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The combination of venetoclax with hypomethylating agents (VEN-HMAs) showed promising activity in newly diagnosed and relapsed/refractory (r/r) acute myeloid leukemia (AML). Treatment with VEN-HMAs results in prolonged cytopenia, thereby exposing patients to invasive fungal infections (IFIs). Here, we retrospectively studied a cohort of 119 AML patients treated with VEN-HMAs and analyzed the occurrence of IFIs, as well as our practice of antifungal prophylaxis, with the aim to identify the nature and risk factors for IFIs and their association with the type of antifungal prophylaxis used. The intended antifungal prophylaxis was micafungin in 38% of patients, azoles in 41% of patients, and none in 21% of patients. Older age was associated with no antifungal prophylaxis or micafungin use and lesser use of azoles (P = .043). We recorded 15 (12.6%) patients who developed probable or proven IFIs, with a median onset of 72 days (range, 35-281) after starting therapy. IFIs were more common among nonresponders compared with responders to VEN-HMA therapy (22% vs 6%, P = .0132) and in r/r compared with newly diagnosed AML (19% vs 5%, P = .0498); however, the antifungal prophylaxis used, patient age, hypomethylating agent schedule, history of prior allogeneic transplant, and initial neutropenia duration did not influence the development of IFIs during therapy. We conclude that the overall risk of IFIs during VEN-HMA therapy is low. The risk of IFIs is higher in nonresponders and in those who were treated in the r/r setting; these patients need reevaluation of their antifungal prophylaxis to minimize the risk of IFIs during therapy.

Efficacy of PTCy after mismatched unrelated donor (MMUD) HCT is unknown. In this pilot clinical trial, we enrolled 38 patients with hematologic malignancies scheduled to undergo MMUD-HCT (≥6/8 HLA-matched donors) onto 1 of 2 conditioning strata: myeloablative using fludarabine and fractionated total body irradiation (n = 19) or reduced intensity with fludarabine/melphalan (n = 19). Graft source was peripheral blood stem cells (PBSCs), and GVHD prophylaxis was PTCy, tacrolimus, and mycophenolate mofetil. Patients’ median age was 53 years (range, 21-72 years). Median number of HLA mismatches was 2 (range, 1-4) of 12 loci. Twenty-three patients (61%) were considered racial (n = 12) or ethnic (n = 11) minorities. Median time to neutrophil engraftment was 16 days (range, 13-35 days). With a median follow-up of 18.3 months (range, 4.3-25.0 months) for surviving patients, 1-year overall survival (OS) and GVHD-free/relapse-free survival (GRFS) were 87% (95% confidence interval [CI]: 71-94) and 68% (95% CI: 51-81), respectively. Cumulative incidence of nonrelapse mortality at 100 days and 1 year were 0% and 11% (95% CI: 4-27), respectively, whereas relapse/progression was 11% (95% CI: 4-27). Cumulative incidence of 100-day acute GVHD grades 2-4 and 3-4 and 1-year chronic GVHD were 50% (95% CI: 36-69), 18% (95% CI: 9-36), and 48% (95% CI: 34-68), respectively. The rate of moderate/severe chronic GVHD was 3% in the entire cohort. We showed highly promising OS/GRFS rates with an acceptable risk profile after PBSC-MMUD-HCT with PTCy. This trial was registered at www.clinicaltrials.gov as #NCT03128359.

Background: CTLA-4 blockade with ipilimumab (IPI) has modest activity in hematologic malignancies relapsed post allogeneic hematopoietic cell transplantation (allo-HCT) (Davids M, NEJM). Adding decitabine (DAC) to IPI may increase efficacy of this approach in myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML), and we further asked the extent to which alloreactivity contributed to this activity. Here, we present safety (Table 1) and clinical activity (Figure 1) from a phase I, multicenter, investigator-initiated study (CTEP 10026) of DAC plus IPI in pts with R/R MDS/AML with (Arm A) and without (Arm B) prior HCT. Methods: Pts ≥ 18 y with R/R MDS (≥ 5% blasts), R/R AML or untreated secondary AML were eligible. Prior HMA was permitted but trial was later amended to exclude those with disease progression on HMA therapy within 12 weeks of study entry. Pts post allo-HCT (Arm A) were required to be > 3 mo from donor cell infusion, have no prior acute GVHD Gr III or higher, be > 2 weeks off of immunosuppression and have donor T-cell chimerism ≥ 20%. Treatment was given in 28-day cycles with a lead-in single agent DAC (cycle 0) followed by combination DAC + IPI for up to a year. DAC infusion was given at 20 mg/m2 days 1-5. IPI infusion was given at 3 mg/kg (DL0), 5 mg/kg (DL1) or 10 mg/kg (DL2) on day 1 of cycles 1-4, 5, 7, 9 and 11. DLT was defined as ≥ Gr 3 non-hematologic adverse event (AE), acute GVHD, and steroid-refractory immune-related AE within 8 weeks of first IPI dose. Results: At data cut-off, 32 of 39 enrolled pts received at least 1 dose of DAC+IPI; 4 of 7 did not move on to C1D1 due to AML-related complications. Median age was 72 y (range 29-85); 25 had AML and 7 had MDS. Median number of prior regimens was 2 (range, 0-5). Twenty of 32 pts had received prior HMA therapy. A median of 3 IPI doses were given (range, 1-8). NGS performed on screening marrows using an 88-gene panel revealed mutations most commonly in ASXL1 (n=9), RUNX1 and STAG2 (n=6 each), and DNMT3A, NRAS and TP53 (n=5 each). Arm A (Post allo-HCT): Sixteen pts received DAC+IPI across the 3 DLs (7 at DL0, 3 at DL1, 6 at DL2; dose-expansion is open at DL2). The most common treatment emergent Gr 3/4 AEs were febrile neutropenia (n=3) and AST elevation, lymphocytopenia, neutropenia, thrombocytopenia, leukopenia (n=2 each). Seven of 16 pts experienced immune-related AE, including 1 with late-onset acute GVHD Gr III (colon/liver), 4 with chronic GVHD (mild, n=2; moderate, n=1; severe n=1), and 2 with Gr 2/3 ipi-induced colitis. All immune-related AEs were reversible with steroids, except for one case of steroid refractory Gr III acute GVHD complicated by fatal septic shock (DLT at IPI 10 mg/kg). In total, 4 of 16 evaluable pts achieved response, including 3 with CR and 1 with marrow CR; 2 of 4 responders had immune-related AE. For these 16 pts, the median OS is 12.8 mo (95% CI: 7.6-NA). Arm B (transplant-naïve): Sixteen pts received DAC+IPI across the 3 DLs (4 at DL0, 3 at DL1, 6 at DL2; 3 are in dose-expansion at DL2). The most common treatment emergent Gr 3/4 AEs were lymphocytopenia, thrombocytopenia and leukopenia (n=5 each); neutropenia (n=4); and anemia, fatigue, lung infection, and febrile neutropenia (n=3 each). In 6 of 16 pts that had ≥ Gr 2 immune-related AEs, all were reversible with steroids (including Gr 3 colitis (n=1), Gr 3 dermatitis (n=2), Gr 2 pneumonitis (n=1), Gr 3 hypophysitis/Gr 2 arthritis (n=1)), except for a case of Gr 2 dermatitis (resolved)/Gr 4 immune thrombocytopenia (refractory to steroids, transfusions and IVIG) (n=1; DLT at IPI 10 mg/kg). No study treatment-related deaths were observed. Objective responses were detected in 8 of 16 evaluable pts with 3 CR, 2 CRi, and 3 marrow CR. Only 2 of 8 responders had immune-related AEs. For these 16 pts, the median OS is 18.3 mo (95% CI: 11.7-NA). Overall, 2 pts discontinued study treatment due to AE. Dose expansion continues at DL2 (MTD) in Arm A and Arm B to further establish safety and tolerability. Correlative science including immunophenotyping is ongoing and will be presented. Conclusion: In this ongoing phase 1 study in pts with R/R or secondary MDS/AML, DAC plus IPI had expected AE profile and exhibited encouraging clinical activity. The rate of immune-related toxicity was frequent but similar to prior observations with IPI 10 mg/kg for melanoma. Further, high clinical activity was observed amongst pts who did not receive allo-HCT, suggesting that an alloreactive environment may not be required to benefit from CTLA-4 blockade. Disclosures Garcia: Pfizer: Research Funding; Genentech: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Eli Lily: Research Funding. Brunner:Astra Zeneca: Research Funding; Janssen: Research Funding; Xcenda: Consultancy; GSK: Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Jazz Pharma: Consultancy; Forty Seven, Inc: Consultancy; Celgene/BMS: Consultancy, Research Funding; Biogen: Consultancy; Acceleron Pharma Inc.: Consultancy. Neuberg:Celgene: Research Funding; Madrigal Pharmaceuticals: Current equity holder in publicly-traded company; Pharmacyclics: Research Funding. Steensma:Takeda: Consultancy; BMS/Celgene: Consultancy; Onconova: Consultancy; Arena: Current equity holder in publicly-traded company; CRISPR: Current equity holder in publicly-traded company; Aprea Therapeutics: Research Funding; Arrowhead Pharmaceuticals: Current equity holder in publicly-traded company; Astex Pharmaceuticals, Onconova Therapeutics, Pfizer, Stemline Therapeutics, Summer Road: Consultancy; H3 Biosciences: Research Funding. Rodig:Bristol Myers Squibb: Research Funding; Merck: Research Funding; Affimed: Research Funding; KITE/Gilead: Research Funding; Immunitas: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees. Lindsley:Takeda Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding; Bluebird Bio: Consultancy; MedImmune: Research Funding. Davids:Research to Practice: Honoraria; Eli Lilly: Consultancy; Adaptive Biotechnologies: Consultancy; Novartis: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Merck: Consultancy; Gilead Sciences: Consultancy; Surface Oncology: Research Funding; MEI Pharma: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding; Ascentage Pharma: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding; Sunesis: Consultancy; Zentalis: Consultancy; Syros Pharmaceuticals: Consultancy; Janssen: Consultancy; BeiGene: Consultancy; Celgene: Consultancy; Genentech: Consultancy, Research Funding; AbbVie: Consultancy; TG Therapeutics: Consultancy, Research Funding; Verastem: Consultancy, Research Funding. Wu:BionTech: Current equity holder in publicly-traded company; Pharmacyclics: Research Funding. Stone:Pfizer: Consultancy; Syros: Consultancy; Stemline: Consultancy; Actinium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gemoab: Consultancy; Syndax: Consultancy, Research Funding; Macrogenics: Consultancy; Trovagene: Consultancy; Biolinerx: Consultancy; Argenix: Other; Jazz: Consultancy; Aztra-Zeneca: Consultancy; Daiichi-Sankyo: Consultancy; Astellas: Consultancy; Syntrix: Other: DSMB; Novartis: Consultancy, Research Funding; Takeda: Other: DSMB; Arog: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; Janssen: Consultancy; Celgene: Consultancy, Other. DeAngelo:Takeda: Consultancy; Blueprint Medicines Corporation: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Incyte Corporation: Consultancy; Abbvie: Research Funding; Glycomimetics: Research Funding; Shire: Consultancy; Autolos: Consultancy; Amgen: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Forty-Seven: Consultancy; Jazz: Consultancy. Soiffer:Rheos Therapeutics: Consultancy; Celgene: Other; Juno: Other; Alexion: Consultancy; Novartis: Consultancy; VOR Biopharma: Consultancy; Mana Therapeutics: Consultancy; Precision Bioscience: Consultancy; Cugene: Consultancy; Gilead: Consultancy; Be The Match/National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Kiadis: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Decitabine plus Ipilimumab to be given in the context of a clinical trial

Pracinostat, a potent oral pan-histone deacetylase inhibitor with modest single-agent activity in acute myeloid leukemia (AML), has shown synergistic antitumor activity when combined with azacitidine. This single-group, multicenter phase 2 study assessed the safety and efficacy of pracinostat combined with azacitidine in patients who were at least 65 years old with newly diagnosed AML and who were ineligible for standard induction chemotherapy. Patients received pracinostat 60 mg/d, 3 d/wk, for 3 consecutive weeks, plus azacitidine 75 mg/m2 daily for 7 days in a 28-day cycle. Primary endpoints were complete remission (CR), CR with incomplete count recovery (CRi), and morphologic leukemia-free state (MLFS) rates of the combination. Secondary endpoints included safety, progression-free survival (PFS), and overall survival (OS) of the regimen. Fifty patients (33 de novo, 12 secondary, and 5 therapy-related AML) were enrolled. Twenty-six patients (52%) achieved the primary endpoint of CR (42%), CRi (4%), and MLFS (6%). Median OS and PFS were 19.1 months (95% confidence interval [CI], 10-26.5 months) and 12.6 months (95% CI, 10-17.7 months), respectively, with a 1-year OS rate of 62%. Forty-three patients (86%) experienced at least 1 grade 3 or worse treatment-emergent adverse event with the combination, with infections (52%), thrombocytopenia (46%), and febrile neutropenia (44%) reported as the most common toxicities. The 30- and 60-day all-cause mortality rates were 2% and 10%, respectively. DNA sequencing revealed somatic mutations at baseline, and clearance rates correlated with response to treatment. Pracinostat plus azacitidine is a well-tolerated and active regimen in the frontline treatment of older patients with AML unfit for intensive therapy. A larger controlled trial is ongoing. This trial was registered at www.clinicaltrials.gov as #NCT01912274.

Although allogeneic hematopoietic cell transplantation (allo-HCT) is the only curative treatment for myelofibrosis (MF), data are limited on how molecular markers predict transplantation outcomes. We retrospectively evaluated transplantation outcomes of 110 consecutive MF patients who underwent allo-HCT with a fludarabine/melphalan (Flu/Mel) conditioning regimen at our center and assessed the impact of molecular markers on outcomes based on a 72-gene next-generation sequencing panel and Mutation-Enhanced International Prognostic Scoring System 70+ v2.0 (MIPSS70+ v2.0). With a median follow-up of 63.7 months, the 5-year overall survival (OS) rate was 65% and the nonrelapse mortality (NRM) rate was 17%. In mutational analysis, JAK2 V617F and ASXL1 mutations were the most common. By univariable analysis, higher Dynamic International Prognostic Scoring System scores, unrelated donor type, and very-high-risk cytogenetics were significantly associated with lower OS. Only CBL mutations were significantly associated with lower OS (hazard ratio [HR], 2.64; P = .032) and increased NRM (HR, 3.68; P = .004) after allo-HCT, but CALR, ASXL1, and IDH mutations did not have an impact on transplantation outcomes. Patient classification per MIPSS70 showed worse OS for high-risk (HR, 0.49; P = .039) compared with intermediate-risk patients. Classification per MIPSS70+ v2.0 demonstrated better OS when intermediate-risk patients were compared with high-risk patients (HR, 0.291) and much lower OS when very-high-risk patients were compared with high-risk patients (HR, 5.05; P ≤ .001). In summary, we present one of the largest single-center experiences of Flu/Mel-based allo-HCT, demonstrating that revised cytogenetic changes and MIPSS70+ v2.0 score predict transplantation outcomes, and thus can better inform physicians and patients in making decisions about allo-HCT.

Background: Allogeneic hematopoietic cell transplantation (alloHCT) is the approach that offers the highest curative rate for acute myelogenous leukemia (AML) with intermediate or high-risk cytogenetics. Graft versus host disease (GvHD) has remained the main cause of post-transplantation mortality and morbidity, despite advances in prophylaxis and therapy, adding significant economic burden and affecting quality of life. It would be desirable to reduce the rate of GvHD among patients in complete remission (CR) without increasing the risk of relapse. In this study, we have developed a novel conditioning regimen of total marrow and lymphoid irradiation (TMLI) at 2000 cGy, together with post-transplant cyclophosphamide (PTCy), to 1) reduce the possibly increased risk of relapse from PTCy, by using escalated radiation doses of TMLI, as increasing radiation doses has the potential to decrease the post-transplantation relapse rate (Blood, vol 76, pp. 1867-1871, 1990); and 2) reduce the risk of chronic GvHD by using PTCy. The major goal of this pilot study of TMLI and PTCy (clinicaltrials.gov: NCT03467386), was to thus improve GvHD-free/relapse-free survival (GRFS), reported to be 45% from total body irradiation (TBI) and tacrolimus/sirolimus prophylaxis (BBMT, vol 26(2), pp. 292-299, 2020), in patients with AML in remission. Patients and Methods: A total of 18 patients were enrolled and treated (see Table) between March 2018 and December 2019. Key criteria were ages 18 to 60, first or second CR, minimal residual disease negative by multi-color flow cytometry, and normal organ function. TMLI was administered on days -4 to 0 without addition of chemotherapy. The radiation dose for all patients (n=18) was 2000 cGy, delivered in 200 cGy fractions twice daily. The radiation dose delivered to the liver and brain was kept at 1200 cGy. Remaining organs were considered non-targeted. All patients received peripheral blood stem cells on day 0. Cyclophosphamide was given on days +3 and +4, 50 mg/kg each day for GVHD prevention. Tacrolimus, 1 mg continuous infusion adjusted to maintain levels from 5 to 10 ng/mL was given from day +5 to day +90, and G-CSF 5 µg/kg daily was administered at day +5 until recovery of neutrophil counts. Endpoints included toxicity, GRFS at 1 year, engraftment, overall survival (OS), and non-relapse mortality (NRM). Toxicities were defined according to the Bearman and CTCAE 4.03 scales, the latter for hematologic toxicity. A patient safety lead-in segment (n=6) was conducted to ensure that there were no unexpected toxicities, allowing for a dose de-escalation to 1800 cGy. GRFS was defined as grade 3-4 acute GvHD, chronic GvHD requiring systemic treatment, relapse, or death (from any cause), whichever occurred first. Results: Bearman toxicity data are available for all patients. Among these patients, grade 2 toxicities were bladder toxicity and stomatitis. No grade 3-4 toxicities or toxicity-related deaths were observed. Acute GVHD (aGVHD) developed in 2 of patients (100-day Grade II-IV aGVHD: 11.1%, 95%CI: 1.7-30.4); of those, only 1 patient developed Grades III-IV (100-day Grade III-IV aGVHD: 5.6%, 95%CI: 0.3-23.1). Five patients developed mild chronic GVHD (1-year cGVHD rate: 28.6%, 95%CI: 7.5%-54.7%). The GRFS rate at 1 year was 59.3% (95% CI: 28.8-80.3) (Figure). The median follow up was 11.3 months (range 4.7 to 25.4) for surviving patients (n=17). All patients engrafted. Time to neutrophil and platelet recovery were 14 days (range 13-32 days) and 20 days (range 11-49 days), respectively. One-year estimates of OS and relapse-free survival were 100% and 80.8% (95% CI: 50.5-93.6), respectively (Figure). Disease relapse at 1 year was 19.2% (95% CI: 4.1-42.6). The estimates of NRM at 100 days and 1 year were both 0%. Relapsed disease after transplant occurred in 3 patients (16.7%). One patient died after relapse. Conclusions: 1) This chemotherapy-free conditioning regimen, together with PTCy and tacrolimus, is safe and feasible, with no NRM. 2) All patients achieved engraftment. 3) Participants with ≥1 year follow-up have discontinued immunosuppressive therapy, reducing financial burden and leading to improved quality of life. The preliminary results suggest an improved GRFS rate. A larger phase 2 trial is in preparation to corroborate these data. Disclosures Stein: Amgen: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau. Al Malki:Neximmune: Consultancy; Jazz Pharmacuticals, Inc: Consultancy; Rigel Pharma: Consultancy. Ali:Incyte Corporation: Consultancy. Aribi:Seattle Genetics: Consultancy. Marcucci:Novartis: Speakers Bureau; Takeda: Other: Research Support (Investigation Initiated Clinical Trial); Pfizer: Other: Research Support (Investigation Initiated Clinical Trial); Abbvie: Speakers Bureau; Merck: Other: Research Support (Investigation Initiated Clinical Trial); Iaso Bio: Membership on an entity's Board of Directors or advisory committees. Nakamura:Alexion: Other: Support on a meeting presentation; Kyowa-Kirin: Other: Support on a meeting presentation; Merck: Other: advisory board meeting; Celgene: Other: Support on seminar; Magenta Therapeutics: Other: Advisory board meeting; Viracor: Consultancy; Kadmon Corporation: Other: Advisory board meeting; NapaJen Pharma: Consultancy. Pullarkat:AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Salhotra:Celgene: Research Funding; Kadmon: Membership on an entity's Board of Directors or advisory committees.

The "7+3" regimen is recommended for treatment in patients with new diagnosis of acute myeloid leukemia (AML) who are fit for intensive chemotherapy. Patients with secondary AML (sAML) [i.e. AML evolving from antecedent hematologic disorders (AHD-AML) or after previous exposure to chemo/radiation therapy for unrelated cancer (t-AML)], have inferior outcomes with "7+3" regimen. A recent phase 3 study demonstrated superior CR rates and overall survival (OS) with upfront use of CPX-351 compared to "7+3" regimen in older patients (≥60 years) with sAML (Lancet et al JCO 2018). The combination of HMA+Ven is FDA approved for upfront treatment in newly diagnosed AML patients > 75 or those unfit for intensive chemotherapy based on CR+ CRi rates of 67% and median OS of 17.5 months. Herein, we compared the outcomes of older patients with sAML who received upfront treatment with either HMA+Ven or CPX-351 at our institution. Our analysis includes 47 consecutive patients with previously untreated sAML treated between 2018-2020 . Patients were treated with either HMA+Ven (n=27) or CPX-351 (n=20) based on physician preference. WHO criteria were used for the diagnosis AHD-AML and review of medical records for documenting exposure to leukemogenic agent for t-AML. Complete remission (CR) was defined by presence of 1000/µL and platelets ≥100,000/µL) were defined as CRh (hematologic recovery) and CR without blood count recovery as CRi (incomplete blood count recovery). Minimal residual disease (MRD) assessment was done on day-28 BM aspirate using multiparametric flow cytometric assay with lower limit of sensitivity of 0.01%. Patients demographic and disease features are summarized in Table 1. Mean age (p=0.39), mean blast percentage in BM aspirate (P=0.82), high-risk cytogenetics (P=0.37) and high-risk molecular mutations (P=0.737) were similar in both treatment groups. Of the 27 cases of sAML in HMA+Ven group, 8 were t-AML arising after prior chemotherapy (Hodgkin's Disease n=2; paraganglioma, desmoid tumor, breast cancer, NHL, multiple myeloma, ALL: one each) while 19 were AHD-AML. In CPX-351 group, 6 cases were t-AML arising after prior chemotherapy (NHL n=2, breast cancer n=2, T-Lymphoblastic Lymphoma and colon cancer one each) while 14 were secondary to AHD. The mean number of cycles were 3.3 (range 1-18) in HMA+Ven group and 1.45 (1-3) in CPX-351 group. Two-sample t test was used to compare continuous and normally distributed covariates, such as age and BM blasts, between HMA+Ven or CPX-351 arms. Pearson Chi-square or Fisher exact test was used to assess the associations between treatment and clinical outcomes. Kaplan-Meier method and log-rank test were used to assess OS or LFS. A P value of ≤ 0.05 was considered as statistically significant. The CR rate in patients treated on HMA+Ven group was 78% (n=21; 95% CI: 58-91%) vs 50% (n=10; 95% CI: 27-73%) in CPX-351 group (P=0.047). CRi was achieved in 52% (n=14) patients in HMA+Ven group compared to 25%(n=5) patients in CPX-351 group(p=0.064). MRD negative remission was achieved in 52% (n=14) patients in HMA+Ven group and in 25% (n=5) patients in CPX-351 group (p=0.064). In HMA+Ven group, 52% patients (n=14) achieved remission after one cycle of therapy compared to 45% (n=9) patients in CPX-351 arm (p=0.642). With a median follow-up of 6.7 months for all patients, the median leukemia free-survival (LFS) for HMA+Ven vs CPX-351 treatments is 16.2 vs NA months (P = 0.098) and the median OS is 13.2 vs NA months (P = 0.395). Ten patients in each group (37% in HMA+Ven and 50% in CPX-351; p=0.47) underwent allo-HCT. At last follow up, 14 patients (52%) have died in HMA+Ven group from: relapsed AML (n=10), sepsis (n=2), congestive heart failure (n=1) and unknown (UK) in one patient, whereas in CPX-351 group, 8 patients (40%) have died from relapsed AML in (n=5), respiratory failure (n=2) and UK causes in one patient. In patients resistant to initial therapy, the median OS is 3.5 vs 6.0 months between HMA+ Ven and CPX-351 groups (P = 0.224). Conclusion: In patients presenting with sAML, upfront treatment with HMA+Ven is feasible and associated with significantly better CR rates and a favorable trend for higher rates of negative MRD compared to CPX-351. A randomized prospective trial in patients with sAML is warranted to determine the most effective frontline regimen in this high-risk AML subgroup. Disclosures Salhotra: Celgene: Research Funding; Kadmon: Membership on an entity's Board of Directors or advisory committees. Al Malki:Rigel Pharma: Consultancy; Neximmune: Consultancy; Jazz Pharmacuticals, Inc: Consultancy. Aribi:Seattle Genetics: Consultancy. Ali:Incyte Corporation: Consultancy. Budde:Gilead Sciences: Consultancy; Merck: Research Funding; Amgen: Research Funding; Kite, a Gilead Company: Consultancy; Mustang Therapeutics: Research Funding; AstraZeneca: Research Funding; Roche: Consultancy. Dadwal:Ansun Biopharma: Research Funding; Karius: Research Funding; Shire/ Takeda: Research Funding; Gilead: Research Funding; Merck: Consultancy, Honoraria, Other: Advisory board meeting, Research Funding, Speakers Bureau; Chimerix: Research Funding; Janssen: Other: Advisory board meeting; Astellas: Speakers Bureau. Nakamura:NapaJen Pharma: Consultancy; Kadmon Corporation: Other: Advisory board meeting; Viracor: Consultancy; Magenta Therapeutics: Other: Advisory board meeting; Celgene: Other: Support on seminar; Kyowa-Kirin: Other: Support on a meeting presentation; Alexion: Other: Support on a meeting presentation; Merck: Other: advisory board meeting. Stein:Amgen: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau. Marcucci:Takeda: Other: Research Support (Investigation Initiated Clinical Trial); Merck: Other: Research Support (Investigation Initiated Clinical Trial); Iaso Bio: Membership on an entity's Board of Directors or advisory committees; Abbvie: Speakers Bureau; Novartis: Speakers Bureau; Pfizer: Other: Research Support (Investigation Initiated Clinical Trial). Pullarkat:Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. OffLabel Disclosure: off label use of HMA+venetoclax in secondary AML

The use of post-transplant cyclophosphamide (PTCy) as graft-versus-host-disease (GvHD) prophylaxis after hematopoietic cell transplantation (HCT) has increased significantly over the past decade due to expansion of donor pool with haploidentical and mismatched unrelated donors. A recently completed phase 2 study, PROGRESS-2 (NCT02345850), has highlighted the efficacy of PTCy in the matched donor setting. Hemorrhagic cystitis (HC) is the most notable toxicity associated with high dose Cy. However, data specific to the incidence and severity of HC in the post HCT setting is sparse, with no consensus on best practices to prevent HC in patients receiving PTCy. Current strategies to prevent HC in PTCy setting have been adapted from data in pre-HCT Cy (conditioning setting), such as hyperhydration with forced diuresis, continuous bladder irrigation, mesna as an intermittent and continuous infusion, or a combination of these methods. The aim of our study was to describe the incidence and severity of HC in patients undergoing HCT with PTCy as GvHD prophylaxis, identifying potential risk factors and impact of HC on HCT outcomes. We retrospectively reviewed 194 consecutive patients who underwent their first HCT with PTCy from 2014 to 2018 at our center. More than half of the patients (53%) received myeloablative conditioning regimen with majority receiving peripheral blood stem cells (81%) from haploidentical donors (96%). GvHD prophylaxis was unified with PTCy (50 mg/kg on Days +3 and +4), in addition to MMF (1 gm 3x daily starting on Day +5) and tacrolimus (1 mg as a continuous infusion daily starting on Day +5). Standard HC prophylaxis was hyperhydration with forced diuresis and mesna at 320% the daily dose of PTCy. Incidence of HC was based on physician documentation or presence of blood in urinalysis up to Day +100. To determine severity of HC, CTCAE 5.0 grading system was used. Median age of patients was 45 years (range: 2-73), with 60% of patients being male. KPS was ≥80% in 83% of patient and 40% had HCT-CI of ≥2. The most common diagnoses included: AML (41%), ALL (24%) and MDS/MPN (19%). There were 55 patients who received ≥3 lines of therapy, 116 patients received In conclusion, hyperhydration with forced diuresis added to aggressive mesna dosing is an effective strategy in preventing severe HC in HCT patients receiving PTCy as GvHD prophylaxis. Incidence of Grade 3 or 4 HC was low and transient and did not impact HCT outcomes. Viral HC had a significantly later onset than non-viral HC, suggesting a different pathophysiology. Older age and myeloablative conditioning were independent factors for higher incidence of HC in our cohort. Disclosures Ali: Incyte Corporation: Consultancy. Salhotra:Celgene: Research Funding; Kadmon: Membership on an entity's Board of Directors or advisory committees. Aribi:Seattle Genetics: Consultancy. Pullarkat:Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie, Inc.: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genetech: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dova: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Stein:Amgen: Consultancy, Speakers Bureau; Stemline: Consultancy, Speakers Bureau. Marcucci:Merck: Other: Research Support (Investigation Initiated Clinical Trial); Pfizer: Other: Research Support (Investigation Initiated Clinical Trial); Abbvie: Speakers Bureau; Novartis: Speakers Bureau; Iaso Bio: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Research Support (Investigation Initiated Clinical Trial). Nakamura:NapaJen Pharma: Consultancy; Viracor: Consultancy; Kadmon Corporation: Other: Advisory board meeting; Magenta Therapeutics: Other: Advisory board meeting; Celgene: Other: Support on seminar; Kyowa-Kirin: Other: Support on a meeting presentation; Alexion: Other: Support on a meeting presentation; Merck: Other: advisory board meeting. Al Malki:Rigel Pharma: Consultancy; Jazz Pharmacuticals, Inc: Consultancy; Neximmune: Consultancy.

The presence of FMS-like receptor tyrosine kinase-3 internal tandem duplication (FLT3-ITD) mutations in patients with acute myeloid leukemia (AML) is associated with poor clinical outcome. FLT3 tyrosine kinase inhibitors (TKIs), although effective in kinase ablation, do not eliminate primitive FLT3-ITD+ leukemia cells, which are potential sources of relapse. Thus, understanding the mechanisms underlying FLT3-ITD+ AML cell persistence is essential to devise future AML therapies. Here, we show that expression of protein arginine methyltransferase 1 (PRMT1), the primary type I arginine methyltransferase, is increased significantly in AML cells relative to normal hematopoietic cells. Genome-wide analysis, coimmunoprecipitation assay, and PRMT1-knockout mouse studies indicate that PRMT1 preferentially cooperates with FLT3-ITD, contributing to AML maintenance. Genetic or pharmacological inhibition of PRMT1 markedly blocked FLT3-ITD+ AML cell maintenance. Mechanistically, PRMT1 catalyzed FLT3-ITD protein methylation at arginine 972/973, and PRMT1 promoted leukemia cell growth in an FLT3 methylation–dependent manner. Moreover, the effects of FLT3-ITD methylation in AML cells were partially due to cross talk with FLT3-ITD phosphorylation at tyrosine 969. Importantly, FLT3 methylation persisted in FLT3-ITD+ AML cells following kinase inhibition, indicating that methylation occurs independently of kinase activity. Finally, in patient-derived xenograft and murine AML models, combined administration of AC220 with a type I PRMT inhibitor (MS023) enhanced elimination of FLT3-ITD+ AML cells relative to AC220 treatment alone. Our study demonstrates that PRMT1-mediated FLT3 methylation promotes AML maintenance and suggests that combining PRMT1 inhibition with FLT3 TKI treatment could be a promising approach to eliminate FLT3-ITD+ AML cells.

Myeloablative autologous hematopoietic stem cell transplantation (HSCT) is a mainstay of therapy for relapsed intermediate-grade B-cell non-Hodgkin lymphoma (NHL); however, relapse rates are high. In phase 1 studies designed to improve long-term remission rates, we administered adoptive T-cell immunotherapy after HSCT, using ex vivo-expanded autologous central memory-enriched T cells (TCM) transduced with lentivirus expressing CD19-specific chimeric antigen receptors (CARs). We present results from 2 safety/feasibility studies, NHL1 and NHL2, investigating different T-cell populations and CAR constructs. Engineered TCM-derived CD19 CAR T cells were infused 2 days after HSCT at doses of 25 to 200 × 10(6) in a single infusion. In NHL1, 8 patients safely received T-cell products engineered from enriched CD8(+) TCM subsets, expressing a first-generation CD19 CAR containing only the CD3ζ endodomain (CD19R:ζ). Four of 8 patients (50%; 95% confidence interval [CI]: 16-84%) were progression free at both 1 and 2 years. In NHL2, 8 patients safely received T-cell products engineered from enriched CD4(+) and CD8(+) TCM subsets and expressing a second-generation CD19 CAR containing the CD28 and CD3ζ endodomains (CD19R:28ζ). Six of 8 patients (75%; 95% CI: 35-97%) were progression free at 1 year. The CD4(+)/CD8(+) TCM-derived CD19 CAR T cells (NHL2) exhibited improvement in expansion; however, persistence was ≤28 days, similar to that seen by others using CD28 CARs. Neither cytokine release syndrome nor delayed hematopoietic engraftment was observed in either trial. These data demonstrate the safety and feasibility of CD19 CAR TCM therapy after HSCT. Trials were registered at www.clinicaltrials.gov as #NCT01318317 and #NCT01815749.

The success of all-trans retinoid acid (ATRA) in acute promyelocytic leukemia (APL) pioneered the concept of differentiation therapy. However, comparable approaches to overcome differentiation blockage for non-APL acute myeloid leukemia (AML) are hampered by lack of an effective drug discovery platform. Recently, we analyzed gene signatures of compounds (ATRA, arsenic trioxide, zalcitabine, and sodium butyrate) that trigger myeloid differentiation in the NCI-60 collection datasets and identified CD38 as the top gene upregulated by differentiation induction. We next initiated an in silico screen in the DTP database of >20,000 compounds to identify compounds that increase CD38 levels. Among those retrieved from "CellMiner" with CD38 as input, we assessed the top 193 available from NCI (r>0.6, p=0) for effects on differentiation utilizing a conditional murine myeloid differentiation-arrest model overexpressing estrogen receptor-HoxA9 (ER-HoxA9) fusion proteins (Cell, 2016). We identified NSC755985 (Nelarabine, NEL) in that screen. NEL is an orphan drug approved to treat relapsed or refractory T-cell acute lymphoblastic leukemia (ALL). NEL at clinically achievable doses (Cmax: 6.73 μM~ 26.91 μM, at a proposed adult dosing schedule of 1,500 mg/m2/day) markedly induced primary AML cell differentiation and death while sparing normal hematopoietic cells (AML vs normal, IC50: 14.7 ± 4.3 μM, n=7, vs 45.3 ± 1.3 μM, n=3), suggesting a therapeutic window in AML. Ex vivo NEL treatment compromised BM engraftment of CD34+ cells from one primary AML specimen in immunodeficient NSG mice at 12 weeks post-transplant (human CD45+ cells in BM: NEL 0.73% vs vehicle 33.42%, n=6/group, p Transcriptome analyses in U397 cells and primary AML specimens revealed that NEL treatment upregulated RAS-related pathways. NEL-elicited RAS activation was confirmed by pull-down assay using a GST-Raf1-RBD affinity probe, followed by blotting with a pan-RAS antibody. We performed functional analysis by infecting ER-HoxA9 cells with lentiviral vector expressing oncogenic RAS and observed enhanced myeloid differentiation, as evidenced by increased CD11b/GFP levels relative to MOCK-infected controls. Given that NEL's active metabolite Ara-GTP perturbs guanine nucleotide metabolism, we asked if NEL-evoked RAS activation was associated with accrual of intracellular GTP. HPLC/MS analyses of U937 cells showed that NEL treatment resulted in a marked increase in GTP (approximately 5-fold higher than baseline at sub-millimolar levels) which was secondary to Ara-GTP. Importantly, either electroporation of GTP into U937 cells or indirect introduction of GTP by addition of guanine utilizing purine salvage pathways activated RAS and recapitulated differentiation induction phenotypes. To determine whether AML cells with higher RAS activity exhibited greater NEL sensitivity, we pretreated U937 cells with a RAS agonist KRA-553 or ectopically expressed RAS mutants and observed enhanced NEL inhibitory effects in both cases. We also observed enhanced vulnerability to NEL treatment in MLL-AF9 transformed murine hematopoietic cells from KrasLox-Stop-Lox (LSL) G12D/+/Vav-Cre mice (Blood, 2009) versus Cre+ counterparts. Relevant to AML line THP-1 which is poorly responsive to NEL (IC50>100 µM), we observed extremely low levels of Ara-GTP, no GTP increase or RAS hyperactivation after NEL treatment; Ara-GTP is inactivated by SAM domain and HD domain-containing protein 1 (SAMHD1), a dNTP hydrolase, whose high expression reportedly underlies NEL resistance in T-ALL. Indeed, SAMHD1 deletion remarkably increased RAS activity in THP-1 cells treated with NEL, thereby fully reversing NEL resistance. Our study provides a preclinical basis for testing NEL efficacy in a large cohort of AML patients, given that RAS activity is generally high in AML, or even against other malignancies harboring RAS mutations, which are considered "undruggable". Additionally, further study to test whether SAMHD1 inhibition enhances NEL efficacy against RAS active cancers is warranted. Disclosures Marcucci: Pfizer: Other: Research Support (Investigation Initiated Clinical Trial); Novartis: Speakers Bureau; Takeda: Other: Research Support (Investigation Initiated Clinical Trial); Iaso Bio: Membership on an entity's Board of Directors or advisory committees; Merck: Other: Research Support (Investigation Initiated Clinical Trial); Abbvie: Speakers Bureau. Sykes:Clear Creek Bio: Current equity holder in private company, Other: co-founder.

Introduction: In the phase 3 QuANTUM-R trial, once-daily, oral, highly potent and selective FLT3 inhibitor Q improved clinical benefits vs SC (median overall survival [mOS], 6.2 vs 4.7 mo [HR, 0.76 (95% CI, 0.58-0.98); P = .02]; composite complete remission [CRc], 48% vs 27%; median duration of CRc, 12.1 vs 5.0 wk) in 367 pts with R/R FLT3-ITD AML (Cortes et al. Lancet Oncol, 2019; NCT02039726). Prior to randomization, 25% (Q) and 23% (SC) of pts had 1 prior HSCT. An OS sensitivity analysis, with censoring at the time of any subsequent HSCT during QuANTUM-R, was supportive (mOS, 5.7 vs 4.6 mo [HR, 0.79 (95% CI, 0.59-1.05)]; P = .05). Post hoc analyses of characteristics and clinical outcomes in pts who underwent subsequent HSCT in QuANTUM-R are reported. Methods: Pts aged ≥ 18 y with FLT3-ITD R/R AML receiving Q (60 mg [30-mg lead-in]) or 1 of 3 prespecified high- or low-intensity SC regimens and underwent subsequent HSCT as part of the open-label, randomized QuANTUM-R trial were analyzed. Pts receiving HSCT in the Q arm could resume maintenance Q 30-100 days after HSCT. Decisions to proceed to HSCT and resume Q after HSCT were made per investigator discretion/institutional policies. Results: Of 367 randomized pts, 85 in the Q arm underwent any subsequent HSCT (allogenic HSCT [allo-HSCT], 84 [6 with and 78 w/o additional AML therapy]; autologous HSCT, 1) and 19 in the SC arm underwent any HSCT (5 with and 14 w/o additional AML therapy]). Median age (range) was lower in pts with any HSCT (Q, 49 [19-71] y; SC, 44 [23-67] y) vs pts w/o (Q, 58 [19-81] y; SC, 59 [18-78] y). Q + SC pooled data showed a longer mOS (95% CI) in 104 pts with any HSCT vs 263 w/o (12.2 [10.0-24.1] vs 4.4 [4.1-4.9] mo; P < .0001; Fig 1); 1-year OS probabilities (95% CI) were 50% (40%-60%) vs 13% (9%-18%). Among pts preselected for high-intensity therapy (Q [n = 188] + SC [n = 93]), mOS in the pooled high-intensity group was 11.9 (10.0-24.0) mo with any HSCT vs 4.6 (4.1-5.4) mo w/o. Among pts preselected for low-intensity therapy, 13/57 in the Q arm and 0/29 in the SC arm underwent any HSCT; mOS in the pooled low-intensity group was 32.4 (6.2-NA) mo with any HSCT vs 4.1 (2.7-4.6) mo w/o. In pts with CRc (last recorded response prior to allo-HSCT), mean time (range) to allo-HSCT was 13.3 (5.9-26.9) wk with Q and 12.1 (6.3-28.6) wk with SC. Q + SC pooled data showed that mOS (95% CI) was longer in pts with a CRc prior to allo-HSCT vs pts w/o CRc (20.1 [11.7-NA] vs 8.8 [7.0-11.4] mo). Survival outcomes by treatment were similar regardless of study treatment, with longer mOS in pts with any HSCT vs pts w/o (Q, 11.9 [10.2-25.1] vs 4.5 [4.1-5.4] mo; SC, 12.7 [6.1-NA] vs 4.0 [2.7-5.0] mo); respective 1-year OS probabilities (95% CI) were 50% (39%-60%) vs 13% (8%-20%) and 51% (26%-70%) vs 12% (6%-21%). In the Q arm, mOS (95% CI) was longer in pts with a best response of CRc who resumed Q after allo-HSCT (27.1 [18.2-NA] mo) vs pts not resuming Q (5.4 [4.7-11.4] mo; Fig 2). In 48 pts (62%) in the Q arm resuming Q after allo-HSCT, median time (range) from allo-HSCT to Q resumption was 65 (30-106) d. Four pts (5%) in the Q arm died < 30 days after allo-HSCT. As of 2/22/2018, 46 of 78 pts in the Q arm (59%) and 9 of 14 pts in the SC arm (64%) with allo-HSCT w/o additional AML therapy died, primarily due to AML disease progression (Q, 31 [40%]; SC, 7 [50%]). The frequency of treatment-emergent adverse events (TEAEs) was mostly lower in pts resuming Q after allo-HSCT than in the overall Q population (Table 1); TEAEs of interest were similar. Long-term survivor data will be presented. Conclusions: Independent of HSCT, Q improved survival vs SC in pts with FLT3-ITD R/R AML in QuANTUM-R. Q + SC pooled analyses showed longer survival in pts with HSCT vs pts w/o and in pts with CRc prior to allo-HSCT. Importantly, survival post-HSCT was similar in the Q and SC arms, indicating that pts eligible for HSCT were appropriately transplanted, and the higher HSCT rate in the Q arm was beneficial to pts. More pts treated with Q underwent HSCT, likely due to a higher rate and duration of CRc with Q vs SC and better overall fitness. In pts preselected for low-intensity SC at study entry, 13 were able to undergo HSCT after Q treatment. Resumption of Q after HSCT was associated with better survival outcomes and was tolerable. These data illustrate the value of using Q to target the FLT3-ITD mutation as a part of the overall treatment sequence in pts with FLT3-ITD R/R AML. Disclosures Ganguly: Seattle Genetics: Speakers Bureau; Janssen: Honoraria, Other: Advisory Board; Kite Pharma: Honoraria, Other: Advisory Board; Daiichi Sankyo: Research Funding. Cortes:Bristol-Myers Squibb: Consultancy, Research Funding; BiolineRx: Consultancy; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; Merus: Consultancy, Honoraria, Research Funding. Krämer:Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Bayer: Research Funding. Levis:Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Daiichi Sankyo Inc: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; FUJIFILM: Consultancy, Research Funding. Martinelli:Daiichi Sankyo: Consultancy, Honoraria; Pfizer: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Amgen: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Novartis: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant. Perl:Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau. Arunachalam:Daiichi Sankyo: Employment. Gammon:Daiichi Sankyo: Consultancy. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Mires:Daiichi Sankyo: Employment. Namuyinga:Daiichi Sankyo: Employment. Zhang:Daiichi Sankyo: Employment. Khaled:Omeros: Consultancy; Daiichi Sankyo: Other: Travel support; Alexion: Consultancy, Speakers Bureau.

Background: Patients (pts) with MDS or AML who relapse after allogeneic transplantation (allo-HCT) have a very poor prognosis. Hypomethylating agents (HMA) and checkpoint blockade with the anti-CTLA4 blocking antibody ipilimumab (IPI) have each induced responses with acceptable toxicity in AML pts who relapse after allo-HCT. We hypothesized that adding decitabine (DAC) would improve response compared with IPI alone by activating and promoting T cell-mediated anti-leukemic immune reactivity. We are conducting a multicenter phase I study (CTEP 10026) of DAC plus IPI in pts with R/R MDS/AML in both post allo-HCT and transplant-naïve settings to assess safety and estimate efficacy. Methods: The primary objective is to determine the maximum tolerated dose (MTD) or RP2D of combination DAC + IPI in pts with R/R MDS/AML who are post allo-HCT (Arm A) or transplant-naïve (Arm B). Cohorts of 3-6 are sequentially enrolled in 3 dose levels (DL) of IPI using a 3+3 design with expansion in each arm; DLs 0-2 are 3, 5 and 10 mg/kg, respectively. Eligibility for both arms: relapsed AML (extramedullary or ≥ 5% blasts) or R/R MDS (≥ 5% blasts) or unfit elderly AML; Arm A only: ≥ 2 wks off systemic immunosuppressive (IS) therapy, T cell chimerism ≥ 20%, and no prior acute GVHD ≥ gr III. DLT is defined as ≥ gr 3 non-heme, ≥ gr 3 acute GVHD or ≥ gr 3 steroid-refractory immune-related adverse events (AEs) occurring within 8 weeks from first IPI dose. Epigenetic priming with DAC lead-in cycle 0 was followed by combination cycles of DAC + IPI. DAC is given at 20 mg/m2 days 1-5 q 28 days. IPI is given on day 1 of cycles 1-4 and every other cycle in cycles 5-12. Pts who discontinued study either in cycle 0 or DLT period without IPI-toxicity were replaced. Arm A opened after safety was confirmed at DL0 in Arm B. Results: As of June 9, 2019, 26 pts (15M, 11 F) have enrolled in this on-going trial. Of the 12 pts (11 AML and 1 MDS) enrolled in Arm A (post allo-HCT), median age was 66.5 (range 29-74) and 9 had previously received HMA. 7 of 8 pts in DL0 (1 progressed in cycle 0) and 3 of 4 pts in DL1 (1 died from pneumonia in cycle 0) received DAC + IPI. DL0 was expanded to 6 to confirm safety without DLT. Median treatment duration after first IPI dose was 5 cycles (range 1-7); 4 pts continue on trial. Common AEs were gr 1-2 dyspnea (n=4), gr 1-3 fatigue (n=4), and gr 1-2 fever (n=4). Gr 3 AEs were febrile neutropenia (n=2), pneumonia (n=1), and candidemia (n=1). Gr 1 immune-related dermatitis (n=1) reversed with steroids. Acute GVHD was not observed. Moderate-severe chronic GVHD was noted in 2 pts mainly involving skin, which was responsive to photopheresis and oral IS. Though 1 CR and 1 marrow CR have been observed at DL0, dose-escalation up to DL2 is on-going to determine MTD. Of the 14 pts (11 AML and 3 MDS) enrolled in Arm B (transplant naïve), median age was 75.5 (range 34-82) and 9 had previously received HMA. 4 of 6 pts in DL0 (1 progressed and 1 withdrew in cycle 0), 3 of 5 pts in DL1 (2 withdrew in cycle 0) and 3 of 3 pts in DL2 received DAC + IPI. Median treatment duration after first IPI dose was 4 cycles (range 1-8); 3 pts remain on study. Common AEs were gr 1-3 fatigue (n=9), gr 1-2 anorexia (n=5), and gr 3 febrile neutropenia (n=8). Immune-related gr 2 colitis (n=1) and gr 2/3 (n=4) dermatitis were all steroid-responsive. Of the 10 pts who received at least one IPI dose, 5 (50%) achieved an objective response including 3 CR, 1 CRi and 1 PR. All responses were observed in AML pts, including 1 with only skin involved. Expansion to confirm MTD is underway. No treatment-related deaths or DLTs were observed in either Arm. Reasons for discontinuation after IPI: progression (n=9), proceeding to allo-HCT or DLI (n=2), withdrawal (n=1), stroke due to underlying atrial fibrillation (n=1) and disseminated nocardiosis (n=1). In both Arms, multiplex immunofluorescence (MIF) staining of BM biopsies revealed a higher density of CD3+CD4+ cells after 4 cycles of DAC + IPI in 4 responders (R) compared to 4 non-responders (NR) (p=0.0433). Longitudinal MIF IHC in an Arm B responder identified the increasing presence of a tumor immune infiltrate composed of CD3+CD8+GZMB+ T cells prior to achieving CR (Fig 1). Conclusions: Combination DAC + IPI is tolerable and has encouraging clinical activity in post allo-HCT and transplant naïve pts with R/R MDS/AML. Ongoing studies focus on comparing the immunologic and genetic characteristics of the tumor immune infiltrate in each cohort to understand the contribution of alloimmunity to treatment response. Disclosures Garcia: Abbvie: Research Funding; Genentech: Research Funding. Keng:agios: Membership on an entity's Board of Directors or advisory committees. Brunner:Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Research Funding. Khaled:Omeros: Consultancy; Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support. Steensma:H3 Biosciences: Other: Research funding to institution, not investigator.; Arrowhead: Equity Ownership; Onconova: Consultancy; Stemline: Consultancy; Aprea: Research Funding; Pfizer: Consultancy; Summer Road: Consultancy; Astex: Consultancy. Winer:Jazz Pharmaceuticals, Pfizer: Consultancy. Cutler:Omeros: Consultancy; Kadmon: Consultancy; BiolineRx: Other: DSMB; Cellect: Other: DSMB; Kalytera: Other: DSMB; ElsaLys: Consultancy; Genentech: Consultancy; Pharmacyclics: Consultancy; Fate Therapeutics: Consultancy; Incyte: Consultancy; Jazz: Consultancy; BMS: Consultancy. Ho:Omeros Corporation: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy. Neuberg:Madrigal Pharmaceuticals: Equity Ownership; Pharmacyclics: Research Funding; Celgene: Research Funding. Lindsley:Takeda Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Research Funding; Medlmmune: Research Funding. Galinsky:ABIM: Other: Member of specialty oncology board; Merus Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; AbbVie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Pfizer Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Ritz:TScan Therapeutics: Consultancy; LifeVault Bio: Consultancy; Kite Pharma: Research Funding; Talaris Therapeutics: Consultancy; Draper Labs: Consultancy; Avrobio: Consultancy; Celgene: Consultancy; Merck: Research Funding; Equillium: Research Funding; Aleta Biotherapeutics: Consultancy. Davids:AbbVie, Acerta Pharma, Adaptive, Biotechnologies, Astra-Zeneca, Genentech, Gilead Sciences, Janssen, Pharmacyclics, TG therapeutics: Membership on an entity's Board of Directors or advisory committees; AbbVie, Astra-Zeneca, Genentech, Janssen, MEI, Pharmacyclics, Syros Pharmaceuticals, Verastem: Consultancy; Acerta Pharma, Ascentage Pharma, Genentech, MEI pharma, Pharmacyclics, Surface Oncology, TG Therapeutics, Verastem: Research Funding; Research to Practice: Honoraria. Wu:Pharmacyclics: Research Funding; Neon Therapeutics: Other: Member, Advisory Board. Stone:AbbVie, Actinium, Agios, Argenx, Arog, Astellas, AstraZeneca, Biolinerx, Celgene, Cornerstone Biopharma, Fujifilm, Jazz Pharmaceuticals, Amgen, Ono, Orsenix, Otsuka, Merck, Novartis, Pfizer, Sumitomo, Trovagene: Consultancy; Argenx, Celgene, Takeda Oncology: Other: Data and Safety Monitoring Board/Committee: ; Novartis, Agios, Arog: Research Funding. DeAngelo:Blueprint: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Abbvie: Research Funding; Glycomimetics: Research Funding; Amgen, Autolus, Celgene, Forty-seven, Incyte, Jazzs, Pfizer, Shire, Takeda: Consultancy. Soiffer:Jazz: Consultancy; Gilead, Mana therapeutic, Cugene, Jazz: Consultancy; Juno, kiadis: Membership on an entity's Board of Directors or advisory committees, Other: DSMB; Kiadis: Other: supervisory board; Mana therapeutic: Consultancy; Cugene: Consultancy. OffLabel Disclosure: Combination of ipilimumab and decitabine for MDS/AML treatment for patients who are post-transplant or transplant naive

Background: Quizartinib is a once-daily, oral, highly potent and selective FLT3 inhibitor with proven single-agent activity and a manageable safety profile in FLT3-ITD R/R AML. In the global, phase 3 QuANTUM-R study, quizartinib demonstrated a significant survival benefit over salvage chemotherapy(Cortes, et al. Lancet Oncol, 2019; NCT02039726). Additional support for the safety profile of quizartinib at the proposed dosing regimen (60 mg QD with a 30-mg starting dose) is provided by a pooled analysis of over 600 patients with R/R AML. Methods: We pooled data from four studies: one phase 3 (QuANTUM-R), two phase 2, (ACC220-002 and 2689-CL-2004; Cortes, et al. Lancet Oncol, 2018; Cortes, et al. Blood, 2018), and one phase 1 (CP0001: only patients assigned to continuous daily dosing regimens are included in this analysis; Cortes, et al. J Clin Oncol, 2013) to provide an integrated safety summary of quizartinib monotherapy for the treatment of R/R AML. Treatment-emergent adverse events (TEAEs), on-treatment deaths, and adverse events of special interest (AESIs; QT prolongation and potential ventricular arrhythmias, hepatic disorders, and sequelae of cytopenias such as infections and bleeding) with quizartinib were analyzed. Results: The pooled data set included 673 patients; 51% were male, and median age was 59 years. Thirty-eight patients were assigned to quizartinib 30 mg, 277 to 60 mg, and 358 to >60 mg up to 300 mg. Overall, median treatment duration was 79 days (range, 1-1296 days) and was longest in the 60-mg dose group (95 days) vs the >60-mg (70.5 days) and 30-mg (66 days) groups. The overall TEAE profile was consistent with the results from the phase 3 QuANTUM-R study. Most on-treatment deaths (215 of 599 evaluable patients [36%]; defined as taking place between the first dose and ≤30 days after the last dose) were attributed to AML disease progression (130/599 [22%]), followed by TEAEs (83/599 [14%]), which were predominantly respiratory tract infections and events related to sepsis. TEAEs leading to discontinuation of quizartinib occurred in 173/673 patients (26%). In the 60-mg dose group (quizartinib proposed dosing regimen), the only TEAE associated with discontinuation in >2% of patients was pneumonia (6/277 patients [2%]). The most frequently reported grade ≥3 TEAEs were febrile neutropenia (240/673 [36%]), anemia (188/673 [28%]) and thrombocytopenia (182/673 [27%]) in the hematologic category and pneumonia (119/673 [18%]) and sepsis/septic shock (124/673 [18%]) in the nonhematologic category (Table 1A). In the 60-mg dose group, the most frequent AESI was infection (210/277 [76%]; Table 1B). Epistaxis and petechiae, mainly grade 1/2, were the most frequently reported hemorrhage TEAEs. TEAEs in the hemorrhage category occurred more frequently in the >60-mg dose group than the 60-mg dose group (215/358 [60%] and 136/277 [49%], respectively). The most frequent serious hemorrhage TEAEs were gastrointestinal hemorrhages (15/673 [2%]) and intracranial hemorrhage (10/673 [2%]). QTcF prolongation >500 ms (grade 3) occurred in 75/673 patients (11%), mostly in those receiving quizartinib >60 mg (n = 64) (Table 1C). In the 60-mg dose group, QTcF prolongation >500 ms occurred in 9/277 patients (3%). The median time to onset of QTcF prolongation >500 ms was shorter in the >60-mg dose group than in the 60-mg dose group (9 and 46 days, respectively). Arrhythmias potentially related to QTcF prolongation were infrequent; one event of torsade de pointes, and one event of fatal cardiac arrest (both at doses >60 mg) were observed. No dose effects were seen with hepatic disorders, cardiac arrhythmias, or cardiac failure AESI categories. Conclusions: The overall safety profile of quizartinib in this R/R AML pooled analysis is consistent with that observed in QuANTUM-R. A reduction in the incidence of QTcF prolongation was noted with lower doses of quizartinib (30 or 60 mg vs >60 mg). There was also a reduced incidence of gastrointestinal symptoms, infections, and bleeding at lower doses of quizartinib (30 or 60 mg vs >60 mg). Results from this pooled analysis demonstrate that quizartinib is well tolerated at the proposed dosing regimen (60 mg QD with a 30-mg starting dose) in patients with R/R AML. Disclosures Cortes: BiolineRx: Consultancy; Biopath Holdings: Consultancy, Honoraria; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding. Ganguly:Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau; Daiichi Sankyo: Research Funding. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Levis:FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding. Martinelli:Daiichi Sankyo: Consultancy, Honoraria; Amgen: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant; Novartis: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant. Perl:Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau. Choi:Daiichi Sankyo: Employment. Mendell:Daiichi Sankyo, Inc.: Employment. Namuyinga:Daiichi Sankyo: Employment. Pham:Daiichi Sankyo: Employment. Said:Daiichi Sankyo: Employment. Wang:Daiichi Sankyo: Employment. Mitov:Daiichi Sankyo UK Ltd: Employment. Kim:Daiichi Sankyo: Employment. Khaled:Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support; Omeros: Consultancy.

Introduction: Patients (pts) with relapsed/refractory (R/R) acute myeloid leukemia (AML) with FLT3-ITD mutations have a dismal prognosis and limited treatment options. Given the aggressiveness of FLT3-ITD AML, therapies that produce rapid and sustained disease control are needed. Quizartinib (Q), a once-daily, oral, highly potent and selective FLT3 inhibitor, demonstrated a clinically meaningful overall survival (OS) benefit in pts with R/R FLT3-ITD AML vs salvage chemotherapy (SC; 6.2 vs 4.7 mo [HR, 0.76 (95% CI, 0.58-0.98); P = .02]) in the phase 3 QuANTUM-R trial (NCT02039726; Cortes et al. Lancet Oncol, 2019). In this post hoc analysis, we characterize clinical outcomes in pts who achieved a composite complete remission (CRc) in QuANTUM-R, including pts with CR with incomplete hematologic recovery (CRi) and transfusion independence. Methods: Pts aged ≥ 18 years with FLT3-ITD AML R/R after standard AML therapy, with or without hematopoietic stem cell transplant (HSCT), were randomized 2:1 to Q (60 mg [30-mg lead-in]) or 1 of 3 prespecified SC regimens. Pts receiving HSCT in the Q arm could resume Q after HSCT. Response was assessed per modified International Working Group criteria (Table 1). Transfusion dependence at baseline (BL) was defined as any platelet (PLT) or red blood cell (RBC) transfusion within 28 days of first dose. Post-BL transfusion independence was defined as no PLT or RBC transfusions for any consecutive 56-day period on treatment. Results: Of 367 randomized pts, 245 and 122 were randomized to Q and SC, respectively. Median duration of treatment was 97 days with Q (including post-HSCT resumption) and ranged from 5 to 10 days with SC depending on the regimen. Median follow-up was 23.5 mo. In the intent-to-treat population, CRc was consistent across prespecified subgroups (eg, sex, response to prior therapy, FLT3-ITD variant allele frequency). Median time to CRc was 1.1 mo with Q and 0.9 mo with SC; median duration of CRc was 2.8 mo with Q and 1.2 mo with SC (Table 2). Most responses in both arms were CRi, achieved in 99 pts (40%) in the Q arm and 32 pts (26%) in the SC arm. Peripheral blood counts in pts who achieved CRi are shown in Table 3. Of pts with CRi, 45 (Q) and 13 (SC) underwent HSCT. Outcomes with HSCT included engraftment failure in 11% (Q), rejection in 2% (Q), relapse in 33% (Q) and 46% (SC), and successful transplant in 47% (Q) and 46% (SC) and were unknown in 7% (Q) and 8% (SC). Of the 205 pts in the Q arm who were transfusion dependent at BL, 46 (22%) became transfusion independent post-BL (29 with HSCT; 17 without). Mean (SD) duration of post-BL transfusion independence was 255 (216.6) days. By response, 24 of 91 pts (26%) with CRi, 7 of 48 (15%) with a partial response (PR), and 4 of 47 (9%) with no response (NR) became transfusion independent post-BL; respective mean (SD) durations were 297.6 (268.3), 84.6 (21.7), and 211.3 (111.9) days. Of the 36 pts in the Q arm who were transfusion independent at BL, 20 (55.6%) maintained transfusion independence post-BL (12 with HSCT; 8 without; mean [SD] duration, 208 [203.1] days). Transfusion independence could not be assessed in the SC arm. Transfusion data was not collected after the end of treatment, and most pts in the SC arm were treated for < 56 days. In the Q arm, median OS (95% CI) was longer in pts with CRi (7.5 [5.4-9.9] mo) vs pts with PR (6.1 [5.1-7.2] mo) or NR (4.1 [3.3-5.9] mo) (Figure 1); respective medians in the SC arm were 8.8 (6.3-20.8), 7.8 (5.4-28.2), and 3.8 (2.7-4.7) mo. In the 34 pts in the Q arm with a last response of CRi prior to allogeneic HSCT, median OS (95% CI) was 25.1 (9.9-NA) mo; in the SC arm (n = 9), median OS (95% CI) was 20.1 (4.3-NA) mo. In the Q arm, median OS (95% CI) was longer in pts with CRi who became transfusion independent post-BL vs pts who did not (27.1 [10.4-NA] vs 5.3 [4.6-6.4] mo); similarly, median OS (95% CI) was longer in pts who maintained transfusion independence vs pts who did not (25.1 [11.4-NA] vs 9.6 [4.6-NA] mo). Conclusions: Q induced rapid, durable, and consistent tumor control in pts with FLT3-ITD R/R AML irrespective of prior therapy, including HSCT. A high proportion of pts with CRi became eligible for HSCT, the only potential curative treatment option. Moreover, a high proportion achieved durable transfusion independence regardless of HSCT, which is also associated with clinical benefit. These data highlight the clinical benefit of achieving CRi with Q in pts with FLT3-ITD R/R AML, a population with a high unmet need. Disclosures Levis: Novartis: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Amgen: Consultancy, Honoraria; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria. Ganguly:Daiichi Sankyo: Research Funding; Seattle Genetics: Speakers Bureau; Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board. Khaled:Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support; Omeros: Consultancy. Krämer:BMS: Research Funding; Bayer: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees. Martinelli:Novartis: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Other: trial grant; Amgen: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Janssen: Consultancy, Other: trial grant. Perl:BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau. Choi:Daiichi Sankyo: Employment. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Mendell:Daiichi Sankyo, Inc.: Employment. Mires:Daiichi Sankyo: Employment. Zhang:Daiichi Sankyo: Employment. Cortes:Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Sun Pharma: Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; BiolineRx: Consultancy; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Biopath Holdings: Consultancy, Honoraria; Takeda: Consultancy, Research Funding; Immunogen: Consultancy, Honoraria, Research Funding.

Introduction: R/R FLT3-ITD AML is an aggressive hematologic malignancy with a generally poor prognosis and high relapse rate even after allogeneic hematopoietic stem cell transplantation (HSCT). QuANTUM-R (NCT02039726), a large, global, phase 3, randomized, controlled trial, showed that single-agent quizartinib significantly prolonged overall survival (OS) vs salvage chemotherapy (SC) in patients with R/R FLT3-ITD AML after first-line treatment with or without HSCT (Cortes et al, Lancet Oncol 2019). To evaluate both quality and quantity of life for patients with R/R FLT3-ITD AML, we conducted a Q-TWiST analysis of QuANTUM-R data to compare survival between patients receiving quizartinib and SC adjusted for quality of life (QOL). Methods: The primary analysis cohort was the intent-to-treat (ITT) QuANTUM-R population, which included 367 patients (245 patients receiving quizartinib; 122 patients receiving SC). The secondary analysis cohort was the per-protocol analysis set (PPS), which excluded patients randomized but not treated and patients with major protocol violations who would affect assessment of efficacy endpoints (231 patients receiving quizartinib; 88 patients receiving SC). Each patient's OS was partitioned into 3 health states: time with any grade 3/4 treatment-emergent adverse events (TEAEs) before relapse (TOX), time without relapse or grade 3/4 toxicity (TWiST), and time after relapse (REL). Q-TWiST was assessed at 104 weeks (approximate median follow-up of QuANTUM-R) as the mean time spent in each state weighted by its respective QOL, represented by health utility (u; 0.0-1.0). Q-TWiST was calculated as follows: Q-TWiST = u(TWiST) × TWiST + u(TOX) × TOX + u(REL) × REL for which u(TWiST), u(TOX), and u(REL) represent the utilities applied to the restricted mean time in TWiST, TOX, and REL, respectively. Relative Q-TWiST gain (ie, Q-TWIST gain divided by mean OS of salvage chemotherapy) of ≥ 15% was considered clinically important, based on published minimally important difference norms (Revicki et al, Qual Life Res 2006). The base case that assessed the Q-TWiST difference between quizartinib and SC for the ITT population included any grade 3/4 TEAEs and set utilities at commonly assumed values: u(REL) = u(TOX) = 0.5, relative to u(TWiST) = 1.0. A sensitivity analysis was conducted for which u(TOX) and u(REL) were varied from 0.0 to 1.0. The following additional scenarios analyses were conducted: (1) including only treatment-related (TR) grade 3/4 TEAEs, (2) assessing Q-TWiST difference between quizartinib and SC for the PPS cohort, and (3) including only TR grade 3/4 TEAEs for the PPS cohort. 95% CIs were estimated via nonparametric bootstrap. Results: For the ITT population, quizartinib was associated with a mean OS gain of 8.5 weeks vs SC at 104 weeks from randomization (Table). In base case, the mean (95% CI) Q-TWiST gain at 104 weeks for quizartinib vs SC was 6.7 weeks (1.7-12.3; relative gain, 20.3%), which was statistically significant and clinically meaningful (Table). For the sensitivity analysis for which u(TOX) and u(REL) were varied from 0.0 to 1.0, Q-TWiST gains for quizartinib ranged from 5.0 (u[REL] = u[TOX] = 0.0) to 8.5 weeks (u[REL] = u[TOX] = 1.0). The relative Q-TWiST gains for quizartinib vs SC remained clinically important, irrespective of the values for u(TOX) and u(REL) and ranged from 15.2% to 25.5% (Figure). In the scenario analyses (Table), (1) when only TR grade 3/4 TEAEs were included, the Q-TWiST gain for quizartinib was 7.4 weeks (2.2-13.0; relative gain, 22.5%), (2) in the PPS cohort, the mean (95 % CI) Q-TWiST gain for quizartinib was 6.9 weeks (0.8-13.5; relative gain, 20.7%), and (3) when including only TR grade 3/4 TEAEs in the PPS, the Q-TWiST gain for quizartinib was 7.5 weeks (1.5-14.2; relative gain, 22.5%). Conclusions: Quizartinib significantly prolonged quality-adjusted survival vs SC in patients with R/R FLT3-ITD AML after disease control, safety, and QOL were accounted for, providing evidence of meaningful clinical benefit in a patient population with few treatment options. To put these results in perspective, the relative Q-TWiST gains for quizartinib reported herein are larger than nearly 90% of the relative Q-TWiST gains reported in a recent systematic review of 81 Q-TWiST comparisons across 13 cancers (Solem et al, Exp Rev Pharmacoecon Outcomes Res 2018). Disclosures Cortes: Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Immunogen: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; BiolineRx: Consultancy; Sun Pharma: Research Funding. Ganguly:Daiichi Sankyo: Research Funding; Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau. Khaled:Omeros: Consultancy; Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Levis:Daiichi Sankyo Inc: Consultancy, Honoraria; Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding. Martinelli:Janssen: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria; Amgen: Consultancy, Other: trial grant; Novartis: Consultancy, Other: trial grant; Ariad: Consultancy, Other: trial grant. Perl:Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.. Russell:Astellas: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau. Botteman:Pharmerit International: Employment, Equity Ownership; Alnylam Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy, Research Funding. Shah:Merck: Research Funding; Bayer: Research Funding; Pfizer: Research Funding. Luo:Pharmerit International: Employment. Shun:Daiichi Sankyo: Employment. Ray:Daiichi Sankyo: Employment, Equity Ownership.

Background: Quizartinib, a once-daily, oral, highly potent and selective FLT3 inhibitor, demonstrated a significant improvement in survival vs SC in FLT3-ITD-positive R/R AML in the global, randomized, phase 3 QuANTUM-R study (Cortes et al. Lancet Oncol, 2019; NCT02039726). Patients with R/R FLT3-ITD-positive AML were randomized 2:1 to receive single agent quizartinib or investigator's choice of pre-selected SC. We investigated the effects of baseline co-mutations and FLT3-ITD VAF on overall survival (OS) and response (composite complete remission [CRc]) to quizartinib and SC in QuANTUM-R. Methods: We analyzed 37 recurrently mutated genes in AML in baseline bone marrow samples from 304 patients (82.8% of ITT population [N = 367; quizartinib, n = 245; SC, n = 122]) with R/R FLT3-ITD-positive AML using next-generation sequencing and a customized Archer® Core Myeloid panel. Positive mutation status was defined as ≥ 1 mutation detected in the gene region using a VAF cutoff of 2.7%. FLT3-ITD VAF was measured separately by the Navigate BioPharma FLT3 Mutation Assay (polymerase chain reaction-based, VAF cutoff of 3%). Low and high FLT3-ITD VAF were defined as ≤25% and >25%, respectively. Results: In addition to FLT3-ITD, 5 key co-mutations were detected: DNMT3Amut (n = 182/304 [59.9%]), NPM1mut (n = 168/304 [55.3%]), TET2mut (n = 98/304 [32.2%]), IDH1/2mut (n = 49/304 [16.1%]) and CEBPAmut (n = 46/304 [15.1%]). Median OS was numerically longer with quizartinib vs SC in patients with DNMT3Amut, TET2mut, IDH1/2mut and NPM1mut, but not CEBPAmut (Table). CRc rates were numerically higher with quizartinib vs SC for each of the 5 key baseline co-mutations. For single gene mutations, the longest median OS was seen in patients with CEBPAmut treated with quizartinib or SC (37 and 37.6 weeks, respectively). As the majority of NPM1mut patients were also DNMT3Amut (138/168, 82%), we examined various permutations of these two mutations. Patients with NPM1wt/DNMT3Amut had significantly longer median OS with quizartinib vs SC (39.3 vs 19.6 weeks, respectively; HR, 0.239; P = 0.003 [Table]) while NPM1mut/DNMT3Amut patients had lower and similar median OS between the 2 arms (23.6 vs 23.4 weeks, respectively). Quizartinib treatment showed significantly longer median OS vs SC in patients with high FLT3-ITD VAF (23.9 vs 17 weeks respectively; HR, 0.689, P = 0.0148), while the median OS in patients with low FLT3-ITD VAF was similar (34.1 vs 26.6 weeks, respectively; HR, 0.857, P = 0.535). Conclusions: This is the first evaluation of the effect of baseline co-mutations on clinical outcomes in a large trial of R/R AML patients with FLT3-ITD mutations treated with quizartinib. Key co-mutations identified in this analysis were found to potentially impact treatment response and OS with quizartinib, relative to SC. Despite relatively low CRc rates in patients with IDH1/2mut, this group-as well as those with NPM1wt-derived the greatest OS benefit from quizartinib compared with SC on QuANTUM-R. CEBPA mutations were associated with high CRc rates and relatively long median OS, regardless of treatment arm. Patients with NPM1mut had a higher CRc rate with quizartinib vs SC, but this did not translate into longer survival on either arm compared with NPM1wt. A high allelic burden of FLT3-ITD at the time of salvage therapy was associated with relatively poorer median OS; quizartinib significantly improved survival of patients with high FLT3-ITD VAF relative to SC. Although these results require confirmation in an independent dataset, the modulatory effects of baseline co-mutations on treatment response and OS with quizartinib appear to differ from other FLT3 inhibitors. Our results indicate that a subset of R/R AML patients may particularly derive clinical benefit from quizartinib. Table Disclosures Perl: Daiichi Sankyo: Consultancy, Honoraria, Other, Research Funding; Arog: Consultancy, Other: Non-financial support included travel costs for advisory board meetings.; AbbVie: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Actinium Pharmaceuticals: Consultancy, Honoraria, Other: Clinical Advisory Board member, Research Funding; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Non-financial support included travel costs for advisory board meetings.; Jazz: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; NewLink Genetics: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Takeda: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings.; Bayer: Research Funding; BioMed Valley Discoveries: Research Funding; FujiFilm: Research Funding; Novartis: Honoraria, Other: Advisory board, Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of the data., Research Funding; Astellas: Consultancy, Honoraria, Other: Non-financial support included travel costs for advisory board meetings as well as a medical writing company that assisted with manuscript preparation/submission and slide deck assembly for academic meeting presentations of trial data., Research Funding. Cortes:Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Merus: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; BiolineRx: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Sun Pharma: Research Funding; Immunogen: Consultancy, Honoraria, Research Funding. Ganguly:Kite Pharma: Honoraria, Other: Advisory Board; Janssen: Honoraria, Other: Advisory Board; Seattle Genetics: Speakers Bureau; Daiichi Sankyo: Research Funding. Khaled:Omeros: Consultancy; Alexion: Consultancy, Speakers Bureau; Daiichi Sankyo: Other: Travel support. Krämer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding. Martinelli:Novartis: Consultancy, Other: trial grant; Roche: Consultancy, Other: trial grant; Janssen: Consultancy, Other: trial grant; Incyte: Consultancy, Other: trial grant; Pfizer: Consultancy, Other: trial grant; Amgen: Consultancy, Other: trial grant; Celgene: Consultancy, Honoraria, Other: trial grant; Ariad: Consultancy, Other: trial grant; Abbvie: Consultancy, Honoraria, Other: trial grant; Daiichi Sankyo: Consultancy, Honoraria. Russell:Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; DSI: Consultancy, Honoraria, Speakers Bureau. Chang:Daiichi Sankyo: Employment. Mires:Daiichi Sankyo: Employment. Kato:Daiichi Sankyo, Inc.: Employment; Celgene: Employment, Equity Ownership. Zhang:Daiichi Sankyo: Employment. Korkhov:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Wang:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Günnel:Precision for Medicine, Inc.: Employment; Daiichi Sankyo: Consultancy. Sumi:Daiichi Sankyo, Inc.: Employment. Isoyama:Daiichi Sankyo Co, Ltd: Employment. Lesegretain:Daiichi-Sankyo Inc.: Employment, Equity Ownership. Berisha:Daiichi Sankyo: Employment. Dos Santos:Daiichi Sankyo: Employment. Levis:Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding; Menarini: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; Daiichi Sankyo Inc: Consultancy, Honoraria.

Background: AZA monotherapy has demonstrated improvement in OS in HR MDS, clinically meaningful and durable responses continue to be limited to a subset of patients (Silverman 2006). One obvious strategy is to develop doublet therapy with drugs that are effective monotherapy in HR MDS and can be administered effectively and safely in combination with AZA. Several agents have been combined with AZA in first line therapy for pts with HR-MDS achieving ORR and CR/PR rates that are comparable to AZA monotherapy (ORR 38% and CR/PR of 24%) (Ades ASH 2018; Sekeres JCO 2017). RAS and other signaling molecules in the Ras pathway are frequently mutated in HR MDS and are proposed to drive leukemic transformation (Takahashi 2013). Given that rigosertib interferes with the RAS-binding domain of RAF kinases and inhibits the RAS-RAF-MEK & the PI3Ks pathways (Athuluri-Divakar, Cell 2016), it is an attractive candidate for combination with AZA. Furthermore, in vitro combo of rigosertib with AZA synergistically inhibits growth and induces apoptosis of leukemic cells in a sequence-dependent fashion (Skiddan AACR 2006). We report updated results from a Phase II study in a subset of patients receiving oral rigosertib in combination with standard dose AZA as first line therapy for HR MDS. Methods: In the Phase II study 09-08, a total of 39 treatment-naïve HR MDS/RAEB-t patients received oral rigosertib in combination with standard dose AZA. Rigosertib was given at 840mg/day (560 mg in the morning & 280mg in the afternoon); or 1120mg/day (560 mg in the morning & 560mg in the afternoon or 840 mg in the morning and 280 mg in the afternoon) (Maniar ASH 2018). Responses were determined by 2006 IWG criteria including transfusion independence (56 days without PBC or PLT transfusions). Oral rigosertib was administered on D1-D21 of a 28D cycle. Parenteral AZA 75mg/m2/day was administered for 7days from D8. Patients were evaluable for response if they received 3 cycles of therapy. Results: Median age of the pts was 64 years (42-90). IPSS-R score at study entry was 9 were Intermediate, 8 were High and 17 were Very High Risk (VHR). In total 20 pts were transfusion-dependent at study entry. CR/PR responses were observed across all IPSS-R cytogenetic prognostic subgroups: Very Poor 60%, Poor 25%, Intermediate 37.5% & Good 25%. CR/PR responses were also observed across all higher IPSS-R prognostic risk categories: Very High 42%, High 17% and Intermediate 25%. A summary of clinical benefit/risk is provided in Table 1 below. Median duration of response was 12.2 mos (0.1-24.2+) and median duration of treatment was 8 mos (1.3-27.3). Time to first and best responses was 1/4 mos. Four pts continue to respond to therapy. 10 AEs led to D/C: urinary tract pain (2), and 1 each for urinary retention, hematuria, hydronephrosis, osteolysis, cerebral haemorrhage, WBC count decreased, neutrophil count decreased, & abd pain. The most frequent AE in table 1, are similar to AEs reported for both rigosertib and AZA as monotherapies, & the GU toxicities were mitigated using specific management guidelines. The majority of MDS pts who experienced AEs ≥Grade 2 were successfully managed and continued to receive the doublet on study. Conclusion: The efficacy (90% ORR & 34% CR) and safety of oral rigosertib and AZA in combination is favorable as first line therapy in pts with HMA naïve HR MDS and are comparable to historical results for standard dose AZA monotherapy (ORR 38% and Disclosures Navada: Onconova Therapeutics Inc: Research Funding. Garcia-Manero:Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Atallah:Helsinn: Consultancy; Jazz: Consultancy; Helsinn: Consultancy; Jazz: Consultancy; Novartis: Consultancy; Takeda: Consultancy, Research Funding; Pfizer: Consultancy. Shammo:Otsuka: Consultancy, Honoraria; CTI Pharma: Research Funding; Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Alexion: Consultancy, Honoraria, Research Funding, Speakers Bureau; Onconova: Research Funding; Apellis: Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Speakers Bureau; Astex Pharma: Research Funding. Griffiths:Abbvie, Inc.: Consultancy, PI on a clinical trial; Celgene, Inc: Consultancy, Research Funding; Genentech, Inc.: Research Funding; Novartis Inc.: Consultancy; Novartis Inc.: Consultancy; Genentech, Inc.: Research Funding; Boston Scientific: Consultancy; Boston Scientific: Consultancy; Persimmune: Consultancy; Persimmune: Consultancy; New Link Genetics: Consultancy; New Link Genetics: Consultancy; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Partner Therapeutics: Consultancy; Appelis Pharmaceuticals: Other: PI on a clinical trial; Onconova Therapeutics: Other: PI on a clinical trial; Appelis Pharmaceuticals: Other: PI on a clinical trial; Onconova Therapeutics: Other: PI on a clinical trial; Abbvie, Inc.: Consultancy; Partner Therapeutics: Consultancy; Celgene, Inc: Consultancy, Research Funding. Khaled:Alexion: Consultancy, Speakers Bureau; Omeros: Consultancy; Daiichi Sankyo: Other: Travel support. Adesanya:Onconova Therapeutics, Inc.: Employment. Zbyszewski:Onconova Therapeutics, Inc.: Employment. Woodman:Onconova Therapeutics, Inc.: Employment. Fenaux:Jazz: Honoraria, Research Funding; Aprea: Research Funding; Celgene Corporation: Honoraria, Research Funding; Astex: Honoraria, Research Funding. Silverman:Medimmune: Research Funding; Celgene: Research Funding; Onconova Therapeutics Inc: Patents & Royalties, Research Funding.

Introduction: Patients (pts) with higher-risk myelodysplastic syndrome (HR-MDS) and those who fail to respond to or relapse/progress after treatment with hypomethylating agents (HMA) have limited therapeutic options and poor prognosis. PD-L1 expression is upregulated in HR-MDS pts (compared with lower-risk MDS pts) and in those who fail HMA therapy. Combining inhibition of the PD-L1/PD-1 pathway with azacitidine may improve outcomes in MDS. Methods: We conducted a Phase Ib trial of the anti-PD-L1 monoclonal antibody atezolizumab, with or without azacitidine, in HMA-failure and HMA-naive MDS pts (NCT02508870). The primary objective was to determine the safety and tolerability of atezolizumab as a single agent or in combination with azacitidine. An initial safety evaluation was performed in three cohorts. Cohort A1 (10 pts) consisted of HMA-failure HR-MDS pts treated with atezolizumab alone (1200mg IV q3w). Cohort B1 (11 pts) consisted of HMA-failure HR-MDS pts treated with atezolizumab (840mg IV q2w) in combination with azacitidine (75mg/m2 qd for 7 days q4w) for 6 cycles, followed by atezolizumab maintenance alone (1200mg IV q3w). Cohort C1 (6 pts) consisted of HMA-naive HR-MDS pts treated with atezolizumab (840mg IV q2w) in combination with azacitidine (75mg/m2 qd for 7 days q4w). If atezolizumab alone or in combination with azacitidine was deemed safe and tolerable in Cohorts A1 and B1, an additional 1:1 randomization into two cohorts of 30 pts each (Cohorts A2 and B2) was planned. If the combination of atezolizumab and azacitidine was found to be safe and tolerable in Cohort C1, an additional expansion cohort (Cohort C2) of 14 pts with HMA-naive HR-MDS was planned. Primary endpoints included determining the safety and tolerability of atezolizumab-based regimens in HR-MDS and defining the recommended Phase II dose for the combination. Results: As of January 2018, 42 HR-MDS pts had been treated with atezolizumab-based regimens: Cohort A, 10 pts; Cohort B, 11 pts; Cohort C, 21 pts. Median age for the entire pt cohort was 76 years (range: 63−89). Median treatment duration for Cohorts A, B, and C was 4.2, 5.5, and 5.8 months, respectively. The overall response rate for Cohorts A, B, and C was 0%, 9% (hematologic improvement [HI]: 9%), and 62% (CR, 14%; mCR, 19%; mCR + HI, 10%; HI, 19%), respectively. All pts in Cohorts A and B have discontinued therapy, with a median overall survival (OS) of 5.9 months and 10.7 months, respectively. For pts in Cohort C, 8/21 pts remain on therapy, and median OS has not been reached. Grade 3−5 adverse events (AEs) in >10% of pts were primarily hematologic; grade 3−5 febrile neutropenia occurred in 29% of all pts and was particularly common in pts receiving the atezolizumab-azacitidine combination (Cohorts B [36%] and C [33%] compared with Cohort A [10%]; Table 1). In Cohort A, 70% (7/10) of pts died, as did 64% (7/11) of pts in Cohort B and 29% (6/21) of pts in Cohort C. Median time to death was 160 days (Cohort A), 299 days (Cohort B), and 53 days (Cohort C). Timing and causes of death were different in the three cohorts. Causes of death were more commonly from disease progression in Cohorts A and B, while serious AEs accounted for all deaths in Cohort C (Table 2). In addition, deaths within 3 months occurred in 10%, 18%, and 29% of pts in Cohorts A, B, and C, respectively. The high early death rate compared with historical controls observed in HMA-naive HR-MDS patients (Cohort C) led to early termination of the study prior to completing recruitment. Biomarker assessment demonstrated PD-L1 expression on variable proportions of AML blasts in samples from all pts analyzed. However, PD-L1 expression was not associated with clinical response (Figure). Conclusions: Combination of atezolizumab plus azacitidine in HMA-naive HR-MDS pts had an unfavorable safety profile, which led to early termination. Limited responses were observed with atezo-based regimens (with or without azacitidine) in HMA-failure HR-MDS pts, without excessive or unexpected toxicity. Better understanding of the reasons associated with the differential toxicity profile observed between HMA-naive versus HMA-failure HR-MDS pts will be crucial for potential future developments of this combination. Disclosures Gerds: Incyte: Consultancy; Celgene: Consultancy; CTI Biopharma: Consultancy; Apexx Oncology: Consultancy. Khaled:Daiichi: Consultancy; Alexion: Consultancy, Speakers Bureau; Juno: Other: Travel Funding. Lin:Jazz Pharmaceuticals: Honoraria. Pollyea:AbbVie: Consultancy, Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Curis: Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees. Dail:Genentech: Employment, Equity Ownership. Green:Genentech: Employment. Ma:Genentech: Employment. Medeiros:Genentech: Employment, Equity Ownership. Phuong:Genentech Inc: Employment, Equity Ownership, Other: Ownership interests PLC. Wenger:F. Hoffmann-La Roche Ltd: Employment, Equity Ownership, Other: Ownership interests PLC. Yan:Roche: Employment.

Introduction: Higher risk MDS is a serious disease associated with poor survival with hypomethylating agents (HMAs) the standard of care in patients ineligible for stem cell transplantation. Unfortunately, HMAs are only effective in 30-40% of patients with duration of response typically shorter than 1.5 years (Fenaux, Lancet Oncol 2009) leading to evaluation of combination therapies to improve outcomes in higher risk MDS. Inhibition of both histone deacetylation and DNA hypermethylation has been shown to induce re-expression of silenced genes in myeloid malignancies in a synergistic fashion. Studies have evaluated HMAs in combination with HDACi but the results have been disappointing due to increased toxicity and early discontinuations. Pracinostat, a potent oral Class I, II, IV HDAC inhibitor, has been studied in combination with standard dose azacitidine in a prior Phase 2 study in 102 patients with untreated IPSS intermediate-2/high risk MDS (Garcia-Manero, Cancer 2017). Pracinostat was administered at 60 mg/day on 3 alternate days/week for 3 weeks/month, with step down dose to 45 mg in case of poor tolerability. Toxicity, primarily cytopenias, nausea, vomiting and fatigue resulted in early discontinuations and insufficient treatment exposure, potentially leading to diminished efficacy and no observed benefit of the pracinostat/azacitidine combination. This follow-up study is evaluating a lower dose of pracinostat (25% reduction) in combination with standard dose azacitidine with the goal of reducing toxicity, decreasing early discontinuations, and improving outcomes. Methods: The primary objective of this Phase 2, two-stage study at 24 sites is to determine the safety/tolerability and efficacy of the pracinostat/azacitidine combination in patients with IPSS-R high-/very high-risk MDS previously untreated with HMAs. Up to 40 subjects were to enroll in Stage 1, treated with pracinostat at 45 mg, 3 days each week for 3 consecutive weeks, followed by 1 week of rest, along with azacitidine at the standard dose of 75 mg/m2 for 7 days of each 28-day cycle. Study drugs are to be administered until disease progression or intolerable toxicity, avoiding early discontinuation ( Results: At the time of the interim analysis (25 May 2018), 39 patients had received ≥1 dose of study treatment and 20 were evaluable for assessment of early discontinuations. Median age was 67 years, 69% were male, and 59% had high-risk MDS. Of the 20 evaluable patients, 2 patients (10%) discontinued prior to the end of Cycle 3 due to AEs (1 febrile neutropenia, Day 45 and 1 fungal infection, Day 90). In 18 subjects evaluated for response at the end of Cycle ≥2, the ORR was 28% (1 complete response, 4 partial responses). Most common Grade ≥3 AEs in the 33 patients with >1 week follow-up were decreased neutrophil count (33%), anemia (30%), febrile neutropenia (27%), and dyspnea (12%). Non-hematologic AEs of fatigue and gastrointestinal events were reduced in this initial group of patients relative to that seen in the prior study. Conclusions: The interim analysis of this study evaluating the efficacy and safety of pracinostat + azacitidine in patients with IPSS-R high-/very high-risk MDS revealed a discontinuation rate and an efficacy response rate meeting the predefined thresholds to allow for expansion of the study. These findings suggest that a reduced dose of pracinostat may allow patients to remain on treatment longer, thus increasing the likelihood of a treatment response. Based on these data, the study IDMC approved expansion of this study to enroll 60 evaluable patients. Updated data, including 6 months efficacy data on the initial cohort, will be presented. Disclosures Khaled: Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy; Juno: Other: Travel Funding. Ramies:MEI Pharma, Inc: Employment. Mappa:Helsinn Healthcare: Employment. Atallah:Jazz: Consultancy; BMS: Consultancy; Abbvie: Consultancy; Pfizer: Consultancy; Novartis: Consultancy.

Several prognostic models have been developed to predict survival outcomes and response in patients with myelofibrosis (MF). MIPSS70 prognostic system, developed by incorporation of all the key clinical characteristics, cytogenetics, and mutational factors into one system, has recently been revised to MIPSS70+ v2.0 with refinements in degrees of anemia, cytogenetics, and HMR. While allogeneic hematopoietic cell transplantation (alloHCT) is the only curative treatment for patients with MF, limited data exists on the impact of molecular markers on transplant outcomes. Here, we evaluated the transplant outcome in MF patients who uniformly received fludarabine/melphalan (FluMel) conditioning at City of Hope and assessed the impact of cytogenetics, somatic mutations on transplant outcomes based on a 72 gene next-generation sequencing (NGS) panel and MIPSS 70+ v2.0. A total of 110 consecutive MF patients (primary: n=58, secondary: n=52) without prior acute leukemic transformation, underwent alloHCT between 2004 and 2017. Median age at the time of transplant was 58.5 years (range: 38-72 years) with median interval from diagnosis of primary or secondary MF to HCT of 15.2 months (range: 1.6-332.5 months). AlloHCT donors were matched related (n=51), matched unrelated (n=44), and mismatched unrelated (n=15). Intermediate-2 and High risk by DIPSS accounted for 83 (76%) of patients at the time of transplant. Tacrolimus/Sirolimus-based GVHD prophylaxis was used in 100 (91%) patients, and 16 had splenectomy prior to alloHCT. Pre-transplant DNA sample were available for 93 patients and cytogenetics information was available for 106 patients; among which 60 had abnormal cytogenetics. Based on recently developed revised cytogenetic risk stratification on transplant outcomes, we identified 67 patients (61%) in favorable, 24 (22%) in unfavorable, and 15 (14%) in very high risk groups. Median number of 2 mutations were detected with at least one mutation in 95% (n=88) of patients. JAK2 V617F was the most common alteration noted in 54 (58.1%) patients. Other common mutations were ASXL1 (n=41, 44%), CALR type 1 (n=15, 16.1%), TET2 (n=12, 13%) SRSF2 and DNMT3A (each n=10, 11%). No detectable mutations were found in 5 (5.4%) patients. HMR genes (ASLX1, EZH2, IDH1/2, SRSF2, and U2AF1) were identified in 48 patients (52%), with 30 patients (32%) carrying one and 18 patients (19%) carrying more than 1 HMRs. With a median follow-up of 63.7 months (range: 11.9-158.5), 5 year overall survival (OS) and non-relapse mortality (NRM) were 65% (95% CI: 54-73) and 17% (95%CI: 10%-24%), respectively. Detailed transplant outcomes were previously reported (Ali et al. American Society of Hematology. Vol. 130. Atlanta, GA: Blood; 2017:199) (Figure 1a). On multivariable analysis, unfavorable and VHR cytogenetic changes had significantly shorter OS and PFS (p=0.001 and 0.008), and relapse risk (p=0.035) (Figure1b). Triple negative status (p=0.063), HMR (p=0.73), and more than 1 HMR (p=0.59) did not significantly impact survival post-HCT. (Figure1c) Similarly, CALR type 1 (p=0.42), and ASXL1 (p=0.29) mutations also did not impact survival after HCT. Only CBL mutation was significantly associated with lower OS (HR=2.64, 95% CI: 1.09-6.38, p=0.032) and lower DFS (HR=4.35, 95% CI: 1.83-10.36, p In summary, we are presenting one of the largest single center experiences of FluMel-based alloHCT for MF patients, demonstrating revised cytogenetic changes and MIPSS70+ v2.0 accurately predicts transplant outcomes, thus would better inform physicians and patients in discussing and decision making about alloHCT. Figure. Figure. Disclosures Ali: Incyte Corporation: Membership on an entity's Board of Directors or advisory committees. Khaled:Juno: Other: Travel Funding; Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy. Salhotra:Kadmon Corporation, LLC: Consultancy. Stein:Amgen Inc.: Speakers Bureau; Celgene: Speakers Bureau. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding.

The current view is that treatment failures of AML patients are due to persistence of leukemia stem cells (LSCs). The presence of FMS-like tyrosine kinase-3 (FLT3) Internal tandem duplication (ITD) is associated with poor prognosis. But, FLT3 tyrosine kinase inhibitors (TKI) demonstrate transient clinical activity in FLT3-ITD+ AML patients. Persistent FLT3-ITD+ AML LSC represent a source of relapse. There is a pressing need to target LSC and improve outcomes for FLT3-ITD+ AML patients. PRMT1, the predominant arginine methyltransferase, has been implicated in pathogenesis of AML rare subtype (i.e., acute megakaryoblastic leukemia). Herein, we show that PRMT1 protein expression is significantly increased in LSC-enriched AML CD34+CD38- cells relative to the counterparts of normal peripheral blood stem cells (PBSC) (AML n=9, normal n=8, p=0.0004,). Following PRMT1-knockdown (KD), AML CD34+ cells (n=15) demonstrated varying degrees of apoptosis while the survival of normal cells were not affected. Interestingly, we observed significant apoptosis-induction in a subset of samples bearing FLT3-ITD mutation (6 out of total 15) upon PRMT1-KD (ShCtrl 13.9±3.6%, ShPRMT1 32.5±4.6%, p Given that PRMT1 directly interacts with FLT3-ITD, we next asked whether PRMT1 catalyzes FLT3-ITD protein methylation. Through mass-spectrometry analysis of a FLT3-ITD+ AML specimen and in vitro methylation assay, we identified that PRMT1 catalyzes FLT3-ITD arginine (R) methylation (Me) at two conserved residues, 972 and 973. Using in-house R972/973 Me antibody, we validated the expression of FLT3 R-Me in FLT3-ITD AML speciemens (7 out of 7). To test R-Me function, we transduced MLL-AF9 (MA9) overexpressing murine c-Kit+ cells with methylation-deficient FLT3-ITD (R972/973K, arginine [R] to lysine [K]) construct, and found that MA9 cells expressing R972/973K underwent more apoptosis than that of WT FLT3-ITD (WT FLT3-ITD 9.7±1.1%, R972/973K 23.7±2.1%, p=0.003). The double transformed cells were further transplanted into recipients for leukemia development. Mice receiving MA9 cells expressing R972/973K exhibited longer survival (median survival: WT FLT3-ITD 36 days, R972/973K 50 days, p=0.002, n=6). Mechanistically, expression of R972/973K did not affect the total tyrosine phosphorylation level of FLT3-ITD. Additionally, FLT3-ITD R-Me expression persisted after a TKI (AC220) treatment. These facts indicated that FLT3-ITD R-Me function is independent of FLT3-ITD kinase activity. We then used a FLT3-ITD+ patient derived xenograft (PDX) model to assess the effects of TKI and PRMT1 inhibition. Following engraftment >1% in peripheral blood, we divided mice (n=24) into 4 groups and treated each with vehicle, MS023 (a type I PRMT inhibitor, ACS Chem Biol. 2016;11:772-781) (160 mg/kg/i.p), AC220 (10 mg/kg/i.g) or combination for 4 weeks. MS023 treatment downregulating FLT3 R-Me levels enhanced elimination of FLT3-ITD AML cells by AC220 treatment (AC220 24.6±13.4% vs combination 7.6±6.5%, p=0.02, n=6). At 16 weeks post-secondary BMT, significant AML burden in single drug treated transplants was observed, but less AML cells were detected in combination-treated transplants (AC220 52.3%, vs combination 25.4%, p In summary, our study demonstrated PRMT1 overexpression contributes to AML stem/progenitor cell survival possibly through FLT3-ITD methylation, supporting further exploration into how PRMT1-mediated FLT3 methylation governs LSC survival. Disclosures Khaled: Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy; Juno: Other: Travel Funding.

Allogeneic hematopoietic stem cell transplant (alloHCT) remains the only potentially curative treatment for patients with myelodysplastic syndrome (MDS). However, this treatment is associated with significant risk of transplant-related mortality/morbidity such as graft-versus-host disease, infections, and regimen-related toxicities. Since there has been no "randomized" trial comparing between patients undergoing or not undergoing transplantation, the relative benefit of this treatment, particularly in elderly patients, is largely unknown. Retrospective comparative studies are significantly limited by the inherent selection bias of healthier/well-supported patients in the alloHCT group. Therefore, a critical knowledge gap exists regarding the survival outcome of MDS patients who are transplant eligible yet did not undergo alloHCT due to lack of suitable donors or other reasons. Herein, we retrospectively identified a consecutive case-series of 73 patients with MDS (excluding CMML), who were considered alloHCT candidates, based on initiation of an official donor search from 2005 to 2015, yet did not proceed with alloHCT. Median age at time of donor search was 60 years (range: 20-79) with the majority (63%) being male. Classifications of MDS were single or multi-lineage dysplasia (n=20), excess blast (n=39), MDS unclassified (n=6) or other/unknown classification (n=8). The cohort included 51 de novo MDS and 14 therapy-related MDS (t-MDS). Per International Prognostic Scoring System (IPSS) 29 patients (39.7%) were Intermediate (Int)-1, 14 (19.2%) were Int-2, and 23 (31.5%) were high risk at the time of donor search (Table 1). Reasons for no alloHCT were lack of donor (n=29), persistent/progressive disease (n=9), patient choice (n=13), or infections/complications after initiating the donor search (n=18). Treatments of these patients included chemotherapy (n=14), hypomethylating agents (n=61) and supportive care (n=23). Of the 73 patients, 15 (20.5%) had disease progression to acute leukemia at 1 year. There were 38 deaths with the median OS of 26.2 months (95%CI: 17.3-48.3 months). The 2-year probability of OS was 51% (95%CI: 36.7-62.9%). We next compared outcomes of these MDS patients who had a donor search without subsequent HCT to a consecutive case-series of MDS patients who underwent alloHCT from matched related and unrelated donors (cord blood and haploidentical transplants were excluded) during the same time period (n=276) at our center (Aldoss et al. Haematologica 2017). Patient demographics and MDS disease characteristics were similar between the two groups (Table 1). Median number of days from HLA typing to HCT were 168. By Kaplan-Meier method, OS (from the time of donor search) was significantly better for the alloHCT group (74% at 2-years) compared with non-HCT group (51% at 2-years), log-rank P In conclusion, using a unique cohort of patients who were referred for a donor search, our study in real-world practice demonstrates that transplant eligible MDS patients (at the time of donor search) who do not undergo alloHCT have worse survival outcomes compared to those undergoing transplantation. A prospective biologic assignment study is currently underway by the BMT CTN (#1102) to more definitively determine the impact and relative benefits of alloHCT in patients (≥50 years old) with Int2/high-risk de novo MDS. Disclosures Khaled: Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy; Juno: Other: Travel Funding. Salhotra:Kadmon Corporation, LLC: Consultancy. Ali:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding. Stein:Celgene: Speakers Bureau; Amgen Inc.: Speakers Bureau.

Background: AZA is first line therapy for pts with HR-MDS with an overall response rate (ORR) between 35 and 60% in various publications; with CR/PR rates ranging between 23 and 29% in 3 randomized phase II/III studies (Silverman et al., JCO 2002; Fenaux et al., Lancet Oncol 2009; Sekeres, JCO 2017). AZA also has demonstrated efficacy in older pts with AML (Dombret et al., Blood 2015; Fenaux et al., JCO 2010). Rigosertib interferes with the RAS-binding domains of RAF kinases and inhibits the RAS-RAF-MEK and the PI3Ks pathways (Athuluri-Divakar, Cell 2016). RAS and other genes in this pathway are frequently mutated in HR MDS and putatively drive the malignant clone (Sperling et al., Nat Rev CA 2017). In vitro, the combination of rigosertib with AZA synergistically inhibits growth and induces apoptosis of leukemic cells in a sequence-dependent fashion (Skidan et al; AACR 2006 Abstract 1310). In a trial in lower-risk MDS, oral rigosertib was studied as a single agent at various doses including 560 mg BID for 14-21 days in 28 day cycles and yielded a transfusion independence (TI) rate of 44% - the highest reported TI rate (Raza, ASH Abstract #108660 2017). Based on this observation we expanded the ongoing Phase I/II trial and tested rigosertib at a total of 1120 mg per day with standard dose parenteral AZA (75mg/m2 x 7 days q28 days) in two different schemes as described in methods (NCT01926587). At a dose of 560 mg AM, 280 mg evening the ORR was 77%; 88% for the HMA naïve group and importantly 60% for the HMA Rel/Ref group. Of note, adverse events of interest have been genitourinary (GU) toxicities, particularly hematuria and dysuria. Thus, risk-mitigation strategies (Table 1) were employed to minimize hematuria with higher dose rigosertib at 1120 mg; including the rationale for the lower afternoon (280 mg) dose. We report here the initial results of efficacy and safety. Methods: In the Phase II Expansion cohort, up to 45 pts with HR MDS/RAEB-t/non-proliferative AML were randomized 1:1 into 2 cohorts both to receive 1120 mg of rigosertib over 24 hours: either 560 mg in the morning and 560 mg in the afternoon, or 840 mg in the morning and 280 mg in the afternoon (part of hematuria/dysuria risk mitigation; moving second dose from evening to afternoon to minimize overnight bladder dwell time as permitted by PK analysis (Maniar, ASH Abstract 2018). Each cohort is stratified among HMA naïve and HMA Rel/Ref pts. Hematologic response is determined per IWG 2006. Results: As of July 2018 in the rigosertib 1120 mg cohort in combination with AZA, 45 pts were enrolled; 43 treated, 31 evaluable for response; 14 pts continue on treatment, and 31 pts discontinued (includes 2 enrolled but not treated). To be evaluable for response, a minimum of 12 weeks of the doublet was required. Of the 31 pts evaluable for response, 17 pts are prior Rel/Ref, 14 pts are HMA naïve. The # of prior HMA cycles is 2-15; 13 failed AZA; 1 failed DAC; 2 failed both; and 1 failed other (experimental). The median duration of treatment at this time point for the overall population is 5 months (1-14+). The ORR (Table 2) for the all patients is 68%; 59% for the prior Rel/Ref cohort and 79% for the HMA naïve cohort. For responding patients, responses are seen in both 1120 mg cohorts as shown. Safety: In 43 patients treated with oral rigosertib at 1120 mg and AZA, with risk-mitigating strategies to minimize hematuria, Grade 1 & 2 hematuria = 16%; ≥3 Grade Hematuria = 5% have been seen to date (Table 3). This compares to an incidence of 12 % Gr 3 hematuria at a lower dose of rigosertib (840 mg); and prior to risk mitigation strategies. Incidence of hematuria of any grade with single agent AZA is 6.3 % & Grade ≥3 2.3% (VIDAZA, package insert 2004). Conclusion: The combination of oral rigosertib and AZA in HMA naïve patients with HR-MDS is encouraging compared to single agent AZA. The combination also has activity and reverses the HMA clinical resistance in a substantial number of patients after Rel/Ref, a finding with potentially significant clinical implications. Dose exploration with a higher dose of oral rigosertib (1120mg) administered in different dosing schemes in combination with standard dose AZA continues to be studied to optimize safety and efficacy. By employing risk mitigation strategies, the incidence of GU AEs, including hematuria, has been substantially reduced. We will update the safety and efficacy data at the time of presentation. Based on this data a pivotal trial is planned. Disclosures Navada: Onconova: Research Funding. Atallah:Pfizer: Consultancy; Abbvie: Consultancy; Jazz: Consultancy; BMS: Consultancy; Novartis: Consultancy. Shammo:Incyte: Consultancy, Honoraria, Research Funding; Onconova: Other: research support; Alexion: Honoraria, Other: research support; Novartis: Consultancy, Honoraria; Celgene: Other: research support. Griffiths:Novartis, Inc.: Research Funding; Celgene, Inc: Honoraria, Research Funding; Astex/Otsuka Pharmaceuticals: Honoraria, Research Funding; Pfizer, Inc.: Research Funding; Alexion Inc.: Honoraria, Research Funding. Khaled:Juno: Other: Travel Funding; Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy. Pemmaraju:abbvie: Research Funding; stemline: Consultancy, Honoraria, Research Funding; celgene: Consultancy, Honoraria; Affymetrix: Research Funding; samus: Research Funding; SagerStrong Foundation: Research Funding; cellectis: Research Funding; daiichi sankyo: Research Funding; novartis: Research Funding; plexxikon: Research Funding. Zbyszewski:Onconova Therapeutics, Inc: Employment, Equity Ownership. Maniar:Onconova Therapeutics, Inc: Employment, Equity Ownership. Petrone:Onconova Terapeutics Inc.: Employment, Equity Ownership. Fruchtman:Onconova Therapeutic Inc: Employment, Equity Ownership. Silverman:Johnson and Johnson: Research Funding; Onconova Therapeutics Inc.: Patents & Royalties, Research Funding; Bayer: Research Funding; Celgene: Research Funding; Medimmune: Research Funding; Mount Sinai School of Medicine: Employment.

Introduction: Treatment of adults with relapsed/refractory (R/R) B-ALL using CD19-targeted chimeric antigen receptor (CAR) T cells has achieved remarkable remission rates, both in pediatric and adult populations. There are multiple CAR constructs and T cell manufacturing platforms in use, and both aspects of the therapy may impact efficacy and toxicity. Park et al. report that 83% of adult patients (pts) achieve complete response (CR) to their CD19 CAR T cells with a CD28 costimulatory domain (NEJM; 3785: 449), using an unselected peripheral blood (PBMC) manufacturing platform. Unfortunately, therapy-associated toxicities in adult and pediatric ALL pts are problematic, with grade 3/4 cytokine release syndrome (CRS) ranging from 26-49 % and neurotoxicity 18-42%. Here we report preliminary data from one arm of a phase 1 clinical trial (NCT02146924) in adult pts with R/R B-ALL testing a memory-enriched T cell starting population engineered to express a CD19-specific, CD28-costimulatory CAR (CD19:28z-CAR). All pts achieved CR or CRi with a low incidence of severe cytokine release syndrome (CRS) and neurotoxicity. Unique to this study is our Tn/mem-enriched manufacturing platform, a naïve/memory T cell-enriched T cell product that is lentivirally transduced to express our CD19:28z-CAR. The manufacturing process starts with patient PBMC, depletes the CD14+ monocytes and CD25+ Tregs, and selects for CD62L+ T cells. The resultant T cell population for CAR transduction includes both the central memory and stem cell memory populations along with naïve T cells. Preclinical studies in mice had suggested that using a more uniform T cell product with a less-differentiated T cell phenotype improved antitumor activity. This Tn/mem manufacturing platform is the same as our Tcm-derived platform (Blood;127:2980) except that CD45RA depletion was omitted. Patients and Methods: This phase I study used the activity constrained for toxicity (ACT) design, an extension of the toxicity equivalence range (TEQR) design of Blanchard and Longmate (Contemp Clin Trials; 32:114), that dose escalates based on lack of activity, while constraining the dose for toxicity. The primary objectives of this study were to test the safety and activity of Tn/mem-enriched CD19:28z CAR T cells, and to determine the phase 2 recommended dose. The primary endpoints were toxicity and disease response. Sixteen pts were consented and received a lymphodepleting regimen (LDR) of 1.5-3 gm/m2 cyclophosphamide over 2-3 days and 25-30 mg/m2 fludarabine for 3 days. Three pts received LDR, but did not receive T cells due to infection or lack of CD19+ disease. Patients received a flat dose of 200 million (M) CD19:28z-CAR T cells: 11 autologous and 2 allogeneic donor products. Of the 13 that received 200 M CAR+ T cells, 2 pts were deemed ineligible for dose escalation / disease response evaluation, as 1 received The median age of the 13 CAR T cell treated pts was 33 years (24-72). All pts had active bone marrow (BM) disease at the time of LDR: 8 pts (62%) had high disease burden (15-91% BM blasts) and 5 had low disease burden ( Results: Toxicity: Table 1 describes the major toxicities of the 13 CAR-treated pts, stratified based on disease burden. There were no DLTs, and T-cell therapy attributed (>/=possibly) toxicities were typically mild and reversible. Eight pts had grade 2 CRS, and 2 had grade 3 CRS. Three pts had grade 2 neurotoxicity and 2 had grade 3. Response: Eleven pts were evaluable for response, with best response of 4 CRs (MRD- by flow) and 7 CRi (6 MRD-, 1 not tested). Median response duration at last contact or HSCT start was 81 days (39-286); 8 pts proceeded to HSCT (in CR or CRi) at a median of 69 days post-CAR infusion (39-103). Conclusions: Our ongoing phase 1 trial demonstrates a 100% response rate to Tn/mem-enriched CD19:28z-CAR T cell therapy in adults with relapsed/refractory (R/R) B-ALL. Although the numbers are small, the unanimous response, combined with a tolerable and reversible toxicity profile in pts with both low and high disease burden is remarkable and suggests promise for this Tn/mem manufacturing platform for CD19 and other CAR targets. Disclosures Khaled: Juno: Other: Travel Funding; Daiichi: Consultancy; Alexion: Consultancy, Speakers Bureau. Wang:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding. Brown:Mustang Therapeutics: Consultancy, Other: Licensing Agreement, Patents & Royalties, Research Funding. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding.

Introduction: FLT3-ITD mutations are among the most common molecular abnormalities in AML, occurring in ≈ 25% of pts. These driver mutations are associated with high leukemic burden and poor prognosis, eg, high risk of relapse, decreased response to salvage therapy, and shorter overall survival (OS). Pts with R/R FLT3-ITD AML have a worse prognosis and represent a population with high unmet medical need. Q is a once-daily, oral, highly potent and selective FLT3i shown in phase 2 trials to have promising single-agent antileukemic activity and a manageable safety profile. QuANTUM-R was the first global, phase 3, randomized controlled trial (NCT02039726) to show that an FLT3i prolonged OS compared with salvage chemotherapy (SC) in pts with R/R FLT3-ITD AML. Final efficacy and safety data from this pivotal phase 3 trial are reported. Methods: Pts aged ≥ 18 years with FLT3-ITD AML refractory to or relapsed (duration of first remission ≤ 6 mo) after standard AML therapy, w/wo hematopoietic stem cell transplant (HSCT) were randomized 2:1 to receive Q (60 mg [30-mg lead-in]) or 1 of 3 preselected investigator's choice (IC) SC: low-dose cytarabine (LoDAC); mitoxantrone, etoposide, and intermediate-dose cytarabine (MEC); or fludarabine, cytarabine, and granulocyte-colony stimulating factor (G-CSF) with idarubicin (FLAG-IDA). Up to 2 cycles of MEC or FLAG-IDA were permitted; Q and LoDAC were given until lack of benefit, unacceptable toxicity, or HSCT. Prior therapy with midostaurin was allowed, but all other FLT3i were not. Pts receiving HSCT in the Q arm could resume Q after HSCT. Primary and secondary endpoints were OS and event-free survival (EFS), respectively. Sensitivity analyses for OS and EFS were conducted: (1) using the per-protocol set (randomized and treated patients without major protocol deviations), (2) censoring at HSCT, (3) censoring at the use of other postbaseline FLT3i (for OS only). Predefined subgroup analyses of OS were also performed. Exploratory endpoints included response rates, duration of CRc, and transplant rate. Results: 367 pts were randomized; 245 to Q and 122 to IC SC (LoDAC, n=29; MEC, n=40; FLAG-IDA, n=53). Four pts randomized to Q and 28 pts randomized to SC did not receive therapy. Median follow-up was 23.5 mo. Six pts were still on initial Q treatment at data cutoff vs 0 in the SC arm. Treatment groups were well balanced for baseline characteristics, including age, response to prior therapy, transplant history, and FLT3-ITD allelic burden. OS hazard ratio (HR) of Q relative to SC was 0.76 (95% CI, 0.58-0.98; stratified log-rank test, 1-sided P=0.0177). Median OS was 6.2 (95% CI, 5.3-7.2) vs 4.7 (95% CI, 4.0-5.5) mo, with an estimated 12-mo OS probability of 27% vs 20% in Q and SC arms, respectively. EFS HR was 0.90 (95% CI, 0.70-1.16; stratified log-rank test, 1-sided P=0.1071); median EFS was 6.0 (95% CI, 0.1-8.3) vs 3.7 (95% CI, 0.4-5.9) wk, respectively. Sensitivity analyses of OS and EFS all supported benefit of quizartinib compared with SC, as did OS analyses across subgroups, including varying allelic ratio, prior HSCT, AML risk score, and response to prior therapy (Tables 1 and 2, Figure). CRc was 48% (95% CI, 42%-55%) and 27% (95% CI, 19%-36%) in Q and SC arms (nominal P=0.0001), respectively. Duration of CRc was 12.1 (95% CI, 10.4-27.1) vs 5.0 (95% CI, 3.3-12.6) wk. Transplant rate was 32% and 12% in Q and SC arms (nominal P Rates of treatment-emergent adverse events (TEAEs) were comparable between the 2 arms, despite higher total drug exposure in Q vs SC arms (101.9 vs 3.7 patient-years [pt-y], respectively). Exposure-adjusted TEAEs were 2.3 vs 25.2 per pt-y, respectively. Most common grade ≥ 3 TEAEs in both arms were infections and those associated with cytopenia. Only 2 pts discontinued Q due to QTcF prolongation. QTcF >500 ms (grade 3) by central laboratory was 3% in the Q arm; no grade 4 QTcF occurred. Q-treated pts post-HSCT had a similar AE profile to those overall. Conclusions: This report confirms the survival benefit observed with single-agent Q compared with SC in pts with R/R FLT3-ITD AML and the favorable Q safety profile, providing evidence of meaningful clinical benefit in pts who have few options. These results are paradigm changing in the R/R FLT3-ITD AML treatment setting. Disclosures Cortes: Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; Arog: Research Funding. Khaled:Juno: Other: Travel Funding; Daiichi: Consultancy; Alexion: Consultancy, Speakers Bureau. Perl:Arog: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Ganguly:Amgen: Consultancy; Janssen: Consultancy; Daiichi Sankyo: Research Funding; Seattle Genetics: Speakers Bureau. Russell:Daiichi Sankyo: Consultancy; Jazz Pharma: Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau. Kramer:Daiichi Sankyo: Consultancy; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding. Dombret:Daiichi Sankyo: Honoraria; Roche/Genentech: Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria; Ariad: Honoraria, Research Funding; Novartis: Honoraria; Celgene: Consultancy, Honoraria; Jazz Pharma: Honoraria, Research Funding; Agios: Honoraria; Sunesis: Honoraria; Karyopharm: Honoraria; Kite Pharma: Honoraria, Research Funding; Menarini: Honoraria; Astellas: Honoraria; Janssen: Honoraria; Servier: Honoraria; Seattle Genetics: Honoraria. Jonas:Accelerated Medical Diagnostics: Research Funding; Incyte: Research Funding; Esanex: Research Funding; LP Therapeutics: Research Funding; AbbVie: Consultancy, Research Funding; Daiichi Sankyo: Research Funding; Kalobios: Research Funding; Pharmacyclics: Research Funding; Celgene: Consultancy, Research Funding; Genentech/Roche: Research Funding; Glycomimetics: Research Funding; Tolero: Consultancy; Amgen: Consultancy; Forma: Research Funding. Leung:Novartis: Speakers Bureau; Daiichi: Research Funding. Mehta:Daiichi Sankyo: Honoraria. Montesinos:Daiichi Sankyo: Consultancy, Speakers Bureau; Novartis: Research Funding, Speakers Bureau. Radsak:Novartis: Consultancy, Honoraria; Jazz Pharmaceuticals: Other: Travel grant; TEVA: Consultancy; Daiichi Sankyo: Honoraria, Other: Travel grant; Gilead: Other: Travel grant; Celgene: Honoraria, Other: Travel grant; Takeda: Consultancy. Arunachalam:Daiichi Sankyo: Employment. Holmes:Daiichi Sankyo: Employment. Kobayashi:Daiichi Sankyo: Employment. Namuyinga:Daiichi Sankyo: Employment. Ge:Daiichi Sankyo: Employment. Yver:Daiichi Sankyo: Employment. Zhang:Daiichi Sankyo: Employment.

The combination of venetoclax and hypomethylating agents (HMA) has demonstrated potent activity in acute myeloid leukemia (AML), both in newly diagnosed patients (pts) and those with relapsed/refractory (r/r) disease. We analyzed the association between response to therapy and leukemic somatic mutations, cytogenetics, and other pertinent patient- and leukemia-related features in a large series of newly diagnosed and r/r AML in adults treated with venetoclax in combination with HMA at City of Hope between October 2016 and May 2018. We identified 107 evaluable adults with AML treated with the combination of venetoclax and HMA. Sixty-one (57%) pts had r/r AML at the time of initiating treatment (median prior lines of therapy: 2; range: 1-10), while 46 (43%) were treated in the frontline setting. The median age of pts was 68 years (range: 19-86). AML was de novo in 57 (53%), therapy-related in 23 (21%) and secondary in 27 (25%) pts. Thirty-six (34%) pts had prior exposure to HMA, and 21 (20%) pts had relapsed following prior allogeneic hematopoietic cell transplantation (HCT). The majority of treated pts had unfavorable (52%) or intermediate-risk (39%) AML based on combined cytogenetics and molecular profiles. The most common detected somatic mutations (majority by next generation sequencing) were FLT3 (17%), followed by DNMT3A (15%), RAS and TET2 (each 14%), RUNX1 (13%), TP53 (12%), and IDH1/2 (11%). Most pts received decitabine in combination with venetoclax (N=97, 91%); only 10 (9%) pts received 5-azacitidine together with venetoclax. Complete remission (CR)/CR with incomplete hematologic recovery (CRi) was achieved in 57 (53%) pts after a median of 2 (range 1-4) cycles. For 36 pts who achieved CR/CRi and had available minimal residual disease (MRD) assessment by multicolor flow cytometry (MFC), 23 (64%) became MRD-. CR/CRi was higher in pts carrying favorable- or intermediate-risk AML compared to poor-risk AML (100% vs. 60% vs. 45%, P=0.029). CR/CRi was 48% in those with complex cytogenetics (N = 31), 45% in monosomal karyotype (N = 22), 36% in KMT2A gene rearrangement (N = 11), 74% in normal karyotype (N = 19), and 25% in inversion 3 (N =4). The CR/CRi rate was not significantly different between newly diagnosed or r/r AML (61% vs. 48%, P = 0.17), nor was there a difference associated with AML type (de novo vs. therapy-related vs. secondary, P= 0.26), patient age (> or ≤ 65 years) at time of therapy (P = 0.13), prior allogeneic HCT (P = 0.29), prior administration of HMA (P = 0.37) and the type or schedule (5- or 10-day decitabine) of HMA (P = 0.52). In multivariate analysis, only favorable- or intermediate-risk cytogenetics was associated with better CR/CRi (P = 0.036). CR/CRi was also comparable regardless of the presence or absence of various analyzed somatic AML mutations. However, in recursive partitioning analysis of detectable somatic mutations and response to therapy, the combined lack of RAS, TP53 and RUNX1 mutations was linked to an improved rate of CR/CRi. When AML cases were stratified into functional gene alteration subgroups (according to the TCGA data set), there was no significant difference in CR/CRi according to the presence or absence of certain functional genes/fusions. Median overall survival (OS) for all pts was 12.5 months and was 14.6 months for pts who achieved CR/CRi, in contrast to 4.6 months for non-responders (P We report remarkable activity with venetoclax and HMA across various high-risk genetics and clinical features in AML patients. Prospective studies are warranted to compare this combination directly with chemotherapy in all AML subsets. This is particularly true for high risk AML where response to conventional chemotherapy is poor. Disclosures Ali: Incyte Corporation: Membership on an entity's Board of Directors or advisory committees. Salhotra:Kadmon Corporation, LLC: Consultancy. Khaled:Alexion: Consultancy, Speakers Bureau; Juno: Other: Travel Funding; Daiichi: Consultancy. Stein:Celgene: Speakers Bureau; Amgen Inc.: Speakers Bureau. Forman:Mustang Therapeutics: Other: Licensing Agreement, Patents & Royalties, Research Funding.

Background: Pracinostat, a potent oral Class I, II, IV histone deacetylase (HDAC) inhibitor, exhibited modest single-agent activity in relapsed AML. Inhibition of histone deacetylation and DNA hypermethylation induces re-expression of silenced genes in myeloid malignancies in a synergistic fashion. A pilot study of pracinostat with azacitidine (AZA) in myelodysplastic syndromes showed the combination to be active and well tolerated (Blood2012;120:3821). We conducted a Phase 2 study to evaluate pracinostat + AZA in patients ≥65 years with AML not eligible for induction chemotherapy. Minimum 1-year survival data were reported previously (Blood 2015;126:453). Here we report long-term survival and response analyses. Methods: Main eligibility: Age ≥65, untreated de novo or secondary AML, ≥20% bone marrow (BM) blasts, not candidate for intensive therapy due to co-morbidities and/or AML features, intermediate or high-risk cytogenetics, and no prior treatment with HDAC inhibitors or hypomethylating agents. Treatment consisted of pracinostat 60 mg orally 3 days/week on alternate days for 3 weeks and AZA 75 mg/m2 subcutaneously or intravenously daily for 7 days, with cycles repeated every 28 days until disease progression, lack of response or poor tolerability. The primary endpoint was a composite complete response rate (cCR) of CR + CRi+ MLFS by IWG criteria. Response was assessed at the end of Cycles 2, 4, 6 and then every 3 cycles or when clinically indicated. Secondary endpoints included overall response rate (cCR + PR), duration of response and overall survival (OS). Study registered under NCT01912274. Results: Between December 2013 and December 2014, 50 patients were enrolled at 15 U.S. sites. Baseline characteristics: Median age 75 years (range 66-84 years); 33 de novo and 17 secondary AML; 27 intermediate-risk and 21 high-risk cytogenetics and 2 not known; median BM blasts 40% (range 20%-89%), ECOG performance status 0-1 in 84% and 2 in 16%. The median number of treatment cycles was 6.5 (range 1-24+). A CR was achieved in 21 patients (42%), CRi in 2 (4%), and MLFS in 3 (6%) for a cCR rate of 52%. Median time to BM blasts 5% of patients: Fatigue 34%; anorexia 10%, cellulitis, pneumonia, asthenia and sepsis in 8%; urinary tract infection, nausea, back pain, hypoxia, hyponatremia, and syncope in 6%. Grade ≥ 3 hematologic toxicities in> 5% of patients: thrombocytopenia 46%; febrile neutropenia 44%; neutropenia 36%; anemia 30%; pancytopenia 6%. The 30-day and 60-day mortality rates were 2% and 10%. Conclusions: Pracinostat + AZA led to a high rate of responses in elderly patients with AML. Responses were durable and observed irrespective of age, cytogenetics risk, ECOG performance status, and de novo or secondary AML. Marrow remission was typically achieved early, but prolonged exposure was required in some patients to maximize response. The results compare favorably with historical single-agent AZA data in a similar AML population. A phase 3 study of AZA +/- pracinostat in untreated patients with AML unfit for standard induction chemotherapy is starting. Table 1. Response and Survival According to Baseline Characteristics Table 1. Response and Survival According to Baseline Characteristics Disclosures Atallah: Incyte: Consultancy; CTI biopharma: Consultancy; Novartis: Consultancy; BMS: Consultancy; Pfizer: Other: Grant review; Takeda: Research Funding; Ariad: Honoraria. Arellano:Cephalon: Research Funding. Odenike:Geron: Research Funding; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi-Aventis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Suneisis: Honoraria, Membership on an entity's Board of Directors or advisory committees; CTI/Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees; Spectrum: Honoraria, Membership on an entity's Board of Directors or advisory committees; Algeta: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ghalie:MEI Pharma: Employment.

Philadelphia (Ph) chromosome [t(9;22)] was reported as a rare recurrent balanced translocation among therapy-related acute leukemia (N=10, 2%) [Gene Chromosomes Cancer. 2002]. Here, we conducted a retrospective analysis of therapy-related acute leukemia with Ph chromosome (Ph+ t-AL) to better understand this entity. We included cases diagnosed at our institution between 2000 and 2016, excluding patients with CML in blastic phase. We defined Ph+ t-AL as acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML) harboring Ph chromosome that developed after prior exposure to cytotoxic therapy (chemotherapy, radiation or both). Of the 330 patients with Ph+ AL, 28 cases (8.4%) met our definition of Ph+ t-AL, including 25 (89%) B-cell ALL, 1 case of T-cell ALL, and 2 cases of AML. The median age at diagnosis was 56 years (range: 29-79), and 64% (N=18) of them were female. Breast cancer was the most common prior malignancy [N=8, 29%], followed by lymphoma [N=6, 21%] and sarcoma [N=4, 14%]. Prior cytotoxic therapy consisted of chemotherapy (32%), radiotherapy (29%) and chemoradiation (39%). Among 20 patients who had prior chemotherapy, 70% had received alkylating agents (i.e., cyclophosphamide, temozolomide), 70% had received topoisomerase II inhibitors (i.e., etoposide, anthracycline), 40% had received antimetabolites, (i.e., methotrexate) and 50% both alkylators and topoisomeraseII inhibitor. The median interval between prior malignancy and Ph+ t-AL diagnosis was 6.8 years (range: 2.5-19.6) and was not different according to prior cytotoxic therapy modality [chemotherapy/radiotherapy vs. either chemotherapy or radiotherapy alone (P = 0.66)]. The median white blood cells count at presentation was 20 x103/µL (range: 1.4-230). Myelodysplastic syndrome preceded one case of AML. Among 22 patients with available standard cytogenetics, 7 (32%) had Ph chromosome as the sole abnormality, while 15 (68%) had an additional cytogenetic abnormality (ACA). Complex (≥ 3 abnormalities) or monosomal karyotypes were observed respectively in 12 and 9 cases. Chromosome 7 abnormality was observed in 6 (27%) cases, including 5 of them with monosomy 7. In 18 patients (ALL = 17; AML = 1) with available molecular study for BCR/ABL1, all were positive for p190 fusion transcript, including 3 patients who carried both p210 and p190 (ALL =2; AML =1). The median time from prior diagnosis to AL onset was not different according to cytogenetics (isolated Ph chromosome vs. complex/monosomy karyotype) (P> 0.99). However, prior exposure to topoisomeraseII inhibitor was more common among patients with isolated Ph chromosome compared to patients with complex/monosomy karyotype (86% vs. 33%, P= 0.02). Tyrosine-kinase inhibitor (TKI) was administered as part of initial induction regimen to all patients except 4 (N= 24, 86%), who received TKI only upon leukemia relapse/progression. Of the 28 patients, 25 (89%) achieved complete remission (CR) with induction, and 17 (61%) patients subsequently underwent alloHCT; of them, 13 (76%) were in CR1. The 2-year overall survival and event-free survival were respectively 48% and 36% for all patients, and 63% and 41% for those who underwent alloHCT, respectively. The 2-year cumulative incidence rates of relapse and non-relapse mortality for transplanted patients were 19% and 25%, respectively. In conclusion, Ph+ chromosome is a recurrent therapy-related chromosomal aberration presenting most often as a B-cell ALL phenotype, and only rarely as T-cell ALL or AML. Ph+ t-AL is associated with high incidence of ACA, including complex and monosomal karyotype as well as chromosome 7 abnormalities, similar to therapy-related myeloid neoplasms. Similar to de novo Ph+ ALL, a high response rate to TKI-based regimen was observed among Ph+ t-AL. Given its therapeutic implication, presence of Ph chromosome should be excluded in all cases of t-AL. Disclosures Song: Seattle Genetics: Consultancy. Ali:Incyte Corporation: Research Funding. Salhotra:Alexion: Consultancy. Snyder:Ariad: Consultancy; Novartis: Consultancy. Stein:Amgen: Consultancy, Research Funding, Speakers Bureau; Seattle Genetics: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Celgene: Research Funding. Forman:Mustang Therpapeutics: Other: Construct licensed by City of Hope.

Introduction Efforts to improve the survival of non-Hodgkin lymphoma (NHL) patients with recurrent disease have focused primarily on the use of consolidative myeloablative autologous hematopoietic stem cell transplantation (HSCT). However, the major limitation of HSCT for NHL is the high incidence of relapse, even at maximally tolerated preparative regimen intensities. In a series of phase I studies designed to improve HSCT longterm remission rates, we have assessed the safety and feasibility of cellular immunotherapy utilizing ex vivo expanded autologous central memory (Tcm)-enrichedT cells that are genetically modified to express CD19-specific chimeric antigen receptors (CD19CAR), given in conjunction with standard of care myeloablative HSCT. Methods Here we present results from the first two studies investigating different starting cell populations and CAR constructs. The NHL1 trial utilized a starting population of CD8+ Tcm and transduced with a lentiviral vector encoding the 1st-generation CD19CAR (CD19R:zeta), consisting of a CD19-specific scFv linked to a CD3-zeta (CD19R:zeta) signaling domain. The NHL2 trial used a bulk Tcm population including both CD4+ and CD8+cells, which were transduced with lentiviral vectors encoding a 2nd-generation CD19CAR that added a CD28 costimulatory domain (CD19R:CD28:zeta) and a selectable marker for cell tracking (EGFRt). Engineered Tcm-derived CD19CAR T cells were infused 2 days after HSCT at dose levels of 25-200 x10^6 CAR T cells (dose levels in table), and all participants were followed for dose limiting toxicity (DLT) for 28 days. Both phase I studies utilized the target equivalence range design, which defines the dose escalation and de-escalation rules for determining maximum tolerated dose based on a target range of acceptable toxicity. Results NHL1 protocol (NCT01318317): Eight participants were consented and received CD8+ Tcm -derived CD19R:zeta T cell therapy. Seven patients had a diagnosis of diffuse large B cell lymphoma (DLBCL) and 1 had mantle cell lymphoma (MCL). Four of the 8 were female, and 3/8 were ≥ age 65 years. The mean age was 62 years (50-75). The median number of prior chemo/immunotherapy regimens was 3 (2-4). Two of the 8 (25%) participants had prior radiation. Five of 8 (63%) participants on NHL1 achieved a best response of CR or continuing CR. Four of 8 (50% 95% CI [16%, 84%]) participants have progressed. The progression free survival (PFS) at both 1 and 2 years is 50%, 95% CI[16%,84%] with a median follow-up of 24.7 (min=24.0, max=26.7) months. There were 2 deaths, both from disease progression. NHL2 protocol (NCT 01815749): Eight participants were consented and received Tcm-derived CD19R:CD28:zeta/EGFRt T cell therapy. Four patients had MCL, 4 had DLBCL, 3/8 were female, 2/8 were ≥ age 65 years. The mean age was 58 years (23-71). The median number of prior chemo/immunotherapy regimens was 2 (1-3). All eight NHL2 participants achieved a best response of CR or continuing CR. The PFS at 6 months is 100%, 95% CI[63%, 100%] with a median follow-up of 12.2 (min=10.0, max=14.1) months. To date 2 participants of the 8 (25%, 95% CI [3%, 65%]) have progressed (one at 6.4 months and one at 12.6 months). There was 1 death from disease progression. Both NHL1 and NHL2 trials demonstrated safety and feasibility. There were no DLTs, delayed hematopoietic reconstitution, or non-relapse mortality on either study. In NHL2, we employed bulk Tcm including both CD4+ and CD8+ cells in the CAR transduction and also added a CD28 co-stimulatory domain in the CAR design, to enhance persistence and antitumor activity. NHL2 exhibited better CAR T cell persistence compared to NHL1 T cell therapy based on area under the curve of log10copies/µg of genomic DNA from day 1 to 25 post infusion (mean difference = 14.8, 95% CI [7.4, 22.3], P Conclusions We conclude that Tcm-derived CD19CAR T cell therapy is very safe for treatment of poor-risk NHL patients undergoing autologous HSCT. We continue follow-up of these patients long-term to assess efficacy, and preliminary data are promising. Meanwhile we are exploring CAR vector design and T cell population modifications to improve the duration of anti-tumor immunity in the setting of immune reconstitution following engineered autograft. Table. Trial CAR+ Cell Dose # of Patients NHL1 25 x 10^6 1 50 x 10^6 4 100 x 10^6 3 NHL 2 50 x 10^6 3 200 x 10^6 5 Disclosures Khaled: Sequenom: Research Funding. Siddiqi:Pharmacyclics/Jannsen: Speakers Bureau; Kite pharma: Other: attended advisory board meeting; Seattle Genetics: Speakers Bureau. Riddell:Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding; Adaptive Biotechnologies: Consultancy; Cell Medica: Membership on an entity's Board of Directors or advisory committees. Jensen***:Juno Therapeutics: Equity Ownership, Patents & Royalties, Research Funding. Forman***:Amgen: Consultancy; Mustang: Research Funding.

Background: High risk AML patients (pts) have poor outcome with low complete remission (CR) rate and long term survival despite intensive chemotherapy. Tyrosine kinases play an important role in AML pathogenesis. Pre-clinical studies performed in our center (Blood. 2013 122:1900) have shown that Src family tyrosine kinases (SFK) including Lyn, Hck and Fgr are abnormally activated in AML compared to normal hematopoietic stem cell and progenitor cells. Other studies have shown that the c-Kit receptor is over-activated in a subset of AML pts and contributes to abnormal leukemia cell growth. We further show that the small molecule SFK and c-Kit inhibitor dasatinib reduces proliferation and survival of AML stem and progenitor cells. Importantly, dasatinib enhances the sensitivity of AML stem and progenitor cells to chemotherapeutic agents by inhibiting Akt signaling, increasing mdm2 phosphorylation and enhancing p53 activity in AML cells. Based on this data we conducted a phase I/II clinical study of the combination of dasatinib with conventional cytarabine-idarubicin ("7+3")-based induction chemotherapy in high-risk AML. Methods: Between September 20013 and July 2015, 18 adult AML pts were enrolled in the study. Eligibility criteria were high-risk AML, age >18 years, and suitability for intensive therapy. High risk AML was defined by one of the following criteria: older age (> 60 yrs), poor-risk cytogenetic and molecular abnormalities (ELN criteria), secondary disease (AML evolving from myelodysplasia or myeloproliferative neoplasm), therapy related (t-AML), or relapsed/refractory. This Phase I study used a 3 + 3 dose escalation design for dasatinib while keeping a fixed dose of cytarabine and idarubicin (cytarabine 200 mg/m2 CIV days 1-7, idarubicin 12 mg/m2 IV days 1-3). Dasatinib was started at a dose of 70 mg (dose level 1; DL-1) days 1-7, and escalated to 100 mg orally days 1-7 (DL 1). Pts who failed to achieve CR received second re-induction with the same regimen. Pts who achieved CR received consolidation high dose cytarabine and/or allogeneic stem cell transplantation (SCT) based on donor availability. Results: Of the 18 pts enrolled on the study, 7 pts (39%) had secondary AML, 5 pts (28%) relapsed AML, 2 pts (11%) t-AML, and 4 (22%) were newly diagnosed older AML pts (one with complex karyotype, one with trisomy 8 and one cytogenetically normal with FTL3-ITD). The median age of all pts was 62 yrs (range 27-73). Of the 18 pts, 13 pts are currently evaluable for response; of which 10 (77%) achieved CR/Cri. Of the 5 non-evaluable pts, one pt withdrew from study after 2 days of therapy, one pt was taken off study after 3 days due to cytarabine neurotoxicity, one pt died of intracranial hemorrhage before the day 14 bone marrow biopsy, one pt had therapy interrupted secondary to pneumonia and sepsis, and one is still receiving therapy. None of the pts required more than one induction to achieve CR. Of the 10 pts who achieved CR/Cri, 8 patients went on to receive allogeneic SCT. As expected, the most commonly reported grade 3 and 4 adverse events (AE) were anemia 50%, thrombocytopenia 44%, neutropenia 38%, and fatigue 27%. The most common grade 1-2 AE were GI toxicities 61% and rash 33%. Correlative studies performed on blood samples obtained from pts on day 3 after initiation of treatment (n=9) demonstrated significant decrease in of SRC activity (as indicated by reduction in phospho-SRC levels on immunoblotting, 0.52±0.11 of control, p=0.01), and increased expression of p53-target genes as evaluated by Q-RT-PCT [including Puma (16.2±6.9 fold, p=0.015), P21 (4.9±1.1 fold, p=0.004), DR5 (3.4±0.9, p=0.004), Bax (3.7±0.9 fold, p=0.001) and HDM2 (2.1±0.5, p=0.02)]. Conclusion: Combination of dasatinib with conventional "7+3" induction chemotherapy is feasible in high-risk AML and leads to higher CR rate compared to historical data without increase in toxicity rate, allowing more pts to receive allogeneic transplantation. Correlative laboratory studies are consistent with pre-clinical studies suggesting that this combination is associated with significant inhibition of SRC activity and enhanced activation of p53-target genes. Disclosures Dos Santos: Amgen: Employment. Stein:Amgen: Speakers Bureau. Chen:Seattle Genetics: Consultancy, Research Funding, Speakers Bureau; Millennium: Consultancy, Research Funding, Speakers Bureau; Merck: Consultancy, Research Funding; genentech: Consultancy, Speakers Bureau. Khaled:Sequenom: Research Funding.

Background: Combination studies with histone deacetylase (HDAC) inhibitors plus hypomethylating agents (HMA) have suggested beneficial clinical activity in higher risk MDS and AML, though exceptions have also been reported. Pracinostat is a potent oral HDAC inhibitor selective for class I, II and IV isoforms. A pilot phase Ib study of pracinostat in combination with azacitidine (AZA) in higher risk MDS demonstrated a complete response (CR)/CR with incomplete blood count recovery (CRi) rate of 89% (Proc ASH:3821, 2012). Preliminary data on 33 patients from a multi-center, open-label, single-arm Phase II study of Pracinostat in combination with AZA in elderly AML also reported a high CR/CRi rate (ASH 2014). Herein we report the latest survival and response results for this study. Methods: Eligibility includes previously untreated AML (≥20% bone marrow blasts), age ≥65 years, unsuitable for intensive therapy due to co-morbidities and/or AML related features, and intermediate or high-risk cytogenetics. Study therapy includes pracinostat, 60 mg p.o. 3 alternate days/week for 3 weeks plus AZA, 75 mg/m2) days 1-7 or days 1-5 and 8-9 either s.c. or i.v. with cycles repeated every 28 days until progressive disease, lack of response or intolerance. The primary endpoint is CR+CRi+ morphologic leukemia free state (MLFS) per IWG criteria. Response assessments occur at the end of cycle 1 or 2 then every other cycle or when clinically indicated. A Simon 2-stage statistical design is utilized with the following assumptions: null=0.10, alternate=0.25, a=0.10, power=0.90. Stage 1 n=27 and total stage 2 n=40. Secondary endpoints include overall response rate (ORR; CR+CRi+MLFS+partial response [PR]+PRi), duration of response and overall survival. Results: Between Dec 2013 and Dec 2014, 50 patients from 15 study sites were enrolled. At this time, 50 are evaluable for efficacy. Baseline disease characteristics for all patients include: median age 75 (range 66-84); 32 de novo AML, 13 evolved from AHD, 5 were treatment-related; 28 intermediate-risk and 20 high-risk cytogenetics and 2 unknown; baseline bone marrow blast counts ranged from 20% to 89% with a median of 40%. Thirty-one patients (62%) continue to be followed for survival (range: 8.5 to 18.5 months). Median overall survival has not been reached in the overall study population and neither in patients with high-risk cytogenics or those with AML secondary to MDS or prior anti-cancer therapy. The 1-year overall survival estimate is 60%. The primary endpoint of CR +CRi +MLFS has been observed in 27/50 evaluable patients (54%) to date, including 21/50 (42%) CR. The 60-day all-cause mortality rate is 10% (5/50). Treatment emergent adverse events (TEAEs) Grade ≥3 seen in >5% of patients: febrile neutropenia 30%; thrombocytopenia 22%; neutropenia 10%; cellulitis 10%; anemia 8%; fatigue 8%; sepsis 6%, and pancytopenia 6%. TEAE's leading to study therapy discontinuation: peripheral motor neuropathy (1), parainfluenza (1), atrial fibrillation/prolonged QTc (1), subdural hematoma after a fall (1), and sepsis (3). Conclusions: Pracinostat plus AZA produces a high rate of durable responses in this AML population. Median overall survival has not been reached; 1-year overall survival is estimated at 60%. Final response data and overall survival estimates will be presented at the meeting. Disclosures Off Label Use: Azacitidine is not approved for use in acute myelogenous leukemia.. Khaled:Sequenom: Research Funding. Arellano:Cephalon Oncology: Research Funding. Butler:MEI Pharma, Inc.: Employment. Ashby:MEI Pharma, Inc.: Employment. Medeiros:Celgene: Honoraria, Research Funding; Agios Pharmaceuticals: Honoraria.

FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) in acute myeloid leukemia (AML) are associated with early relapse after standard chemotherapy and poor survival. Hematopoietic cell transplantation (HCT) is a recommended treatment for patients with FLT3-ITD(+) AML. However, a high rate of relapse after a HCT is observed when compared to FLT3-ITD(-) patients with the 2 year relapse rate of 30% vs. 16% in FLT3-ITD(+) and FLT3-ITD(-) patients, respectively (Brunet, J. Clin. Oncol. 2012). Quizartinib (AC220) is an oral FLT3 receptor tyrosine kinase inhibitor that has shown a high level of single agent activity in nearly 500 patients with FLT3(+) relapsed or refractory AML and is currently in a Phase 3 study. This Phase 1 study examined maintenance therapy with quizartinib in AML patients (aged 18 years or older) in remission after receipt of an allogeneic HCT. Dose escalation was conducted using a modified 3+3 design, where 6 subjects were enrolled at each dose level. Two dose levels were tested; dose level 1 (DL1) at 40 mg and dose level 2 (DL2) at 60 mg given daily in continuous 28 day cycles. Dose limiting toxicities (DLTs) were assessed for the first 2 cycles and subjects were allowed to continue up to a maximum of 24 cycles. Thirteen subjects were recruited and enrollment was completed in June 2013. The median age was 43 (range 23 to 61) years. All subjects had received an HLA-matched allogeneic HCT (3 related and 10 unrelated) a median of 56 (range 41 – 70) days before study enrollment. All subjects were positive for the FLT3-ITD mutation by local testing at the time of diagnosis. Seven subjects were enrolled at DL1, including one who relapsed after 22 days on study and was replaced per protocol as deemed not evaluable for DLTs. There was 1 DLT of Grade 3 gastric hemorrhage which resolved and the subject was able to continue on a reduced dose (30 mg) of quizartinib. Six subjects were enrolled at DL2, including one subject who experienced 1 DLT of Grade 3 anemia but was able to continue on a reduced dose (30 mg). Of the 13 total subjects, 10 (77%) received quizartinib for more than a year. Six (45%) subjects are continuing to receive quizartinib currently (15, 16, 18, 18, 23, and 23 cycles) and 2 (15%) subjects have completed 24 cycles. Three subjects (23%) discontinued due to AE: Grade 4 neutropenia (Cycle 4), Grade 2 corneal epithelium defect (Cycle 9), and Grade 3 autoimmune hemolysis (Cycle 15); 1(8%) discontinued for disease relapse (Cycle 1) and 1 (8%) for protocol non-compliance (Cycle 13). The most common (≥20%) treatment-related adverse events (AEs) were diarrhea (38%; 5 subjects), neutropenia (31%; 4 subjects), nausea (23%; 3 subjects) and leukopenia (23%; 3 subjects). This is the first study conducted to determine whether or not quizartinib can be safely administered as post-transplant maintenance therapy in patients with AML. The data from this study support the use of post-transplant maintenance therapy with quizartinib and show early evidence indicating a reduced relapse rate with only 1 relapse reported out of 13 subjects, which compares favorably to historical reference data. No MTD was identified but 60 mg daily was selected as the highest dose for continuous daily administration based on Phase 2 study data in relapsed or refractory subjects (J Cortes, Blood (ASH Annual Meeting Abstracts) 2013 [Abstract]). Quizartinib maintenance has been included in the current Phase 3 QUANTUM-R study comparing quizartinib vs. salvage chemotherapy in relapsed or refractory FLT3-ITD(+) AML. Disclosures Sandmaier: Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding. Khaled:Ambit Bioscience Corporation: Research Funding; Astellas Pharma, Inc: Research Funding. Oran:Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding. Gammon:Ambit Bioscience Corporation: Employment, Equity Ownership. Trone:Ambit Bioscience Corporation: Employment, Equity Ownership. Frankfurt:Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding.

Background: Pracinostat is a potent oral inhibitor of histone deacetylases (HDAC’s), selective for class I, II and IV isoforms. In-vitro cytotoxicity assays in AML cell lines revealed an IC50 of

Allelic variants implicated in drug absorption, distribution, metabolism, and excretion (ADME) affect drug pharmacokinetic variability and have been increasingly recognized as important factors in medical therapy. In solid organ transplantation, certain ADME genes affect the blood level of immunosuppressants as well as clinical outcomes despite rigorous traditional therapeutic drug monitoring (TDM). The influence of ADME pharmacogenetics in Hematopoietic Stem Cell Transplantation (HSCT) has not been well studied, with few publications and none reporting the effects in the setting of the tacrolimus (TAC)/ sirolimus (SIR) GVHD-preventive combination. In this exploratory pilot study, the objective was to evaluate possible associations between ADME variants with TAC/SIR blood levels and clinical outcomes in the allogeneic HSCT setting. The primary focus was on 3 ADME genes [ABCB1 (MDR1), CYP3A4, and CYP3A5] known to influence TAC/SIR outcomes in solid organ transplant. Secondarily we explored associations with other gene variants on the ADME panel. We analyzed archived DNA samples from 179 HSCT recipients on the Sequenom MassARRAY® platform. This panel is based on the PharmADME Working Group core list and interrogates 184 allelic variants and 12 copy number variants and 4 gene conversions (in 36 pharmacogenetically relevant genes). Blood levels of TAC and SIR were collected for all patients at least once weekly for the first 100 days post-transplant. For this analysis, median blood levels of TAC and SIR were obtained for the first 7 and 14 days post-transplant. Conditioning regimens consisted of fludarabine/melphalan (n=106), total body irradiation (TBI)/cyclophosphamide (n=11), TBI/etoposide (n=46) and busulfan/cyclophosphamide (n=14). All patients received TAC/SIR-based GVHD prophylaxis according to Shayani et al. (Biol Blood Marrow Transplant 2013). No azoles were used as fungal prophylaxis. Of 179 samples genotyped, 178 showed high quality data. The average call rate for these samples was 98.85% over 200 assays, with a median call rate of 100%. Of these assays, 66 variants were identified that could be evaluated for association with TAC/SIR levels and clinical outcomes; other assays were excluded due to homozygosity or >10% missing data. In the setting of the TAC/SIR combination, the median SIR blood level over the first 14 days post-HSCT was higher in rs2032582 (ABCB1) T carriers vs other groups (p=0.01), as was the median concentration/dose (C/D) ratio (p=0.05) (Table). We also found that the median TAC blood level over the first 7 days post-HSCT was lower in the rs776746 ( CYP3A5) AA group compared to GG or GA groups (p Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Khaled: Sequenom: Research Funding. Off Label Use: Use of tacrolimus and sirolimus immunosuppressants for prevention of graft-versus-host disease following allogeneic hematopoietic stem cell transplantation..