6.1, 95% CI: 1.8-20, p=0.003), CBL (HR: 7.3, 95% CI: 1.7-31, p=0.007), and FLT3 (HR: 19.9, 95% CI: 2.5-155, p=0.004) were significantly associated with inferior survival. In the functional pathway analysis, MTs in activated signaling pathway were significantly associated with death (HR: 4.1, 95% CI: 1.8-9, p1 MT was not statistically significantly associated with higher risk of death (HR: 1.5, 95% CI: 0.7-3.0, p=0.28) (Figure 4). After adjustment for co-MT status and comorbidities, baseline Hb Conclusion: This large retrospective study summarizes the CCUS pts' characteristics, with different MT patterns and VAF. We confirmed the impact of having >1 MT on DP, but not OS. Genes involved in activated signaling had a significant impact on both DP and OS. TP53 MT was not associated with worse outcome. Findings may be due to limited cases in the particular genes and different gene panels from multiple institutions. A longer follow-up is planned to further describe the predictors for outcome in this ongoing study. Figure 1 Figure 1. Disclosures Komrokji: Jazz: Consultancy, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMSCelgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Acceleron: Consultancy; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy; Taiho Oncology: Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy. Zeidan: BioCryst: Other: Clinical Trial Committees; Kura: Consultancy, Other: Clinical Trial Committees; Ionis: Consultancy; Geron: Other: Clinical Trial Committees; Incyte: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy, Research Funding; Novartis: Consultancy, Other: Clinical Trial Committees, Travel support, Research Funding; Janssen: Consultancy; Cardiff Oncology: Consultancy, Other: Travel support, Research Funding; Loxo Oncology: Consultancy, Other: Clinical Trial Committees; Aprea: Consultancy, Research Funding; AstraZeneca: Consultancy; Agios: Consultancy; BeyondSpring: Consultancy; Gilead: Consultancy, Other: Clinical Trial Committees; Daiichi Sankyo: Consultancy; Jazz: Consultancy; Astex: Research Funding; BMS: Consultancy, Other: Clinical Trial Committees, Research Funding; Acceleron: Consultancy, Research Funding; Pfizer: Other: Travel support, Research Funding; Genentech: Consultancy; Epizyme: Consultancy; Jasper: Consultancy; Astellas: Consultancy; ADC Therapeutics: Research Funding; AbbVie: Consultancy, Other: Clinical Trial Committees, Research Funding. Madanat: Blue Print Pharmaceutical: Honoraria; Stem line pharmaceutical: Honoraria; Onc Live: Honoraria; Geron Pharmaceutical: Consultancy. 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. Griffiths: Celgene/Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Takeda Oncology: Consultancy, Honoraria; Taiho Oncology: Consultancy, Honoraria; Apellis Pharmaceuticals: Research Funding; Novartis: Honoraria; Alexion Pharmaceuticals: Consultancy, Research Funding; Boston Biomedical: Consultancy; Astex Pharmaceuticals: Honoraria, Research Funding; Genentech: Research Funding; Abbvie: Consultancy, Honoraria. Lai: Astellas: Speakers Bureau; Jazz Pharma: 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; Daiichi-Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Speakers Bureau; Macrogenics: 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. Foran: trillium: Research Funding; actinium: Research Funding; kura: Research Funding; boehringer ingelheim: Research Funding; takeda: Research Funding; abbvie: Research Funding; aptose: Research Funding; pfizer: Honoraria; novartis: Honoraria; servier: Honoraria; bms: Honoraria; revolution medicine: Honoraria; OncLive: Honoraria; gamida: Honoraria; certara: Honoraria; sanofi aventis: Honoraria; syros: Honoraria; taiho: Honoraria; h3bioscience: Research Funding; aprea: Research Funding; sellas: Research Funding; stemline: Research Funding. Badar: Pfizer Hematology-Oncology: Membership on an entity's Board of Directors or advisory committees. Desai: Astex: Research Funding; Janssen R&D: Research Funding; Kura Oncology: Consultancy; Takeda: Consultancy; Bristol Myers Squibb: Consultancy; Agios: Consultancy. Ades: ABBVIE: Honoraria; CELGENE/BMS: Honoraria; NOVARTIS: Honoraria; TAKEDA: Honoraria; JAZZ: Honoraria, Research Funding; CELGENE: Research Funding. Brunner: Novartis, Celgene, Takeda, AstraZeneca: Research Funding; Celgene, Forty Seven Inc, Jazz: Other: Advisory Board. Carraway: Celgene, a Bristol Myers Squibb company: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Other: Independent review committee; Stemline: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Other: Independent review committee; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Agios: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astex: Other: Independent review committee; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Prebet: BMS: Research Funding; BMS, Curios, Daichi: Consultancy. 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. Savona: Karyopharm: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy, 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. Al-Kali: Novartis: Research Funding; Astex: Other: Research support to institution.

Introduction A standard therapy for fit older adults (≥60 years) with acute myeloid leukemia (AML) being treated with curative intent consists of induction chemotherapy with cytarabine and an anthracycline followed by 1-4 cycles of shorter course post-remission therapy with cytarabine +/- anthracycline. Historically, HiDAC has been reserved for younger patients due to the high incidence of cytarabine-induced neurotoxicity, febrile neutropenia, and hospital re-admissions in older patients (Mayer et al. 1994). In select older adults (e.g., those with good-risk cytogenetic/molecular abnormalities, or requiring reinduction for persistent AML), the risk/benefit for HiDAC may favor its use. Real world evidence is lacking on the safety of full dose HiDAC (total 18 grams/cycle) in fit older adults in the 60-75 age range. Methods We performed a retrospective analysis of AML patients ≥60 years who received at least one cycle of HiDAC, defined as 3g/m2 every 12 hours for 6 doses, either days 1-3 or days 1, 3, 5, as post-remission therapy or primary re-induction (i.e., after failure of primary induction with 7+3 or CPX-351) between July 1, 2014 and May 28, 2021. AML risk was defined by European LeukemiaNet (ELN) guidelines. All patients had daily neurologic exams including prior to each dose of HiDAC and at the beginning of each nursing shift. The primary endpoint was tolerability, defined as average dose per cycle, rate of dose reductions, incidence of febrile neutropenia, cerebellar toxicity, and rate of hospital re-admissions. Secondary endpoints were overall survival (OS), composite complete remission (CCR) for patients treated with HiDAC re-induction, and duration of relapse-free survival (RFS) (from day 1 of treatment) in all patients. Results From July 2014 to May 2021, 34 patients ≥60-years-old were treated with HiDAC at our center. Median age at HiDAC administration was 64 (60-73) [Table 1]. Approximately half the patients were Hispanic and male and almost all (97%) had ECOG performance scores of 0-1. HiDAC was used as post-remission therapy (following 7+3-type induction in 80%) in 25 patients and as re-induction in 14. Eleven patients (32%) were ELN favorable risk, 8 (25%) were intermediate, and 15 (44%) were poor risk. For post-remission therapy, the average total dose of cytarabine per cycle was 16.6 gm/m2 (6-18 gm/m2) and the median number of cycles was 4 (1-4) [Table 2]; 6 patients (24%) required dose reductions, the most common reason being upcoming allogeneic stem cell transplant (n=4). No cerebellar toxicity was observed. Duration of neutropenia was on average 15 days (7-53) in the re-induction group and 7.5 days (1-29) in the post-remission group, with 23 post-remission patients (92%) receiving granulocyte colony stimulating factors (G-CSF). Eleven hospital readmissions occurred, most commonly (73%) for febrile neutropenia. Early mortality rates were low, with one patient on the post-remission arm and one patient on the re-induction arm dying within 30 and 60 days, respectively, both due to sepsis. Median OS was 15.8 months (95% CI 0-31.8) in patients who received post-remission HiDAC, with 44% of patients still alive with a median follow up of 17.2 months (95% CI 7.2-55.8). Favorable risk patients (n=11) receiving post-remission HiDAC had median OS of 15.8 months (95% CI 0-43.1), while intermediate/poor risk patients (n=14) had median OS of 11.3 months (95% CI 9.3-13.2) [p=0.53]. Median OS was 9.8 months (95% CI 2.5-17.1) in patients who received HiDAC re-induction, with 29% of patients still alive with a median follow up of 28.6 months (95% CI 16.6-39.9) [Table 3]. Five patients (36%) achieved CCR after HiDAC re-induction, all of whom went on to receive post-remission HiDAC. Median RFS was 8.5 months for re-induction and 8.8 months for post-remission patients [Table 3]. Conclusions HiDAC (18 grams) can be safely given to select patients over age 60. Critical to tolerability is rigorous screening of "fitness," limiting the upper age receiving HiDAC to 75, ensuring adequate renal function and euvolemia, and advances in supportive care. Encouraging survival outcomes were observed in older adults receiving post-remission or re-induction HiDAC, independent of ELN risk. Figure 1 Figure 1. Disclosures Bradley: AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Sekeres: Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Watts: Rafael Pharmaceuticals: Consultancy; Genentech: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Aptevo Therapeutices: Research Funding.

Introduction Venetoclax in combination with a hypomethylating agent (VEN-HMA) has become a standard of care for older or unfit patients with newly diagnosed AML. Although primarily administered in the outpatient setting, VEN-HMA is associated with significant cytopenias and infectious complications, requiring careful monitoring and dose adjustments. Patients treated with VEN-HMA on clinical trials had a median age of ~75 years. The optimal dose and schedule, safety, and efficacy of VEN-HMA in octo- and nonagenarians is not clearly defined. Methods We performed a retrospective analysis of AML patients ≥80-years-old who received at least 1 day of VEN-HMA at our institution from 11/2018 to 7/2021. Patients with de novo or secondary AML with or without prior HMA or chemotherapy were included. Venetoclax starting dose was 200-400 mg for 14-28 days. Dose adjustments for drug interactions with azole anti-fungals were implemented. HMA was started at 50-75 mg/m2 for 5-7 days of azacitidine or 20mg/m2 for 5 days of decitabine. Dose reduction was defined as any decrease from the starting dose and schedule. Patients who did not complete cycle 1 were included in the overall survival and safety analysis but excluded from response assessment. Results Among 21 patients ≥80-years-old treated with VEN-HMA (20 newly diagnosed, 1 relapsed/refractory), median age was 82 years (range: 80-89) (Table 1), 57% had antecedent MDS, and 38% received HMAs previously. Most patients (81%) were ELN adverse risk, 38% had a complex karyotype, 24% had a TP53 mutation, and 43% had ECOG PS of 2-3. Median overall survival for all patients was 8.0 months (0.5-31.4 months). At time of analysis, 12 patients (57%) were still alive and in remission on VEN-HMA with a median follow-up of 11.5 months (range 2.3-31.4 months). Five patients (24%) died during cycle 1 from sepsis. Of these 5 patients, 4 had a TP53 mutation, 3 had prior MDS, and 3 had received prior therapy for lymphoma. In the remaining 16 patients, median overall survival was 9.9 months (2.3-31.4 months) and the CR/CRh rate was 81% (13/16 patients). Median duration of response was 8.9 months (range 1.0-30.0). Consistent with previous reports, all patients who achieved CR/CRh did so by the end of cycle 2 (median 2 cycles). Most patients also received the standard dose and schedule of VEN (75%) and HMA (57%) during the first cycle. All patients (100%) required venetoclax dose and schedule reduction, with a median final venetoclax dose of 200 mg and duration of 14 days. Average final cycle length was 35 days. Most patients (69%) also required dose reduction of HMA. Median duration of treatment was 7.5 months (range 0.5-31.4). Treatment emergent grade 3-4 anemia occurred in 67% of patients, thrombocytopenia in 81%, and neutropenia in 86%; 17 patients (81%) had treatment emergent febrile neutropenia. There were no infectious deaths in patients who survived cycle 1. The median number of neutropenic fever episodes per patient was 1 (0 to 2). The 4 deaths after cycle 1 were due to progressive disease (n=3) or relapse (n=1). Conclusion VEN-HMA can be safely and effectively given to octogenarians with careful monitoring and dose adjustments. All patients required dose reduction of venetoclax after CR/CRh was achieved, and most also required adjustment of HMA. Despite this, over half of patients achieved durable remissions. The greatest risk of infectious death was in the first cycle, in patients who were heavily pre-treated and enriched for TP53 mutations. When compared to historical controls, outcomes in octogenarians who survive the first cycle appear similar to younger age groups. This work highlights the need for a prospective multi-center effort to optimize the dose and schedule of VEN-HMA in older patient populations. Figure 1 Figure 1. Disclosures Bradley: AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Sekeres: Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Watts: Rafael Pharmaceuticals: Consultancy; Genentech: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Aptevo Therapeutices: Research Funding.

INTRODUCTION: Luxeptinib (CG-806) is a potent oral small molecule inhibitor of the wild type and all mutant forms of the FLT3 kinase, including ITD, D835Y, and F691L. Luxeptinib simultaneously suppresses additional signaling pathways in AML cells (CSF1R, PDGFRα, TRK, SYK, BTK, LYN, AKT, ERK, MAPK), kills primary AML cells insensitive to other FLT3 inhibitors at pM and low nM concentrations, and shows enhanced activity in combination with venetoclax. Patient-derived AML cells retain sensitivity to luxeptinib even when harboring mutations of NPM1, IDH1, ASXL1, or TP53. Luxeptinib is being evaluated in a Phase 1a/b trial in patients with relapsed or refractory (R/R) AML (NCT04477291). AIMS: The primary objectives are to assess the safety and tolerability of luxeptinib and to determine the recommended expansion dose for future clinical trials in patients with R/R AML. Key secondary objectives include elucidation of the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics, and evidence of antitumor activity. METHODS: The study is enrolling patients with relapsed or refractory de novo AML, secondary AML, or therapy-related AML. Luxeptinib is administered continuously as oral capsules BID in 28-day cycles, in ascending cohorts of 3 or 4 patients. Treatment emergent adverse events (TEAEs) and tumor responses are evaluated using CTCAE and European Leukemia Net criteria, respectively. RESULTS: As of June 7, 2021, a total of 10 patients (median age 74.5 years, 6 (60%) FLT3-ITD, and 4 (40%) FLT3-WT per local labs) with a median of 3 prior treatments (range, 1 - 8) have been treated with luxeptinib at dose levels of 450 mg BID (n=6) and 600 mg BID (n=4). Majority of patients (≥ 60 %) were RBC and / or platelet transfusion dependent. Drug related TEAEs at Grade ≥ 3 included decreased platelet count, anemia, and pericardial effusion (n=1, 10% each). One patient, who received 450 mg BID (Cohort 1), had Grade 3 pericardial effusion, was assessed initially as a DLT possibly related to luxeptinib and led to expansion of Cohort 1 to treat 6 patients. No DLT was observed in the other 5 patients in Cohort 1 and supported dose escalation to 600 mg BID (Cohort 2), where no DLT was observed in 4 patients and escalated to 750 mg BID (Cohort 3). The steady-state (C min) plasma levels of luxeptinib in the patients treated with 600 mg BID were 0.6 - 1.6 µM by the end of Cycle 1. PD analysis demonstrated luxeptinib in the plasma of patients reduced FLT3 phosphorylation > 85% at concentrations > 0.2 µM while significantly reducing phosphorylation of ERK, SYK and PDGFRα in MOLM14 and / or EOL-1 reporter cells in a plasma inhibitor activity assay, demonstrating target engagement by luxeptinib. Disease evaluation via flow cytometry, PCR-based FLT3 mutation tests and targeted exome sequencing on bone marrow and peripheral blood revealed anti-leukemic activity of luxeptinib in 3 relapsed AML patients with FLT3-ITD mutations in Cohort 1. One heavily pretreated AML patient (8 prior regimens including alloSCT and FLT3 inhibitors gilteritinib and crenolanib) had 99% reduction of blasts in peripheral blood (from 6.38x10 3/µL at C1D1 to 0.09x10 3/µL at C1D15), though the decrease in blasts reversed during Cycle 2. Another AML patient (2 prior regimens) had FLT3-ITD VAF 0.62 at screening, which decreased 80% to 0.12 by C4D9. This patient had simultaneous reductions of clones with mutations of GATA2 R337K, TET2 R1359C, SRSF2 P95L and ASXL1 E635R, whereas a PTPN11 mutant clone emerged. MRD-negative complete remission (CR) was confirmed in one FLT3-ITD AML patient (6 prior regimens including 2 alloSCT and FLT3 inhibitor sorafenib) at Cycle 5 of treatment evidenced by reduction of FLT3-ITD VAF and blasts in bone marrow to below limit of detection (LOD) of PCR-based FLT3-ITD assay and high-sensitivity flow cytometry (LOD < 0.1%), respectively. CONCLUSIONS: As of June 7, 2021, luxeptinib is well tolerated at dose levels of 450 and 600 mg BID over multiple cycles and escalated to 750 mg BID (Cohort 3). Pharmacodynamic studies documented inhibition of FLT3 signaling, and anti-leukemic activity has been observed in heavily pretreated relapsed FLT3-ITD AML patients as evidenced by significant reduction of FLT3-ITD VAF and blasts in bone marrow and / or peripheral blood. One FLT3-ITD AML patient has had confirmed MRD negative CR and continues treatment. Enrollment of patients with R/R AML in Cohort 3 is ongoing and updated clinical data will be presented at the meeting. Disclosures Goldberg: Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celularity: Research Funding; DAVA Oncology: Honoraria; Arog: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Research Funding; Prelude Therapeutics: Research Funding; Aptose: Consultancy, Research Funding; Aprea: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Koller: Novartis: Consultancy. Altman: Amgen: Research Funding; Astellas: Consultancy, Other: Advisory Board, Research Funding; Kura Oncology: Consultancy; Biosight: Consultancy, Other: Travel fees, Research Funding; Kura: Research Funding; GlycoMimetics: Other: Participation on an advisory board; Daiichi Sankyo: Consultancy; ALZ Oncology: Research Funding; Syros: Consultancy; Theradex: Consultancy, Other: Advisory boards; Kartos: Research Funding; AbbVie: Consultancy, Other: Advisory Board, Research Funding; Aprea: Research Funding; BMS: Research Funding; Boehringer Ingelheim: Research Funding; Fujifilm: Research Funding; Immunogen: Research Funding. Cherry: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Zhang: Aptose Biosciences, Inc.: Current Employment. Rastgoo: Aptose Biosciences, Inc.: Current Employment. Benbatoul: Aptose Biosciences, Inc.: Current Employment. Jin: Aptose Biosciences, Inc.: Current Employment. Su: Aptose Biosciences, Inc.: Current Employment. Marango: Aptose Biosciences, Inc.: Current Employment, Current equity holder in publicly-traded company. Howell: Aptose Biosciences, Inc.: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees, Research Funding. Rice: Aptose Biosciences, Inc.: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties; Oncolytics Biotech Inc.: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Bejar: Astex: Consultancy; Epizyme: Consultancy, Honoraria; Silence Therapeutics: Consultancy; BMS: Consultancy, Research Funding; Gilead: Consultancy, Honoraria; Aptose Biosciences, Inc.: Current Employment, Current equity holder in publicly-traded company; Takeda: Research Funding.

Introduction: Liposomal daunorubicin and cytarabine (CPX-351) was approved based on data which showed improved overall survival (9.56 v 5.95 months; p = .003) and remission rates (47.7% v 33.3%; p = .016) compared to conventional cytarabine and daunorubicin (7+3) chemotherapy in older patients with newly diagnosed secondary acute myeloid leukemia (sAML). Patients receiving CPX-351 had prolonged time to neutrophil and platelet count recovery compared to 7+3, which was not associated with adverse outcomes (Lancet et al, JCO 2018). Based on these data, our center adopted CPX-351 as a first-line agent in this patient population. Considering the significant cost differences and delays in count recovery, we conducted a comparison of outcomes in patients who received CPX-351 versus 7+3 at our center. Methods: The objective of this study was to compare efficacy and safety of CPX-351 versus 7+3 in patients with sAML. Primary outcome was response rate as defined by CR or CRi. Secondary outcomes included duration of neutropenia, incidence of invasive fungal infections (IFIs), and number of patients proceeding to allogeneic hematopoietic cell transplant (HCT). Patients with sAML receiving induction with 7+3 (daunorubicin dosed at 60 or 90 mg/m2 per treating physician's discretion) or CPX-351 from July 2014 to April 2020 were reviewed. Secondary AML was defined as: AML with a history of myelodysplastic syndrome (MDS) or chronic myelomonocytic leukemia (CMML), AML with myelodysplasia-related changes, or therapy-related AML. Patients with prior myeloproliferative neoplasms, myelofibrosis, or FLT3 mutations were excluded. Patient characteristics were summarized using descriptive statistics (TABLE 1) including mean for continuous measures and proportions and frequencies for categorical measures. The association between continuous variables and patient groups were assessed using ANOVA or Student's t-test. The associations between categorical variables and patient groups were evaluated using Chi-square test. Results: Over the study period, 65 patients with sAML received induction therapy with either CPX-351 (n = 31) or 7+3 (n = 34). Of these, 61 patients had an evaluable bone marrow biopsy at count recovery. The data is summarized in Table 2. The response rates (CR or CRi) were no different (36% 7+3 vs 36% CPX-351, p = 0.958) among the study population. Longer duration of neutropenia was observed with CPX-351 (33 days 7+3 vs 47 days CPX-351, p = 0.026). More patients in the 7+3 arm proceeded to allogeneic HCT; however, this was not statistically significant (59% 7+3 vs 39% CPX-351, p = 0.105). In an efficacy subgroup analysis of patients with TP53 mutation, there was no difference in response rates (33% 7+3 vs 11% CPX-351, p = 0.224). There was no difference in IFI between the groups (38% 7+3 vs 42% CPX-351, p = 0.761). Upon further analysis of IFI characteristics, there was no difference in choice of mold-active vs non mold-active prophylaxis (ppx) and the incidence of IFIs (40% mold ppx vs 39% non-mold ppx, p = 0.91). Patients with baseline neutropenia prior to induction did not have increased risk of IFIs (65% 7+3 vs 74% CPX-351, p = 0.626). Additionally, there were no between group differences in incidence of IFIs in patients who were neutropenic prior to induction. Conclusions: In the evaluable dataset of patients receiving 7+3 or CPX-351, there was no difference in CR/CRi rate between the two subgroups. There was a longer duration of neutropenia in the CPX-351 group without increased incidence of IFI. However, we report a higher incidence of IFI compared to the study population in Lancet et al (18% Lancet vs 40% Miami) despite appropriate anti-fungal prophylaxis, which may be due to patient selection on the clinical trial, demographic differences (e.g., age, ethnicity), or locoregional environmental factors. In our population, a greater percentage of patients who received 7+3 proceeded to allogeneic HCT. While this study was not powered to detect a significant difference between the two regimens and these findings require validation in larger cohorts, they do not support superior outcomes in patients who receive CPX-351. Data on differences in hospital costs will also be presented. Future directions include a larger multi-center real-world analysis to evaluate patient outcomes, safety, and the financial implications of these two regimens. Disclosures Watts: Genentech: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Rafael Pharma: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Aptevo Therapeutics: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees.

Background: The normal function of isocitrate dehydrogenase 1 (IDH1) is to catalyze the conversion of cytoplasmic isocitrate to α-ketoglutarate (aKG) in the Krebs cycle. In hematologic malignancies a hotspot mutation at arginine 132 within the conserved active site of IDH1 leads to loss of the expected Krebs Cycle reaction as well as production of the oncometabolite 2- hydroxyglutarate (2-HG). In acute myeloid leukemia (AML) increased cellular 2-HG levels has been shown to impact the tumor microenvironment and promotes tumorigenesis via paracrine stimulation as well repression of the tumor associated immune system. Ivosidenib (AG-120) is a small molecule inhibitor of mIDH1 and is FDA approved for the treatment of patients (pts) with relapsed refractory IDH1 mutant AML. Ivosidenib is known to lower 2-HG levels, independent of response. By reducing 2-HG levels that promote immune escape of IDH-mutant tumors with ivosidenib, we hope to harness the known programmed death receptor pathway dysregulation in AML and high risk myelodysplastic syndrome (MDS). Study Design and Methods: IVO-NIVO is a single arm, multi-institutional phase II investigator initiated clinical trial with a safety cohort to confirm safety and tolerability of combination AG-120 and nivolumab. To be included pts must have MDS or AML with a documented IDH1 mutation in blood or bone marrow within 30 days of inclusion based on mutational testing by PCR or sequencing in a CLIA certified laboratory and be willing to undergo a bone marrow biopsy. Pts will initially start therapy with AG-120, 500mg by mouth daily for 1 cycle. A cycle is defined as 28 days of therapy. On cycle 2 day 1 enrolled pts will receive nivolumab 480 mg that will subsequently be infused every four weeks. Disease response to treatment will be serially assessed through the evaluation of blood (at least monthly) and bone marrow biopsies and aspirates. A complete response assessment will be performed after 6 cycles of therapy. Transplant eligible pts may proceed to allogeneic stem cell transplant (ASCT) if complete response (CR) or morphologic complete remission with incomplete count recovery (CRi) is achieved. Pts that are not eligible for ASCT will continue to receive AG-120- nivolumab combination therapy until documented progression or unacceptable toxicity (figure 1). Safety Cohort: We will have an interim safety analysis after the first 6 pts finishing the first cycle of combination therapy to ensure dosing is safe and tolerable. Pts will undergo clinical assessment with each cycle of therapy, with particular attention to known toxicities like differentiation syndrome that may be life threatening. If 0 to 1 of the first 6 subjects experienced unacceptable toxicities the study will continue as planned. If 2 pts experienced unacceptable toxicities, accrual will be temporarily suspended in order to conduct a review of safety data. If after review, a safety issue is identified and can be corrected, the protocol will be amended accordingly, and enrollment will restart. If an additional 2 pts (4 of 12) or more experience an unacceptable toxicity the patient will be taken off trial and the trial will be terminated. Statistical plan: It is estimated that 45 pts will be enrolled on trial. Using optimal Simon Stage 2 minimax design, if less than 7 of the first 16 pts respond the treatment will be study will be stopped for futility (type 1 error 0.05, type 2 error 0.2). Primary endpoint: We aim to improve the cumulative response rate after 6 cycles of therapy from 40% to 60% (Two-sided alpha risk of 0.05, 1-Beta of 0.8 = 38 pts + 7 additional pts for potential drop-off observed in prior studies) in pts with mIDH1 relapsed/ refractory AML and MDS. Based on published data, it is known that overall response rate is approximately 40% to single agent AG-120 in the relapsed/ refractory IDH1 mutant AML population. Therefore, we expect a 20% ORR improvement compared to historical control after 6 cycles of treatment, based on MDS International Working Group 2006 criteria and AML MDS International Working group MDS/AML criteria. Secondary endpoints: Progression-free survival (the interval between the time of initiation of olaparib to the time of documentation of olaparib failure or last follow-up), overall survival (the interval between the time of initiation of olaparib to the time of death or last follow-up) and percentage of pts that can be bridged to ASCT. Disclosures Prebet: novartis: Honoraria; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; pfizer: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Boehringer Ingelheim: Research Funding; Genentech: Consultancy; novartis: Honoraria; pfizer: Honoraria; novartis: Honoraria; Boehringer Ingelheim: Research Funding; novartis: Honoraria; pfizer: Honoraria; pfizer: Honoraria; Tetraphase: Consultancy; Agios: Consultancy, Research Funding; pfizer: Honoraria; novartis: Honoraria; Boehringer Ingelheim: Research Funding. OffLabel Disclosure: We will use Ivosidenib and nivolumab in combination as a part of a clinical trial to improve care of patients with relapsed/ refractory AML and MDS

Background: Recurring mutations have been identified in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) which translate to therapeutic targets. Isocitrate dehydrogenase-1 and -2 (IDH1/2) mutations occur in ~20% of AML, and up to 12% of patients with MDS. Three conserved mutational hotspots in the IDH enzymes alter their function and lead to the production of (R)-2-hydroxyglutarate (2HG), an oncometabolite with numerous downstream effects, including impaired DNA damage repair. Specifically, homologous recombination (HR) is impaired by inhibiting the function of histone demethylases that are critical for HR and recruitment of the HR machinery to sites of DNA damage. In HR deficient tumors poly-ADP ribose polymerase (PARP) enzymes mediate a key salvage pathway. PARP inhibition in HR deficient tumors leads to synthetic lethality via simultaneous inhibition of HR and SSB mediated DNA repair. Our group previously demonstrated synthetic lethality with PARP inhibition in IDH mutant cells lines, and other IDH mutant models including primary patient-derived cell lines and genetically-matched tumor xenografts. Study Design and Methods: The PRIME trial (NCI10264) is a proof of concept, biomarker-driven, multi-institution, phase II open label clinical trial to assess the overall response of IDH1/2 mutant relapsed/refractory AML and MDS to PARP inhibitor monotherapy with olaparib. The clinical trial is executed by the Experimental Therapeutics Clinical Trials Network of the NCI. The Cancer Therapy Evaluation Program will provide olaparib. Eligibility criteria include documented IDH1 or IDH2 mutation in blood or bone marrow within 30 days of enrollment based on mutational testing by PCR or sequencing in a CLIA certified laboratory and willingness to undergo a bone marrow biopsy. Patients will be treated with olaparib 300 mg q12hrs each day of a 28-day cycle, using a tablet formulation, until disease progression, unacceptable toxicity, withdrawal of consent or death. Blood and bone marrow samples for 2-HG analysis will be collected prior to starting therapy and after 1 cycle (28 days), cycle 2, 3, 6, 9, 12 or when there is concern for disease progression (Figure 1). A Simon two-stage optimal design will be used to test the null (ORR=10%) versus the alternative hypothesis (ORR=40%) in each arm. In the first stage, 9 patients will be accrued in each arm. If one or fewer responses are observed in these 9 patients, that arm will be stopped early for futility. Otherwise, 11 additional patients will be accrued for a total of 18 in each arm. We reject the null hypothesis if at least 5 responses are observed in these 20 patients. In each arm, we have approximately 90% power to detect a 30% increase in ORR at a one-sided type I error rate of 0.05. Primary endpoint: Overall response rate (ORR) of 40%, i.e., a 30% ORR improvement (40% vs. historical control ORR = 10%) based on MDS International Working Group 2006 criteria and AML MDS International Working Group 2003 criteria after 6 cycles of treatment. Cumulative ORR will include complete remission, complete remission with incomplete blood count recovery, partial response, and bone marrow complete remission. Secondary endpoints: Progression-free survival (the interval between the time of initiation of olaparib to the time of documentation of olaparib failure or last follow-up) and overall survival (the interval between the time of initiation of olaparib to the time of death or last follow-up) for the trial. Exploratory studies: The PRIME trial will also test the utility of 2-HG and DNA damage markers such as γ-H2AX as potential biomarkers of response to olaparib. Using multiple viability assays on leukemia cell lines and bone marrow cultures we will assess synergistic therapeutic combinations to further improve outcomes in this patient population. To confirm efficacy in vivo without undue toxicity, promising combination therapies will be confirmed in cytokine-humanized immunodeficient "MISTRG" mice. We will also examine the impact of PARP inhibitors on the genomic, proteomic, metabolomic and immunologic landscape of IDH 1/2-mutant hematologic malignancies using DNA whole exome sequencing (WES), RNA-Seq, and liquid chromatography-mass spectrometry assessment of oncometabolites. Disclosures Bindra: Cybrexa: Consultancy, Equity Ownership. Prebet:pfizer: Honoraria; pfizer: Honoraria; pfizer: Honoraria; Boehringer Ingelheim: Research Funding; pfizer: Honoraria; Tetraphase: Consultancy; novartis: Honoraria; novartis: Honoraria; Genentech: Consultancy; Boehringer Ingelheim: Research Funding; novartis: Honoraria; Boehringer Ingelheim: Research Funding; Agios: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; pfizer: Honoraria; novartis: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; novartis: Honoraria. OffLabel Disclosure: We will be using PARP inhibitors as a novel therapy for patients with relapsed or refractory AML and high risk MDS based on preclinical data.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are heterogeneous clonal disorders. Isocitrate dehydrogenase-1 and -2 (IDH1/2) mutations are detected in ~20% of AML and ~5% of MDS, in which they confer gain of a neomorphic function that leads to the production of (R)-2-hydroxyglutarate (2HG). Targeted inhibition of mutant IDH1/2 has resulted in significant responses in IDH1/2 mutant MDS and AML but is not curative and patients relapse (Stein et al. Blood 2016, DiNardo et al. N Engl J Med 2018). 2HG accumulation inhibits the function of histone demethylases (KDM4A and KDM4B) that are critical for the homologous recombination (HR) DNA repair pathway and consequently for the repair of DNA double strand breaks (DSBs) (Mallette et al. EMBO J 2012, Sulkowski et al. Sci Transl Med 2017). In HR deficient tumors, Poly-ADP-Ribose Polymerase (PARP) is essential for DNA single strand break (SSB) repair. In IDH mutant tumors PARP inhibitors induce synthetic lethality by suppressing the repair of SSBs, which eventually get converted into DSBs (Javle and Curtin Br J Cancer 2011). We previously demonstrated that in AML, IDH1/2 mutations impair DNA damage response by inducing a defect in HR, and that this renders leukemia cells susceptible to PARP inhibitors in vitro. We hypothesized that this vulnerability would also exist in IDH mutant MDS and more importantly, that this vulnerability would persist in MDS/AML resistant to IDH1/2 inhibitors. To determine whether PARP inhibition targets IDH mutant MDS/AML in vivo, we took advantage of 2 syngeneic mouse models of MDS and AML relying on co-mutation of SRSF2/IDH2 and FLT3/IDH2, respectively. Olaparib (PARP inhibitor) effectively targeted IDH2 mutant but not IDH2 wild type MDS/AML (Fig. 1A). We next sought to determine whether PARP inhibition mediated synthetic lethality persists in MDS/AML resistant to targeted IDH inhibition. We transduced IDH2 mutant murine cells with IDH2 WT or IDH2 MUT lentiviral vectors carrying one of two published resistance mutations. While these resistance mutations conferred resistance to the targeted IDH2 inhibitor Enasidenib, cells remained sensitive to Olaparib (Fig. 1B). Patient MDS/AML is heterogeneous and in general carries additional genetic mutations and epigenetic alterations. We therefore engrafted IDH1/2 WT and MUT MDS/AML patient samples in cytokine humanized immunodeficient mice and treated with vehicle of Olaparib. Engrafted mice were assigned to vehicle or Olaparib 8 weeks after transplantation based on equal engraftment levels determined by BM aspiration. Mice were treated with vehicle or Olaparib via IP injection for 21 days. Human engraftment levels and plasma 2-HG levels were significantly reduced in Olaparib treated animals when compared to pre-treatment and vehicle-treated mice (Fig. 1C). Of note, when equal numbers of huCD34+ cells from vehicle or Olaparib treated mice were transplanted into next generation mice, engraftment was significantly higher for recipients of human cells from vehicle than Olaparib treated mice, suggesting that Olaparib is toxic to leukemia initiating cells. In contrast, IDH WT MDS/AML was insensitive to Olaparib treatment (Fig. 1C). In conclusion, PARP inhibition is effective in vivo against IDH mutant MDS/AML and can overcome targeted IDH inhibitor resistance. Disclosures Flavell: Zai labs: Consultancy; SMOC: Equity Ownership; Troy: Equity Ownership; Artizan Biosciences: Equity Ownership; GSK: Consultancy; Rheos Biomedicines: Equity Ownership. Prebet:Boehringer Ingelheim: Research Funding; Boehringer Ingelheim: Research Funding; novartis: Honoraria; pfizer: Honoraria; Boehringer Ingelheim: Research Funding; Agios: Consultancy, Research Funding; novartis: Honoraria; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; pfizer: Honoraria; Genentech: Consultancy; pfizer: Honoraria; novartis: Honoraria; Tetraphase: Consultancy; novartis: Honoraria; pfizer: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; novartis: Honoraria; pfizer: Honoraria. Bindra:Cybrexa: Consultancy, Equity Ownership.

Introduction: Aggressive T cell lymphomas (TCL) are a heterogenous group of lymphomas that are frequently associated with poor outcomes. Autologous stem cell transplantation (ASCT) is recommended according to the NCCN guidelines and by practice standards for most subtypes as a consolidation for patients in first remission. A large prospective study of up-front ASCT by the Nordic Lymphoma group identified age, ECOG performance status Methods: We retrospectively analyzed data from consecutively treated patients (pts) with aggressive T-cell lymphomas who underwent ASCT at our institution from July 2009 to February 2019. Patient and disease characteristics were summarized using descriptive statistics. Kaplan-Meier analysis was used to estimate progression free survival (PFS) that was defined as the time from SCT to the first evidence of recurrence, and overall survival (OS) that was defined as the time from SCT to death or last institutional follow up with a hematologist. We collected data on age, co-morbidities, disease subtype, stage, response to therapy and treatment both pre and post SCT. Flow cytometry was obtained at diagnosis and phenotype of atypical circulating cells was compared with immunophenotype from tumor biopsy specimens. Results: 50 pts with TCL who received ASCT were identified for this analysis. Of this population, 41 (80%) of pts had peripheral blood flow available at the time of initial diagnosis. T-cell lymphoma types included peripheral T cell lymphoma not otherwise specified (PTCL NOS, 17 pts), angioimmunoblastic T cell lymphoma (AITCL, 15pts), ALK negative anaplastic large cell lymphoma (ALCL, 1pt), enteropathy-type T-cell lymphoma (EATL, 2pts), extranodal natural killer T-cell lymphoma (NKTCL, 2pts) and panniculitis like T cell lymphoma (2 pts) (Table 1). Median age of the cohort was 62 years (range 20-75 years) and all patients included had an ECOG PS 0-1 at the time of diagnosis. The majority had stage 4 disease (36/41, 87.8%), but analysis included a small number of patients with stage 2 (1/41, 2.4%) and stage 3 (4/41,9.7%) disease. Bone marrow involvement by morphologic criteria was noted on bone marrow biopsy in 8/41 (19.5%) pts; bone marrow was negative in 28/41 or 61% pts and not evaluated in 8/41 or 19.5% pts. Flow cytometry of peripheral blood performed as part of initial staging was positive for circulating malignant cells in 13/41 pts (31.7%) at the time of diagnosis. All patients underwent ASCT in first remission. The median PFS and OS were 15.2 and 29.9 months respectively in the flow positive group, while neither median PFS nor OS were reached in the flow negative group (Figures 1 and 2). Flow cytometry results from time of diagnosis was not strongly associated with PFS (log rank, p = 0.39), however, it was associated with overall survival (log rank, p = 0.012). There were 11 deaths in the cohort- 4 in the flow negative group and 7 in the flow positive group. Further, when bone marrow involvement was evaluated, 7 of 13 pts with positive flow cytometry (53.8%) and 5 of 28 (17.8%) pts with negative flow cytometry had BM involvement, suggesting a correlation between positive bone marrow and detection of lymphoma cells in the peripheral blood at the time of diagnosis. Conclusions: We demonstrate in our cohort of patients that detection of circulating lymphoma cells at diagnosis by flow cytometry was associated with a worse outcome in patients with aggressive T cell lymphomas undergoing ASCT as a consolidation in first remission. Larger cohorts will be needed to validate these findings, but these results suggest peripheral blood involvement by sensitive flow cytometry may identify patients with worse outcomes who might benefit from a more aggressive strategy such as allogeneic stem cell transplantation or alternative consolidation strategies. Disclosures Huntington: Bayer: Consultancy, Honoraria; Pharmacyclics: Honoraria; Celgene: Consultancy, Research Funding; DTRM Biopharm: Research Funding; Genentech: Consultancy; AbbVie: Consultancy. Isufi:Celgene: Consultancy; Novartis: Consultancy; Astra Zeneca: Consultancy. Foss:Seattle Genetics: Consultancy, Other: fees for non-CME/CE services ; Mallinckrodt: Consultancy; miRagen: Consultancy; Spectrum: Other: fees for non-CME/CE services ; Eisai: Consultancy; Acrotech: Consultancy.