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Uproleselan (GMI-1271) is a novel E-selectin antagonist that disrupts cell survival pathways, enhances chemotherapy response, improves survival in mouse xenograft and syngeneic models, and decreases chemotherapy toxicity in vivo. A phase 1/2 study evaluated the safety, tolerability, and antileukemic activity of uproleselan (5-20 mg/kg) with MEC (mitoxantrone, etoposide, and cytarabine) among patients with relapsed/refractory (R/R) acute myeloid leukemia (AML). Among the first 19 patients, no dose-limiting toxicities were observed. The recommended phase 2 dose (RP2D) was 10 mg/kg twice daily. An additional 47 patients with R/R AML were treated with uproleselan at the RP2D plus MEC. At the RP2D, the remission rate (complete response [CR]/CR with incomplete count recovery [CRi]) was 41% (CR, 35%), and the median overall survival (OS) was 8.8 months. In a separate cohort, 25 newly diagnosed patients age ≥60 years received uproleselan at the RP2D plus cytarabine and idarubicin (7 + 3). In these frontline patients, the CR/CRi rate was 72% (CR, 52%), and the median OS was 12.6 months. The addition of uproleselan was associated with low rates of oral mucositis. E-selectin ligand expression on leukemic blasts was higher in patients with relapsed vs primary refractory AML and in newly diagnosed older patients with high-risk cytogenetics and secondary AML. In the R/R cohort, E-selectin expression >10% was associated with a higher response rate and improved survival. The addition of uproleselan to chemotherapy was well tolerated, with high remission rates, low induction mortality, and low rates of mucositis, providing a strong rationale for phase 3 randomized confirmatory studies. This trial was registered at www.clinicaltrials.gov as #NCT02306291.

Background: Myelodysplastic syndromes (MDS) represent a heterogeneous group of malignancies that are characterized by aberrant hematopoiesis and consequently abnormal blood counts. Patients with MDS have an increased likelihood of developing acute myeloid leukemia (AML). Next generation sequencing (NGS) is currently being used to study the genetic landscapes of diverse cancer types in finer detail than has previously been possible, owing to its ease-of-use and widespread availability. Crucially, the accuracy and broad breadth of genomic coverage provided by NGS approaches may permit the study of mutations that are rare in MDS patients, yet well studied in AML or other cancer types. Based on the fact that much less is known about particular rare somatic mutations in MDS, we decided to investigate 6 genes. IDH1 and IDH2 are targetable in patients with AML. Mutations in JAK2 are found in high proportions in patients with myeloproliferative neoplasms (MPNs) or MDS/MPN overlap neoplasms. Finally, other mutations in genes such as BCOR, BCORL1, and MUTYH also occur in MDS patients with appreciable-but generally low-frequencies such that their overall impact on MDS patients is largely unknown. Methods: We utilized the Tempus LENS platform to retrospectively characterize 236 MDS patients who underwent genomic-testing with the Tempus|xT assay (DNA-seq of 595-648 genes at 500x coverage; full transcriptome RNA-seq; data accessed on 06/28/2021). The patient population was 28% female, with a median age of 71.6 years. Mutations identified included germline and/or somatic single nucleotide variants (though we only considered somatic variants in this study), insertions/deletions and copy number variations (gains defined as ≥8 copies). For a subset of patients processed at Rush University Medical Center (RUMC), we additionally performed a curated clinical investigation into laboratory variables, prognostic data, treatment history and outcomes data. Results: Within the Tempus MDS dataset, we observed a range of mutation frequencies. In total, 58 patients had mutations in at least one of either: JAK2, BCOR, IDH2, IDH1, BCORL1, and MUTYH. When comparing the observed frequencies against values that have previously been reported, mutations in these 6 genes occurred with higher frequency in our dataset while most other mutations were in accordance with the relative frequencies reported by other sources (Table 1). We observed the largest deviation from expectation for BCOR. Whereas prior reports list this mutation as occurring with a frequency of Conclusions: We identified a higher frequency of BCOR/BCORL1 mutations among patients with MDS than has been previously reported. At the same time, most other mutation frequencies were in relative accordance with existing reports. We observed complex cytogenetic abnormalities in 75% of patients for which we had extensive clinical information. Our data suggest an association between BCOR/BCORL1 mutations and complex karyotypes, a finding that may establish a prognostic role of BCOR/BCORL1 and have potential therapeutic implications. This hypothesis is, however, subject to further investigation and will require larger sample sizes that are likely to become available with the rapidly increasing utilization of next generation sequencing techniques and availability of high-quality, curated clinical information. Figure 1 Figure 1. Disclosures Hockenberry: Tempus Labs, Inc: Current Employment, Current holder of stock options in a privately-held company. Okeke: Tempus Labs, Inc: Current Employment. Mahon: Tempus Labs, Inc: Current Employment. Hassane: Tempus Labs, Inc: Current Employment. Enschede: Tempus Labs, Inc: Current Employment, Current holder of stock options in a privately-held company. Shammo: Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Astra zeneca: Research Funding; CTI pharma: Research Funding; Stemline therapeutics: Research Funding; Kartos Pharma: Research Funding; Takeda: Consultancy, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Honoraria, Research Funding; Abbvie: Current holder of individual stocks in a privately-held company, Research Funding; Baxter: Current holder of stock options in a privately-held company; sanofi: Consultancy, Honoraria, Speakers Bureau; NS Pharma: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Apellis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Alexion: Consultancy, Honoraria, Research Funding, Speakers Bureau.

Introduction Blast-phase (BP), or leukemic transformation is a rare and devastating complication of myeloproliferative neoplasms (MPNs) (primary myelofibrosis (PMF), polycythemia vera (PV), essential thrombocythemia (ET), and post-PV/ET myelofibrosis). Patients with BP-MPNs have a poor prognosis with a median overall survival of less than 6 months, and there is no standard treatment regimen for these aggressive diseases (Dunbar et al, Blood. 2020). The development of hypomethylating agent (HMA)/venetoclax (Ven) combination offers new hope for some with AML, but has been relatively disappointing in BP-MPN, though data are limited and retrospective (Masarova et al, Blood Adv. 2021; Gangat et al, Am J Hematol. 2021). Here, we add our experience with several common treatment regimens for BP-MPN. Methods We retrospectively analyzed data from 39 consecutive patients with BP-MPNs diagnosed from December 2008 to February 2021 who received treatment at the University of Michigan. We included all patients with a previous diagnosis of MPNs who had ≥ 20% blasts in the peripheral blood or bone marrow, and subsequently received systemic therapy. One patient with a myeloid sarcoma was included as well. Disease characteristics at time of BP-transformation were noted. Patients were divided into the following groups based on 1 st-line induction therapy: 7+3 (daunorubicin and cytarabine), FLAG (fludarabine, high-dose cytarabine and G-CSF), hypomethylating agent only (decitabine or azacitidine), and HMA/Ven. Patients were followed for 2 years post-diagnosis. Differences in induction response were assessed using the Chi-square test. Differences in overall survival were calculated using the Kaplan-Meier regression with the log-rank test. Two patients who received alternate induction therapy outside of the four groups were not included in these analyses. Results The composite BP-MPN population had a median advanced age of 69 years old and a median ECOG performance status (PS) of 1. Most (97.4%) had received systemic treatment prior to their transformation for their MPN, with 71.8% receiving hydroxyurea and 41.0% receiving ruxolitinib. The rate of response (CR, CRi, MLFS) was highest in the HMA/Ven group at 42.9%, followed by FLAG (29.4%), HMA only (11.1%), and 7+3 (0%), p = 0.033 (Table 3). Despite the higher response rate, differences in 2-year OS were not significantly different among the 4 groups: 7+3 (25.0%), FLAG (7.7%), HMA (0%), HMA/Ven (20.0%) (p=0.92, Figure 1). Median time to relapse after achieving remission ranged from 2-10 months, and did not vary significantly based on induction regimen. Patients in the HMA and HMA/Ven groups had higher incidences of death with induction at 77.8% and 28.6%, respectively (Table 3). Conclusions The highest rates of response, including complete remission, were achieved with the combination of HMA and venetoclax compared to intensive induction chemotherapy or HMA alone. However, this did not translate into significant differences in OS, which is consistent with other retrospective reports. No responses were seen with 7+3 induction, though several patients were able to go on salvaged with other therapies and subsequent allogeneic stem cell transplantation thereafter. Finally, the baseline poor ECOG PS of the HMA group and borderline ECOG PS of the HMA/Ven group also contribute to their low survival rates.Larger, prospective studies comparing currently available treatment regimens in BP-MPN would be helpful, but ultimately new therapies are desperately needed for this high-risk disease. Figure 1 Figure 1. Disclosures Bixby: Takeda: Consultancy. Talpaz: Constellation: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Grant/research support ; Celgene: Consultancy; Imago: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Introduction: Cytarabine is a backbone of intensive acute myeloid leukemia (AML) chemotherapy; yet it is associated with toxicity which precludes its use in older patients and in those with comorbidities. Aspacytarabine (BST-236) is a prodrug of cytarabine, which is inactive in its intact prodrug form until cytarabine is gradually released in the plasma and inside the cells. Due to the pharmacokinetics and metabolism of aspacytarabine, the peak toxic systemic exposure to cytarabine is decreased, resulting in reduced systemic toxicity with relative sparing of normal tissues, thus enabling delivery of high cytarabine doses to AML patients otherwise unfit to receive intensive cytarabine therapy. Presented herein are the data, including final primary endpoint analysis, from a phase 2b study that recently completed enrollment. Aims: To evaluate the efficacy and safety of aspacytarabine as a single agent for induction and consolidation therapy of newly diagnosed AML patients unfit for standard induction chemotherapy. Methods: Aspacytarabine was administered at 6-day courses of 4.5 g/m 2/d (equimolar to 3 g/m 2/d cytarabine) daily 1-hour intravenous infusions, for 1-2 induction and 1-3 consolidation courses, to AML patients age ≥75 years or otherwise unfit for intensive chemotherapy. Patients with secondary or therapy related AML, and patients who received prior hypomethylating agents (HMA) ± venetoclax therapy for a preceding condition were eligible. Primary endpoint is complete remission with complete hematological recovery (CR). Secondary and exploratory endpoints include safety, duration of response (DOR), overall survival (OS), and minimal residual disease (MRD). NCT03435848. Results: Enrollment into the study was completed in May 2021. Sixty-five newly diagnosed AML patients unfit for standard chemotherapy (median age 75 years, range 54-88 years) were treated with aspacytarabine and completed 1-4 courses (median 1 course) at doses of 4.5 g/m 2/d, including 39 patients (60%) with de novo AML and 26 patients (40%) with secondary AML. Eleven patients (17%) were previously treated for MDS/CMML with HMA (median 14 courses), including 1 patient (2%) with HMA + venetoclax. Thirty-two patients (49%) and 15 patients (23%) had adverse or intermediate European LeukemiaNet (ELN) scores, respectively. The baseline median bone marrow blasts was 43%, and 25 patients (38%) had ECOG PS 2 or 3 at enrollment (Table 1). Aspacytarabine was well-tolerated in repeated-course administration. Grade ≥3 drug-related adverse events included hematological events and infections, with, importantly, no severe gastrointestinal or neurological events. The 30-day all-cause mortality rate was 12.5% (95% CI, 5.9-23.7). Of the 65 intention-to-treat AML patients, 24 (37%) achieved a CR following 1 (17 patients) or 2 (7 patients) courses. The median time to complete neutrophil and platelet recovery were 27 days (range 11-39 days) and 26 days (range 18-40), respectively. The CR rates in de novo and secondary AML patients were 44% and 27%, respectively. Twenty-seven percent of the patients with prior HMA therapy achieved a CR, including the 1 patient with prior HMA + venetoclax treatment. The CR rates in patients at the age of ≥75 years and patients with adverse ELN scores were 35% and 34%, respectively. Of the 21 patients in CR evaluable to date for MRD analysis by multiparameter flow cytometry, 11 (52%) became MRD negative following aspacytarabine treatment. Follow up is ongoing, with a current median duration of follow up of 5.2 months. The median DOR has not yet been reached at 12 months, and median OS of responders not reached at 24 months (Figure 1). Conclusions: Aspacytarabine appears to be an effective regimen for AML with a considerable reduction of the attendant toxicities that typically are associated with standard intensive cytotoxic therapies. The results of the phase 2b study are consistent with the previously completed phase 1/2a study, which demonstrated safety and a 36% CR rate in a similar population, suggest that aspacytarabine, given as monotherapy, is generally safe and effective as a first-line therapy for AML patients who are unfit for intensive chemotherapy These data support a role for aspacytarabine as a new treatment option for older patients with AML. Furthermore, this agent may serve as a backbone for combination therapy with targeted or other chemotherapy agents, as well as in younger patients with AML. Figure 1 Figure 1. Disclosures Altman: Boehringer Ingelheim: Research Funding; BMS: Research Funding; Immunogen: Research Funding; Syros: Consultancy; GlycoMimetics: Other: Participation on an advisory board; Daiichi Sankyo: Consultancy; AbbVie: Consultancy, Other: Advisory Board, Research Funding; Fujifilm: Research Funding; Kura Oncology: Consultancy; Kartos: Research Funding; Biosight: Consultancy, Other: Travel fees, Research Funding; Astellas: Consultancy, Other: Advisory Board, Research Funding; ALZ Oncology: Research Funding; Amgen: Research Funding; Aprea: Research Funding; Theradex: Consultancy, Other: Advisory boards; Kura: Research Funding. Koprivnikar: Bristol Myers Squibb: Speakers Bureau. McCloskey: Amgen: Speakers Bureau; Takeda: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Pfizer: Consultancy; Novartis: Consultancy; Incyte: Speakers Bureau; BMS: Honoraria, Speakers Bureau; COTA: Other: Equity Ownership. Kota: Pfizer: Consultancy; Novartis: Consultancy; Incyte: Research Funding. Emadi: Secura Bio.: Consultancy; Servier: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Servier: Research Funding; NewLink Genetics: Research Funding; Jazz Pharmaceuticals: Research Funding; KinaRx, Inc.: Membership on an entity's Board of Directors or advisory committees, Other: Co-founder. Zuckerman: BioSight Ltd: Honoraria; AbbVie: Honoraria; Janssen: Honoraria; Orgenesis Inc.: Honoraria; Cellect Biotechnology: Honoraria; Novartis: Honoraria; Gilead Sciences: Honoraria, Speakers Bureau. Levy: Bristol Myers Squibb: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Takeda: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Beigene: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Gilead Sciences, Inc.: Consultancy, Honoraria, Speakers Bureau; Janssen Pharmaceuticals: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Other: Promotional speaker; Amgen Inc.: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; AbbVie: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Karyopharm: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Morphosys: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Promotional speaker, Speakers Bureau; TG Therapeutics: Consultancy, Honoraria, Speakers Bureau; GSK: Consultancy, Other: Promotional speaker; Epizyme: Consultancy, Other: Promotional speaker; Dova: Consultancy, Other: Promotional speaker. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Wolach: Novartis: Consultancy; Amgen: Research Funding; Janssen: Consultancy; Abbvie: Consultancy, Honoraria, Research Funding; Astellas: Consultancy; Neopharm: Consultancy. Percival: AbbVie: Research Funding; Biosight: Research Funding; BMS/Celgene: Research Funding; Cardiff Oncology: Research Funding; Glycomimetics: Research Funding; Nohla therapeutics: Research Funding; Oscotec: Research Funding; Pfizer: Research Funding; Trillium: Research Funding. Roboz: Actinium: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy; AbbVie: Consultancy; Jazz: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Mesoblast: Consultancy; Glaxo SmithKline: Consultancy; Novartis: Consultancy; Bayer: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Janssen: Research Funding; Daiichi Sankyo: Consultancy; Blueprint Medicines: Consultancy; Bristol Myers Squibb: Consultancy; Helsinn: Consultancy; Jasper Therapeutics: Consultancy; Astellas: Consultancy; Astex: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Otsuka: Consultancy; Roche/Genentech: Consultancy. Levi: AbbVie: Consultancy, Research Funding. Flaishon: BioSight Ltd.: Current Employment. Cohen: BioSight Ltd.: Current Employment. Tessler: BioSight Ltd.: Current Employment. Blumberg: BioSight Ltd.: Current Employment. Gengrinovitch: BioSight Ltd.: Current holder of individual stocks in a privately-held company. Ben Yakar: BioSight Ltd.: Current Employment. Rowe: Biosight Inc.: Consultancy.

Introduction Aplastic anemia is a challenging disease to treat due to its rarity and severity. The current standard of care for severe and very severe aplastic anemia includes consideration of frontline allogeneic stem cell transplant (ASCT) in patients who are under 40 years of age and have an HLA-matched sibling. For patients who do not meet this criteria, immunosuppressive therapy (IST) consisting typically of horse antithymocyte-globulin (ATG) and cyclosporine (CsA) is considered, with recent data supporting the addition of eltrombopag. The main risks of IST are infusion reactions, serum sickness, kidney injury, and infection. While it is generally well tolerated in younger patients, older patients have historically been treated with transfusion support alone due to concerns for higher complications. Unfortunately, data to support clinical decisions regarding these concerns is limited, with small studies showing that reduced dosing or attenuated doses of ATG with or without CsA is safe and can be effective. At the University of Michigan, we have been treating older patients with attenuated doses of ATG +/- CsA since the late-2000s and have recently added eltrombopag to our standard of care. Herein, we present the results of our experience using IST to treat aplastic anemia, specifically presenting our outcomes in patients over 60 years old at the time of initiation of IST. Methods We used the Electronic Medical Record Search Engine (EMERSE) to query patients with aplastic anemia who were treated at the University of Michigan between 1995 and 2021. Patients included in our analysis were diagnosed with idiopathic aplastic anemia or hepatitis-associated aplastic anemia, were 18 years or older at the date of initiating IST, were treated with IST first-line, had adequate physician follow up at the University of Michigan, and were reported as being complaint with IST. Patients diagnosed or with high concern for hypoplastic myelodysplastic syndrome (MDS) were excluded in addition to those who received treatment for paroxysmal nocturnal hemoglobinuria (PNH). Statistical analysis was performed using SPSS Statistics v.27 (IBM, 2020). Results We identified 62 patients aged 18 - 60 and 54 patients over 60 years old who met inclusion criteria. Descriptive statistics of the two cohorts are available in Table 1. All patients in our study received horse ATG in addition to cyclosporine. 63% of patients over 60 received full dose horse ATG (20mg/kg for 5 days) and 37% received attenuated horse ATG (20mg/kg for 5 days), while 46% received eltrombopag as part of their IST. OS was superior in patients 18-60 receiving IST with median OS NR vs. 2760 days (Figure 1; p=0.009). In patients over 60, no difference in OS was observed in those who received attenuated (3646 days) vs. full dose IST (2760 days) (Figure 2, p=0.83). Lastly, no difference in median OS was seen in patients > 60 years old who received eltrombopag compared to those who did not (2821 vs 2760 days, Figure 3, p=0.795). Using a Chi-squared test, no statistically significant differences in rates of PR at 12 months, CR at 12 months, primary refractory disease, febrile neutropenia within 6 months of IST, bacterial infections within 6 months IST, and viral infections within 6 months of IST were noted between those who received dose attenuated ATG and those who received full dose ATG in patients > 60. PR in older patients was 48% (12) and 36% (9) at 3 and 12 months with eltrombopag, compared to 40% (10) and 36% (9) without. CR in older patients was 12% (3) and 16% (4) with eltrombopag at 3 and 12 months, compared to 12% (3) and 12% (3) without. In patients > age 60 who received dose attenuated IST, the addition of eltrombopag did not affect OS (Figure 4). A trend toward better OS was seen in patients 18-60 who received eltrombopag, but this was not statistically significant (Figure 5). Discussion In conclusion, we present our experience using IST to treat aplastic anemia at the University of Michigan. Dose attenuated IST has been proposed as a potential option for elderly patients, but we found no significant difference in OS, rates of response, or rates of infection between patients who received full dose and those who did not. There was also a trend toward improved survival with the addition of eltrombopag in younger patients, but additional follow up time is needed. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Introduction: BST-236 (aspacytarabine), a novel pyrimidine antagonist, is a cytarabine prodrug designed to deliver high cytarabine doses with reduced systemic toxicity. BST-236 pharmacokinetics and metabolism reduce peak systemic exposure to free cytarabine and enable intensive treatment to patients otherwise unfit for intensive therapy. An open label phase 2b study, following a completed phase 1/2a dose escalation study, is ongoing. Enrolled are newly-diagnosed acute myeloid leukemia (AML) patients unfit for standard therapy, including patients with treatment-related AML or AML secondary to myelodysplastic syndrome (MDS) with prior exposure to hypomethylating agents (HMA). Aims: To evaluate the efficacy and safety of BST-236 induction and consolidation in AML patients unfit for standard induction therapy. Methods: BST-236, at a dose of 4.5 g/m2/d (containing 3 g/m2/d of cytarabine), is evaluated as a first-line induction and consolidation therapy in newly-diagnosed AML patients unfit for standard chemotherapy. Patients with secondary AML, previously treated with HMA, as well as patients with therapy-related AML, are eligible. Each BST-236 induction and consolidation course consists of 6 daily 1-hour intravenous infusions. Results: To date, in the phase 1/2 and phase 2 studies, 42 AML patients were treated with BST-236, of whom 20 newly-diagnosed AML patients unfit for standard chemotherapy (median age 73 years) completed 1-4 courses of 4.5 g/m2/d BST-236. Of these, 40% had de novo AML and 60% had secondary AML. Thirty percent of patients were previously treated with HMA for MDS (median 10 courses), and 10% received prior chemo- or radiotherapy. The median baseline bone marrow blast percentage was 38 (range 13-94), and 35% and 53% of patients had intermediate or adverse European LeukemiaNet (ELN) score, respectively. BST-236 is safe and well-tolerated in repeated-course administration. Grade >2 adverse events include mainly hematological events and infections, with no other drug-related typical high-dose cytarabine events such as severe mucositis or cerebellar toxicity. Related serious adverse events include only cytopenia and pneumonia. The 30-day mortality rate is 7%. The complete remission (CR) rate in the evaluable patients to date who received 4.5 g/m2/d BST-236 is 50% in the de novo patients, 20% in secondary AML patients, and 20% in patients with prior HMA treatment. Forty-three percent of patients with adverse cytogenetics attained a CR, including 1 of 3 patients with a TP53 mutation. The median number of courses for reaching a CR is 1, and notably, all patients with bone marrow remission achieved complete hematological recovery within 36 days. BST-236 consolidation was well-tolerated and did not result in increased toxicity, enabling full count recovery. While none of the patients have undergone stem cell transplant, considered ineligible by the treating investigator, responses to BST-236 were durable and median overall survival (OS) for responders is not reached at 23 months (Figure 1A). Median OS for secondary AML patients was 6.8 months, and not reached for the de novo AML patients (Figure 1B). Follow up is ongoing with additional patients enrolling on study; updated analysis of response, minimal residual disease (MRD), duration of response, and OS will be presented at the meeting. Conclusions: The cumulative clinical data suggest that BST-236 as a single agent treatment is a safe and efficacious induction and consolidation therapy for patients who are unfit for standard intensive chemotherapy, including patients with adverse cytogenetics and prior exposure to HMA. The data may establish BST-236 as a new intensive therapy backbone of AML and may, for the first time, allow older adults deemed unfit for standard intensive induction and consolidation therapy, to benefit from an intensive treatment. Disclosures Altman: Genentech: Research Funding; Novartis: Consultancy; Syros: Consultancy; Theradex: Other: Advisory Board; Agios: Other: advisory board, Research Funding; Glycomimetics: Other: Data safety and monitoring committee; Daiichi Sankyo: Other: Advisory Board - no payment but was reimbursed for travel; Kura Oncology: Other: Scientific Advisory Board - no payment accepted, Research Funding; BioSight: Other: No payment but was reimbursed for travel , Research Funding; AbbVie: Other: advisory board, Research Funding; Fujifilm: Research Funding; Kartos: Research Funding; Celgene: Research Funding; Boehringer Ingelheim: Research Funding; ImmunoGen: Research Funding; Amgen: Research Funding; Aprea: Research Funding; Amphivena: Research Funding; Janssen: Consultancy; Immune Pharmaceuticals: Consultancy; Bristol-Myers Squibb: Consultancy; ASH: Consultancy; Cancer Expert Now: Consultancy; PeerView: Consultancy; Astellas: Other: Advisory Board, Speaker (no payment), Steering Committee (no payment), Research Funding; PrIME Oncology: Consultancy; France Foundation: Consultancy. Luger:Ariad: Research Funding; Biosight: Research Funding; Kura: Research Funding; Onconova: Research Funding; Agios: Honoraria; Acceleron: Honoraria; Bristol-Myers Squibb: Honoraria; Pfizer: Honoraria; Daiichi-Sankyo: Honoraria; Hoffman La Roche: Research Funding; Loxo Oncology: Honoraria. Koprivnikar:Amgen: Speakers Bureau; Novartis: Speakers Bureau; Alexion: Speakers Bureau; BMS: Speakers Bureau. Kota:Novartis: Consultancy, Honoraria; Incyte: Honoraria; Pfizer: Consultancy, Honoraria; Ariad: Honoraria; Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical, Company Ltd, Cambridge, MA, USA: Honoraria; Xcenda: Honoraria. Emadi:Jazz Pharmaceuticals: Research Funding; NewLink Genetics: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; KinaRx: Other: co-founder and scientific advisor. Bhatnagar:Novartis: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; KITE: Membership on an entity's Board of Directors or advisory committees; KaryoPharm Therapuetics: Research Funding; Cell Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding. Bixby:GlycoMimetics: Research Funding. Burch:Janssen: Other: paid speaker. Wolach:Amgen: Other: Fees for lectures and Consultancy; Janssen: Other: Fees for lectures and Consultancy; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Fees for lectures and Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Other: Fees for lectures and Consultancy; Astellas: Consultancy, Honoraria, Other: Fees for lectures and Consultancy; Pfizer: Consultancy, Honoraria. Levi:Abbvie Inc: Consultancy, Research Funding. Flaishon:BioSight Ltd.: Current Employment. Tessler:BioSight Ltd.: Current Employment. Gengrinovitch:BioSight Ltd.: Current Employment. Ben Yakar:BioSight Ltd.: Current Employment. Rowe:Pluristem ltd: Consultancy.

Background: CFI-400945 is a potent, selective, orally administered, first-in-class inhibitor of the serine/threonine kinase, Polo-like kinase 4 (PLK4). PLK4 is a highly conserved master regulator of centriole duplication, and is critical for maintenance of genomic integrity. Aberrant expression of PLK4 results in a number of effects including the centrosome amplification often seen in aneuploid cancers, pointing to a potentially causative role for PLK4 in genome instability and cancer progression. A Phase 1 study has been completed evaluating CFI-400945 as a monotherapy in solid tumors, showing a tolerable safety profile and promising signs of activity. As acute myeloid leukemia (AML) is a disease characterized by genomic instability, it is of significant interest as a potential indication for the clinical evaluation of CFI-400945. pre-clinical studies, CFI-400945 showed potent activity towards leukemia cell lines and primary human samples in vitro, as well as marked efficacy in two subcutaneous models of leukemia, specifically the MV4-11 FLT3-ITD AML. A Phase 1 trial in AML was initiated at the Princess Margaret Cancer Center in 2018, and of six patients evaluable for response, two (33%) achieved complete remission (CR), and 3 patients (50%) had stable disease (with one patient having a 78% reduction in marrow blast count) [re: Murphy et al, ASH 2020]. These promising results have led to a plan for an expanded trial examining CFI-400945 in AML, particularly focused on complex karyotype (CK). Study Design and Methods: The study will have 4 parts, Part 1A (1A): a single agent dose escalation portion, Part 1B (1B): a food effect portion once the MTD of 1A is determined, and combinations with azacitidine (2A), and decitabine (2B). For parts 1A and 1B, patients with relapsed and/or refractory AML, MDS, or CMML after >1 prior therapy will be included. Patients with MDS or CMML must have progressed or had a lack of response after at least 4 cycles of hypomethylating agents. For parts 2A and 2B, patients should have relapsed and/or refractory AML or untreated MDS or CMML. Untreated patients who decline or are ineligible for intensive therapy may be included. The study will use a standard 3 + 3 design. The maximum tolerated dose (MTD) will be defined as the dose level where the number of dose limiting toxicities (DLTs) is Biomarker Selection and companion Diagnostics: No biomarker based pre-selection of patients. PD evaluations will include blast reduction and markers of mitosis. Study Treatment and Endpoints: Part 1: Each cycle will be 28 days (21 days on/7 days off). Starting does of CFI-400945 will be 32mg po. Once the MTD of 1A is determined, 1B will explore the food effect of a high fat meal on the PK of CFI-400945 at the MTD. 2A and 2B will explore the combination of CFI-400945 with standard dose of either azacitidine (2A) or decitabine (2B). The starting dose of CFI-400945 will be 32mg po for 21 days on/7 off. The DLTs will be defined as NCI CTCAE V5.0 Grade >3 related non-hematologic event(s) occurring during cycle 1 or prolonged pancytopenia in the presence of a hypocellular bone marrow > day 42 without evidence of disease. The efficacy endpoints for AML, MDS, and CMML include the overall response rate, and the CR rate per standard criteria. The aim of the food effect part of the study is the asses the effect of high fat food on the PK of CFI-400945. The safety endpoint is the incidence of treatment emergent adverse events. PK endpoints include evaluations of parameters such as half-life, AUC, etc. Exploratory endpoints include eval of minimal residual disease, genomic alterations and other molecular features associated with response and biological effects of PLK4 inhibition. Disclosures Jonas: Amgen: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; AbbVie: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; GlycoMimetics: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Sigma Tau: Research Funding; Jazz: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Takeda: Consultancy; Tolero: Consultancy; Treadwell: Consultancy; Forty Seven: Research Funding; Accelerated Medical Diagnostics: Research Funding; AROG: Research Funding; Daiichi Sankyo: Research Funding; F. Hoffmann-La Roche: Research Funding; Forma: Research Funding; Genentech/Roche: Research Funding; Hanmi: Research Funding; Incyte: Research Funding; LP Therapeutics: Research Funding; Pfizer: Research Funding; Pharmacyclics: Research Funding. Bixby:GlycoMimetics: Research Funding. Brandwein:Pfizer: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Astellas: Honoraria; Taiho: Honoraria; Roche: Honoraria; Jazz Pharmaceuticals: Honoraria. Michelson:Treadwell Therapeutics: Consultancy. Bray:TIO Discovery: Current Employment; Treadwell Therapeutics: Current Employment. Roberts-Thomson:Treadwell Therapeutics: Current Employment. Borthakur:BioTherix: Consultancy; FTC Therapeutics: Consultancy; Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy; PTC Therapeutics: Consultancy; Argenx: Consultancy; Oncoceutics: Research Funding; Xbiotech USA: Research Funding; Polaris: Research Funding; AstraZeneca: Research Funding; BMS: Research Funding; BioLine Rx: Research Funding; Jannsen: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding; BioLine Rx: Consultancy; PTC Therapeutics: Research Funding; Curio Science LLC: Consultancy; Cyclacel: Research Funding; GSK: Research Funding.

Follicular lymphoma (FL) constitutes the second most common non-Hodgkin lymphoma in the western world. FL carries characteristic recurrent structural genomic aberrations. However, information regarding the coding genome in FL is still evolving. Here, we describe the results of massively parallel exome sequencing and single nucleotide polymorphism 6.0 array genomic profiling of 11 highly purified FL cases, and 1 transformed FL case and the validation of selected mutations in 102 FL cases. We report the identification of 15 novel recurrently mutated genes in FL. These include frequent mutations in the linker histone genes HIST1H1 B-E (27%) and mutations in OCT2 (also known as POU2F2; 8%), IRF8 (6%), and ARID1A (11%). A subset of the mutations in HIST1H1 B-E affected binding to DNMT3B, and mutations in HIST1H1 B-E and in EZH2 or ARID1A were largely mutually exclusive, implicating HIST1H1 B-E in epigenetic deregulation in FL. Mutations in OCT2 (POU2F2) affected its transcriptional and functional properties as measured through luciferase assays, the biological analysis of stably transduced cell lines, and global expression profiling. Finally, multiple novel mutated genes located within regions of acquired uniparental disomy in FL are identified. In aggregate, these data substantially broaden our understanding of the genomic pathogenesis of FL.

Introduction: Aspacytarabine (BST-236) is a prodrug of cytarabine, a backbone of acute myeloid leukemia (AML) therapy. Due to its unique pharmacokinetics and metabolism, treatment with aspacytarabine evades peak exposure to free cytarabine, which reduces non-hematological toxicity and enables delivery of high-dose cytarabine also to patients unfit for standard therapy. Data from a completed phase 1/2a and an ongoing phase 2b studies in AML patients unfit for standard therapy, including patients with AML secondary to therapy and myelodysplastic syndrome (MDS) with prior exposure to hypomethylating agents (HMA), demonstrate promising single-agent efficacy and safety of aspacytarabine as a potential first-line AML treatment for this challenging population. Aims: To evaluate the efficacy and safety of aspacytarabine in AML patients unfit for standard induction therapy. Methods: A completed phase 1/2a study and an ongoing phase 2b study evaluate the efficacy and safety of aspacytarabine as a single-agent therapeutic for AML. The phase 1/2a, dose-escalation study enrolled newly-diagnosed patients unfit for standard therapy and patients with relapsed/refractory AML. Patients were treated with 0.3-6 g/m2/d aspacytarabine in 6 dose-escalating cohorts. The ongoing multi-center phase 2b study expands the subgroup of newly-diagnosed AML patients unfit for standard therapy, to evaluate the efficacy and safety of aspacytarabine as a first-line therapy for this population. Secondary AML patients, treated with HMA, chemotherapy, or radiotherapy for a prior condition, are allowed. Patients in the phase 2b study are treated with the selected aspacytarabine dose of 4.5 g/m2/d, containing approximately 3 g/m2/d of cytarabine. Each aspacytarabine treatment course (induction and consolidation) consists of 6 1-hour daily intravenous infusions. Results: To date, 34 AML patients, median age 76 years, received at least 1 dose of aspacytarabine, including 30 patients unfit for standard induction therapy due to age or comorbidities. Overall, 25 patients completed 1 course of aspacytarabine, 4 patients completed 2 courses, 1 patient completed 3 courses, and 1 patient completed 4 courses of aspacytarabine. Three patients (in the phase 1/2a study) did not complete the first course. Aspacytarabine was safe and well-tolerated in repeated-course administration, including in older and unfit patients. Adverse events included mainly hematological "on-target" events with no drug-related mucositis or cerebellar toxicity. Twenty-one patients were newly-diagnosed with AML, either de novo or secondary to MDS or therapy. The patient population was characterized by older age (median 76 years, range 67-88 years), and the majority (67%) of patients had secondary AML, including 10 patients (48%) who were previously treated with HMA (median of 10 courses) or radiotherapy. The median baseline bone marrow blast percentage of this population was 75, and 43% and 48% had intermediate or adverse European LeukemiaNet (ELN) cytogenetic score, respectively. Despite these poor-prognostic characteristics, the 30-day mortality rate in the group of patients receiving ≥4.5 g/m2/d aspacytarabine was 7%. The combined complete remission (CR) rate of all doses was 33%, including 1 patient reaching a CR with partial platelet recovery (CRp). The CR rate in patients treated with at least 4.5 g/m2/d aspacytarabine is 36%, with median time for complete hematological recovery of 27 days (range 21-30) following induction and consolidation. Notably, among the 7 patients who reached a CR/CRp (median age 77), 3 secondary AML patients reached a CR, including 2 patients with prior exposure to HMA (5 and 10 courses) and 1 with prior exposure to radiotherapy (Table 1). Duration of response and overall survival follow up is ongoing and will be presented at the meeting. Conclusions: The accumulating clinical data suggest that aspacytarabine is safe and efficacious for the treatment of AML patients who are unfit for standard induction therapy, including patients with prior exposure to HMA, which may establish aspacytarabine as a new therapeutic backbone for AML, either as a single agent or in combination with targeted therapy. Disclosures Altman: Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Glycomimetics: Consultancy, Honoraria, Other: Data Safety and Monitoring Committee; Daiichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Biosight: Other: US Lead; Novartis: Consultancy; Agios: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Cancer Expert Now: Consultancy; France Foundation: Speakers Bureau; prIME Oncology: Speakers Bureau; PeerView: Speakers Bureau; Theradex: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Luger:Seattle Genetics: Research Funding; Pfizer: Honoraria; Onconova: Research Funding; Kura: Research Funding; Jazz: Honoraria; Genetech: Research Funding; Daichi Sankyo: Honoraria; Cyslacel: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Ariad: Research Funding; Agios: Honoraria. Kota:Takeda: Honoraria; Xcenda: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Pfizer: Honoraria. Flaishon:BioSight Ltd.: Employment. Tessler:BioSight Ltd.: Employment. Gengrinovitch:BioSight Ltd.: Employment. Ben Yakar:BioSight Ltd.: Employment. Rowe:BioSight: Consultancy.

Leukemic myeloblasts expressing E-selectin ligand (E-sel ligand) adhere to E-selectin on bone marrow endothelium resulting in environment-mediated drug resistance (EMDR). Uproleselan, a potent E-selectin inhibitor, disrupts the adhesion of AML cells in the bone marrow, re-sensitizing blasts to the cytotoxic effects of chemotherapy. Retrospective data demonstrated that E-sel ligand expression in AML patients is higher in relapsed disease compared to newly diagnosed AML, is more commonly seen in biologically adverse risk patients, and is present on leukemic stem cells (Chien et al ASH 2018). Preliminary data from a phase 1-2 trial of uproleselan combined with mitoxantrone, etoposide, cytarabine (MEC) chemotherapy in R/R AML demonstrated enhanced survival in patients with E-sel ligand expression on AML cells of > 10% compared to lower levels (DeAngelo et al ASH 2018). In order to more fully understand the relationship of E-sel ligand to the activity of uproleselan, we examined the clinical variables of patients with both high (> 10%) and low E-sel ligand levels in comparison to the total population of patients treated on the phase 1-2 trial. Uproleselan, combined with MEC chemotherapy was studied in 66 patients with relapsed and/or refractory AML. The expression level of E-sel ligand on the surface of AML cells (blasts/leukemic stem cells (LSCs)) in the bone marrow was measured by a flow cytometric assay using the HECA 452 antibody that recognizes a functional trisaccharide domain shared by sialyl Lea and sialyl Lex and known to bind to E-selectin. Data on E-sel ligand was available in 36 patients at study entry in the phase 1-2 study and E-sel ligand was detectable on blasts in all patients. E-sel ligand on LSCs was demonstrated at levels ≥ 10% in 22 patients (61%) and at levels < 10 % in 14 patients (39%). Overall, the clinical characteristics confirmed a highly resistant population of R/R AML patients (see table) with 79% categorized as either poor risk by the European Prognostic Index (EPI) for first salvage therapy or ≥ second salvage, with an expected 1 year survival of less than 20% (Breems et al JCO 2005, Giles et al Cancer 2005). Although the sample size was small (n=36), substantially more patients with high E-sel ligand had achieved an initial remission and were in relapse (68%) whereas low E-sel ligand patients were more likely to be primary refractory (57%) (p=0.17). Patients with high E-sel ligand were more likely to have adverse ELN risk disease (55%) compared to low E-sel ligand patients (28%) (p=0.053). These data are consistent with previous findings demonstrating that higher E-sel ligand expression contributes to clinical chemotherapy resistance, particularly increasing the risk of relapse, whereas alternative resistance mechanisms may more commonly contribute to primary resistance. Importantly, the 45% response rate and 12.7 months median overall survival (OS) in the high E-sel ligand patients suggests that E-selectin inhibition by uproleselan contributed to their significantly improved outcomes when compared to the historically dismal outcomes with standard of care alone in these poor risk R/R AML patients. Table. Disclosures DeAngelo: Incyte Corporation: Consultancy; Celgene Corporation: Consultancy; Pfizer, Inc.: Consultancy; GlycoMimetics: Research Funding; AbbVie, Inc.: Research Funding; Takeda Pharmaceuticals: Consultancy; Shire: Consultancy; Amgen: Consultancy; Blue Print Medicines: Consultancy, Research Funding; Jazz Pharmaceuticals, Inc.: Consultancy; Novartis Pharmaceuticals Corporation: Consultancy, Research Funding. Jonas:AbbVie, Accelerated Medical Diagnostics, AROG, Celgene, Daiichi Sankyo, Esanex, Forma, Genentech/Roche, GlycoMimetics, Incyte, LP Therapeutics, Pharmacyclics: Research Funding; AbbVie, Amgen, Celgene, GlycoMimetics, Jazz, Pharmacyclics, Tolero: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie, Amgen, GlycoMimetics: Other: Travel expenses. Liesveld:Abbvie: Membership on an entity's Board of Directors or advisory committees; Onconova: Other: Data safety monitoring board. Advani:Pfizer: Honoraria, Research Funding; Glycomimetics: Consultancy, Research Funding; Amgen: Research Funding; Kite Pharmaceuticals: Consultancy; Abbvie: Research Funding; Macrogenics: Research Funding. Marlton:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. O'Dwyer:Onkimmune: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; GlycoMimetics Inc: Research Funding; BMS: Research Funding. Fogler:GlycoMimetics Inc: Employment, Equity Ownership. Magnani:GlycoMimetics Inc: Employment, Equity Ownership. Chen:GlycoMimetics: Employment. Feldman:GlycoMimetics Inc: Employment. Thackray:GlycoMimetics Inc: Employment. Becker:AbbVie, Amgen, Bristol-Myers Squibb, Glycomimetics, Invivoscribe, JW Pharmaceuticals, Novartis, Trovagene: Research Funding; Accordant Health Services/Caremark: Consultancy; The France Foundation: Honoraria.

BACKGROUND Secondary AML (sAML) that develops after an antecedent hematologic disorder or exposure to genotoxic therapy is associated with a poor prognosis and historical long-term survival rates of 5-10% (Granfeldt Østgård et al. 2015). Liposomal daunorubicin and cytarabine (CPX-351) was recently FDA approved for the treatment of sAML, based on a randomized phase III trial that found a higher complete remission (CR) rate, event-free survival (EFS), and overall survival (OS) with CPX-351 compared to 7+3 chemotherapy (Lancet et al. 2018). Retrospective studies conducted in this patient population suggest that high-dose cytarabine (HIDAC)-based regimens may also be safe and effective in sAML (Vulaj et al. 2018, Talati et al. 2018). With an average wholesale price of up to $150,000 for induction, CPX-351 represents a large financial burden when compared to HIDAC-based regimens. Because HIDAC-based regimens employ older, generic medications, and sAML is a relatively rare diagnosis, it is unlikely these two induction strategies will be compared prospectively. This real-world, multicenter study retrospectively compared clinical outcomes in patients with sAML receiving CPX-351 and HIDAC-based regimens. METHODS Adult patients with newly diagnosed sAML treated between January 2013 and January 2019 from 7 academic medical centers (University of Michigan n=73, MD Anderson Cancer Center n=27, Barnes Jewish Hospital n=22, University of North Carolina n=21, Huntsman Cancer Institute n=9, University of Rochester n=9, Indiana University n=8) were divided into 2 cohorts based on induction regimen: HIDAC-based or CPX-351. Demographics, disease characteristics, and outcomes were collected in accordance with the institutional review board approved protocol. The primary endpoint of composite complete response/complete response with incomplete count recovery (CR/CRi) as well as secondary efficacy endpoints were defined using 2003 International Working Group Criteria. For the primary endpoint, a sample of 96 patients was established a priori as necessary to demonstrate non-inferiority of HIDAC-based regimens using a non-inferiority margin of 7.5% and historical CR/CRi rates or 65% and 47.7% for HIDAC-based and CPX-351 respectively. Chi-square or Fisher's exact tests were utilized to evaluate dichotomous variables. Continuous variables were analyzed via Student's t-test or Mann-Whitney U test. Kaplan-Meier analysis with log-rank test was performed to estimate progression-free survival (PFS) and overall survival (OS). RESULTS A total of 169 patients were included (HIDAC-based: n=75; CPX-351: n=94). HIDAC-based regimen distribution was as follows: fludarabine/cytarabine ± G-CSF (n=73) and clofarabine/cytarabine ± G-CSF (n=2). Baseline characteristics were well balanced (table 1) with the exception of a higher Charlson Comorbidity Index in patients who received HIDAC-based therapy. The median age of all patients was 67 years and the majority of patients had sAML due to an antecedent hematologic disorder. CR/CRi rate was numerically higher and non-inferior with HIDAC-based therapy (62.7%) compared with CPX-351 (47.9%) (p=0.002 [one-sided for non-inferiority]). Median OS was 10.06 vs 10.59 months and median EFS was 5.56 vs 4.11 months with HIDAC-based regimens compared with CPX-351, respectively. Thirty-day mortality (1.3 vs 8.5%; p=0.039) and confirmed infection in induction (56% vs 74.5%; p=0.012) were significantly higher with CPX-351. Additionally, the time to absolute neutrophil count (ANC) and platelet count (PLT) recovery in CR/CRi were significantly longer with CPX (ANC: 18 vs 35.5 days; p CONCLUSIONS HIDAC-based regimens yield CR/CRi rates that are non-inferior to CPX-351 in patients with sAML with similar EFS and OS. In a primarily elderly population, HIDAC-based therapy demonstrates greater tolerability with lower induction mortality, infection rates, and a more favorable duration of cytopenias. With non-inferior efficacy, better tolerability, and significantly lower cost, HIDAC-based regimens may be preferred to CPX-351 in patients with sAML. Disclosures Klaus: Jazz Pharmaceuticals: Other: Advisory Board, Speakers Bureau. Clark:Elliott Benson Research: Consultancy. Pettit:Samus Therapeutics: Research Funding.

To further our understanding of the genetic basis of acute myelogenous leukemia (AML), we determined the coding exon sequences of ∼ 18 000 protein-encoding genes in 8 patients with secondary AML. Here we report the discovery of novel somatic mutations in the transcriptional corepressor gene BCORL1 that is located on the X-chromosome. Analysis of BCORL1 in an unselected cohort of 173 AML patients identified a total of 10 mutated cases (6%) with BCORL1 mutations, whereas analysis of 19 AML cell lines uncovered 4 (21%) BCORL1 mutated cell lines. The majority (87%) of the mutations in BCORL1 were predicted to inactivate the gene product as a result of nonsense mutations, splice site mutation, or out-of-frame insertions or deletions. These results indicate that BCORL1 by genetic criteria is a novel candidate tumor suppressor gene, joining the growing list of genes recurrently mutated in AML.

Introduction: SY-1425 (tamibarotene) is an orally available, synthetic retinoid in Phase 2 development for non-APL AML and MDS patients (pts) positive for the RARA and/or IRF8 biomarkers of RARA pathway activation (McKeown et al, Cancer Discovery, 2017). Biomarker-selected pts treated with SY-1425 single agent showed myeloid differentiation, improved blood counts and reduced bone marrow blasts, and treatment was generally well tolerated with manageable and/or reversible side effects (Jurcic et al, ASH 2017). SY-1425 showed evidence of combination activity in preclinical models. Synergy was observed with HMAs, with DNA damage and apoptosis in vitro, and in an AML PDX model the combination of SY-1425 and azacitidine (Aza) demonstrated increased tumor reduction, deeper, more durable responses and improved survival relative to Aza or SY-1425 alone (McKeown et al, ASH 2016). SY-1425 induced CD38 expression in preclinical models and the combination with daratumumab (Dara), a CD38 targeting antibody indicated for multiple myeloma (MM), induced immune-mediated cell death ex vivo (Austgen et al, AACR 2017). SY-1425 also increased CD38 expression in bone marrow blasts in AML/MDS pts (Jurcic et al, ASH 2017). These data support the ongoing investigation of the efficacy and safety of SY-1425 in non-APL AML and MDS pts, in combination with Aza or Dara (NCT02807558). Methods: Biomarker positive (Bm+), unfit pts with newly-diagnosed (ND) AML received SY-1425 + Aza. The SY-1425 + Aza combination arm was recently expanded to include biomarker negative pts. Bm+ pts with relapsed/refractory (R/R) AML or R/R higher-risk MDS received SY-1425 + Dara. All enrolled pts received SY-1425 at 6 mg/m2/day PO with twice daily dosing. Aza (75 mg/m2 IV/SC) and Dara (16 mg/kg IV) were dosed as approved in MDS and MM, respectively. Objectives included characterization of activity by overall response rate (per IWG), duration of response, event-free, relapse-free and overall survival, hematologic improvement, and assessment of safety. For pts treated with SY-1425 + Dara, the kinetics and magnitude of CD38 increases were evaluated on peripheral blasts using a centralized assay. Results: With 10 ND AML pts currently enrolled to receive SY-1425 + Aza, 6 were Bm+. Data through 9 July 2018 were available for 5 Bm+ pts, 4 (80%) male and median age 76 years (64-83). Pts were reported to have poor (3 pts) and intermediate (2 pts) ELN genetic risk. Median time on treatment was 25.4 weeks (9.7-42.1). Early clinical responses at 4 weeks (C2D1) were reported in 4 of 5 pts. Best responses were CR (1 pt), CRi (1 pt) and PRi (2 pts), defined as PR with incomplete blood count recovery. A 5th pt with ND AML developing from prior CMML with 2 distinct blast populations had stable disease (AML blasts), but with CR of CMML marrow blasts by flow at 8 weeks (C3D1). 2 pts remained on treatment, including 1 with CR at 9 months (C10D1). 3 pts discontinued due to PD/lack of efficacy (2 pts) and AE (1 pt). 10 Bm+ pts have enrolled to receive SY-1425 + Dara. Data were available for 4 pts (3 R/R AML and 1 R/R MDS), 4 (100%) female and median age 60 years (36-68). Pt risk was poor (2 pts) and intermediate (1 pt) per ELN for AML, and good (1 pt) per IPSS-R for MDS. Median time on treatment was 5.9 weeks (0.7-8.9). 1 of 3 evaluable pts achieved a PRi at 4 weeks (C2D1) but progressed at C3D1. Initial data demonstrate that 3 of 4 pts showed an increase in CD38 expression levels in peripheral AML blasts as early as 3 days following SY-1425 treatment, up to 2.6-fold by 1 week. All 4 pts discontinued treatment due to disease progression. AEs (most common, all causality) reported in >2 pts receiving SY-1425 combination treatment included febrile neutropenia (44%), and hypertriglyceridemia, pruritus, abdominal pain and peripheral edema (33% each). Overall, AEs, including AEs ≥ grade 3 and SAEs, were consistent with those of single agent SY-1425, Aza or Dara. Conclusion: SY-1425 in combination with Aza in non-APL AML shows preliminary evidence of clinical activity with early objective responses observed. CD38 expression increased in 3 of 4 pts with R/R AML or R/R MDS within 3 days of SY-1425 treatment and reduction in marrow blasts was observed in 1 pt treated with SY-1425 in combination with Dara. No new safety signals have been identified with either combination regimen. In summary, early data suggest SY-1425 in combination has clinical potential in pts with non-APL AML and MDS. Updated results will be presented. Disclosures Cook: Syros Pharmaceuticals: Consultancy. Liesveld:Abbvie: Honoraria; Onconova: Other: DSMB. Rizzieri:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Arog: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy. Stein:Novartis: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Daiichi Sankyo: Consultancy; Celgene: Consultancy; Bayer: Consultancy. Roboz:Argenx: Consultancy; Jazz Pharmaceuticals: Consultancy; AbbVie: Consultancy; Astex Pharmaceuticals: Consultancy; Cellectis: Research Funding; Daiichi Sankyo: Consultancy; Pfizer: Consultancy; Astex Pharmaceuticals: Consultancy; Cellectis: Research Funding; Sandoz: Consultancy; Bayer: Consultancy; Otsuka: Consultancy; Novartis: Consultancy; Daiichi Sankyo: Consultancy; Novartis: Consultancy; Eisai: Consultancy; Celgene Corporation: Consultancy; Celltrion: Consultancy; AbbVie: Consultancy; Roche/Genentech: Consultancy; Pfizer: Consultancy; Orsenix: Consultancy; Celgene Corporation: Consultancy; Roche/Genentech: Consultancy; Orsenix: Consultancy; Argenx: Consultancy; Janssen Pharmaceuticals: Consultancy; Eisai: Consultancy; Bayer: Consultancy; Celltrion: Consultancy; Aphivena Therapeutics: Consultancy; Aphivena Therapeutics: Consultancy; Janssen Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy; Otsuka: Consultancy; Sandoz: Consultancy. Sekeres:Opsona: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Opsona: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Jurcic:Actinium Pharmaceuticals, Inc: Research Funding; Daiichi-Sankyo: Research Funding; Forma Therapeutics: Research Funding; Syros Pharmaceuticals: Research Funding; AbbVie: Consultancy, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Research Funding; Genetech: Research Funding; Incyte: Consultancy; Celgene: Research Funding; Astellas: Research Funding. Raza:Kura Oncology: Research Funding; Geoptix: Speakers Bureau; Novartis: Speakers Bureau; Celgene: Research Funding; Janssen: Research Funding; Onconova: Research Funding, Speakers Bureau; Syros: Research Funding. Bixby:GlycoMimetics: Research Funding. Cortes:Pfizer: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Arog: Research Funding. Stephens:Syros Pharmaceuticals: Employment, Equity Ownership. Volkert:Syros Pharmaceuticals: Employment, Equity Ownership. Kang:Syros Pharmaceuticals: Employment, Equity Ownership. Di Tomaso:Syros Pharmaceuticals: Employment, Equity Ownership. Roth:Syros Pharmaceuticals: Employment, Equity Ownership.

Background Binding of E-selectin (E-sel) to sialyl Lex on the leukemic cell surface activates cell survival pathways and promotes chemotherapy resistance in AML. Expression of the E-sel ligand (E-sel-L) is associated with increased relapse and poor survival. Uproleselan (GMI-1271), a novel E-sel antagonist, disrupts cell survival pathway activation, enhances chemotherapy response and protects from toxicity with improved survival in vivo. We added uproleselan to mitoxantrone, etoposide, cytarabine (MEC) chemotherapy for R/R AML patients (pts) and to cytarabine and idarubicin (7+3) induction for older, treatment naïve (TN) AML pts. Here we report on final outcomes and correlative studies. Methods A Phase (Ph) 1/2 trial evaluated safety and efficacy of escalating doses of upro (5-20 mg/kg) combined with MEC in pts with R/R AML. The recommended Ph 2 dose (RP2D) was 10 mg/kg. Ph 2 added pts ≥60 yrs with TN AML treated with upro and 7+3. Uproleselan was given 24 hrs prior, every 12 hrs during and 48 hrs post chemotherapy. Responders could receive consolidation therapy (1 cycle MEC or 1-3 cycles IDAC) with uproleselan. Baseline E-sel-L expression on AML blasts (CD45+,SSC) and leukemic stem cells (LSC, CD34+CD38-CD123+) in blood and bone marrow (BM) was assessed by flow cytometry, for percentage of blasts binding to E-sel-Fc chimeric protein and HECA452 (antibody to sialyl Lex). Post-induction measurable residual disease (MRD-/MRD+) was assessed locally. Results 91 pts were enrolled (Ph 1 R/R=19; Ph 2 R/R=47. TN=25). Median age in R/R pts was 59 yrs (26-84) with 22/66 (33%) primary refractory, 22 (33%) CR1 Median age in TN pts was 67 yrs (60-79). 48% had adverse risk (ELN) and 52% secondary AML (sAML). Uproleselan was well tolerated, with no increase in adverse events, no Grade 3/4 mucositis, and mortality 8% (30d) and 12% (60d). CR/CRi was 72% (all), and 69% (sAML). 5/9 (56%) evaluable pts were MRD-. 19/25 (76%) proceeded to further anti-leukemic therapy; 11 (44%) proceeded to SCT. Median (95% CI) EFS, OS, and remission duration were 9.2 m (3.0-12.6), 12.6 m (9.9-NR), and 10.4 m (7.1-17.8) respectively; 1-year OS was 52%. For sAML, median (95% CI) EFS and OS were 7.7 m (1.1-9.5) and 10.5m (4.4-NR), respectively. For TN/MRD-, 1-year OS was 60%. E-sel-L was detectable on BM blasts in all 24 evaluable pts: median expression 31% (2-92) of blasts. In a subset of MRD evaluable pts (N=8), E-sel-L expression was higher in those who were MRD+ (35% vs 8%). In BM blasts (Figure N=24), LSC expression of E-sel-L correlated with blast E-sel-L (R2=0.87, p Conclusion The addition of uproleselan to chemotherapy was well tolerated, with low oral mucositis rates, high remission rates, high MRD- and transplant rates, and promising survival outcomes in pts with R/R and TN AML. High E-sel-L expression is associated with improved remission and survival with uproleselan treatment in R/R AML. Phase III studies in pts with R/R and (older) TN AML are underway. Figure. Figure. Disclosures DeAngelo: Shire: Honoraria; Amgen: Consultancy; BMS: Consultancy; ARIAD: Consultancy, Research Funding; Blueprint Medicines: Honoraria, Research Funding; Takeda: Honoraria; Glycomimetics: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria; Amgen: Consultancy; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Glycomimetics: Research Funding; Blueprint Medicines: Honoraria, Research Funding; Pfizer Inc: Consultancy, Honoraria; Shire: Honoraria; BMS: Consultancy; Takeda: Honoraria; Incyte: Consultancy, Honoraria; Pfizer Inc: Consultancy, Honoraria; ARIAD: Consultancy, Research Funding. Jonas:Glycomimetics: Research Funding; Genentech/Roche: Research Funding; Celgene: Consultancy, Research Funding; Accelerated Medical Diagnostics: Research Funding; Daiichi Sankyo: Research Funding; Incyte: Research Funding; Esanex: Research Funding; Tolero: Consultancy; Kalobios: Research Funding; LP Therapeutics: Research Funding; Amgen: Consultancy; Pharmacyclics: Research Funding; Forma: Research Funding; AbbVie: Consultancy, Research Funding. Liesveld:Onconova: Other: DSMB; Abbvie: Honoraria. Bixby:GlycoMimetics: Research Funding. Advani:Glycomimetics: Consultancy; Novartis: Consultancy; Amgen: Research Funding; Pfizer: Honoraria, Research Funding. Marlton:GlycoMimetics: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. O'Dwyer:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Onkimmune: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Glycomimetics: Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees. Fogler:GlycoMimetics: Employment, Equity Ownership. Wolfgang:GlycoMimetics: Employment, Equity Ownership. Magnani:GlycoMimetics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Thackray:GlycoMimetics: Employment, Equity Ownership. Becker:GlycoMimetics: Research Funding.

Background: CPX-351 (Vyxeos®) is a dual-drug liposomal encapsulation of cytarabine and daunorubicin at a synergistic ratio. In a large randomized, open-label, multicenter, phase 3 study (NCT01696084) of CPX-351 versus conventional cytarabine/daunorubicin chemotherapy (7+3 regimen) in patients (pts) aged 60-75 years with newly diagnosed, high-risk/secondary AML, CPX-351 significantly improved overall survival (OS) and remission rates (Lancet JE, et al. J Clin Oncol. 2018). CPX-351 was approved by the US FDA in 2017 for the treatment of adults with newly diagnosed therapy-related AML or AML-MRC and is currently under review by the EMA. The WHO 2016 AML-MRC designation applies to AML pts who meet any of the following criteria: 1) a history of myelodysplastic syndrome (MDS) or myelodysplastic/myeloproliferative neoplasm (MDS/MPN), 2) an MDS-related cytogenetic abnormality, or 3) multilineage dysplasia in >50% of ≥2 cell lineages in the absence of NPM1 or biallelic CEBPA mutations. Pts with AML-MRC typically face a poor prognosis, with inferior outcomes in response to standard induction chemotherapy. A subgroup analysis of the phase 3 study was performed to specifically compare the efficacy and safety of CPX-351 versus 7+3 in pts with AML-MRC. Methods: Pts enrolled in the phase 3 study who met the WHO 2008 AML-MRC classification were included in this subgroup analysis; however, pts with a history of MPN other than CMML or combined MDS/MPN and pts with only morphologic evidence of multilineage dysplasia were excluded from the phase 3 study. Pts were randomized 1:1 to receive up to 2 inductions with CPX-351 (100 units/m2 [cytarabine 100 mg/m2 + daunorubicin 44 mg/m2] on Days 1, 3, and 5 [2nd induction: Days 1 and 3]) or 7+3 (cytarabine 100 mg/m2/day continuously for 7 days [2nd induction: 5 days] + daunorubicin 60 mg/m2 on Days 1-3 [2nd induction: Days 1-2]). Pts achieving complete remission (CR) or CR with incomplete platelet or neutrophil recovery (CRi) could receive up to 2 consolidations with CPX-351 (65 units/m2 [cytarabine 65 mg/m2 + daunorubicin 29 mg/m2] on Days 1 and 3) or 5+2 (as in 2nd induction). Pts could receive hematopoietic cell transplantation (HCT) at the discretion of their treating physician. Results: The study enrolled 309 pts, 246 of whom met the criteria for AML-MRC (CPX-351: n = 123; 7+3: n = 123). Of these 246 pts, 59.0% had antecedent MDS, 9.3% had antecedent CMML, and 31.7% had de novo AML with MDS karyotype. Baseline characteristics were similar between treatment arms (median age 68 years; 64.6% male; 11.0% with ECOG status of 2). A second induction cycle was received by 33.3% of pts in the CPX-351 arm and 37.8% of pts in the 7+3 arm. Among pts with AML-MRC, CPX-351 was associated with a significant OS benefit versus 7+3 (median: 9.07 vs 5.95 months; HR = 0.70 [95% CI: 0.53-0.93]). CPX-351 was also associated with higher rates of CR+CRi (48.0% vs 32.5%; OR = 1.83 [95% CI: 1.09-3.09]), CR (37.4% vs 24.4%; OR = 1.80 [95% CI: 1.02-3.17]), and HCT (33.3% vs 24.4%; OR = 1.53 [95% CI: 0.86-2.74]). Among pts who received HCT, median OS was longer with CPX-351 versus 7+3 when calculated from the date of randomization (not reached vs 15.21 months; HR = 0.50 [95% CI: 0.26-0.99]) or date of HCT (not reached vs 10.68 months; HR = 0.48 [95% CI: 0.24-0.96]). Early mortality rates in the CPX-351 and 7+3 arms, respectively, were 4.9% and 8.9% at Day 30 and 13.8% and 20.3% at Day 60. The treatment-emergent adverse event (TEAE) profile of CPX-351 in pts with AML-MRC was consistent with the overall study population and generally comparable between treatment arms (Table). Two pts treated with CPX-351 and 1 treated with 7+3 discontinued treatment due to a TEAE (cardiac failure [CPX-351], cardiomyopathy [CPX-351], and ejection fraction decreased [7+3]). Grade 5 TEAEs occurred in 8.9% and 14.3% of pts treated with CPX-351 and 7+3, respectively; those occurring in >1 pt in a treatment arm included sepsis (2.4% and 0.8%), disease progression (1.6% and 3.4%), multi-organ failure (0.8% and 1.7%), and respiratory failure (0.8% and 1.7%). Conclusions: In this subgroup analysis, CPX-351 improved OS and remission rates compared with 7+3 in older adults with AML-MRC, while maintaining a similar safety profile. Importantly, CPX-351 is the first agent to be associated with prolonged OS compared with standard-of-care chemotherapy (7+3 regimen) in adults with newly diagnosed AML-MRC, which supported FDA approval in this population. Disclosures Ryan: AbbVie: Equity Ownership; University of Rochester: Patents & Royalties. Uy:Curis: Consultancy; GlycoMimetics: Consultancy. Cortes:Astellas Pharma: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Arog: Research Funding; Pfizer: Consultancy, Research Funding. Ritchie:Bristol-Myers Squibb: Research Funding; Incyte: Consultancy, Speakers Bureau; NS Pharma: Research Funding; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Astellas Pharma: Research Funding; Celgene: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; Pfizer: Consultancy, Research Funding; ARIAD Pharmaceuticals: Speakers Bureau. Stuart:Sunesis Pharmaceuticals: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding; Agios: Research Funding; Astellas: Research Funding; Bayer AG: Research Funding; Celator/Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding. Strickland:Sunesis Pharmaceuticals: Consultancy, Research Funding; Tolero Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Baxalta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas Pharma: Consultancy. Bixby:GlycoMimetics: Research Funding. Kolitz:Magellan Health: Consultancy, Honoraria. Schiller:bluebird bio: Research Funding; Astellas Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding. Wieduwilt:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Shire: Research Funding; Reata Pharmaceuticals: Equity Ownership; Leadiant: Research Funding; Amgen: Research Funding; Merck: Research Funding. Ryan:Jazz Pharmaceuticals: Employment, Other: Stock and stock options. Chiarella:Celator/Jazz Pharmaceuticals: Employment, Equity Ownership. Louie:Celator/Jazz Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties.

Intro: Acute myeloid leukemia (AML) is a heterogeneous clonal hematopoietic neoplasm. The cytogenetic changes associated with AML impact response rate and survival, and is one of the most important independent prognostic factors. AML with inv(3)(q21.3q26.2) or; GATA2, MECOMaccounts for 1-2% of all forms of AML. This form is associated with a younger age at diagnosis, poor response to standard induction chemotherapy, and very poor long-term prognosis with an overall survival of Methods: We conducted a single-center, IRB-approved, retrospective cohort analysis of 939 patients who received therapy for AML at the University of Michigan between March 2005-June 2018. 15/939 (1.6%) patients tested positive for inv(3)(q21.3q26.2), and they were divided into two cohorts: a lenalidomide-based regimen or other chemotherapy induction approaches. Data abstraction of patient, disease and treatment-related variables was performed through manual chart review. The primary outcome was overall response rate (ORR), reported as the combination of complete remission (CR) and complete remission with incomplete count recovery (CRi). Secondary endpoints included overall survival (OS), 30- and 60-day mortality, event free survival (EFS), and duration of response. All data were analyzed using SPSS software, version 24.0 (SPSS, Inc., Chicago, IL). Results: In total, 15 patients were positive for inv(3)(q21.3q26.2) and underwent treatment at the University of Michigan. 4/16 (25%) received lenalidomide and HMA as primary therapy. Patient demographics and lab values at diagnosis are shown in Table 1. 4/4 (100%) of patients receiving lenalidomide with HMA as first line therapy achieved CR/CRi while 3/11 (27.3%) of patients receiving other chemotherapeutic agents initially achieved CR/CRi (p=0.0256). Duration of response was numerically longer in patients receiving lenalidomide-based therapies (7.4 months vs. 1.45 months; p=0.057). Primary and secondary outcomes in patients receiving lenalidomide plus HMA and other chemotherapies are shown in Table 2. 2/13 patients requiring salvage therapy received lenalidomide with HMA. Both of these patients achieved CR/CRi, while 3/11 (27.3%) of patients receiving other chemotherapy achieved CR/CRi. Combining initial and salvage inductions, 6/6 (100%) achieved CR/CRi with lenalidomide with HMA versus 6/22 (27.3%) with other chemotherapy (p=0.0025). Discussion: AML with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOMis notorious for a poor response to standard induction chemotherapy and a reported remission rate of 10-20% with traditional chemotherapy (Raya et al. Hematology 2015;20(8):435-441).In this cohort, all patients who received lenalidomide with or without a HMA achieved CR/CRi compared to 27% of patients receiving other chemotherapy. Importantly, the median duration of response with lenalidomide and HMA was longer than traditional chemotherapy, although not statistically significant, likely due to the small sample size. The high ORR and reasonable duration of response could allow for potentially curative alloHCT in these high-risk AML patients. Our study is limited by the small sample size due to the rarity of this AML subtype, but the initial data suggests that lenalidomide plus HMA is a promising approach for patients with AML with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM. A multicenter, prospective trial should be considered to compare the efficacy of traditional cytotoxic chemotherapy approaches versus lenalidomide plus HMA to improve outcomes in this subtype of AML. Disclosures Bixby: GlycoMimetics: Research Funding.

Background: Outcomes for the treatment of AML with conventional induction chemotherapy (eg, 7+3 cytarabine/daunorubicin regimen) are poor for older adults and those with high-risk/secondary AML. CPX-351 (Vyxeos®), a dual-drug liposomal encapsulation of cytarabine and daunorubicin in a synergistic ratio, was approved by the US FDA in 2017 for the treatment of adults with newly diagnosed, therapy-related AML or AML with myelodysplasia-related changes and is currently under review by the EMA. A large randomized, open-label, multicenter, phase 3 study (ClinicalTrials.gov #NCT01696084) evaluated the efficacy and safety of CPX-351 versus conventional 7+3 chemotherapy in adults aged 60-75 y with newly diagnosed, high-risk/secondary AML (Lancet JE, et al. J Clin Oncol. 2018). In this study, CPX-351 significantly improved median overall survival (OS; primary endpoint) versus 7+3 (9.56 vs 5.95 mo; HR = 0.69 [95% CI: 0.52-0.90]; 1-sided P = 0.003), as well as event-free survival (EFS; 2.53 vs 1.31 mo; HR = 0.74 [95% CI: 0.58-0.96]; 2-sided P = 0.021). CPX-351 was also associated with higher rates of complete remission (CR; 37.3% vs 25.6%; 2-sided P = 0.040) and CR or CR with incomplete platelet or neutrophil recovery (CR+CRi; 47.7% vs 33.3%; 2-sided P = 0.016) versus 7+3, which likely contributed to the higher rate of patients undergoing hematopoietic cell transplantation (HCT) with CPX-351 (34.0% vs 25.0%; 2-sided P = 0.098). HCT is a potentially curative therapy, and the higher rate of HCT observed in the CPX-351 arm could therefore have an impact on long-term survival outcomes. To better understand the contribution of HCT and treatment with CPX-351 versus 7+3 to survival, exploratory analyses using a time-dependent proportional hazards model were performed to evaluate survival in patients who underwent HCT and assess the impact of treatment with CPX-351 versus 7+3 on survival independent of HCT status. Methods: Patients were randomized 1:1 to receive up to 2 induction cycles with CPX-351 (100 units/m2 [cytarabine 100 mg/m2 + daunorubicin 44 mg/m2] on Days 1, 3, and 5 [2nd induction: Days 1 and 3]) or 7+3 (cytarabine 100 mg/m2/d continuously for 7 d [2nd induction: 5 d] + daunorubicin 60 mg/m2 on Days 1-3 [2nd induction: Days 1-2]). Patients achieving CR or CRi could receive up to 2 consolidations with CPX-351 (65 units/m2 [cytarabine 65 mg/m2 + daunorubicin 29 mg/m2] on Days 1 and 3) or 5+2 (as in 2nd induction). Patients could receive HCT at the discretion of the treating physician. Results: A total of 309 patients were enrolled in the study (CPX-351: n = 153; 7+3: n = 156), and baseline characteristics were balanced between arms. A total of 52 (34.0%) patients in the CPX-351 arm and 39 (25.0%) in the 7+3 arm underwent HCT; most were 60-69 y of age (CPX-351: 69.2%; 7+3: 84.6%), had ECOG performance status ≤1 (CPX-351: 92.3%; 7+3: 94.9%), and were in CR (CPX-351: 57.7%; 7+3: 48.7%) or CRi (CPX-351: 19.2%; 7+3: 12.8%). Median time to HCT from first study dose was similar with CPX-351 (114.5 d) and 7+3 (113.0 d). Similar to the primary endpoint analysis, median OS landmarked from the time of HCT was significantly improved with CPX-351 versus 7+3 (not reached vs 10.25 mo; HR = 0.46 [95% CI: 0.24-0.89]). Further, in the current exploratory analyses in which HCT was treated as a time-dependent covariate, the HRs remained strongly in favor of CPX-351 versus 7+3 for OS (HR = 0.71) and EFS (HR = 0.74), with the upper bounds of the 95% CIs below 1.0 (Table). These results suggest CPX-351 may be associated with prolonged OS and EFS that is independent of HCT. The adverse event profile of CPX-351 was generally consistent with the known safety profile of conventional 7+3. Grade 3-5 adverse events reported in ≥10% of patients in the CPX-351 or 7+3 cohorts included febrile neutropenia (68.0% vs 70.9%), pneumonia (19.6% vs 14.6%), and hypoxia (13.1% vs 15.2%). Early mortality rates with CPX-351 and 7+3, respectively, were 5.9% and 10.6% at Day 30 and 13.7% and 21.2% at Day 60. Conclusions: Treatment with CPX-351 was associated with significantly longer median OS and EFS, as well as a higher proportion of patients achieving remission and undergoing HCT, compared with conventional 7+3 chemotherapy in this population of older patients with newly diagnosed, high-risk/secondary AML. Further, while it is expected that HCT had a positive impact on survival in this study, exploratory analyses suggest that CPX-351 produced positive OS and EFS outcomes independent of HCT. Disclosures Lin: Jazz Pharmaceuticals: Honoraria. Cortes:Novartis: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Arog: Research Funding. Ritchie:NS Pharma: Research Funding; Bristol-Myers Squibb: Research Funding; Incyte: Consultancy, Speakers Bureau; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; ARIAD Pharmaceuticals: Speakers Bureau; Astellas Pharma: Research Funding; Celgene: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; Pfizer: Consultancy, Research Funding. Stuart:Sunesis Pharmaceuticals: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding; Agios: Research Funding; Astellas: Research Funding; Bayer AG: Research Funding; Celator/Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding. Strickland:Tolero Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Baxalta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas Pharma: Consultancy; Sunesis Pharmaceuticals: Consultancy, Research Funding. Bixby:GlycoMimetics: Research Funding. Kolitz:Magellan Health: Consultancy, Honoraria. Schiller:bluebird bio: Research Funding; Astellas Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding. Wieduwilt:Leadiant: Research Funding; Reata Pharmaceuticals: Equity Ownership; Merck: Research Funding; Shire: Research Funding; Amgen: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Ryan:University of Rochester: Patents & Royalties; AbbVie: Equity Ownership. Ryan:Jazz Pharmaceuticals: Employment, Other: Stock and stock options. Chiarella:Celator/Jazz Pharmaceuticals: Employment, Equity Ownership. Louie:Jazz Pharmaceuticals: Employment, Equity Ownership, Patents & Royalties. Uy:GlycoMimetics: Consultancy; Curis: Consultancy.

Background Binding of E-selectin (E-sel), an adhesion molecule expressed in the vasculature of the bone marrow, to sialyl Lex on the leukemic cell surface activates cell survival pathways and promotes chemotherapy resistance in AML. GMI-1271 is a novel E-selectin antagonist that disrupts activation of cell survival pathways, enhances chemotherapy response with improved survival in mouse xenograft and syngeneic models and protects from chemotherapy toxicity in vivo (Becker 2013; Winkler 2013, 2014, 2016). We added GMI-1271 to salvage with MEC for relapsed/refractory AML patients or to induction with 7+3 for older treatment naïve (TN) AML patients. Methods A Phase (Ph) 1 trial escalated GMI-1271 (5-20 mg/kg) combined with MEC (mitoxantrone, etoposide, cytarabine) in pts with R/R AML, to evaluate safety, tolerability and anti-leukemic activity. Dose limiting toxicity (DLT) was defined as persistent cytopenias in the absence of disease or any Grade 3-5 non-hematologic toxicity beyond day 42. The recommended Ph 2 dose (RP2D) of GMI-1271 was 10 mg/kg. A Ph 2 study then enrolled 47 pts with R/R AML for GMI-1271 plus MEC chemotherapy. Responders could receive 1 cycle of consolidation with GMI-1271 plus MEC. We also enrolled a separate Ph 2 cohort of 25 pts ≥60 yrs with TN AML for GMI-1271 (10 mg/kg) plus cytarabine and idarubicin (7+3). Two cycles of induction were allowed. Responders could receive 3 cycles of consolidation with GMI-1271 plus intermediate dose cytarabine. Prior treatment of MDS was allowed; for R/R disease prior SCT was allowed. GMI-1271 was given 24 hrs prior, then every 12 hrs during and for 48 hrs post chemotherapy. E-sel ligand expression on leukemic blasts in blood and bone marrow was assessed by flow cytometry, for the percentage of blasts binding to E-sel-Fc chimera and HECA452 (antibody to sialyl Lex). Results 91 pts were enrolled (Ph 1 R/R=19; Ph 2 R/R=47, TN=25). Median age for R/R pts was 59 yrs (range 26-84) and 62% were males. Prior AML history included 32% primary refractory, 33% CR1 Median age for TN pts was 67 yrs (range, 60-79) 56% were males, and 32% had high-risk CG. 56% had secondary AML (sAML), 43% of sAML had prior hypomethylating therapy. GMI-1271 was well tolerated, adverse events were typical for AML induction in the TN population, and Grade 3/4 mucositis was not seen. 30 and 60 d mortality were 8 and 12%, respectively; two deaths were from sepsis before response assessment and one involved persistent disease. Median time to ANC 500 was 28d (range 21-63). 8 pts required two induction courses, and 4 (16%) proceeded to SCT by data cut-off. The CR/CRi rate was 68% (73% for de novo and 64% for sAML) and ORR was 80%. Median OS and DFS are not yet reached; median follow up is 6 mos. Median E-sel ligand expression (binding to HECA452) at baseline was 31% (range, 2-92%) of bone marrow blasts. Conclusion The addition of GMI-1271 to chemotherapy was well tolerated with high remission rate, low induction mortality, and low rate of mucositis suggesting improved tolerance of chemotherapy. In R/R AML, correlative studies showed blasts expressing the E-sel ligand were predictive of response. Initial survival outcomes are promising and updated survival outcomes will be presented at ASH. FDA granted Breakthrough Therapy Designation to GMI-1271 for treatment of adults with R/R AML and randomized trials are planned. Disclosures DeAngelo: Amgen: Consultancy, Research Funding; BMS: Consultancy; Immunogen: Honoraria, Research Funding; Celgene: Research Funding; ARIAD: Consultancy, Research Funding; Blueprint Medicines: Honoraria, Research Funding; Incyte: Consultancy, Honoraria; Glycomimetics: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding; Takeda Pharmaceuticals U.S.A., Inc.: Honoraria; Shire: Honoraria; Pfizer Inc.: Consultancy, Honoraria, Research Funding. Jonas: Celgene: Membership on an entity's Board of Directors or advisory committees; AbbVie, Celgene, Daiichi Sankyo, Pharmacyclics, Genentech/Roche, Glycomimetics, Esanex, Kalobios: Research Funding; Rigel: Consultancy. Liesveld: Seattle Genetics: Honoraria; Onconova: Honoraria. Advani: Pfizer: Consultancy; Takeda/ Millenium: Research Funding. O'Dwyer: Onkimmune Ltd: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; GlycoMimetics Inc: Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Magnani: GlycoMimetics, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Thackray: GlycoMimetics, Inc.: Employment, Equity Ownership. Becker: GlycoMimetics, Inc.: Research Funding.

Background: Ponatinib, an oral tyrosine kinase inhibitor with potent activity against native and mutant BCR-ABL1, is approved for patients with refractory chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) for whom no other tyrosine kinase inhibitor (TKI) therapy is indicated, or for patients with the T315I mutation. The efficacy and safety of ponatinib in patients with resistant/refractory hematologic malignancies were evaluated in a phase 1 trial (NCT00660920). Here, we report 4-year follow-up data from chronic-phase (CP)-CML patients; final data (approximately 5-year follow-up) will be presented. Methods: In this open-label, dose-escalation, phase 1 trial, 81 patients with resistant/refractory hematologic malignancies (CP-CML, 43 patients; accelerated-phase CML, 9 patients; blast-phase CML, 8 patients; Ph+ ALL, 5 patients) were enrolled. Patients were treated with ponatinib at a starting dose of 2 mg/d - 60 mg/d; intra-patient dose escalation was permitted. In Oct 2013, dose reduction instructions were provided in response to an observed accumulation of arterial occlusive events (AOEs) with longer follow-up across the ponatinib clinical program. For data presented herein, the data cutoff date is 2 Feb 2015, with median follow-up of 53.1 months (range, 1.7 - 69.9 months) for CP-CML patients. Results: Among CP-CML patients, at baseline, median age was 55 years and median time since diagnosis was 6.6 years; BCR-ABL1 kinase domain mutations were reported in 63% of patients, with T315I confirmed at a central laboratory in 28% of patients. Patients were heavily pretreated, with 37% having received 2 prior TKIs and 60% having received ≥3 prior TKIs. Of 43 CP-CML patients, 22 (51%) remained on ponatinib treatment at data cutoff. Adverse events (AEs; 26%) and disease progression (9%) were the most common reasons for discontinuation of treatment. Cumulative response rates were: major cytogenetic response (MCyR), 72%; complete cytogenetic response (CCyR), 65%; major molecular response (MMR; assessed at a central laboratory), 56%; molecular response 4 (MR4), 42%; MR4.5, 28%. Responses were durable (Table), with median durations of response not reached for MCyR, CCyR, and MMR. Among patients who received ponatinib at starting doses of ≤30 mg/d (n = 15), MCyR was achieved by 67%, CCyR by 53%, and MMR by 47%; ponatinib dose was ≤30 mg/d in all but one of these patients at the time of response. Of 19 patients who were ongoing and in MCyR as of Oct 2013, 13 had their dose reduced; all 13 dose-reduced patients maintained MCyR at data cutoff. Of the 22 ongoing patients at the time of the present analysis, 18 (82%) had CCyR and 17 (77%) had MMR or better (MMR, 6 patients; MR4, 1 patient; MR4.5, 9 patients; MR5, 1 patient) as their response at the data cutoff; 14/22 (64%) ongoing patients were receiving 15 mg/d as their current dose as of the data cutoff. Rash (65%), fatigue (63%), abdominal pain (58%), headache (58%) and arthralgia (53%) were the most common treatment-emergent AEs. The incidence of AOEs (any/serious) was 40%/30% (by subcategory: cardiovascular, 30%/21%; cerebrovascular, 9%/7%; peripheral vascular, 14%/9%). Conclusions: With median follow-up of over 4 years in this phase 1 study, ponatinib continues to provide clinical benefit to heavily pre-treated CP-CML patients, approximately half of whom continue to receive ponatinib, with a majority in deep response that has been long-lasting; final study data will be presented. The most common treatment-emergent AEs were consistent with the AE profile across the clinical program. Potential for long-term benefit, demonstrated herein, versus risk should be considered when using ponatinib in this patient population. Study sponsor: ARIAD Pharmaceuticals, Inc. Disclosures Mauro: BMS: Consultancy, Honoraria; ARIAD: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria. Cortes:ARIAD: Consultancy, Research Funding; Bristol-Myers Squib: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding. Kantarjian:Bristol-Myers Squibb: Research Funding; Amgen: Research Funding; ARIAD: Research Funding; Pfizer Inc: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding. Shah:ARIAD: Research Funding; BMS: Research Funding; Daiichi-Sankyo: Research Funding; Pfizer: Research Funding; Plexxikon: Research Funding. Flinn:Janssen: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Gilead Sciences: Research Funding; ARIAD: Research Funding; RainTree Oncology Services: Equity Ownership. Rivera:ARIAD: Employment, Equity Ownership. Lustgarten:ARIAD: Employment, Equity Ownership. Santillana:ARIAD: Employment, Equity Ownership. Heinrich:Novartis: Consultancy, Patents & Royalties, Research Funding; Pfizer: Consultancy; Bayer: Research Funding; BMS: Research Funding; Blueprint Medicines: Consultancy; MolecularMD: Consultancy, Equity Ownership; ARIAD: Consultancy, Research Funding; Onyx: Consultancy. Druker:Agios: Honoraria; Ambit BioSciences: Consultancy; ARIAD: Patents & Royalties, Research Funding; Array: Patents & Royalties; AstraZeneca: Consultancy; Blueprint Medicines: Consultancy, Equity Ownership, Other: travel, accommodations, expenses ; BMS: Research Funding; CTI: Equity Ownership; Curis: Patents & Royalties; Cylene: Consultancy, Equity Ownership; D3 Oncology Solutions: Consultancy; Gilead Sciences: Consultancy, Other: travel, accommodations, expenses ; Lorus: Consultancy, Equity Ownership; MolecularMD: Consultancy, Equity Ownership, Patents & Royalties; Novartis: Research Funding; Oncotide Pharmaceuticals: Research Funding; Pfizer: Patents & Royalties; Roche: Consultancy. Deininger:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Research Funding; CTI BioPharma Corp.: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees. Talpaz:Novartis: Research Funding; Incyte Corporation: Other: Travel expense reimbursement, Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Pfizer: Consultancy, Other: travel accomodation expenses, Research Funding.

Background CD33is expressed in approximately 90% of AML cases, representing a promising target despite age, prior therapies, or mutational heterogeneity. Vadastuximab talirine (33A) is a CD33-directed antibody conjugated to 2 molecules of a pyrrolobenzodiazepine (PBD) dimer. Upon binding, 33A is internalized and transported to the lysosomes where PBD dimer is released via proteolytic cleavage of the linker, crosslinking DNA, and leading to cell death. Methods The dose-escalation portion of this phase 1 study (NCT01902329) was designed to evaluate the safety, tolerability, pharmacokinetics, and antileukemic activity of 33A as monotherapy. After dose escalation, 40 mcg/kg was identified as the recommended monotherapy dose. Eligible patients (ECOG status 0-1) in this expansion cohort must have had CD33-positive AML and considered ineligible for or declined conventional induction/consolidation. 33A monotherapy was administered outpatient IV every 3 weeks for up to 2 cycles, followed by optional low-dose maintenance treatment for patients who achieved a CR/CRi. Investigator assessment of response was per IWG criteria; CRi required either platelet count of ≥100,000/µL or neutrophils of ≥1,000/µL (Cheson 2003). Results Twenty-seven treatment naive patients (48% male) with a median age of 74 years (range, 67-89) were treated with 40 mcg/kg of 33A. Most patients had intermediate (70%) or adverse (26%) cytogenetic risk by MRC and 48% of patients had underlying myelodysplasia. Twenty-four patients were considered unfit for intensive therapy and 3 patients declined intensive therapy. At baseline, patients had a median of 47% BM blasts. Three patients remain on treatment. The most common Grade 3 or higher adverse events (AE) were thrombocytopenia (44%), febrile neutropenia (41%), anemia (33%), fatigue, and pneumonia (19% each). Other common treatment-emergent AEs regardless of relationship to 33A were decreased appetite, diarrhea, fatigue, peripheral edema, thrombocytopenia (44% each), febrile neutropenia (41%), dizziness (37%), anemia, chills, cough, dyspnea, and epistaxis (33% each). The 30- and 60-day mortality rates were 0% and 15%. Of the 26 efficacy evaluable treatment naive patients, 6 patients (23%) achieved a best clinical response of CR, 8 (31%) achieved CRi, and 5 patients (19%) achieved a morphologic leukemia-free state. Most remissions were achieved after 1 cycle and were observed in many patients with adverse risk including underlying myelodysplasia (6/12, 50%), FLT3/ITD+ (3/4, 75%), and in patients ≥75 years of age (8/12, 67%). Of the responding patients with available minimal residual disease (MRD) data, 6 of 13 (46%) achieved MRD negativity by flow cytometry. In patients who achieved at least a CRi, the median time to full count recovery from first dose was 6.1 weeks for neutrophils (≥1,000/µL) and 5.1 weeks for platelets (≥100,000/µL). Median OS continues to evolve with 10 patients (37%) alive at the time of this data cut. Pharmacokinetic data for treatment naive patients is consistent with previously reported results; 33A exhibits rapid elimination consistent with target-mediated drug disposition. Conclusions In an expansion cohort of 33A monotherapy at 40 mcg/kg, AEs observed were generally manageable and commonly associated with on-target myelosuppression. 33A has demonstrated favorable antileukemic activity as a single agent with 54% achieving a CR+CRi in this high risk treatment naive older AML population, more than doubling the response rate expected with standard non-intensive therapies such as hypomethylating agents or low-dose cytarabine. The rapid clearance of marrow blasts, high rate of MRD-negative remissions, and low early mortality rate are encouraging. These data support exploration of 33A in combination with standard induction, consolidation, and pre- and post-transplant regimens. Disclosures Stein: Celgene: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau; Seattle Genetics: Research Funding. Fathi:Agios Pharmaceuticals: Other: Advisory Board participation; Bexalata: Other: Advisory Board participation; Seattle Genetics: Consultancy, Other: Advisory Board participation, Research Funding; Celgene: Consultancy, Research Funding; Merck: Other: Advisory Board participation. Kovacsovics:Seattle Genetics: Research Funding. Levy:Seattle Genetics: Research Funding; Jansen: Speakers Bureau; Amgen: Speakers Bureau; Millennium: Speakers Bureau. Erba:Daiichi Sankyo: Consultancy; Jannsen: Consultancy, Research Funding; Celator: Research Funding; Incyte: Consultancy, DSMB, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Juno: Research Funding; Astellas: Research Funding; Ariad: Consultancy; Millennium Pharmaceuticals, Inc.: Research Funding; Pfizer: Consultancy; Agios: Research Funding; Novartis: Consultancy, Speakers Bureau; Gylcomimetics: Other: DSMB; Seattle Genetics: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Sunesis: Consultancy. Jillella:Seattle Genetics: Research Funding. Ravandi:Seattle Genetics: Consultancy, Honoraria, Research Funding; BMS: Research Funding. Stein:Novartis: Consultancy; Seattle Genetics: Research Funding; Agios Pharmaceuticals: Other: Advisory Board, Research Funding; Celgene: Other: Advisory Board, Research Funding. Faderl:Astellas: Research Funding; Pfizer: Research Funding; Seattle Genetics: Research Funding; Celator Pharmaceuticals: Research Funding; BMS: Research Funding; Ambit Bioscience: Research Funding; Karyopharm: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; JW Pharma: Consultancy; Amgen: Speakers Bureau. DeAngelo:Baxter: Consultancy; Amgen: Consultancy; Novartis: Consultancy; Incyte: Consultancy; Pfizer: Consultancy; Ariad: Consultancy; Celgene: Consultancy. Ho:Seattle Genetics: Employment, Equity Ownership. O'Meara:Seattle Genetics: Employment, Equity Ownership. Voellinger:Seattle Genetics: Employment, Equity Ownership. Advani:Seattle Genetics: Consultancy, Research Funding.

Background The treatment of patients with relapsed acute myeloid leukemia (AML) remains a significant challenge with poor outcomes due to a low response rate. Although cytotoxic chemotherapy remains the standard approach for treatment, novel agents are needed to improve clinical outcomes. Binding of leukemic blasts to E-selectin (E-sel), an adhesion molecule expressed constitutively in the bone marrow endothelium, activates leukemic cell survival pathways, thereby contributing to chemotherapy resistance. GMI-1271 is a novel antagonist of E-sel, putatively disrupting leukemia cell survival pathways and enhancing chemotherapy response. We performed a phase 1/2 trial of GMI-1271 plus MEC (mitoxantrone, etoposide and cytarabine) for the treatment of relapsed/refractory (R/R) and a pilot study adding GMI-1271 to 7+3 for previously untreated elderly patients with AML. Methods A phase 1/2 open label trial of patients with R/R AML, with escalation of a single cycle of GMI-1271 across 3 dose levels combined with MEC, was conducted to assess safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD) and antileukemic activity. In addition, a pilot study was performed at the recommended phase 2 dose (RP2D) plus infusional cytarabine and idarubicin (7+3) in patients ≥60 years with untreated AML. Eligible patients (R/R AML) had an ECOG score of 0-2, received ≤2 prior induction regimens, WBC Results The phase 1 (Ph1) dose escalation in the R/R AML arm was completed with 19 subjects treated with GMI-1271 BID at 5 mg/kg (N=6), 10 mg/kg (N=7), and 20 mg/kg (N=6). The median age was 51 (range 26-77); 13 were male; 6 were refractory to prior intensive induction; 10 relapsed in ≤12 mos and 3 in >12 mos; number of prior induction regimens: 1 (N=15) and 2 (N=4); risk based on the SWOG cytogenetic classification was intermediate (9) or unfavorable (10). There were no DLTs observed in the R/R dose escalation and no early deaths (30 d). Transient mucositis developed in only 5 subjects (4 at 5 mg/kg), of whom 2 required IV nutrition (5 mg/kg). Median time to count recovery was 37d (ANC >1K) and 35 d (platelets >100K) in responders. AEs were typical for MEC. Ph1 CR/CRi rate was 47% (42% CR%) with no observable dose response; 26% proceeded to subsequent stem cell transplant. Six of 9 remain in CR at data cut-off. Median OS and PFS have not been reached. One subject >70yrs with refractory disease who achieved CR (negative by flow) was retreated with GMI-1271/MEC again off protocol and remains in CR (9mo). PK analysis showed linear kinetics; an average 50 y.o. had clearance 1.28 L/h with elimination t1/2>3h; Cl decreased 2%/yr of increased age, and was 28% lower than in healthy adults. No accumulation was seen. Time over IC50 for E-sel binding was >50% of the dosing interval for most patients at 10 mg/kg, and well in excess of effective preclinical exposure. PD analysis showed sE-sel on Day 8 decreased below baseline (p˂0.0013) with no dose response, suggesting on-target activity at all dose levels. Normal HSCs were not mobilized into the periphery after sentinel GMI-1271 dose. RP2D was determined to be 10 mg/kg BID based on drug exposure, time over IC50 for E-sel binding, lack of DLT, and similar on-target PD and clinical outcomes. To date, 10 patients enrolled on the Ph2 R/R AML arm; an additional 37 will be enrolled. In the previously untreated elderly AML arm, 3 patients enrolled in the safety run-in and no DLTs were observed, therefore an additional 22 patients will be enrolled. Updated response data will be presented at ASH. Conclusion We report on early clinical assessment of novel E-selectin antagonist GMI-1271 in R/R AML patients, with a high response rate (CR/CRi 47%) in this challenging group. No significant toxicities and no DLT were observed for GMI-1271. Ph2 dose expansion is ongoing. Disclosures DeAngelo: Celgene: Consultancy; Ariad: Consultancy; Baxter: Consultancy; Incyte: Consultancy; Amgen: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Liesveld:Onconova: Other: Data safety monitoring board; Astex: Honoraria; glycomimetics: Research Funding. O'Dwyer:Glycomimetics: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Magnani:GlycoMimetics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Thackray:GlycoMimetics: Employment, Equity Ownership. Becker:GlycoMimetics: Research Funding.

Background Spleen tyrosine kinase (SYK) is a nonreceptor cytoplasmic protein kinase and a key mediator of immunoreceptor signaling that has been shown to play an important role in the pathogenesis of both B-cell and myeloid malignancies. SYK has also been shown to directly bind and activate FMS-like tyrosine kinase 3 (FLT-3), a Class III receptor tyrosine kinase that is commonly mutated in approximately 30% of pts with AML (Puissant et al. Cancer Cell 2014;25:226-42). TAK-659 is an investigational, reversible, and potent dual inhibitor of SYK and FLT-3. Preclinical studies with TAK-659 have demonstrated growth inhibition of cell lines and xenograft tumor models of B-cell lymphoma or AML origin. Moreover, TAK-659 has exhibited antitumor activity in lymphoma pts in an ongoing clinical trial (Petrich et al. Blood 2015;126:2693). The primary objectives of the phase 1b dose-finding portion of this study are to evaluate the safety, tolerability, and maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D) of TAK-659, as well as preliminary efficacy in the phase 2 expansion study. Secondary objectives include evaluation of TAK-659 pharmacokinetics (PK) in this pt population. Methods During dose escalation using a 3x3 schema, adult pts with R/R AML received oral TAK-659 daily (QD) in 28-d cycles (C) starting with a dose of 60 mg. Adverse events (AEs) were assessed per NCI-CTCAE v4.03. Response per IWG criteria for AML was assessed between d22 and d28 of C1, C2, and C4. Blood samples for plasma pharmacokinetic (PK) assessments were collected pre-dose and at multiple times post-dose on d1 and d15 of C1. The pharmacodynamic effect of TAK-659 was assessed at multiple time points by measuring the phosphorylation of ribosomal protein S6 (pS6) in peripheral AML blasts using flow cytometry. FLT-3 mutation status (wild type [FLT-3-WT], FLT-3-ITD, or point mutation [FLT-3-D835Y]) was assessed using a PCR-based assay at a central laboratory. The effect of TAK-659 treatment on FLT-3-ITD phosphorylation was evaluated using a plasma inhibitory assay (PIA) as previously described (Levis et al. Blood 2006;108:3477-83). Results At data cut-off (June 9, 2016), 15 pts had been enrolled at TAK-659 QD 60 mg (n=4), 100 mg (n=7), or 120 mg (n=4). No dose-limiting toxicity per protocol has been observed. Dose escalation is currently ongoing at 160 mg QD. In the safety population (n=13), median age was 67 yrs (range 25-86), 69% of pts were male, and 38% had received ≥4 prior lines of therapy. Baseline mutation data was available for 12 pts: 6 pts were FLT-3-WT, 3 pts had FLT-3-ITD, 1 pt had FLT-3-D835Y, and 2 pts had concurrent FLT-3-ITD/D835Y mutations. In the safety population, all-grade drug-related AEs occurred in 12 (92%) pts overall; the most common were elevated AST (31%), ALT (23%), and amylase levels (23%). Grade ≥3 drug-related AEs occurred in 7 (54%) pts including: increased ALT, AST, and amylase levels, cataract, positive fungal test, macular fibrosis, pancreatitis, pneumocystis jirovecii pneumonia, rash, and fungal sinusitis (each 1pt). Blood LDH levels were increased in almost all pts (significance unknown). Three pts discontinued TAK-659 due to AEs and 3 pts died on study; none of these events were considered related to the study drug. Preliminary plasma PK of TAK-659 (n=11, 60-100 mg) was characterized by rapid absorption (median Tmax of 2 hours), moderate variability in steady-state exposures (42% coefficient of variation for C1 d15 dose-normalized AUCtau), and mean accumulation of 2.1-fold after repeated QD dosing for 15 days. Of 9 pts evaluated to date, pS6 was detected at baseline and reduced after dosing in 4 pts (2 FLT-3-ITD; 2 FLT-3-WT). At 60 mg and 100 mg TAK-659, up to 70% inhibition of FLT-3-ITD phosphorylation was observed as assessed by PIA. Early signs of clinical activity were observed, with decreases in peripheral blood myeloblasts observed in some pts. Assessment is ongoing and preliminary efficacy data will be presented. Conclusions TAK-659 has a unique mechanism of action with dual inhibition of SYK and FLT-3. Dose escalation to determine the MTD/RP2D is ongoing. TAK-659 exhibits an acceptable PK profile in R/R AML pts, supporting continuous oral QD dosing. Disclosures Kaplan: Seattle Genetics: Research Funding; Janssen: Research Funding. Morris:Boehringer-Ingelheim: Speakers Bureau. Altman:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Syros: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Wise-Draper:Merck: Research Funding. Collins:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Kannan:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Wang:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Faucette:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Lee:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Shou:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Levis:Millennium: Consultancy, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi-Sankyo: Consultancy, Honoraria.

Background: Ponatinib is a tyrosine kinase inhibitor (TKI) approved for adult patients (pts) with relapsed/refractory CML or Ph+ ALL and those with the BCR-ABL T315I mutation, which is uniformly resistant to other TKIs approved for the treatment of CML and Ph+ ALL. Prior to the availability of ponatinib, resistant pts with the T315I mutation (T315I+) had worse outcomes than those without the mutation; in a matched pair analysis in chronic phase (CP)-CML pts, median overall survival (OS) was 48.4 mos after development of resistance in T315I+ pts versus not reached in those without the mutation (Nicolini FE, et al. Haematologica 2013). Methods: We evaluated the efficacy and safety of ponatinib in a pooled analysis of a subgroup of CP-CML pts with the T315I mutation (detected in a central laboratory by Sanger sequencing at baseline) from the phase 1 (NCT00660920) and pivotal phase 2 PACE (NCT01207440) trials. In addition, we evaluated the impact of continuation of ponatinib treatment at a 2-yr landmark time point on OS at 1-yr past the landmark in T315I+ CP-CML pts in PACE. The phase 1 trial is an open-label, dose escalation study of ponatinib (starting dose 2-60 mg once daily) in 81 adults with relapsed/refractory hematologic malignancies. PACE is an open-label, single-arm trial of ponatinib (starting dose 45 mg daily) in 449 adults with CML or Ph+ ALL resistant or intolerant to dasatinib or nilotinib or with the T315I mutation. Dose reductions were instructed in Oct 2013 in response to an accumulation of arterial occlusive events (AOEs) reported with longer follow-up across the ponatinib clinical program. Response assessments included major cytogenetic response (MCyR), complete cytogenetic response (CCyR), major molecular response (MMR; assessed in a central laboratory), and molecular response 4.5 (MR4.5). OS and progression-free survival (PFS) data were only collected in PACE; 3-yr outcomes were examined for all evaluable T315I+ CP-CML pts, along with a log-rank test for OS by treatment status as of the 2-yr landmark time point. Exposure-adjusted incidence rates of new AOEs are reported as number of events/100 pt-yrs. Pooled data as of February 2, 2015 is reported here. Results: There were 76 T315I+ CP-CML pts included in this analysis (phase 1, n=12; PACE, n=64). At the time of analysis, median duration of follow-up in T315I+ CP-CML pts was 40 (range: 1.5-74) mos; 37 pts (49%) remain on study. Median baseline ponatinib dose intensity was 33 (range: 5-56) mg daily; 25/37 (68%) ongoing pts were receiving 15 mg daily as their current dose as of the data cut-off. Primary reasons for discontinuation in T315I+ CP-CML pts were disease progression [10/76 (13%)], adverse events [AEs; 9/76 (12%)], consent withdrawn [5/76 (7%)], physician/administrative decision [4/76 (5%)], death [3/76 (4%)], lack of efficacy [2/76 (3%)], and other [6/76 (8%)]; criteria for disease progression included death, development of advanced phase CML, loss of CHR (in absence of cytogenetic response) and loss of MCyR. Cumulative response rates in T315I+ CP-CML pts (n=76) were: MCyR, 75%; CCyR, 72%; MMR, 61%, and MR4.5, 37%. In PACE, estimated 3-yr PFS/OS rates for 64 T315I+ CP-CML pts were 60%/78% (medians not reached). One yr post-landmark outcomes for T315I+ CP-CML pts by treatment status at the 2-yr landmark time point are displayed in the table. Most common treatment-emergent AEs (≥40%) in the pooled group of T315I+ CP-CML pts (n=76 phase 1 and PACE) were: rash, 55%; dry skin, 49%; headache, 46%; abdominal pain, 43%; nausea, 41%; and fatigue, 41%. Among these pts, the cumulative incidence of any AOE (grade 3/4) was 32% (20%); by subcategory: cardiovascular 20% (15%), cerebrovascular 12% (5%), and peripheral vascular 13% (8%) events. Two T315I+ CP-CML pts had grade 5 AOEs. The exposure-adjusted incidence rate of new AOEs in T315I+ CP-CML pts was 12/100 pt-yrs. Conclusions: Ponatinib continues to provide deep and durable responses with >3 yrs median follow-up in T315I+ CP-CML pts. Survival outcomes with ponatinib treatment in these highly refractory pts were high overall and compare favorably with those observed in T315I+ CP-CML pt populations prior to the availability of ponatinib. Although pt numbers are limited for the landmark analysis, continuation of ponatinib treatment at 2 yrs was associated with a trend for improved OS, where data continue to mature. Updated data in all T315I+ pts will be presented. Study sponsor: ARIAD Pharmaceuticals, Inc. Disclosures Jabbour: ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding. Talpaz:Incyte Corporation: Other: Travel expense reimbursement, Research Funding; Novartis: Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Pfizer: Consultancy, Other: travel accomodation expenses, Research Funding. Baccarani:ARIAD: Consultancy, Honoraria, Other: travel, accommodations, expenses , Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria, Other: travel, accommodations, expenses , Speakers Bureau; Pfizer: Honoraria, Speakers Bureau. Mauro:BMS: Consultancy, Honoraria; ARIAD: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria. Hochhaus:Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding. Hughes:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Honoraria. Guilhot:ARIAD: Honoraria. Deininger:BMS: Consultancy, Research Funding; Gilead: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Consultancy, 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; CTI BioPharma Corp.: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees. Shah:ARIAD: Research Funding; Daiichi-Sankyo: Research Funding; BMS: Research Funding; Pfizer: Research Funding; Plexxikon: Research Funding. Flinn:Janssen: Research Funding; Gilead Sciences: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; ARIAD: Research Funding; RainTree Oncology Services: Equity Ownership. Lustgarten:ARIAD: Employment, Equity Ownership. Rivera:ARIAD: Employment, Equity Ownership. Santillana:ARIAD: Employment, Equity Ownership. Kantarjian:Amgen: Research Funding; ARIAD: Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer Inc: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding.

Introduction CPX-351 (Vyxeos), a liposomal formulation of cytarabine and daunorubicin encapsulated at a 5:1 molar ratio, has shown enhanced efficacy compared with standard induction in older adults with high-risk AML in phase II clinical trials. Presented here are pre-specified secondary subgroup results from a phase III randomized, open-label study of CPX-351 versus 7+3 (cytarabine plus daunorubicin) in newly diagnosed patients with high-risk features, focusing on efficacy results stratified by age group. Methods Eligible patients were aged 60 to 75 years and had secondary AML, either therapy-related or an antecedent myelodysplastic syndrome (MDS), chronic myelomonocytic leukemia, or AML with World Health Organization-defined MDS-related cytogenetic abnormalities. Patients were randomized 1:1 to receive CPX-351 induction (100 units/m2 [100 mg/m2 cytarabine + 44 mg daunorubicin mg/m2] on days 1, 3, and 5 [first induction only]) or 7+3 induction (cytarabine 100 mg/m2/day x 7 days plus daunorubicin 60 mg/m2 on days 1, 2, and 3 [first induction] or x 5 days [reinduction/consolidation] plus daunorubicin 60 mg/m2 on days 1 and 2). A dynamic allocation procedure was performed to stratify patients by age group (60-69 or 70-75 years) for each arm of the study. The distribution of overall survival (OS) by treatment arm was estimated using the method of Kaplan-Meier. Efficacy for each age group was reported in terms of median OS in months and percentage of patients with a morphologic complete remission (CR) or CR with incomplete platelet or neutrophil recovery (CRi) according to International Working Group criteria. Results Three hundred and nine patients were enrolled from December 2012 to November 2014 at 39 US and Canadian sites, with 153 patients randomized to the CPX-351 arm and 156 to the 7+3 arm. Among patients aged 60-69 years, there were 96 patients in the CPX-351 arm and 102 in the 7+3 arm; for patients aged 70-75 years, there were 57 and 54 patients in each arm, respectively. Demographic data for these age subgroups were similar between the CPX-351 and 7+3 arms of the study. The CR+CRi rates for patients aged 60-69 years were 50.0% for patients in the CPX-351 arm and 36.3% in the 7+3 arm, with an odds ratio (OR) of 1.76 (95% confidence interval [CI], 1.00-3.10); for patients aged 70-75 years, the rates of CR+CRi were 43.9% and 27.8%, respectively, with an OR of 2.03 (95% CI, 0.92-4.49). Kaplan-Meier curves for OS by age group are shown in the Figure. Median OS in months for patients aged 60-69 years was 9.63 in the CPX-351 arm and 6.87 in the 7+3 arm, with a hazard ratio of 0.68 (95% CI, 0.49-0.95); for patients aged 70-75 years these were 8.87 for the CPX-351 arm and 5.62 for the 7+3 arm, with a hazard ratio of 0.55 (95% CI, 0.36-0.84). The allogeneic hematopoietic cell transplant (HCT) rate in patients aged 60-69 years was 37.5% in the CPX-351 arm and 32.4% in the 7+3 arm, with an OR of 1.25 (95% CI, 0.70-2.25). For patients aged 70-75 years, the allogeneic HCT rates were 28.1% and 11.1%, respectively, with an OR of 3.12 (95% CI, 1.12-8.72). Incidence of grade 3-5 adverse events were virtually equal (92% vs 91%) and were similar in frequency and severity in both arms. The most common grade 3-5 nonhematologic adverse events (>10% overall) were febrile neutropenia (CPX-351: 68%; 7+3: 71%), pneumonia (CPX-351: 20%; 7+3: 15%), and hypoxia (CPX-351: 13%; 7+3: 15%). Conclusions This subgroup analysis of patients aged 60-69 and 70-75 years with untreated secondary AML demonstrated that CPX-351 treatment had substantially greater median OS and higher CR+CRi rates than standard 7+3 (cytarabine and daunorubicin) in both age groups. In addition, somewhat more patients in each age group in the CPX-351 arm received allogeneic HCT compared with the 7+3 arm, with the greatest difference in the older age group. Future studies with larger patient groups are warranted. Support: Celator Pharmaceuticals, Inc., a subsidiary of Jazz Pharmaceuticals plc. Disclosures Medeiros: Agios: Consultancy, Research Funding; Amgen: Consultancy; ARIAD: Consultancy; Celgene: Consultancy, Other: Travel, Accomodations, Expenses, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy; Roche/Genentech: Consultancy, Research Funding; Celator: Other: Travel, Accomodations, Expenses, Research Funding; MEI Pharma: Research Funding; Merck/Schering Plough: Research Funding. Lancet:Celgene: Consultancy, Research Funding; Quantum First: Consultancy; Kalo Bios: Consultancy; Pfizer: Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy; ERYtech: Consultancy; Biopath Holdings: Consultancy; Karyopharm: Consultancy; Boehringer-Ingelheim: Consultancy; Seattle Genetics: Consultancy; Baxalta: Consultancy; Amgen: Consultancy. Cortes:ARIAD: Consultancy, Research Funding; Bristol-Myers Squib: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding. Ritchie:Celgene: Consultancy, Other: Travel, Accomodations, Expenses, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Ariad: Speakers Bureau; Pfizer: Consultancy, Research Funding; Astellas Pharma: Research Funding; Bristol-Meyers Squibb: Research Funding; NS Pharma: Research Funding. Stuart:Astellas: Research Funding; Incyte: Research Funding; Agios: Research Funding; Sunesis: Consultancy, Honoraria, Other: Travel, Accomodations, Expenses, Research Funding; Bayer: Research Funding; Celator: Research Funding. Strickland:Sunesis Pharmaceuticals: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy, Research Funding; Celator: Research Funding; Astellas Pharma: Research Funding; Alexion Pharmaceuticals: Consultancy; Sanofi: Research Funding; CTI Biopharma: Consultancy; Karyopharm Therapeutica: Research Funding; Baxalta: Consultancy; Daiichi Sankyo: Consultancy; Ambit: Consultancy; Abbvie: Research Funding; Cyclacel: Research Funding; GlaxoSmithKline: Research Funding. Hogge:Sanofi: Consultancy; Roche: Other: Travel, Accomodations, Expenses. Stone:ONO: Consultancy; Xenetic Biosciences: Consultancy; Seattle Genetics: Consultancy; Amgen: Consultancy; Agios: Consultancy; Karyopharm: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Juno Therapeutics: Consultancy; Celator: Consultancy; Roche: Consultancy; Sunesis Pharmaceuticals: Consultancy; Merck: Consultancy; Pfizer: Consultancy; Jansen: Consultancy. Kolitz:Gliead Sciences: Consultancy; Seattle Genetics: Consultancy; Pharmacyclics: Consultancy. Schiller:Celator: Research Funding. Ryan:AbbVie: Equity Ownership; U of Rochester: Patents & Royalties. Chiarella:Celator Pharmaceuticals, Inc., a subsidiary of Jazz Pharmaceuticals plc.: Employment, Equity Ownership. Louie:Celator Pharmaceuticals, Inc., a subsidiary of Jazz Pharmaceuticals plc.: Employment, Equity Ownership. Uy:Glycomimetics: Consultancy; Boehringer Ingelheim: Consultancy.

Background: SL-401 is a novel targeted therapy directed to the interleukin-3 receptor (CD123), a target overexpressed on acute myeloid leukemia (AML) blasts and AML cancer stem cells (CSCs), and a variety of additional hematologic malignancies. While conventional chemotherapy can induce remission in a majority of treatment-naive AML patients, relapse rates remain high. Outcomes are particularly poor when minimal residual disease (MRD), as determined by genetic and/or flow cytometric analyses, remains after therapy, with high rates of relapse and short disease-free survival. Conceivably, a therapy directed at lowering MRD burden may improve long-term outcomes. Given the association of MRD with CD123+ AML CSCs, SL-401 is being evaluated in patients with AML in first or second complete remission (CR1 or CR2, respectively) with high risk of relapse including persistent MRD. Preliminary results are reported here. Methods & Results: This multicenter, single-arm Phase 2 trial of AML patients in CR1 or CR2 with high risk of relapse includes a lead-in (stage 1) and expansion (stage 2). In stage 1, patients (MRD+ or MRD-) receive SL-401 as a daily IV infusion at 7, 9, or 12 ug/kg/day for days 1- 5 of a 28 day cycle in a 3x3 design. In stage 2, patients (MRD+ only) receive SL-401 at the dose determined in stage 1. Presence of MRD for eligibility requires either molecular (by cytogenetics, FISH, PCR, or next-generation sequencing of AML-associated mutations) or multiparameter flow cytometry (MFC) evidence of persistent abnormalities in the setting of morphologic CR. In stage 2, MRD assessment will include MFC of bone marrow aspirates conducted at a central laboratory for uniformity. Objectives include characterization of SL-401 safety with determination of the maximum tolerated or tested dose, and preliminary assessment of efficacy including changes in MRD burden and response duration. As of 7/27/16, stage 1 has been completed and stage 2 is open for enrollment. Nine patients (stage 1) received SL-401 (7 ug/kg, n=3; 9 ug/kg, n=3; 12ug/kg, n=3). The median age was 63 years (range: 51-78 years); 6 males and 3 females were treated; 8 patients were in CR1 and 1 patient was in CR2 at enrollment. The 12 ug/kg dose level was the highest tested dose with no DLTs; MTD was not reached. The most common treatment-related AEs, all grades, were thrombocytopenia (3/9; 33%) and hypoalbuminemia (3/9; 33%); the most common ≥ grade 3 treatment-related AE was thrombocytopenia (1/9; 11%); there was no DLT. Patients treated at all doses received 1+ to 5+ cycles (ongoing) of SL-401, including 3 MRD+ patients treated at 7 ug/kg (n=1) or 9 ug/kg (n=2) who received 1-5 cycles, and 1 MRD+ patient treated at 12 ug/kg who is receiving ongoing SL-401 for 4+ cycles. For all 3 patients treated at 12 ug/kg (MRD+, n=1; MRD-, n=2), 2 patients remain on SL-401 and have received 1+ and 4+ cycles (both ongoing); one other patient treated at 12 ug/kg discontinued the study because of infection unrelated to study drug. Notably, the one MRD+ patient treated at 12 ug/kg (ongoing at 4+ cycles) had marked MRD reduction as determined by MFC at the local institution; this patient is being considered for stem cell transplant (SCT). Conclusions: Stage 1 is complete without DLT or MTD, and stage 2 (expansion) is open to enroll AML patients in CR1 or CR2 who are MRD+ at the highest tested dose of 12 ug/kg. The safety profile has been similar to that observed in other SL-401 clinical studies, with no unexpected AEs. Targeting MRD with SL-401 has the potential to reduce this chemo-resistant cell population and offer improved long-term outcomes for AML patients in remission with high risk of relapse. Updated data will be presented. Clinical trial information: NCT02270463. Disclosures Lane: N-of-1: Consultancy; Stemline Therapeutics: Research Funding. Sweet:Pfizer: Speakers Bureau; Karyopharm: Honoraria, Research Funding; Incyte Corporation: Research Funding; Novartis: Consultancy, Speakers Bureau; Ariad: Consultancy, Speakers Bureau. Wang:Immunogen: Research Funding; Incyte: Speakers Bureau. Stein:Seattle Genetics: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Celgene: Research Funding. Carraway:Incyte: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding, Speakers Bureau; Baxalta: Speakers Bureau. Prebet:celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Chen:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Lindsay:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Shemesh:Stemline Therapeutics: Employment, Equity Ownership. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Stone:Novartis: Consultancy; Juno Therapeutics: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy; Amgen: Consultancy; Celator: Consultancy; Karyopharm: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; ONO: Consultancy; Merck: Consultancy; Roche: Consultancy; Seattle Genetics: Consultancy; Sunesis Pharmaceuticals: Consultancy; Xenetic Biosciences: Consultancy. Jabbour:ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy. Konopleva:Cellectis: Research Funding; Calithera: Research Funding.

Background Treatment of AML among the elderly is challenging due to intolerance of intensive therapy and greater prevalence of therapy-resistant biology. Hypomethylating agents (HMAs) are commonly used in this setting, but yield suboptimal remission rates and modest survival (Dombret 2015, Kantarjian 2012). Vadastuximab talirine (33A) is a CD33-directed antibody conjugated to 2 molecules of a pyrrolobenzodiazepine (PBD) dimer. Upon binding, 33A is internalized and transported to the lysosomes where PBD dimer is released via proteolytic cleavage of the linker, crosslinking DNA, and leading to cell death. In preclinical studies, HMA priming followed by 33A resulted in upregulated CD33 expression, increased DNA incorporation of the PBD dimer, and enhanced cytotoxicity. Methods A combination cohort in a phase 1 study (NCT01902329) was designed to evaluate the safety, tolerability, pharmacokinetics, and antileukemic activity of 33Ain combination with an HMA. Eligible patients (ECOG status 0-1) must have had previously untreated CD33-positive AML andhad declined intensive therapy. A single dose level of 33A, 10 mcg/kg,was administered outpatient IV every 4 weeks on the last day of HMA (azacitidine or decitabine [5-day regimen], standard dosing). Investigator assessment of response was per IWG criteria; CRi required either platelet count of ≥100,000/µL or neutrophils of ≥1,000/µL (Cheson 2003). Results Fifty-three patients (median age 75 years; range, 60-87) have been treated with 33A+HMA. All patients had adverse (38%) or intermediate (62%) cytogenetic risk by MRC criteria; 40 patients (75%) were considered unfit for intensive therapy and 13 patients (25%) declined intensive therapy.Of the patients with secondary AML (23/53, 43%), median age was 77 years (range 60-87) with most of the patients ≥75 years (70%). The median treatment duration is currently 19.3 weeks (range, 2-86) with 13 patients remaining on treatment; no DLTs or infusion reactions were reported. G3 or higher AEs reported in ≥15% of patients were thrombocytopenia (55%), anemia (43%), febrile neutropenia (43%), neutropenia (38%), pneumonia (19%), and leukopenia (17%); no G4 or 5 bleeding events were observed. Other non-hematologic treatment-emergent AEs regardless of relationship to study treatment and reported in ˃25% of patients were fatigue (58%), nausea (47%), constipation (43%), decreased appetite, peripheral edema (40% each), pyrexia (32%), dyspnea (28%), diarrhea (26%), and dizziness (25%). 30- and 60-day mortality rates were 2% and 8% with no treatment-related deaths reported. A total of 37% (90/246) of doses were delayed due to AEs primarily related to myelosuppression (neutropenia 16%, thrombocytopenia 6%, febrile neutropenia 4%).Thirty-six of the 49 efficacy evaluable patients (73%)achieved CR (21, 43%) or CRi (15, 31%); an additional 4 patients were not efficacy evaluable by protocol definition, due to death (n=2) or withdrawal of consent (n=2) before a response assessment marrow could be obtained. Remissions were achieved after a median of 2 cycles (range, 1-4) and were observed in most of the patients with adverse risk disease including antecedent myelodysplasia (16/22, 73%), adverse cytogenetics (15/18, 83%), FLT3/ITD (5/5, 100%), and patients≥75 years (17/26, 65%). Seventeen of 22 efficacy-evaluable patients with secondary AML (77%) achieved CR (11, 50%) or CRi (6, 27%). Of all responding patients, 17 of 36 (47%) achieved MRD negativity by flow cytometry. The median relapse-free survival was 9.1 months (range, 0.1-16.5+) andOS continues to evolve with22 patients (42%) alive with a median follow-up of 10 months. Conclusions The combination of 33A+HMA is well tolerated with no identified pattern of off-target toxicity. Activity with the combination appears markedly improved when compared to the historical experience of HMA monotherapy in this patient population (Table 1). The CR+CRi rate of 73% in older AML patients with poor risk factors in the setting of low early mortality is particularly encouraging. Activity was maintained even in the highest risk patient groups (adverse risk cytogenetics, underlying myelodysplasia, secondary AML, FLT3/ITD). Survival data are evolving and compare favorably to historical controls. CASCADE, a phase 3 trial investigating 33A+HMA v. HMA alone in older AML patients is now enrolling (NCT02785900). Disclosures Fathi: Merck: Other: Advisory Board participation; Agios Pharmaceuticals: Other: Advisory Board participation; Bexalata: Other: Advisory Board participation; Seattle Genetics: Consultancy, Other: Advisory Board participation, Research Funding; Celgene: Consultancy, Research Funding. Erba:Gylcomimetics: Other: DSMB; Millennium Pharmaceuticals, Inc.: Research Funding; Jannsen: Consultancy, Research Funding; Ariad: Consultancy; Sunesis: Consultancy; Pfizer: Consultancy; Celator: Research Funding; Juno: Research Funding; Seattle Genetics: Consultancy, Research Funding; Agios: Research Funding; Astellas: Research Funding; Novartis: Consultancy, Speakers Bureau; Incyte: Consultancy, DSMB, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Amgen: Consultancy, Research Funding; Daiichi Sankyo: Consultancy. Stein:Celgene: Other: Advisory Board, Research Funding; Agios Pharmaceuticals: Other: Advisory Board, Research Funding; Seattle Genetics: Research Funding; Novartis: Consultancy. Ravandi:Seattle Genetics: Consultancy, Honoraria, Research Funding; BMS: Research Funding. Faderl:JW Pharma: Consultancy; Amgen: Speakers Bureau; Karyopharm: Consultancy, Research Funding; Ambit Bioscience: Research Funding; BMS: Research Funding; Celator Pharmaceuticals: Research Funding; Astellas: Research Funding; Pfizer: Research Funding; Seattle Genetics: Research Funding; Celgene: Consultancy, Research Funding. Advani:Seattle Genetics: Consultancy, Research Funding. DeAngelo:Baxter: Consultancy; Pfizer: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Ariad: Consultancy; Incyte: Consultancy; Novartis: Consultancy. Kovacsovics:Seattle Genetics: Research Funding. Jillella:Seattle Genetics: Research Funding. Levy:Seattle Genetics: Research Funding; Jansen: Speakers Bureau; Amgen: Speakers Bureau; Millennium: Speakers Bureau. O'Meara:Seattle Genetics: Employment, Equity Ownership. Ho:Seattle Genetics: Employment, Equity Ownership. Stein:Seattle Genetics: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau; Stemline Therapeutics: Consultancy, Research Funding; Argios: Research Funding; Celgene: Research Funding.

Background Older patients with AML who are not candidates for intensive therapy are typically treated with hypomethylating agents (HMAs) or other low intensity therapy. HMAs have been shown to upregulate CD33 and to increase sensitivity to cytotoxic chemotherapy by decreasing apoptotic threshold in tumor cells. SGN-CD33A (or 33A) is a CD33-directed antibody conjugated to 2 molecules of a pyrrolobenzodiazepine (PBD) dimer. Upon binding, 33A is internalized and transported to the lysosomes where PBD dimer is released via proteolytic cleavage of the linker, crosslinking DNA, and leading to cell death. In preclinical studies combining 33A with an HMA (azacitidine and decitabine), synergy has been demonstrated in multidrug resistant AML models (Sutherland ASH 2014). Methods A combination cohort in a phase 1 study (NCT01902329) was designed to evaluate the safety, tolerability, pharmacokinetics (PK), and anti-leukemic activity of 33A in combination with an HMA. Eligible patients (ECOG 0-1) must have previously untreated CD33-positive AML, and have declined intensive therapy. A single dose level of 33A, 10 mcg/kg, was administered outpatient IV every 4 weeks on the last day of HMA (azacitidine or decitabine [5 day regimen], standard dosing). Patients with clinical benefit may continue treatment until relapse or unacceptable toxicity. Investigator assessment of response is per IWG criteria; CRi requires either platelet count of ≥100,000/µL or neutrophils of ≥1,000/µL (Cheson 2003). Results To date, 24 patients (63% male) with a median age of 77 years (range, 66-83) have been treated with the combination therapy. 42% of patients had adverse cytogenetics (MRC), 23 patients were treatment naïve and 1 patient had received prior low intensity therapy for MDS. At baseline, patients had a median of 60% BM blasts (range, 2%-90%) and a median of WBC of 2.2 (range, 1-132). At the time of this interim analysis, patients were on treatment for a median of 13.5+ weeks with 17 patients continuing treatment; no DLTs have been reported. Grade 3 or higher adverse events (AE) reported in >20% of patients were fatigue (54%), febrile neutropenia (46%), anemia (25%), neutropenia (25%), and thrombocytopenia (21%). Other treatment-emergent AEs regardless of relationship to study treatment reported in ˃20% of patients were nausea (29%), decreased appetite (25%), and constipation (21%). Thirty- and 60-day mortality rates are 0% and 4% respectively with no treatment-related deaths reported. Fifteen of the 23 efficacy evaluable patients (65%) achieved CR (5) or CRi (10). Remissions were generally obtained after 2 cycles of treatment and were observed in many patients with adverse risk including underlying myelodysplasia (6/8, 75%) and adverse cytogenetics (8/9, 89%). Median OS has not been reached with 20 patients alive at the time of this data cut. Conclusions The combination of 33A with HMA appears to be well-tolerated, active, and has no identified off-target toxicities. Activity with the combination compares favorably with historical experience with HMAs alone in this patient population. The CR+CRi rate of 65% in AML patients with poor risk factors with the observed low 60-day mortality (4%) are particularly encouraging. These promising data warrant further evaluation in future trials. Disclosures Fathi: Agios Pharmaceuticals: Other: Advisory Board participation; Merck: Other: Advisory Board participation; Seattle Genetics: Other: Advisory Board participation, Research Funding. Off Label Use: SGN-CD33A is an investigational agent being studied in patients with CD33-positive AML. SGN-CD33A is not approved for use.. Erba:GlycoMimetics; Janssen: Other: Data Safety & Monitoring Committees; Sunesis;Pfizer; Daiichi Sankyo; Ariad: Consultancy; Millennium/Takeda; Celator; Astellas: Research Funding; Seattle Genetics; Amgen: Consultancy, Research Funding; Novartis; Incyte; Celgene: Consultancy, Patents & Royalties. Lancet:Seattle Genetics: Consultancy; Pfizer: Research Funding; Boehringer-Ingelheim: Consultancy; Kalo-Bios: Consultancy; Amgen: Consultancy; Celgene: Consultancy, Research Funding. Stein:Seattle Genetics, Inc.: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees. Walter:Pfizer, Inc.: Consultancy; Covagen AG: Consultancy; AstraZeneca, Inc.: Consultancy; CSL Behring: Research Funding; AbbVie, Inc.: Research Funding; Amgen: Research Funding; Amphivena Therapeutics, Inc.: Consultancy, Research Funding; Seattle Genetics, Inc.: Consultancy, Research Funding. DeAngelo:Incyte: Consultancy; Amgen: Consultancy; Pfizer: Consultancy; Ariad: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Agios: Consultancy. Faderl:Celator: Research Funding; Ambit: Research Funding; BMS: Research Funding; Astellas: Research Funding; Karyopharm: Consultancy, Research Funding; Seattle Genetics, Inc.: Research Funding; JW Pharma: Consultancy; Celgene: Consultancy, Research Funding, Speakers Bureau; Pfizer: Research Funding; Onyx: Speakers Bureau. Jillella:Seattle Genetics, Inc.: Research Funding. Bixby:Seattle Genetics, Inc.: Research Funding. Kovacsovics:Seattle Genetics, Inc.: Research Funding. O'Meara:Seattle Genetics, Inc: Employment, Equity Ownership. Kennedy:Seattle Genetics, Inc.: Employment, Equity Ownership. Stein:Amgen: Speakers Bureau.

CD98 is a heterodimeric cell surface protein that is implicated in the pathogenesis of many hematological and solid malignancies. Elevated tumor CD98 expression has been correlated with poor prognosis. Previous studies demonstrated that CD98 functions in integrin signaling and amino acid transport processes that support tumor cell proliferation, anchorage independence, invasion, and metastasis. IGN523 is a humanized monoclonal antibody targeting CD98 with multiple mechanisms of action including antibody-dependent cellular cytotoxicity (ADCC), direct cell death induction, and interference with the normal amino acid transport function of CD98. IGN523 elicits potent anti-tumor activity against a variety of leukemic xenograft models (Hayes et al., Int. J. Cancer 2015). Here we present the results of a Phase I dose escalation study of IGN523 in adult patients with relapsed or refractory AML. IGN523 was administered intravenously (IV) as a single agent to 19 patients at weekly doses ranging from 0.1 mg/kg to 20 mg/kg, including 3 single-patient cohorts starting at 0.1, 0.3, and 1 mg/kg, 6 patients treated at 10 mg/kg, 3 at 20 mg/kg, and 7 at 15 mg/kg. Median age was 71 years (range 23-78). Patients received a median of one 4-week cycle of treatment (range The most common treatment-related adverse events observed were part of infusion-related reactions (IRRs) occurring primarily with the first infusion, and were generally Grade 1 or 2 (CTCAE V4.03), including chills (52.6%), fever (pyrexia or febrile neutropenia, 36.9%), nausea (26.3%), and vomiting (26.3%). Premedication with acetaminophen, diphenhydramine, and hydrocortisone was instituted after a dose-limiting toxicity (DLT) of significant IRR with the first dose was observed in 1 of 3 patients treated at 10 mg/kg, and the cohort was expanded to 6 patients. Treatment-related Grade 3 and 4 AEs occurring in >1 patient included febrile neutropenia (26.1%), pyrexia (10.5%), and altered mental status (confusional state or mental status changes in 15.8% and 10.5% respectively). DLTs all occurred with the first dose of IGN523 and were observed in 1 of 6 patients at 10 mg/kg, 2 of 3 at 20 mg/kg, and 2 of 7 at 15 mg/kg. The maximum tolerated dose (MTD) of IGN523 administered weekly was 10 mg/kg. PK studies of IGN523 in all patients demonstrated evidence of target-mediated drug disposition at doses below 10 mg/kg/week, as pre-dose (trough) CD98 receptor occupancy (%RO) levels tended to be < 90%. By the 10 mg/kg dose cohort, pre-dose %RO levels were 50 to > 90% during the first few weeks of dosing, and consistently > 90% after 4-8 weeks of dosing. At 15 and 20 mg/kg/week doses, %RO was consistently > 90% from the first dose. Therefore, dose levels of 10 mg/kg/week and above should be suitable for most patients to maintain >90% receptor occupancy over time. Anti-drug antibodies (ADA) were not detected in any patient. Evidence of transient anti-leukemic activity was observed in 3 patients, including improvement in platelet count and reduction in marrow blast percentage, early reduction and control of blasts, and an episode of tumor lysis and peripheral blast count reduction. No complete or partial responses were observed. In conclusion, IGN523 was safe when administered at 10 mg/kg IV weekly with DLTs of significant first-dose infusional toxicity that may be manageable with prophylactic steroids or a modified dosing regimen. IGN523 demonstrated modest evidence of anti-leukemic activity as a single agent. Preclinical data demonstrating greater than additive activity of IGN523 when combined with cytarabine and significant monotherapy and combination activity with standard chemotherapy in patient-derived xenograft models of NSCLC and colorectal cancer support further development of IGN523 in combination with standard therapies in AML and solid tumors. Disclosures Bixby: Seattle Genetics, Inc.: Research Funding. Akard:Novartis: Research Funding, Speakers Bureau; BMS: Research Funding, Speakers Bureau; Celgene: Speakers Bureau; Millenium: Speakers Bureau; Ariad: Research Funding, Speakers Bureau; Gilead: Speakers Bureau; Pfizer: Research Funding; Incyte: Research Funding. Khoury:Pfizer: Honoraria; Ariad: Honoraria; Bristol-Meyer-Squibb: Honoraria. Becker:Igenica: Research Funding. Van Der Horst:Igenica: Employment. Ho:Igenica: Employment. Cortes:Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding; BerGenBio AS: Research Funding; BMS: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Ambit: Consultancy, Research Funding; Arog: Research Funding; Celator: Research Funding; Jenssen: Consultancy.

Background CD33is expressed in approximately 90% of AML, representing a promising target despite age, prior therapies, or mutational heterogeneity. SGN-CD33A (or 33A) is a CD33-directed antibody conjugated to 2 molecules of a pyrrolobenzodiazepine (PBD) dimer. Upon binding, 33A is internalized and transported to the lysosomes where PBD dimer is released via proteolytic cleavage of the linker, crosslinking DNA, and leading to cell death. Methods The dose-escalation portion of this phase 1 study (NCT01902329) is designed to evaluate the safety, tolerability, pharmacokinetics (PK), and antileukemic activity of 33A as monotherapy. Eligible patients (ECOG 0-1) must have CD33-positive AML, and have either relapsed disease following initial remission (CR) of >3 months, or have declined conventional induction/consolidation. 33A monotherapy is administered outpatient via IV every 3 weeks for up to 2 cycles, followed by optional low-dose maintenance treatment for patients who achieve a CR/CRi. Investigator assessment of response is per IWG criteria; CRi requires either platelet count of ≥100,000/µL or neutrophils of ≥1,000/µL (Cheson 2003). Results To date, 87 patients (62% male) with a median age of 74 years (range, 27-89) have been treated. 34 patients had relapsed AML after 1st CR with intensive therapy; 52 had declined conventional intensive therapy (40 of these patients had received 1-2 prior low intensity therapies, primarily hypomethylating agents). Most patients had intermediate I-II (51%) or adverse (31%) risk by ELN classification and 54% of patients had AML with underlying myelodysplasia-related changes. 9% of patients displayed NPM1 mutations without FLT3 mutation (NPM1+/FLT3-). Dose levels ranged from 5-60 mcg/kg (n=75) and also included fractionated dosing of 20 mcg/kg on Day 1 and Day 4 (n=12). Five patients remain on treatment. Six dose-limiting toxicities were reported in the monotherapy escalation cohorts: 2 Grade 4 bone marrow failures (40 and 60 mcg/kg), 2 mucositis (Grade 3 at 50 mcg/kg; Grade 3 at fractionated 20+20 mcg/kg), Grade 3 pulmonary embolism (20 mcg/kg), and Grade 5 sepsis (50 mcg/kg). The most common Grade 3 or higher adverse events (AE) reported were febrile neutropenia (69%), thrombocytopenia (29%), and anemia (23%). Increased myelosuppression was observed at doses higher than 40 mcg/kg and the fractionated dosing cohort, including febrile neutropenia observed in 68% of patients and sepsis observed in 26% of patients. Other common treatment-emergent AEs regardless of relationship to study treatment were fatigue (48%), decreased appetite (28%), constipation, diarrhea, dyspnea, nausea (26% each), and peripheral edema (25%). The 30-day mortality was 6%. Across all dose levels, the CR+CRi rate was 86% in the patients with NPM1+/FLT3- disease (n=7). Of the 21 efficacy evaluable patients treated at 40 mcg/kg, 3 patients achieved a best clinical response of CR, 4 achieved CRi, and 5 had morphologic leukemia-free state (mLFS). Three of 5 treatment-naïve patients within the 40 mcg/kg dose level achieved a CR or CRi. In patients across dose levels who achieved at least mLFS, the mean time to full count recovery was 5 weeks for neutrophils (≥1,000/µL) and 6 weeks for platelets (≥100,000/µL). Median OS in patients treated at 40 mcg/kg is 10 months with 17 patients alive at the time of this data cut. Across all dose levels, 8 patients went on to receive an allogeneic SCT. PK data demonstrated generally dose-dependent increase in plasma ADC exposures and target-mediated rapid clearance. Conclusions Dose escalation is complete and a recommended monotherapy 33A dose of 40 mcg/kg was identified. AEs observed were generally manageable, often associated with underlying myelosuppression. 33A has demonstrated favorable antileukemic activity with 33% achieving a CR+CRi at the 40 mcg/kg dose level (60% CR+CRi in treatment naïve patients). The rapid clearance of marrow blasts in patients with poor risk factors and low 30-day mortality (6%) are encouraging. Enrollment is ongoing in multiple expansion cohorts, including previously untreated AML patients who declined intensive therapy, relapsed NPM1 mutant disease, and relapsed APL. In addition, a study evaluating 33A with intensive therapy in newly diagnosed patients with AML is ongoing. Disclosures Stein: Amgen: Speakers Bureau. Off Label Use: SGN-CD33A is an investigational agent being studied in patients with CD33-positive AML. SGN-CD33A is not approved for use. Walter:Pfizer, Inc.: Consultancy; Covagen AG: Consultancy; AstraZeneca, Inc.: Consultancy; CSL Behring: Research Funding; AbbVie, Inc.: Research Funding; Amgen: Research Funding; Amphivena Therapeutics, Inc.: Consultancy, Research Funding; Seattle Genetics, Inc.: Consultancy, Research Funding. Erba:GlycoMimetics; Janssen: Other: Data Safety & Monitoring Committees; Sunesis; Pfizer; Daiichi Sankyo; Ariad: Consultancy; Millennium/Takeda; Celator; Astellas: Research Funding; Seattle Genetics; Amgen: Consultancy, Research Funding; Novartis; Incyte; Celgene: Consultancy, Patents & Royalties. Fathi:Agios Pharmaceuticals: Other: Advisory Board participation; Seattle Genetics: Other: Advisory Board participation, Research Funding; Merck: Other: Advisory Board participation. Lancet:Seattle Genetics: Consultancy; Pfizer: Research Funding; Boehringer-Ingelheim: Consultancy; Kalo-Bios: Consultancy; Amgen: Consultancy; Celgene: Consultancy, Research Funding. Kovacsovics:Seattle Genetics, Inc.: Research Funding. DeAngelo:Pfizer: Consultancy; Amgen: Consultancy; Ariad: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy; Incyte: Consultancy; Agios: Consultancy; Celgene: Consultancy. Bixby:Seattle Genetics, Inc.: Research Funding. Faderl:Onyx: Speakers Bureau; BMS: Research Funding; Seattle Genetics, Inc.: Research Funding; JW Pharma: Consultancy; Karyopharm: Consultancy, Research Funding; Celgene: Consultancy, Research Funding, Speakers Bureau; Pfizer: Research Funding; Astellas: Research Funding; Celator: Research Funding; Ambit: Research Funding. Jillella:Seattle Genetics, Inc.: Research Funding. O'Meara:Seattle Genetics, Inc: Employment, Equity Ownership. Zhao:Seattle Genetics, Inc.: Employment, Equity Ownership. Stein:Seattle Genetics, Inc.: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees.

B lymphoblastic leukemia (B-ALL) in adults has a higher risk of relapse and lower long-term survival than pediatric B-ALL, but data regarding prognostic biomarkers are much more limited for adult patients. Microarray-based genome-wide profiling studies in pediatric B-ALL patients have revealed recurrent abnormalities in B-cell development and cell cycle regulation. IKZF1 alterations convey a negative prognostic impact in pediatric B-ALL, but their significance is not well characterized in adult B-ALL. CDKN2A alterations have been associated with a poorer prognosis in adult Ph+ ALL, possibly by mediating resistance to targeted therapy. The copy number landscape of adult B-ALL has not been fully assessed and is likely distinct from its pediatric counterpart. In addition, the copy number changes in relapsed adult B-ALL, including comparison with initial diagnostic samples, have not been characterized. We identified 70 adult B-ALL patients (median age 45 years, range 18-83) from 1998-2013 at three institutions. DNA was isolated from formalin-fixed, paraffin-embedded (FFPE) diagnostic bone marrow clots, as well as relapse samples when available, and assessed with the OncoScan FFPE Express genome-wide single nucleotide polymorphism (SNP) assay (Affymetrix). Copy number alteration (CNA) and loss of heterozygosity (LOH) analysis was performed using Nexus Software V7 (Biodiscovery) and in-house coding. For cases with adequate DNA, IKZF1 sequencing was also performed. Clinical data included age, gender, hematologic laboratory values at presentation, CSF involvement, receipt of allogeneic transplant, cytogenetic profile, presence of t(9;22), event-free survival (EFS), and overall survival (OS). Recurrent deletions in the diagnostic samples were noted at several loci, including CDKN2A (48.6%), IKZF1 (40%), ICR (38.6%), PAX5 (24.2%), BTG1 (17.1%), ETV6 (15.7%), BTLA (14.3%), RB1 (5.7%), EBF1 (5.7%), LEF1 (2.9%), and TCF3 (2.9%). Recurrent gains were identified at the following loci: ERG (30%), ETS2 (21.4%), MYB (20%), UBASH3B (20%), PTEN (20%), PRKCH (18.6%), CDK6 (17.1%), and ETV6 (12.9%). In addition, LOH was observed in all loci with recurrent CNAs named above. 27 samples obtained at the time of relapse were screened for the recurrent CNAs identified in the diagnostic samples. The cumulative incidence of CNAs at these genes was lower in the relapse cohort than the initial diagnostic cohort, although there was a higher frequency of CNAs at PAX5, BTLA, ETS2, RB1, LEF1, PTEN, and TCF3 in the relapse samples. 16 patients had samples available at both the time of diagnosis and time of relapse. The average number of CNAs at diagnosis and relapse was the same, but analysis of paired samples revealed frequent changes at the previously defined loci of CNAs. There were a number of new CNAs at these loci in relapse samples, but there was also a similar incidence of reversion to the copy neutral state in loci that previously had CNAs in the diagnostic samples. Sequencing data was available on 26 diagnostic samples for the IKZF1 gene. Only two samples had mutations corresponding to amino acid changes. One of these two had a heterozygous deletion at IKZF1, indicating that the mutated isoform was the only one expressed. 11 other samples had a SNP without a corresponding amino acid change. 14 relapse samples were sequenced, two of which harbored a point mutation in IKZF1. Neither of these samples had a CNA at this locus. 10 of the remaining 12 relapse samples had a SNP without a corresponding amino acid change. When correlated with outcomes, no individual CNA heralded a significant prognostic impact in the entire cohort or in subgroup analyses stratified by presence of t(9;22) for either EFS or OS. However, the combination of both CDK2NA and IKZF1 deletions (26%) correlated with a significantly worse OS than having only one or neither of these deletions (both vs. CDKN2A only: p=0.028, both vs. IKZF1 only: p=0.027, both vs. neither deleted: p=0.048). Age was the only other covariate significant in univariate analyses for OS, yet IKZF1/CDKN2A co-deletion remained significant in multivariate analysis adjusting for age. Adult B-ALL demonstrates recurrent copy number changes, and the pattern of CNAs is often different at relapse than at diagnosis indicating clonal evolution. When identified in diagnostic samples, co-deletion of CDKN2A /IKZF1 is a negative prognostic marker in adult B-ALL. Disclosures South: Illumina: Consultancy, Honoraria; Affymetrix: Consultancy, Honoraria; ARUP Laboratories: Employment; Lineagen Corporation: Consultancy. Bixby:Seattle Genetics, Inc.: Research Funding. Gastier-Foster:Bristol-Myers Squibb: Research Funding.

Background: All-Trans Retinoic Acid (ATRA, Tretinoin, Vesinoid, Teva Pharmaceuticals Industries, North Wales, PA) serves as a uniform backbone in the care and management of patients with acute promyelocytic leukemia (APL). While first investigated as a salvage therapy for patients with relapsed or refractory disease, current National Comprehensive Cancer Network (NCCN) and European LeukemiaNet (ELN) guidelines call for its early use in patients suspected of having APL even prior to the genetic confirmation of the disease. Because ATRA can significantly mitigate disseminated intravascular coagulopathy (DIC), one of the early complications of APL, the NCCN and ELN guidelines support the prescription of ATRA as soon as there is a clinical suspicion of the diagnosis. As a regional referral center for the care of patients with advanced myeloid malignancies, we receive numerous requests for the transfer of care for patients suspected of having APL. Yet many of the referring centers have not instituted treatment with ATRA, typically due to a lack of access to the medication in the referring hospital’s formulary. Therefore, we conducted an exploratory analysis of the clinical availability of ATRA for patients with a suspected diagnosis of APL and also to explore the potential hurdles limiting the availability of this drug. Methods: We divided the United States into six geographical regions: Northwest, Southwest, Central, Southeast, Northeast, and the Great Lakes. A state from each of these regions was selected (Washington, Arizona, Missouri, Georgia, Massachusetts, and Michigan). To select the 120 hospitals, an online hospital directory – American Hospital Directory (ahd.com) was utilized. We went to each state’s specific hospital list page and assigned a number to all hospitals with a bed capacity of greater than 100. We then entered these numbers into a random number generator and selected the first 20 hospitals to be generated (excluding repeats). We then asked the following set of questions to the inpatient pharmacist of the hospital: 1. Does your hospital treat Acute Leukemia or do they refer to other hospitals; 2. Do you have All Trans Retinoic Acid (oral) – 10 mg tablets on the formulary or available in stock as a non-formulary request; 3. If no, why not. Results: Based upon the responses we received, ATRA was available in less than half of the hospitals queried (46%) (Table 1). There were no identifiable differences in the percentages based upon hospital size (inpatient beds) or academic versus non-academic status of the hospital. Interestingly, of the hospitals that refer to other institutions for the care of their leukemia patients, only 19% (8/43) had ATRA on their formulary or available in stock as a non-formulary request that could act as a bridge prior to the transfer. The analysis identified three common barriers to the availability of ATRA in these hospitals including: a) that it has not been recently requested by a physician and therefore was not available, b) the inpatient pharmacist had never heard of the drug, and c) that the hospital relied on associated hospitals or cancer centers to provide the drug to the patient. Table 1 Clinical Availability of All-Trans Retinoic Acid in Participating Hospitals Region State Percentage of Hospitals Possessing ATRA Northwest Washington 65% Southwest Arizona 45% Midwest Missouri 35% Great Lakes Michigan 58% Southeast Georgia 35% Northeast Massachusetts 40% Conclusion: While national guidelines support the rapid introduction of ATRA as soon as there is a morphologic consideration for APL, the majority of hospitals caring for these patients can not rapidly institute therapy due to a lack of availability of the medication. Moreover, only 19% (8/43) of hospitals that we studied that refer patients to tertiary care centers can provide ATRA as a bridge prior to their transfer. While much has been written about the early 30-day mortality seen in patients with APL, we can not specifically comment on the impact of these findings on the rates of mortality of APL patients treated in hospitals without ready access to ATRA versus those with the medication available on formulary. However, we propose that these findings should spur an investigation of this possibility together with a call by hematologists nationwide to their formulary committees to ensure that this lifesaving medication is available to patients in as timely a manner as possible. Disclosures Off Label Use: All Trans Retinoic Acid (ATRA) is indicated for the use in patients with acute promyelocytic leukemia (APL) who are refractory to, or who have relapsed from, anthracycline chemotherapy, or for whom anthracycline based chemotherapy is contraindicated. We will be discussing the availability of ATRA for the use in patients with newly diagnosed APL..

Background: Ponatinib is a potent oral pan–BCR-ABL tyrosine kinase inhibitor (TKI) active against native and mutated forms of BCR-ABL, and is approved for patients with refractory CML and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia and those with the T315I mutant. Long-term follow-up of the anti-leukemic activity and safety of ponatinib in patients with CML or Ph+ ALL in this phase 1 clinical trial is reported. Methods: Patients (N=81) with resistant/refractory hematologic malignancies were enrolled in this ongoing, open-label, dose-escalation, phase 1 study ([NCT00660920][1]) . Ponatinib was dosed once daily (2 mg-60 mg). Intra-patient dose escalation was permitted. The 43 patients who had CP-CML are the focus of this analysis (data as of 6 Jan 2014). Median follow-up for CP-CML patients was 42.5 (1.7-59.1) months. Results: The median age of patients was 55 years; median time since diagnosis was 6.6 years. Patients were heavily pretreated (61% received ≥3 prior TKIs; 37% received 2 prior TKIs). At baseline, 63% of patients had BCR-ABL mutations (28% with T315I). At the time of analysis, 56% of patients remained on study. Significant anti-leukemic activity was observed: major cytogenetic response (MCyR), complete cytogenetic response (CCyR), major molecular response (MMR) and molecular response 4 (MR4) rates were 72%, 65%, 51%, and 40% respectively; 76% of patients with MCyR and 54% with MMR are estimated (Kaplan-Meier [KM]) to maintain response for at least 4 years (3-year KM estimates: 76% MCyR, 70% CCyR, 54% MMR; [Figure 1][2] ). 15 patients started at a dose of 30 mg or below, and 10 of these patients (67%) achieved MCyR; all were receiving a dose of 30 mg or below at time of response ( Table 1 ). Of 28 patients with CCyR, 22 remained on study (16 with continuous CCyR); of 22 patients with MMR, 19 remained on study (11 with continuous MMR). Adverse events (AEs, 23%) and progression (9%) were the most common reasons for discontinuation. Of the 10 patients that discontinued due to AEs, 5 were in MCyR and, of those, 1 was in MMR. The most common treatment-emergent AEs were rash (63%), fatigue (61%), abdominal pain (58%), headache (56%), and arthralgia (54%). The most common treatment-emergent AEs occurring after 1 year of therapy were fatigue (35%), hypertension (31%), and abdominal pain (30%). Treatment-emergent arterial thrombotic events (AE [SAE]) were observed in 37% [28%] of patients (composite of cardiovascular 28% [19%], cerebrovascular 9% [7%], and peripheral vascular 12% [7%] events), and venous thromboembolic AEs were observed in 5% [no SAEs] of patients. Updated data will be presented. Conclusions: With a median follow-up of 42.5 months in CP-CML patients (maximum follow-up, 59.1 months), ponatinib continues to provide benefit to heavily pretreated patients with limited treatment options. Substantial and durable responses were observed with ponatinib, and responses were observed in patients treated with doses at or below 30 mg. The most common treatment-emergent AEs occurring after one year of therapy were similar to the overall AE profile, albeit with lower incidence rates. Risk and benefit considerations should be evaluated when utilizing ponatinib in this patient population. ![Figure 1:][3] Figure 1: Duration of Response in CP-CML Patients aLoss of response is defined as a single time point at which the criteria for response are not met. | Starting Dose | MCyR | MMR | | ------------- | ---------------------------------- | ----------------- | ---------------------------------- | | N (%) | Dose intensity*, Median (min, max) | N (%) | Dose intensity*, Median (min, max) | | 4 mg, N=3 | 2 (67) | 3.7 (3.5, 3.9) | 1 (33) | 14.3 (14.3, 14.3) | | 15 mg, N=7 | 5 (71) | 14.8 (14.7, 23.7) | 4 (57) | 15.0 (14.7, 36.6) | | 30 mg, N=5 | 3 (60) | 27.4 (10.6, 29.6) | 1 (20) | 29.9 (29.9, 29.9) | | ≤30 mg, N=15 | 10 (67) | 14.8 (3.5, 29.6) | 6 (40) | 15.0 (14.3, 36.6) | | 45 mg, N=14 | 13 (93) | 44.5 (23.4, 45.0) | 11 (79) | 43.5 (16.6, 45.0) | | 60 mg, N=14 | 8 (57) | 42.6 (14.2, 59.3) | 5 (36) | 56.5 (14.7, 59.5) | Table 1: Ponatinib Response Rate for CP-CML Patients by Dose *Dose intensity (mg/day) until time of response for responders only Disclosures Talpaz: ARIAD Pharmaceuticals, Inc., BMS, Sanofi, Incyte, Pfizer: Research Funding. Cortes: ARIAD Pharmaceuticals, Inc., BMS, Novartis, Pfizer, Teva: Consultancy, Research Funding. Kantarjian: ARIAD, Pfizer, Amgen: Research Funding. Shah: ARIAD, BMS: Research Funding. Flinn: ARIAD Pharmaceuticals, Inc.: Research Funding. Hu: ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Rivera: ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Clackson: ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Turner: ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Haluska: ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Druker: BMS: Research Funding; ARIAD Pharmaceuticals, Inc.: PI and co-investigator on clinical trials, PI and co-investigator on clinical trials Other; MolecularMD: Consultancy, Equity Ownership. Deininger: BMS, Novartis, Celgene, Genzyme, Gilead: Research Funding; BMS, ARIAD, Novartis, Incyte, Pfizer: Advisory Board, Advisory Board Other; BMS, ARIAD, Novartis, Incyte, Pfizer: Consultancy. Mauro: ARIAD Pharmaceuticals, Inc.: Consultancy. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00660920&atom=%2Fbloodjournal%2F124%2F21%2F4558.atom [2]: #F1 [3]: pending:yes

Background: Resistance to tyrosine kinase inhibitors (TKIs) in patients (pts) with chronic myeloid leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) is frequently caused by mutations in the BCR-ABL kinase domain. Ponatinib is the only approved oral TKI that inhibits the T315I mutant, which is uniformly resistant to other TKIs. Here we report long-term follow-up of the efficacy and safety of ponatinib in pts with the T315I mutation at baseline from the Phase 1 (Ph1) and PACE trials. Methods: The Ph1 trial (NCT01207440) evaluated safety and anti-leukemic activity of ponatinib (2-60 mg qd) in pts with CML or Ph+ ALL (N=81); the PACE trial (NCT00660920) evaluated efficacy and safety of ponatinib (45 mg qd) in CML and Ph+ ALL pts (N=449) resistant/intolerant to dasatinib or nilotinib or with the T315I mutation. Data reported are for pts with the T315I mutation at baseline, detected by Sanger sequencing at a central lab. Results: The Ph1 and PACE trials included 19 (29%) and 128 (29%) pts with the T315I mutation, respectively. Median age and median time since diagnosis were 47 and 2.7 years for Ph1, and 53 and 3.6 years for PACE.Pts were heavily pretreated: 89% in Ph1 and 84% in PACE had received ≥2 prior TKIs. As of Jan 6, 2014, median follow-up was 42 (1-59) months in Ph1, and 20 (0.1-40) months in PACE; 58% Ph1 (92% CP-CML) and 33% PACE (52% CP-CML) pts remained on study. Most-common reasons for discontinuation: administrative decision (16%) and progressive disease (16%) for Ph1, and progressive disease (31%) and adverse events (AEs; 13%) for PACE. Of the pooled chronic phase (CP)-CML pts, 75%, 72%, and 61% achieved MCyR, CCyR, and MMR, respectively, with deeper responses (MR4, MR4.5) observed in over a third of the pts (Table). MaHR was achieved in 58%, 27% and 38% of pooled AP-CML, BP-CML and Ph+ ALL pts, respectively. For Ph 1 CP-CML pts, 3-year CCyR duration estimates were 80%. For PACE CP-CML pts, 2-year MCyR/CCyR duration, PFS and OS estimates were 93%/79%, 72% and 82%, respectively. Only 1 CP-CML pt in PACE lost MCyR and 1 transformed to AP-CML. For AP-CML, BP-CML, and Ph+ ALL, estimated OS/PFS at 2 years was 69%/54%, 14%/10%, and 10%/N/A, respectively. The most frequent treatment-emergent AEs (TEAEs) observed in Ph1 CP-CML pts were dry skin (83%), rash (83%), arthralgia (75%), fatigue (75%), headache (67%), abdominal pain (58%), hypertension (58%), hypertriglyceridemia (58%), myalgia (58%), and nausea (58%). None of the 19 serious TEAEs that occurred in Ph1 CP-CML pts occurred in >1 pt. The most common (≥25%) TEAEs in PACE CP-CML pts were rash (48%), dry skin (42%), headache (41%), abdominal pain (39%), nausea (36%), constipation (33%), fatigue (33%), thrombocytopenia (28%), myalgia (28%), hypertension (27%), arthralgia (25%), and upper respiratory tract infection (25%). Most common (≥5 %) serious TEAEs in PACE CP-CML pts were acute myocardial infarction (8%), pancreatitis (8%), atrial fibrillation (6%), coronary artery disease (6%), congestive cardiac failure (5%), pneumonia (5%), cerebral infarction (5%), pyrexia (5%), increased lipase (5%), and dyspnea (5%). Arterial thrombotic events occurred in 1 (8%) Ph1, and 20 (31%) PACE pts. Venous thromboembolic events occurred in 1 (8%) Ph1, and 3 (5%) PACE pts. Despite the higher median dose intensity for T315I CP-CML pts (38 vs 30.8 mg/day overall CP-CML) in PACE, the safety profiles were similar. For CP-CML pts in PACE, responses achieved by 12 months were generally maintained after dose reduction primarily to manage AEs: 100% maintained MCyR; 100% maintained CCyR, and 79% maintained MMR. Conclusions: In Ph+ leukemia pts with the T315I mutation, where effective treatment options are limited, ponatinib continued to exhibit deep and durable responses with up to 6 years follow-up. Dose reductions to manage AEs did not impact maintenance of cytogenetic responses. The response rates and safety profile of T315I pts were comparable to, if not better than, those observed in the overall population of refractory CML and Ph+ ALL pts in ponatinib clinical trials. Table. Responses at Any Time in Ponatinib Treated Pts with T315I Mutation Phase 1 PACE Phase 1 and PACE Pooled n (%) n (%) n (%) CP-CML N=12 N=64 N=76 MCyR 11 (92) 46 (72) 57 (75) CCyR 10 (83) 45 (70) 55 (72) MMR 9 (75) 37 (58) 46 (61) MR4 7 (58) 25 (39) 32 (42) MR4.5 4 (33) 21 (33) 25 (33) AP-CML N=1 N=18 N=19 MaHR 0 11 (61) 11 (58) BP-CML N=2 N=24 N=26 MaHR 0 7 (29) 7 (27) Ph+ ALL N=4 N=22 N=26 MaHR 2 (50) 8 (36) 10 (38) Disclosures Mauro: ARIAD Pharmaceuticals, Inc.: Consultancy. Cortes:ARIAD, BMS, Novartis, Pfizer, Teva: Consultancy, Research Funding. Hochhaus:ARIAD Pharmaceuticals, Inc.: Research Funding. Baccarani:ARIAD, Novartis, BMS: Consultancy; ARIAD, Novartis, BMS, Pfizer, Teva: Honoraria; ARIAD, Novartis, BMS, Pfizer, Teva: Speakers Bureau. Hughes:Novartis, BMS, ARIAD: Honoraria, Research Funding. Guilhot:ARIAD Pharmaceuticals, Inc.: Honoraria. Deininger:BMS, Novartis, Celgene, Genzyme, Gilead: Research Funding; BMS, ARIAD, Novartis, Incyte, Pfizer: Advisory Board, Advisory Board Other; BMS, ARIAD, Novartis, Incyte, Pfizer: Consultancy. Kantarjian:ARIAD Pharmaceuticals, Inc., Pfizer, Amgen: Research Funding. Shah:ARIAD Pharmaceuticals, Inc., BMS: Research Funding. Flinn:ARIAD Pharmaceuticals, Inc.: Research Funding. Lustgarten:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Rivera:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Haluska:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Clackson:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Talpaz:ARIAD Pharmaceuticals, Inc., BMS, Sanofi, Incyte, Pfizer: Research Funding.

Abstract 147 Introduction: Follicular lymphoma (FL) constitutes the second most common non-Hodgkin's lymphoma in the Western world. FL carries characteristic recurrent structural genomic aberrations. However despite recent advances, knowledge regarding the coding genome in FL is still evolving and currently incomplete. Methods: To further our understanding of the genetic basis of Follicular Lymphoma (FL), we used solution exon capture of sheared and processed genomic DNA isolated from FACS-sorted lymphomatous B-cells and paired CD3+ T-cells isolated from eleven cases of FL and one case of DLBCL transformed from prior FL followed by paired-end (96 base pair read length per side) massively parallel sequencing. Data from three independent HiSeq2000-based runs were pooled to maximize coverage. The sequence data were characterized by excellent technical QC parameters including a depth of coverage range of 43–73 and with 90% of bases in the target region covered by at least 10 reads. Data were subsequently analyzed using a validated bioinformatics pipelines (Personal Genome Diagnostics Inc., Baltimore, Maryland) serving as the primary data source to nominate candidate mutated genes. To complement the next gen sequencing data, we analyzed the 12 FL cases that constituted the discovery cohort for next generation sequencing for acquired genomic copy number aberrations (aCNA/LOH) and acquired uniparental disomy (aUPD) using SNP 6.0 array profiling. Data for paired DNA samples (sorted FL B-cells versus CD3 cells) were analyzed using dChip-based visual and algorithmic data analysis methods. Results: The bioinformatics pipeline nominated between 13 and 86 (mean of 47) somatically mutated genes per FL case; of these, 480 represented distinct genes. Importantly, 32 genes were nominated to be mutated in ≥2 out of 12 cases and all these candidate recurrent gene mutations and various other genes for a total of N=122 genes were subjected to Sanger sequence validation. Overall, we validated 68 genes as mutated in at least 1/12 FL discovery set cases. These included frequent mutations in MLL2 (8/12), CREBBP (7/12) and BCL2 (5/12). In addition, we identified 19 novel recurrently mutated genes (≥2 out of 12 FL cases with mutations). From these 19 genes and functionally related genes we selected 10 genes for a complete mutation analysis in a total 57 FL cases. Within the group of recurrently mutated genes we have identified a gene involved in apoptosis threshold regulation as well as multiple novel genes involved in B-cell transcriptional control. Further, we identify frequent mutations in the linker Histone genes HIST1H1 B-E. Finally, through incorporation of SNP array profiling data, we identify multiple candidate target genes for frequent aUPD in FL and further a list of single mutated genes (PTEN, A20, ARID1A, VAV1, TLR2 and TLR8 and others) that can be directly implicated in the pathogenesis of afflicted FL cases. Conclusion: This large genomic profiling study identifies 19 novel recurrently mutated genes in FL, including an apoptosis regulator, transcription factors and linker histones, thereby substantially broadening our understanding of the genetic basis of FL. Disclosures: Lebovic: Genentech: Speakers Bureau.

Abstract 3743 Background: Tyrosine kinase inhibitors (TKIs) are the mainstay of therapy for patients (pts) diagnosed with Philadelphia chromosome-positive (Ph+) leukemia. Failure of therapy may occur as a result of intolerance or resistance. Ponatinib is a potent oral pan-BCR-ABL inhibitor that is active against native BCR-ABL, as well as mutated forms of the protein, including the uniformly refractory T315I mutant. Methods: In this ongoing, open-label, dose escalation, phase 1 clinical trial, the safety and anti-leukemic activity of ponatinib were evaluated in pts with Ph+ leukemia and other hematologic malignancies who were refractory or resistant to available therapy or for whom no therapies were available. Pts (N=81) at least 18 yrs of age were enrolled from June 2008 through October 2010. Ponatinib was administered once daily at doses from 2–60 mg. Long-term follow-up of pts with chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL) is reported. At the time of analysis (March 23, 2012), the median follow-up among these pts was 19.4 (0.5 to 38) mos. Results: A total of 65 pts with Ph+ leukemia received ponatinib. Of those, 43 had chronic phase CML (CP-CML), 9 had accelerated phase CML (AP-CML), 8 had blast phase CML (BP-CML), and 5 had Ph+ ALL. Fifty-seven percent of pts were male, the median age was 55 yrs, and the median time from diagnosis to first dose was 6.5 (0.8 to 24) yrs. Previous therapies included imatinib (97%), dasatinib (89%), and nilotinib (55%); 94% had experienced failure of ≥2 prior TKIs and 63% had experienced failure of ≥3 prior TKIs. At study entry, baseline BCR-ABL mutations were detected in 42 of 65 (65%) pts; the most common were T315I (19/65; 29%) and F317L (7/65; 11%). Thirty-three (51%) pts remained on therapy (CP-CML [n=31]; AP-CML [n=2]). The most common reasons for discontinuation were disease progression (17%, n=11) and adverse events (AEs; 13.8%, n=9). The AEs observed in this long-term follow-up, as well as their respective incidences, are consistent with those observed in earlier analyses. The most common treatment-related AEs were rash (42%, n=27), thrombocytopenia (32%, n=21), arthralgia (20%, n=13), as well as increased serum lipase and fatigue (18%, n=12 for both). Among the 43 CP-CML pts, 42 (98%) achieved or maintained complete hematologic response (CHR), including all 26 pts who entered the study with CHR. Thirty-one (72%) pts had major cytogenetic response (MCyR), 28 (65%) with complete cytogenetic response (CCyR). Nineteen (44%) pts achieved major molecular response (MMR), including 10 pts who achieved MR4 (4-log reduction of BCR-ABL transcripts). Significant activity was also seen among CP-CML pts with T315I: CHR (12/12, 100%), MCyR (11/12, 92%), CCyR (10/12, 83%), and MMR (8/12, 67%). The duration of response among CP-CML pts ranged from 1.8 to 35.7+ mos for MCyR and from 3.7 to 29.7+ mos for MMR (median not reached for MCyR or MMR). The median follow-up among the 43 CP-CML pts was 23.3 mos; 27 of 31 CP-CML pts who had MCyR remained on study, with 25 in continuous MCyR; 18 of 19 pts who achieved MMR remained on study, with 12 in continuous MMR. Estimates (Kaplan-Meier) suggest that 83% of MCyR responders and 55% of MMR responders will maintain their response at 2 yrs. For pts with T315I, the 2-yr estimates are 82% for MCyR and 50% for MMR. Among the 22 advanced disease pts (AP-CML, BP-CML, or Ph+ ALL), 8 of 20 (40%) achieved MHR (2 pts with MHR at baseline excluded), and 7 (32%) pts had MCyR, including 4 who achieved CCyR. The median duration of MHR in advanced pts was 3.6 (0.02 to 14.7) mos. The impact of ponatinib exposure and other factors (eg, age) on the development of AEs and anti-leukemic activity was examined in exploratory multivariate analyses. The models varied by disease type, but data generally suggest that higher ponatinib plasma concentration, younger age, less pretreatment, and higher dose intensity are positively correlated (P < 0.2) with response; higher exposure was also correlated with pancreatitis, increased serum lipase, rash, and neutropenia. Pts who were younger and less heavily pretreated showed a general trend toward lower AE rates. Conclusion: Ponatinib induced high response rates in heavily pretreated pts with resistant or refractory CP-CML (including those with the T315I mutation); responses to ponatinib were durable. Ponatinib was generally well tolerated, and no new safety findings have emerged during long-term follow-up. Updated data will be presented. Disclosures: Cortes: Novartis, BMS, ARIAD, Pfizer, and Chemgenex: Consultancy, Research Funding. Kantarjian:ARIAD: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Research Funding. Shah:ARIAD, Bristol Myers-Squibb, and Novartis: Consultancy, Research Funding. Flinn:ARIAD Pharmaceuticals, Inc.: Research Funding. Hu:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Dorer:ARIAD: Employment, Equity Ownership. Rivera:ARIAD Pharmaceuticals, Inc.: Employment, Equity Ownership. Clackson:ARIAD: Employment, Equity Ownership. Turner:ARIAD: Employment, Equity Ownership. Haluska:ARIAD: Employment, Equity Ownership. Druker:ARIAD: OHSU receives clinical trial funding. Dr. Druker is currently principal investigator or co-investigator on Novartis, Bristol-Myers Squibb, and ARIAD clinical trials. His institution has contracts with these companies to pay for patient costs, nurse and da Other; Bristol-Myers Squibb: OHSU receives clinical trial funding, OHSU receives clinical trial funding Other; Novartis: OHSU receives clinical trial funding, OHSU receives clinical trial funding Other; MolecularMD: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Scientific Founder; OHSU and Dr. Druker have a financial interest in MolecularMD. OHSU has licensed technology used in some of these clinical trials to MolecularMD. This potential individual and institutional conflict of interest has been reviewed and man, Scientific Founder; OHSU and Dr. Druker have a financial interest in MolecularMD. OHSU has licensed technology used in some of these clinical trials to MolecularMD. This potential individual and institutional conflict of interest has been reviewed and man Other. Talpaz:ARIAD: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Millenium: Research Funding; Celgene: Research Funding; Deciphera: Research Funding.

Abstract 601 Background. DCC-2036 is a novel and potent tyrosine kinase inhibitor (TKI) which binds to a novel region called the switch pocket, thereby preventing BCR-ABL from adopting a conformationally active state. Efficacy against multiple imatinib-resistant BCR-ABL mutants has been demonstrated both in vitro and in vivo (Chan et al., Cancer Cell 2011;19:556). Importantly, DCC-2036 retains full potency against the T315I mutant in preclinical efficacy studies. Methods. This study was designed to find the maximal tolerated dose (MTD) of DCC-2036 when administered daily as a single-agent on a 28-day cycle. Eligible patients included adults with Ph+ CML/ALL who were refractory/intolerant to ≥2 TKI's or were T315I positive. Initially DCC-2036 capsules were administered orally once daily (QD) at increasing dose levels. Only 1 patient was enrolled in each of the lowest dose cohorts of 57mg QD and 114 mg QD. For higher doses, 3– 6 patients were enrolled into each ascending dose cohort with standard dose limiting toxicity (DLT) rules evaluating safety in cycle 1 to determine dose escalation. A transition from unformulated capsules (C) to formulated tablets (T) occurred after the 1200 mg QD dose level. Paired blood samples were obtained for PK and PD assessments. Results. 30 patients (16 males, 14 females; median age 59, range 31 – 80) with CML including 19 in Chronic (CP); 8 in Accelerated (AP) and 3 in Blast (BP) Phase were enrolled. Enrolled patients had received 1–6 prior CML treatments, and 11 patients had the T315I mutation. To date, a total of 212.5 (median 5.6; range 0.2 – 23.4) 28-day cycles were administered over 10 dose levels either as C (7 dose levels) or T (3 dose levels). The 7 C dose levels were studied first and included 57 mg QD through 1200 mg QD. Following transition to T, evaluation continued with 100 mg QD, 100 mg twice daily (BID), and 200 mg BID. Two reversible DLTs (Grade 3 peripheral neuropathy and Grade 4 lower extremity weakness) occurred during the initial treatment cycle at the 200 mg T BID dose level. Evaluation of 6 patients at the 150 mg T BID dose level determined that dose to be the MTD. Preliminary safety data show that other Grade (Gr) 3/4 adverse events (AEs) were Gr 3 slurred speech and Gr 3 eruptive nevi. Gr 1/2 AEs included dry mouth, constipation, diarrhea, paresthesias, and retinal vein occlusion. There was 1 case of Gr 2 pancreatitis that recurred on rechallenge in a patient with previous pancreatitis with nilotinib. Preliminary responses include one major molecular response in a CP patient with T315I mutation who started on capsules and transitioned to 100 mg T QD. There was one complete cytogenetic response in a CP patient at 100 mg T BID, and one partial cytogenetic response in a CP patient who started on capsules and transitioned to 100 mg T BID. One patient with AP CML and T315I mutation had a complete hematologic response at 450 mg C QD. Another patient with AP CML had a partial hematologic response after receiving 200 mg BID for 1 cycle and then downdosing to 100 mg T BID. Four out of 8 patients receiving 100 mg tablets and evaluable for efficacy (completed 3 cycles of treatment) had responses. PK results indicate dose-related, nonlinear increases in both peak plasma concentration (Cmax) and exposure (AUC). PD results reveal both acute and steady state post-treatment reductions in phospho-protein levels on Days 1 and 8. Marked reductions in pSTAT5 and pCRKL have been observed in subjects with both CP and AP and appear to be required for clinical response. Conclusion. The MTD of DCC-2036 tablets is 150 mg BID. Preliminary results suggest that DCC-2036 is well tolerated and has anti-leukemia activity in subjects with refractory CML and T315I positive disease. PD results are consistent with inhibition of BCR-ABL signaling in this first-in-man study of a switch pocket tyrosine kinase inhibitor. Disclosures: Cortes: Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Chemgenex: Consultancy, Research Funding; Deciphera Pharmaceuticals: Research Funding. Bixby:Novartis: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; GlaxoSmithKline: Speakers Bureau. Rafferty:Deciphera Pharmaceuticals: Employment. Berger:Deciphera Pharmaceuticals: Employment. Wise:Deciphera Pharmaceuticals LLC: Employment. Rutkoski:Deciphera Pharmaceuticals: Employment. Smith:Deciphera Pharmaceuticals: Employment. Van Etten:Deciphera Pharmaceuticals: Consultancy, Research Funding.

Abstract 602 Background: Ponatinib is a potent, oral, pan-BCR-ABL inhibitor active against the native enzyme and all tested resistant mutants, including the uniformly resistant T315I mutation. Initial findings of a phase 1 trial in patients (pts) with refractory hematologic malignancies have been reported. The effect of duration of treatment, prior treatment, and mutation status on response to treatment was examined in CML chronic phase (CP) pts who responded to ponatinib. Methods: An open-label, dose escalation, phase 1 trial of ponatinib in pts with hematologic malignancies is ongoing. The primary aim is to assess the safety; anti-leukemic activity is also being investigated. Pts resistant to prior treatments or who had no standard treatment available were enrolled to receive a single daily oral dose of ponatinib (2 mg to 60 mg). Subset analyses of factors impacting cytogenetic and molecular response endpoints (MCyR and MMR) were performed for pts with CP-CML. Data are presented through April 15, 2011. Results: In total, 81 pts (54% male) received ponatinib. Overall, 43 pts had CP with 34 ongoing at analysis. MCyR was observed as best response in 31/43 (72%), 27 (63%) CCyR. The median time to MCyR was 12 (3 to 104) wks. Response rates were assessed by duration of treatment (1 pt in CCyR at entry was excluded; 6 pts in PCyR had to achieve CCyR). At the 3 month assessment, 22/42 (52%) CP pts achieved MCyR; at 6 months, 24/42 (57%); at 12 months, 29/42 (69%) had MCyR. The impact of prior treatment on response and time to response was assessed. 42 pts (98%) had >2 prior TKIs and 28 (65%) ≥3 prior TKIs, including investigational agents. Of approved TKIs, all pts were previously treated with imatinib, 19 dasatinib or nilotinib after imatinib, and 21 both dasatinib and nilotinib after imatinib. MCyR rate decreased with number of prior TKIs (2 prior TKIs 13/14 [93%], ≥3 prior TKIs 17/28 [61%]) and number of approved TKIs (imatinib followed by dasatinib or nilotinib 17/19 [90%], or by both dasatinib and nilotinib 12/21 [57%]). Time to response was prolonged in pts more heavily treated with prior TKIs. Median time to MCyR increased with the number of prior TKIs and approved TKIs (2 TKIs 12 wks, ≥3 TKIs 32 wks). The effect of mutation status on response and time to response was also evaluated. At entry, 12 pts had the T315I mutation, 15 had other BCR-ABL kinase domain mutations, 12 had no mutations detected, 4 did not allow sequencing. MCyR response rate for CP pts with T315I was 11/12 (92%); for other mutations, 10/15 (67%); and no mutation, 7/12 (58%). Similarly, mutation status had an impact on time to response: median time to MCyR was 12 wks for those with T315I or other mutations and 32 wks in resistant pts with no mutation. All CP patients were evaluable for MMR. At analysis, MMR was 17/43 (40%). MMR rate was inversely related to number of prior TKIs (2 TKIs 10/14 [71%], ≥3 TKIs 6/28 [21%]), approved TKIs (imatinib followed by dasatinib or nilotinib 12/19 [63%], or by both dasatinib and nilotinib 4/21 [19%]), and was higher for T315I pts (7/12, 58%) and those with other mutations (7/15, 47%) compared with no mutation (2/12, 17%). Median time to MMR for CP pts was 97 wks; median time to MMR was shorter for pts who were less heavily treated (2 prior TKIs 24 wks) and those with T315I or other mutations (63 wks). Conclusion: In this subset analysis of the phase 1 data, ponatinib had substantial activity in all subgroups analyzed. Time on treatment, less prior therapy and kinase domain mutations were associated with higher response rates and early responses in CP pts. Cytogenetic responses improved over the first 12 months of treatment and were higher in less heavily treated pts. Disclosures: Cortes: Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Ariad: Consultancy, Research Funding. Kantarjian:Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; BMS: Consultancy, Research Funding; ARIAD: Research Funding. Shah:Ariad: Consultancy, Research Funding. Bixby:Novartis: Speakers Bureau; BMS: Speakers Bureau; GSK: Speakers Bureau. Mauro:ARIAD: Research Funding. Flinn:ARIAD: Research Funding. Hu:ARIAD: Employment. Clackson:ARIAD: Employment, Equity Ownership. Rivera:ARIAD: Employment, Equity Ownership. Turner:ARIAD: Employment, Equity Ownership. Haluska:ARIAD: Employment, Equity Ownership. Druker:MolecularMD: OHSU and Dr. Druker have a financial interest in MolecularMD. Technology used in this research has been licensed to MolecularMD. This potential conflict of interest has been reviewed and managed by the OHSU Conflict of Interest in Research Committee and t. Deininger:BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Genzyme: Research Funding. Talpaz:ARIAD: Research Funding.

Abstract 4441 Background: Ponatinib, an oral multiple tyrosine kinase inhibitor (TKI), is a potent pan-BCR-ABL inhibitor. Preliminary anti-leukemia activity of ponatinib was observed in patients with refractory chronic myeloid leukemia (CML) and advanced hematologic malignancies in a phase 1 study. Due to the QT prolongation noted with other TKIs, the effect of ponatinib on ECGs was examined in this population. Methods: This ongoing phase 1, open-label, dose-escalation, multicenter trial was designed to evaluate the safety of oral ponatinib administered to patients with advanced hematologic malignancies who failed available therapies. Patients received ponatinib orally once daily (2 mg to 60 mg) over at least 1 cycle (28 days) of study treatment unless an unacceptable toxicity or disease progression occurred. Inclusion criteria required screening QTc < 450 ms and prohibited concomitant use of medications known to prolong QTc. For the last 3 cohorts (30 mg, 45 mg and 60 mg), 12-lead ECGs (supine) were recorded using GE MAC1200 ECG recorders at the following time-points: C1D1 pre-dose (triplicate); C1D15 pre-dose (single); C2D1 pre-dose (triplicate); C2D1 2-hour post-dose (triplicate); C2D1 4-hour post-dose (triplicate); C2D1 6-hour post-dose (triplicate). Matching plasma ponatinib concentration data were also obtained at these time-points. This analysis of the cardiac safety of ponatinib only included patients who had replicate ECGs at baseline and a minimum of 1 additional on-treatment time-point with matching plasma ponatinib concentration data. The primary assessment was Fridericia corrected QT (QTcF). Results: A total of 81 patients were enrolled in the phase 1 study; 39 patients who received 30 mg or more of ponatinib daily were included in this analysis. There was no significant effect on cardiac repolarization as measured by the lack of a significant change in QTcF at all doses. Mean QTcF change from baseline was −10.9, −3.6, and −5.9 ms for the 30 mg, 45 mg and 60 mg cohorts, respectively. In addition, the pharmacokinetic-pharmacodynamic models show the slope of the relationship for QTcF versus plasma ponatinib concentration was negative, indicating no exposure-effect relationship, with an estimated QTcF mean change of −6.4 (upper confidence interval −0.9) ms at Cmax for the 60 mg group. ECG data revealed no significant change in heart rate (+3.5, −3.3, and +1.0 bpm for 30 mg, 45 mg and 60 mg cohorts, respectively). There was no signal of any effect on atrioventricular conduction as measured by the PR interval duration (mean change: −0.4, −3.6, and −0.7 ms, respectively). There was a slight, dose responsive, non-clinically significant increase in QRS duration (mean change: −0.8, +1.3, and +3.6 ms, respectively) that may be due to variability secondary to the limited sample size. There were 2 subjects with new atrial fibrillation and new T wave inversion. These morphological changes likely reflect the patient population being studied rather than any potential drug effect. Adverse event (AE) reports from the trial had 3 patients with ECG QT prolonged (2 mg, 4 mg and 45 mg) documented as a treatment-related AE; 2 were grade 3 (4 mg and 45 mg). On review, all 3 patients were found to have baseline (C1D1) prolongation of QTc or were on concomitant medications associated with QTc prolongation. There were no clinical consequences of the ECG findings in these patients. Conclusion: This analysis of the QTc intervals of patients who received ponatinib 30 mg or higher in the phase 1 clinical trial revealed there was no significant effect of ponatinib on cardiac repolarization. Disclosures: Sonnichsen: ARIAD: Consultancy. Dorer:ARIAD: Employment. Cortes:Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Ariad: Consultancy, Research Funding. Talpaz:ARIAD: Research Funding. Deininger:BMS: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding; ARIAD: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Celgene: Research Funding; Genzyme: Research Funding. Shah:Bristol-Myers Squibb: Consultancy, Research Funding; Novartis: Consultancy; Ariad: Consultancy, Research Funding. Kantarjian:Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; BMS: Consultancy, Research Funding; ARIAD: Research Funding. Bixby:Novartis: Speakers Bureau; BMS: Speakers Bureau; GSK: Speakers Bureau. Mauro:ARIAD: Research Funding. Flinn:ARIAD: Research Funding. Litwin:ARIAD: Consultancy. Turner:ARIAD: Employment, Equity Ownership. Haluska:ARIAD: Employment, Equity Ownership.

Abstract 210 Background: Despite progress in CML therapy, patients (pts) who fail 2 or more tyrosine kinase inhibitors (TKI), or pts with T315I mutation, have no available treatment options. Ponatinib (AP24534), an oral multiple TKI, is a potent pan-BCR-ABL inhibitor with activity against all tested imatinib-resistant mutants, including T315I. It also inhibits other kinases, including FLT3. Methods: An ongoing, open-label, dose escalation, phase 1 trial aims to assess the safety of ponatinib, establish a recommended dose, and investigate anti-leukemic activity. Pts with refractory hematologic malignancies were enrolled to receive a single daily dose of ponatinib in capsule or tablet form. Results: As of July 16, 2010, 67 pts (55% males) were enrolled: median age, 58 (range 26–85) years; median time from initial diagnosis to start of ponatinib, 5.2 (range 0–21) years. Diagnoses included 57 CML (42 chronic [CP], 7 accelerated [AP], 8 blast phase [BP]), 3 Ph+ acute lymphoblastic leukemia (ALL), 3 acute myeloid leukemia (AML), and 4 other hematologic malignancies. Prior therapies in CML/Ph+ pts included imatinib (96%), dasatinib (89%), nilotinib (55%); 95% and 64% failed ≥2 and ≥3 prior TKIs, respectively; 72% had BCR-ABL mutations at study entry or documented history, including 23 (38%) T315I, and 7 (12%) F317L. At the time of reporting, pts were treated at doses up to 60 mg, 43 (64%) pts remained on therapy, 24 (36%) discontinued: 8 (12%) progressive disease; 8 (12%) investigator decision; 5 (8%) unrelated deaths; 2 (3%) consent withdrawn; 1 (2%) unrelated adverse event (AE), CNS bleed. The most common drug-related AEs (≥10% any grade) were thrombocytopenia (24%), headache (14%), nausea (14%), arthralgia (13%), fatigue (13%), anemia (11%), increased lipase (11%), muscle spasms (11%), rash (11%), myalgia (10%), and pancreatitis (10%). At 60 mg, elevation of pancreatic enzymes and pancreatitis were dose-limiting toxicities (DLTs) in 4/14 treated pts. To date, 1/22 pt treated at 45 mg had a DLT (grade 3 rash). All DLTs were reversible. Overall, 48 Ph+ pts were evaluable for response (at least 1 response assessment). Of 32 evaluable CML CP pts, 30 (94%) had complete hematologic response (CHR), and 20 (63%) had major cytogenetic response (MCyR): 12 complete CyR (CCyR), 8 partial CyR (PCyR). Of 20 CML CP cytogenetic responders, 18 remain on treatment (mean duration 326 [range 142–599] days) without progression, 13 of whom had response confirmed with at least a second assessment (9 with MCyR ≥6 months), and 2 pts treated at 4 and 15 mg progressed after PCyR. Of 11 CML CP pts with T315I mutation, 11 (100%) had CHR, 9 (82%) had MCyR (8 CCyR). For 16 evaluable CML AP/BP or Ph+ ALL pts, 5 (31%) had major hematologic response (MHR), 3 (19%) had MCyR, 1 (6%) had minor CyR. Of 9 CML AP/BP or Ph+ ALL pts with T315I mutation, 3 (33%) had MHR, 2 (20%) had MCyR. Responses were also observed in heavily refractory pts with no mutations, and pts with other mutations, who are resistant to approved TKIs: 1 CCyR and 1 PCyR in 2 F317L pts who each failed imatinib, dasatinib, and nilotinib; a F359C pt who failed imatinib and nilotinib had CHR and CCyR. Overall, 13/60 (22%) Ph+ pts achieved major molecular response (MMR), including 12/42 (28%) CP pts, 6/15 (40%) with T315I mutation confirmed at baseline, 10/40 (25%) with starting doses ≥30 mg. 12 MMRs occurred in pts who were on treatment '4 months (4 MMRs ≤2 months). MMRs were also achieved in pts with M351T, F359C, F317L, M244V, G250E mutations, and 1 pt with no mutation. PD data demonstrate sustained inhibition of CrkL phosphorylation above 15 mg. Evaluation of ponatinib tablets began in April 2010 with intent to transition from capsules to tablets for future studies. To date, 10 pts received ponatinib tablets: n=9, 45 mg; n=1, 60 mg. Initial safety, PK/PD, and molecular response data suggest both dosage forms behave similarly. Importantly, at doses ≥30 mg, both result in trough concentrations >40 nM—the target concentration for inhibiting all BCR-ABL mutants, including T315I. Conclusion: ponatinib has an acceptable safety profile at clinically effective doses in this refractory population. The 45 mg dose (tablet form) was chosen as the recommended dose for further study. There is strong and continually increasing evidence of anti-leukemic activity in pts with T315I mutations, and pts resistant to second generation TKIs. Emerging MMR data demonstrate early responses in pts refractory to second line agents. Disclosures: Cortes: ARIAD: Research Funding; Chemgenex: Research Funding; Deciphera: Research Funding. Talpaz:Novartis: Honoraria. Deininger:ARIAD: Advisory Board, Consultancy, Honoraria; Novartis: Advisory Board, Consultancy, Honoraria; BMS: Advisory Board, Consultancy, Honoraria; Genzyme: Research Funding. Shah:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy. Flinn:ARIAD: Research Funding. Hu:ARIAD: Employment. Kan:ARIAD: Employment. Rivera:ARIAD: Employment. Clackson:ARIAD: Employment. Haluska:ARIAD: Employment. Kantarjian:Novartis: Consultancy, Research Funding; BMS: Research Funding; Pfizer: Research Funding.