Tallman, Martin S.

Abstract Abstract 924 Background: Therapy-related myeloid neoplasia (t-MN), including myelodysplastic syndrome and acute myeloid leukemia, has been reported at a higher frequency with chlorambucil + fludarabine as compared to fludarabine alone, but has not been rigorously studied in the context of cyclophosphamide as an alkylator agent. The intergroup prospective randomized Phase 3 trial, E2997, compared FC with F alone as initial therapy for patients (pt) with chronic lymphocytic leukemia (CLL). FC therapy led to higher complete and overall response rates and longer progression-free survival at the initial analysis (Flinn et al JCO 2007). One rationale for combining F with C is that F can inhibit repair of DNA damage induced by C. FC did cause more myelosuppression that could lead to more long-term effects on myeloid hematopoietic function, including t-MN. Methods: E2997 enrolled 278 pts, 141 on FC and 137 on F. These cases were assessed for t-MN by required reporting of these events. Baseline genetic and molecular features of CLL were available through a companion lab correlative trial for 235 pts, 122 on FC and 113 on F. Results: With median follow-up of 6.4 yrs, there have been 13 (4.7%) reported cases of t-MN, 9 after FC and 4 after F. By cumulative incidence methodology, adjusting for the competing risk of death, the rates of t-MN at 7 yr are 8.2% after FC and 4.6% after F (p=0.18 by the Gray test). Median age at study entry of the t-MN pts was 60 (range 45–80) yrs vs 61 (range 33–86) yrs among those not reported to have t-MN. Median time from initial therapy to diagnosis of t-MN was 5 (range 0.7–8) yrs and did not differ between FC and F. Ten of 13 affected pts received 6 chemotherapy cycles. Additional therapy prior to occurrence of t-MN was given to only 2 of 9 FC pts, in contrast to 3 of 4 F pts. Thus, t-MN occurred in only 1 pt treated with F and no further therapy vs 7 who received FC and no further therapy. Ten of 12 pts with available cytogenetics at diagnosis of t-MN had an abnormality of chromosome 5 and/or 7, common to alkylating agent-induced t-MN, usually (n=8) with complex karyotype. Of the 9 pts with t-MN after FC, all 7 with available CLL data had lower risk IgVH mutated disease, in contrast to 1 of 4 with t-MN after F and 44% in the entire cohort. Conclusion: Our analysis suggests that a higher incidence of t-MN has occurred after FC than after F. t-MN after FC occurred most often without additional therapy and in IgVH mutated CLL which is associated with more favorable outcome. The increased incidence of t-MN after FC in this study, usually in the absence of additional treatment, suggests that FC is more leukemogenic than F. This finding emphasizes a need for longer follow-up of toxicity and survival before concluding that FC is preferable to F as the chemotherapy backbone for initial therapy of both low and high risk CLL. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 702 Background: Large granular lymphocyte (LGL) leukemia is characterized by clonal expansion of cytotoxic T cells. Prominent clinical features include neutropenia, anemia, and rheumatoid arthritis. The terminal effector memory phenotype (CD3+/CD8+/CD57+/CD45RA+/CD62L-) of leukemic LGL suggest a pivotal chronic antigen driven immune response. LGL survival is then promoted by PDGF and IL-15 (Proc Natl Acad Sci USA 105:16308, 2008), resulting in global dysregulation of apoptosis and resistance to normal pathways of activation-induced death (Blood 112:770, 2008). These pathogenic features explain why treatment of LGL leukemia is based on immunosuppression therapy. However, no standard therapy has been established due to the absence of large prospective trials. Methods: Eligibility criteria included increased number of LGL (CD3+CD57+ cells > 400/ul or CD8+ cells >650/ul) plus evidence of clonal rearrangement of T cell receptor gene. Treatment indications included the following categories: a) severe neutropenia (ANC < 500/ul); b) neutropenia associated with recurrent infections; c) symptomatic anemia; and, d) transfusion-dependent anemia. Initial Treatment: (Step 1) consisted of methotrexate (MTX) at 10 mg/m2 po in divided doses once weekly. Prednisone was given at 1 mg/kg po × 30 days and then tapered off in the subsequent 24 days. Patients not responding to MTX received cyclophosphamide (CY) at 100 mg po daily with the same prednisone schedule (Step 2). Treatment response was assessed after four months of therapy as: complete remission (CR): normal CBC (ANC ≥ 1,500/ul, lymphocyte count <4,000/ul, hemoglobin ≥ 11 g/dl, and platelet count > 100,000/ul. In addition, LGL counts needed to be within normal range. Partial response (PR) was defined as improvement in hematologic parameters in the absence of CR: 1) ANC > 500, as long as this represented 50% increase (category a); 2) improvement in ANC ≥ 50% over baseline (category b); 3) increase in hemoglobin by ≥ 1 g/dl for at least four months duration (category c); and, 4) decrease in monthly transfusion requirement of > 50% for at least four months (category d). Progressive disease (PD) was defined as worsening of hematologic parameters in patients previously achieving PR/CR. No response (NR) was defined as lack of CR/PR. Results: Response data are shown for Step 1 (Table 1) and for Step 2 (Table 2). Overall response rate (CR/PR) for MTX was 37%. In patients failing MTX, the overall response to CY was 64%. There were two infectious deaths during Step 1 therapy. Conclusion: Data documenting efficacy of immunosuppressive therapies commonly utilized in LGL leukemia (MTX, CY, Cyclosporine) are limited to 300 patients published primarily as small retrospective studies. Such data show an overall response rate to MTX of 58% (56/96 patients). Here in the only large prospective trial we observed an overall response rate of 37%. Overall response rate of 64% for CY was not statistically different than MTX. However, given that CY response rate was observed in MTX failures, future studies should consider evaluation of CY as initial therapy. Disclosures: Off Label Use: Immunosuppressive therapies for LGL leukemia including Methotrexate and Cyclophosphamide.

Abstract Abstract 3619 Extramedullary (EM) acute myeloid leukemia (AML) is generally associated with a poor prognosis. We evaluated the baseline characteristics, response and survival characteristics in a subset of patients age ≤ 60 years with de novo AML and EM manifestations at presentation, treated on the Eastern Cooperative Oncology Group E1900 protocol: daunorubicin 45 or 90 mg /m2 x3 days in conjunction with cytarabine 100 mg/m2 × 7 days followed by risk-stratified consolidation. (Fernandez et al New Engl J Med 2009) Methods: Patient baseline characteristics were compared using Fisher's exact test if they were categories and Wilcoxon rank sum tests if they were continuous. Logistic regression models were used for complete remission (CR) rates and Cox regression models were used for overall survival (OS) and disease-free survival (DFS). The univariate models included indication of whether patient had extramedullary disease involvement, adjusted by induction treatment. The multivariate models were further adjusted for age, gender, cytogenetic risk, ECOG PS, WBC, platelets, marrow blast, hemoglobin, peripheral blasts, and secondary AML. All P values were based on 2-sided tests. Results: 58 (8.9%) of 651 patients in the study presented with evidence of EM at diagnosis. Patients with EM disease were younger and presented with higher peripheral WBC counts and circulating blasts than those without. Immunophenotyping did not demonstrate a difference in baseline CD56 expression (p=0.77). Sites of EM involvement included gingival hypertrophy (n= 33), skin (n= 7), central nervous system (n= 6), lymphadenopathy (n=6), mediastinum (n=2) and other (n=6). 3 patients had multiple sites. Cytogenetic risk in the EM subgroup was favorable (8.6%), indeterminate (inadequate/missing) (34.5%), intermediate (37.9%) and unfavorable (19%) and did not differ statistically from those without EM disease. The complete remission (CR) rates were similar for patients with EM disease compared to those patient's without, regardless of the anthracycline dose (univariate model p= 0.93; multivariate model p=0.88. DFS (patients in CR) and OS of patients with EM disease was not significantly different in the univariate (p= 0.99, p=0.49) or multivariate models (p= 0.92, p=0.37), respectively. On multivariate modeling patients with EM AML who received the standard-dose of daunorubicin had a shorter OS (HR 1.86, 95% CI 1.20 to 2.91, p=0.006). OS was not improved in EM patients treated with high-dose daunorubicin (HR 0.62, 95% CI 0.34 to 1.14, p=0.12) (Table). There was a significant difference in OS for patients with EM treated with the 90 mg/m2 dose of daunorubicin compared to patients with EM treated with the 45 mg/m2 dose (multivariate model: HR 0.30, 95% CI 0.12 to 0.76, p=0.01). Conclusion: Younger patients with de novo EM AML are sensitive to higher doses of anthracycline in induction therapy and should be treated in a similar fashion as patients without EM involvement. For both groups the higher doses of anthracycline are recommended as CR rates, DFS and OS are improved. Further evaluation of immunophenotypic and molecular/ genetic characteristics should be undertaken in this subset of patients. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 493 The International MRC UKALL XII/ECOG E2993 trial for adults with newly diagnosed acute lymphoblastic leukemia (ALL) recruited 1,914 patients to the main part of the trial from 1995 up to its closure in 2006, of whom 100 were over the age of 55 years (median 57, range 55–65). Beginning in 2003 (MRC) or 2004 (ECOG), patients with Philadelphia chromosome positive (Ph+ve) disease were entered into an Imatinib sub-study. We report here baseline characteristics, treatment course and outcomes, and discuss implications for future management strategies. Direct comparison of the 100 patients over 55 yrs with 1,814 under 55 yrs showed that the groups are comparable for gender, immunophenotype and white cell count but there is an indication that more elderly patients had Ph+ve disease (28% aged ≥55 vs 17% aged <55 of those entered before the start of the Imatinib trial; p=0.02). All patients in this trial received a 2 stage induction regimen, consisting of Daunorubicin, Vincristine, Asparaginase and Steroid followed by Cyclophosphamide, Cytarabine, 6-Mercaptopurine and Methotrexate. CNS prophylaxis with IT Methotrexate and Cytarabine was given during both phases. There was a randomisation to autograft or chemotherapy, but only a small number of patients in this age group were randomised (13 autograft and 13 consolidation chemotherapy). Outcomes Complete remission (CR) rate, event-free survival (EFS) and overall survival (OS) were all worse in the over 55 age group, and even after achieving CR, the 5-year OS rate was reduced. There were more infections in phase I induction (67% vs 45%, p<0.0001) and more deaths during induction chemotherapy (18% vs 4% p<0.0001). Excluding those who died in induction, 47% had drug dose reductions in phase I or phase II vs 27% <55 yrs (P=0.0006). Of these, Asparaginase was the most common in those aged ≥55 years, usually due to hepatotoxicity. Age p-value <55 vs ≥55 <55 ≥55 Number 1814 100 CR No v Yes p<0.0001 No 131 (7%) 27 (27%) No (died in induction) 70 (4%) 18 (18%) No (but survived induction) 61 (3%) 9 (9%) Yes 1641 (90%) 70 (70%) Unknown 42 (2%) 3 (3%) Deaths 1112/1814 (61%) 78/100 (78%) Relapses 750/1683 (45%) 36/73 (49%) Overall survival at 5 years (95% CI) 41% (38–43%) 21% (12–29%) p<0.0001 Event free survival at 5 years (95% CI) 37% (34–39%) 19% (10–27%) p<0.0001 Relapse free survival at 5 years (95% CI) 50% (48–53%) 38% (25–52%) p=0.08 Overall survival at 5 years (95% CI) in those who achieved CR 44% (41–46%) 30% (18–41%) p=0.03 In those patients aged ≥55 years, baseline factors causing a significantly worse 5-yr EFS were Ph-positivity (0% vs 23%, p=0.005), unfavourable vs standard cytogenetic risk (7% vs 26%, p=0.02) and a presenting WCC >50 × 109/l (0% vs 25% for WCC between 10 and 49.9 × 109/l and 23% for WCC <10 × 109/l, p=0.003). Infection during induction chemotherapy predicted for worse EFS; this was especially significant in those who had infection in both phases of induction (6% vs 38%, p=0.007). In those patients who received chemotherapy and were not transplanted, the differences in outcome were smaller: 5-yr OS 25% in ≥55 years vs 38% in <55 years (p=0.06), 5-yr EFS 22% vs 32% (p>0.1). Conclusion Older adults fared significantly worse than younger adults both in terms of achieving an initial CR and long-term survival. This difference cannot be explained solely by a difference in disease characteristics, and the marked increase in infection and deaths during induction reflect the inability of many older patients to tolerate the intensive level of treatment. This is also supported by the large numbers of drug omissions or dose reductions seen. Our data show that this inability to tolerate induction chemotherapy is a major contributor to the poor outcomes seen in this age group. The less marked differences between age groups when transplant patients are excluded, indicates the significant mortality associated with these procedures in older patients. Alternative approaches to consider in this group include less intensive induction with a steroid and vinca alkaloid combination, in conjunction with targeted therapies (eg Rituximab in B-lineage CD20+ disease, Imatinib Mesylate in Ph+ disease). Even amongst those patients who do achieve CR however, the long-term outcome is worse. Reduced intensity allografts may play a role in carefully selected patients in this age group, and the emerging use of MRD monitoring may also assist in selecting patients for more or less intensive approaches. Disclosures: McMillan: EUSA: Honoraria. Goldstone: Roche: Honoraria, Speakers Bureau.

Abstract This study was coordinated by the ECOG-ACRIN Cancer Research Group (Robert L. Comis, MD and Mitchell D. Schnall, MD, PhD, Group Co-Chairs) and the Medical Research Counsel, United Kingdom, and supported in part by Public Health Service Grants CA180820, CA180794, CA180790, CA189859, CA180853, CA180791, and from the National Cancer Institute, National Institutes of Health and the Department of Health and Human Services. Its content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute. Background: Late relapse in acute leukemia is considered a relatively rare event. Patients with acute myeloid leukemia (AML) are often considered cured of the disease at 3 years, but information regarding adult acute lymphoblastic leukemia (ALL) patients is scarce. Data are presented from one of the largest prospective adult ALL studies, the MRC UKALLXII/ECOG E2993, to evaluate the rate and characteristics of late relapse in ALL. For this purpose, late relapse was defined, arbitrarily, as relapse 3 years post achievement of complete remission (CR) and very late relapse was defined as relapse > 5 years from CR. Methods: The UKALLXII/ECOG E2993 was an international ALL trial conducted jointly by the MRC in the United Kingdom and ECOG in the United States. All patients received identical induction therapy, followed by central nervous system prophylaxis. Patients with a sibling donor (or a matched unrelated donor in Philadelophia-chromosome-positive ALL) were assigned to receive an allogeneic hematopoietic stem cell transplant (HSCT); all others were randomized to undergo an autologous transplant or protracted standard consolidation/ maintenance therapy. The study accrued 2109 patients from 1993 to 2008. Following relapse, patients were followed for survival. For this report only patients registered before the tyrosine kinase inhibitors era are included in the analysis. Results: 1518 study patients were eligible for this analysis, 1208 (79.6%) Philadelphia-chromosome negative (Ph-neg) and 267 (17.5%) Philadelphia-chromosome positive (Ph-pos). 1381 (91%) of the patients achieved CR; 93% of the Ph-neg and 82% of the Ph-pos. 572 patients (37.7%) underwent allogeneic HSCT. The median duration of follow-up of patients who achieved CR was 10 years. Among the 1381 patients who achieved CR, 626 (45.3%) had a documented relapse; 566 (90.4%) relapsed within 3 years of CR and 60 (9.6%) relapsed beyond 3 years ('late relapse') (Figure 1). Among these 60 patients, 18(2.9%) relapsed after 5 years ('very late relapse'). Table. Patients n CR All relapses Relapses< 3 years Relapses≥ 3 years Relapses≥ 5 years All patients 1518 1381 (91%) 626 (45.3%) 566 (90.4%) 60 (9.6%) 18 (2.9%) Ph-neg 1208 (79.6%) 1123 (93%) 485 (40.1%) 429 (88.5%) 56 (11.5%) 17 (3.5%) Ph-pos 268 (17.5%) 219 (82%) 124 (56.6%) 122 (98.4%) 2 (1.6%) 1 (0.8%) Relapse beyond 3 years occurred in 4.3% of all who achieved CR, in 5% of Ph-neg and 0.01% of Ph-pos patients. Among the 60 late relapses, the median time to relapse was 46 months. 61.7% of the late-relapse patients were males, median age was 32 years, 88.3% were B-lineage ALL and the median white cell count at diagnosis was 6000/ul. 56.7% were in cytogenetic standard risk, 8.3% at high risk and the data of 35% are unknown. The median survival for the late relapse patients was longer than for those who relapsed within 3 years. The overall survival (OS) of the 56 Ph-neg patients who relapsed beyond 3 years is shown in Fig 2. Table.Relapse > 3 yearsRelapse > 3 yearsMedian survival from relapse (months)5.411.23-year OS from relapse6.5%29%5-year OS from relapse5.6%19% Conclusions: Late relapses in adults with Ph-neg ALL are not uncommon. About 10% of relapses occur beyond 3 years and 4.3% of all ALL patients who achieved a CR can expect to have a late relapse. These data are in contrast to AML where only 1% of patients relapse beyond 3 years (Watts JM et al, 2014). Most of the late relapse patients were at standard risk and appeared to have a relatively favorable outcome post relapse. Patients with ALL, particularly those who are Ph-neg, cannot be considered as cured at 3 years and need to be closely followed. Figure 1. Time to relapse of Ph-pos and Ph-neg ALL Figure 1. Time to relapse of Ph-pos and Ph-neg ALL Figure 2. Survival from relapse for Ph-neg patients who relapsed after 3 years from CR. Figure 2. Survival from relapse for Ph-neg patients who relapsed after 3 years from CR. Disclosures Rowe: Amgen: Consultancy; BioSight Ltd.: Consultancy, Membership on an entity's Board of Directors or advisory committees; BioLineRx Ltd.: Consultancy. Douer:Gilead: Consultancy.

Abstract Background: Despite advances, the majority of patients (pts) with acute myeloid leukemia (AML) will die of their disease. Current genetics-based risk classification schemes inadequately predict outcome. We sought to determine if a novel methylation-based biomarker could enhance risk stratification in AML. Methods: Using a novel methylation assay (xMELP) validated for the clinical laboratory, we performed DNA methylation assessment at 17 previously identified prognostic loci to calculate a summary methylation statistic (M-score, Wertheim et al. Clin Chem 2015) for 166 pts with de novo AML treated at the University of Pennsylvania (UPENN). Targeted next-generation sequencing (NGS) of 33 hematologic malignancy-associated genes was performed for a 136 pt subset. The association of M-score with other prognostic variables and outcome [complete remission (CR) and overall survival (OS)] was evaluated. Median follow-up was 68.1 mos (range 1.4-150.2) among 38 survivors and 10.5 mos (range 0.1-95.2) among those (n=128) deceased. The optimal M-score for identifying groups with differing OS in the total UPENN cohort defined a binary classifier. The classifier was validated in UPENN subgroups and in a separate ECOG ACRIN E1900 trial cohort. Results: The mean and median M-score for the UPENN cohort was 92.3 (95% confidence interval [CI], 87.4-97.2) and 91.4 (range, 30.8-97.3), respectively; the M-score was not significantly associated with age, gender, specimen type, blast percent, NPM1, or FLT3-ITD. Patients with favorable cytogenetics had a lower mean M-score than those with non-favorable cytogenetics; there was no difference between intermediate and unfavorable cytogenetic groups. Univariate analyses demonstrated that a 10-unit increase in M-score was associated with a 10% increase in the hazard of death (HR 1.1; P<.0001) and a 20% increase in the odds of failing to achieve CR (OR 1.2, P<.0001). In multivariable Cox analysis, higher M-score (HR 1.1, P=.011) and older age (P=.001) were significantly associated with increased hazard of death, while NPM1+/FLT3-ITD-status (P=.031) was associated with decreased hazard of death. In a multivariable logistic analysis, higher M-score (HR, 1.1, P=.034) and older age (P=.007) were associated with increased odds of failing to achieve CR, while favorable cytogenetics (P=.030) was associated with achievement of CR. Based on the maximization of the log-rank statistic, the optimal M-score cutpoint was 86, which defined a binary risk classifier (hazard of death for high vs low M-score: unadjusted HR 2.5, P<.0001; adjusted HR 1.9, P=.003). Median OS was 26.6 vs. 10.6 mos for low and high M-score groups (Figure). The CR rates for low and high M-score groups were 84% and 61%, respectively. The performance of the M-score classifier was confirmed in pts ≤ 60 yrs with intermediate cytogenetics (log-rank P=.001, OS in high vs low M-score groups: 36.4 vs 14.0 mos) and among pts who achieved CR with initial therapy (log-rank P<.00001, OS 43.9 vs 17.2 mos). The M-score classifier identified groups with different outcome regardless of allogeneic transplant. The M-score classifier was validated in the E1900 cohort (n=383). The mean and median M-scores were similar to the UPENN cohort and M-score was significantly associated with OS on multivariable analysis (P<0.0001). The M-score classifier identified E1900 subgroups with different OS (log-rank P<.00001; OS 29.5 vs 12.6 mos), a finding confirmed in the intermediate cytogenetics group, in those aged <50 and ≥50 yrs, and among pts assigned to both standard and high dose daunorubicin. Notably, high dose daunorubicin benefited patients with high M-scores (P=.001), but not those with low M-scores (P=.328). We also evaluated the prognostic value of the M-score in the context of an extended molecular profile. Random forest analysis of the UPENN cohort showed that M-score and age are the most robust predictors of OS, while a subset of recurrent mutations (FLT3-ITD, NPM1, IDH2, TET2, TP53, NRAS, CEBPA) also contribute to prognosis, but to a lesser degree. Conclusion: The M-score and associated classifier represent promising tools for clinical decision-making in AML and deserve further investigation. The prognostic value of the M-score may be superior to mutational analysis. Optimal methods for integration of M-score, clinical and genetic information are being defined. Figure 1. Figure 1. Disclosures Loren: Merck: Research Funding. Levine:Foundation Medicine: Consultancy; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Loxo Oncology: Membership on an entity's Board of Directors or advisory committees.

Abstract Introduction: Aberrant fusion proteins involving the MLL histone methyltransferase (HMT) result in recruitment of another HMT, DOT1L, to a multi-protein complex. This leads to abnormal methylation of Histone H3 lysine 79 (H3K79) at MLL target genes and enhanced expression of leukemogenic genes such as HOXA9 and MEIS1 ( Krivstov, 2007). Pinometostat is a small molecule inhibitor of DOT1L with sub-nanomolar affinity and >37,000 fold selectivity against non-MLL HMTs. Pinometostat treatment of MLL-rearranged cells and xenografts reduced histone H3K79 methylation, decreased MLL target gene expression, and induced selective leukemia cell kill (Daigle, 2013). We report the safety, activity, pharmacokinetics (PK) and pharmacodynamics (PD) in the phase 1 trial of pinometostat in adult patients (pts) with relapsed/refractory (R/R) leukemia. Methods: This open label dose escalation/expansion study of pinometostat enrolled pts >18 years (yrs) with R/R leukemia (NCT01684150). In the dose-escalation phase, pts with AML, ALL, mixed lineage leukemia (MLL), myelodysplastic syndrome, myeloproliferative neoplasm or chronic myeloid leukemia were eligible. Eligibility in the two expansion cohorts: 90 mg/m2 (n = 17) and 54 mg/m2 (n = 6), was restricted to pts with MLL-r or MLL-partial tandem duplication (MLL-PTD). Pinometostat was given via continuous intravenous infusion (CIV) for 21 of 28 day cycles in the dose escalation phase and CIV for 28 of 28 day cycles in the expansion phases, until disease progression or unacceptable toxicity. All pts underwent serial collection of PK and peripheral blood mononuclear cells (PBMC) for PD. Leukemic blasts were isolated from PBMCs using flow cytometry and quantified for dimethylation of H3K79 (H3K79-me2) by ChIP-Seq. Results: As of 28-June-2015, 49 pts have enrolled in the dose escalation and expansion phases. Pts receiving 21/28 day infusions: 12 (n=1), 24 (n=5), 36 (n=4), 54 (n=6) and 80 mg/m2/day (n=3). Pts receiving 28/28 day infusions: 54 (n=6) and 90 mg/m2/day (n=24). Table 1. Patient Characteristics n (%) Median age, yrs (range) 51 (19 - 81) Sex (M / F) 27/22 Diagnosis MLL-r* 29 (59) AML MLL-PTD** 5 (9) MLL-wt 7 (14) ALL MLL-r* 5 (10) MLL-wt 1 (2) MLL MLL-r 1 (2) CMML MLL-r 1 (2) # of prior therapeutic regimens 1 - 2 29 (59) 3 - 4 18 (36) >4 2 (4) Prior allogeneic hematopoietic cell transplant 20 (41) * centrally confirmed by karyotype/FISH ** centrally confirmed by NGS (next generation sequencing) Adverse events (AEs) reported in >15% of pts regardless of attribution were: nausea, constipation, vomiting, abdominal pain, diarrhea, hypocalcemia, hypokalemia, hypomagnesemia, fatigue, fever, peripheral edema, mucositis, febrile neutropenia, leukocytosis, anemia, cough, dyspnea, and pneumonia. Grade ≥3 non-hematologic related toxicities include: hypophosphatemia (n=1), decreased ejection fraction (n=3), or elevated transaminases (n=1). Nine patients had leukocytosis (absolute monocyte and neutrophil 50% above baseline and above upper limit of normal) or differentiation. The median days of pinometostat treatment was 35 days (range 3-189 days). To date, objective responses observed are morphologic CR (1 pt), cytogenetic CR (MLL negative by FISH) (1 pt), PR (1 pt) and resolution of leukemia cutis (3 pts). Dose proportional PK was observed with rapid attainment of steady-state plasma concentrations (Css) on Day 1 of treatment. Plasma Css correlated with inhibition of global H3K79-me2 in PBMCs. H3K79-me2 ChIP-Seq demonstrated pinometostat induced reductions in methylation at MLL -r target genes HOXA9 and MEIS1 (median inhibition = 61%: range = 13-91%) in all 9 pts analyzed to date from the 90 mg/m2 expansion cohort. Inhibition of H3K79-me2 in leukemic blasts is consistent with DOT1L suppression. PK-PD relationships in both expansion cohorts using both free and total plasma Css are being explored. Conclusions: Pinometostat administered as a CIV to adults with R/R leukemia has an acceptable safety profile. Clinical activity as demonstrated by both marrow responses and resolution of leukemia cutis were observed. In addition, analysis of H3K79-me2 by ChIP-Seq demonstrated PD reductions in the methylation of MLL-r target genes following pinometostat exposure, as expected from DOT1L inhibition. Relationships between PK exposure, reductions in pinometostat induced H3K79-me2 levels and clinical response are being interrogated. Disclosures Stein: Seattle Genetics: Consultancy; Agios Pharmaceuticals: Consultancy. Rizzieri:Teva: Other: ad board, Speakers Bureau; Celgene: Other: ad board, Speakers Bureau. Berdeja:Novartis: Research Funding; Takeda: Research Funding; BMS: Research Funding; Curis: Research Funding; MEI: Research Funding; Abbvie: Research Funding; Onyx: Research Funding; Array: Research Funding; Janssen: Research Funding; Celgene: Research Funding; Acetylon: Research Funding. Altman:Novartis: Other: Advisory board; Spectrum: Other: Advisory board; Ariad: Other: Advisory board; Seattle Genetics: Other: Advisory board; BMS: Other: Advisory board; Astellas: Other: Participation in an advisory board December 2013. Thomson:Epizyme, Inc: Employment. Blakemore:Epizyme: Employment. Daigle:Epizyme, Inc: Employment. Fine:Epizyme: Employment. Waters:Epizyme, Inc: Employment. Armstrong:Epizyme, Inc: Consultancy. Ho:Epizyme, Inc: Employment.

Abstract Abstract 4013 Background: In recent years, azacytidine (AZA) has become the standard of treatment for high risk myelodysplasia (MDS). The approved schedule of AZA uses a 75mg/m2/d s.c. regimen for 7 days based on the CALGB-9221 (Silverman, JCO 2002) and the AZA-001 studies (Fenaux, Lancet Oncol 2009). The clinical response rates after AZA have been extensively presented but there is only limited data on the rates of cytogenetic response (CyR). Based on the review of the literature, there are no specific cytogenetic data published on prospective trials. Methods: We based our analysis on a randomized phase 2 study from the US Leukemia Intergroup (E1905 study, NCT00313586) testing 10 days of AZA (50mg/m2/d s.c.) vs 10 days of AZA+ the histone deacetylase inhibitor entinostat (4 mg/m2/d PO days 3 and day 10). MDS, CMML, and AML with myelodysplasia-related changes were included. This analysis includes all patients with cytogenetic abnormalities (at baseline or acquired following treatment) with available cytogenetic follow-up (cycle 6). Of 150 patients, 70 demonstrated baseline cytogenetic abnormalities. To date, forty patients (27 MDS and 13 AML) were evaluable for both time points. Karyotypes were performed at local laboratories, and reviewed centrally (RPK and GH). Cytogenetic response was assessed using IWG 2000 (Cheson et al, Blood 2000) criteria. Results: The clinical response rate (CR+PR+ trilineage HI) according to IPSS cytogenetic risk stratification were of 20%, 33%, and 35% for favorable, intermediate and poor cytogenetic risk groups respectively (p=NS). Patients with Chr 7 abnormalities (i.e. -7 or -7q, n=18) had a response rate of 28% including 17% CR. Of patients with complete cytogenetic data, the rate of overall CyR was 52% (n=21): 22% (n=9) complete CyR, 30% (n=12) partial CyR. This represents a complete CyR of 13% and a partial CyR of 23% as a proportion of all treated patients with initial cytogenetic abnormalities (including those who did not receive six cycles of therapy). To date, confirmatory FISH analyses were available for 4 patients with CyR (2 CCyR and 2 PCyR). All four had complete clearance of their cytogenetic clone. Among the cytogenetic responders, 15 had MDS and 6 had AML (p=NS). CyR did not differ between the two treatment arms. CyR and clinical response were highly correlated (p<0.001): all patients with complete CyR and 7/10 partial CyR had a clinical CR. Only 3 patients (1 CCyR and 2 PCyR) had a CyR without associated clinical response. Among 8 patients with cytogenetic progression, 3 pts showed increased frequency of a known aberration and 5 showed new or additional aberration including 2 cases involving Chr7. 65 AZA-treated patients from AZA001 had comparable cytogenetic results available. Only 3 patients experienced complete CyR 4.6% with 33.8% partial CyR (n=22). In contrast, the reported rate of clinical response was similar in the two studies. Complete CyR were more frequent in the E1905 10 days AZA schedule compared to the 7 days AZA schedule (p=0.007). There was no difference in overall CyR between the two studies. Conclusions: Both the standard AZA schedule and the 10 day schedule administered on E1905 lead to high rates of cytogenetic response. The novel schedule explored in E1905 demonstrated a particularly high rate of complete CyR (22%) with complete clearance of abnormal clone by FISH in 4 tested patients. Further prospective comparison of different AZA schedules will be needed to confirm this higher rate of complete CyR and determine its clinical significance. Disclosures: Beach: Celgene: Employment. Gore:Celgene: Consultancy, Research Funding, stock options; Syndax: Consultancy.

Abstract Introduction: High-dose cytarabine consolidation chemotherapy for acute myeloid leukemia (AML) induces profound transient myelosuppression. Thrombocytopenia is a limiting factor in chemotherapy administration for maintaining dose intensity and schedule as thrombocytopenic-related hemorrhage may contribute to significant morbidity and mortality. Therapeutic and prophylactic platelet (plt) transfusions remain the treatment of choice but the benefits typically last only 3-7 days, are expensive, time consuming, and may induce alloimmunization and transmit infection. PrE0901 was a phase I multi-center study to evaluate the safety and toxicity of eltrombopag, an orally bioavailable thrombopoietin (TPO) receptor agonist, for plt recovery in AML patients (pts) receiving consolidation therapy. Methods: The primary objectives were to determine the safety, tolerability, and optimal dosing of eltrombopag while describing the kinetics of plt recovery in AML pts receiving intensive consolidation. Plt recovery was defined as a sustained plt count of ≥ 20 x 109/L following the nadir with no plt transfusions in prior 7 days or a continued upward trend in plt count for at least 2 successive measurements despite no plt transfusions in 48 hours. We used a standard 3+3 design utilizing a novel dose escalation/de-escalation strategy for pts in either first or second complete remission, ≥18 and ≤70 years of age, who had an ECOG performance status of 0-2. Cytarabine was administered at 3 g/m2 (1.5 g/m2 for pts >60 years) IV over 3 hours twice daily on days 1,3,5. Eltrombopag at assigned dose was administered with a first cycle of cytarabine only. Planned eltrombopag dose levels -2, -1, 1, 2, 3, 4, and 5 were 50, 100, 150, 150, 150, 200, and 300 mg, respectively (Table 1). Eltrombopag was to start on days X, X, 3, -1, -5, -5, and -5 relative to day of cytarabine start and levels -2, -1, 1, 2, 3, 4, and 5, respectively, with day X being variable depending on timing of observed dose limiting toxicities (DLTs). The eltrombopag was continued until plt recovery or for up to 35 consecutive days, whichever occurred first. An exploratory objective was to determine if eltrombopag had an effect on TPO and EPO blood concentrations in this setting. Results: Accrual began on July 31, 2012 and the trial closed on January 8, 2016 upon recommendation after an independent Data and Monitoring Committee reviewed a separate trial of eltrombopag therapy in MDS which demonstrated futility. 104 pts were screened. 54 declined participation and 35 were deemed medically ineligible. A total of 15 eligible pts were enrolled; 14 were treated on study with one pt being withdrawn prior to starting treatment due to infection. Three pts were treated at each of dose levels 1-4 and two were treated on dose level 5. No DLTs were observed. Median time to plt recovery of all pts treated on study was 22.5 (range 16-43) days. Pts in cohort 1 dosed with eltrombopag 150 mg daily starting on day 3 of consolidation demonstrated the fastest plt recovery (median =19 days; range 19, 19, 19) compared to cohort 2 who received 150 mg daily starting on day -1 of consolidation and recovered the slowest (median 23 days; range 16, 23, 43). Dose escalation in terms of starting eltrombopag further in advance of chemotherapy exposure as within cohort 3 (150 mg starting day -5) was associated with a median plt recovery of 27 (range 22, 27, 27) days. Eltrombopag dose intensification with cohort 4 at 200 mg daily and cohort 5 at 300 mg daily was associated with median plt recoveries of 24 (range 18, 24, 26) and 23 (range 19, 27) days, respectively. Kinetics of plt recovery for all cohorts are represented in Figure 1 and duration of eltrombopag exposure for each individual patient is represented in Table 2. Conclusions: Endogenous cytokine (TPO and EPO) levels varied inversely with plt and hematocrit values and did not appear to be affected by eltrombopag dose / schedule (details to be provided at ASH Annual Mtg). Unusually high screen fail numbers warrant examination to guide future trial design in the post-remission setting. The addition of eltrombopag to high-dose cytarabine consolidation therapy was well-tolerated and no DLTs were observed. The results for cohort 1 [eltrombopag 150 mg daily starting on day 3 of consolidation] demonstrated the fastest plt recovery. Further investigation is needed to define the optimal role, dose, and schedule of eltrombopag in the treatment of chemotherapy associated myelosuppression. Disclosures Strickland: Alexion Pharmaceuticals: Consultancy; Ambit: Consultancy; Baxalta: Consultancy; Boehringer Ingelheim: Consultancy, Research Funding; CTI Biopharma: Consultancy; Daiichi Sankyo: Consultancy; Sunesis Pharmaceuticals: Consultancy, Research Funding; Abbvie: Research Funding; Astellas Pharma: Research Funding; Celator: Research Funding; Cyclacel: Research Funding; GlaxoSmithKline: Research Funding; Karyopharm Therapeutica: Research Funding; Sanofi: Research Funding.

Abstract Background: Persistence of minimal residual disease (MRD) after induction, consolidation and salvage therapies is an independent poor prognostic marker in AML. The bone marrow (BM) microenvironment is a protective niche that promotes chemotherapy resistance of leukemia cells. This residual subset of chemotherapy-resistant cells present during remission eventually contributes to the leukemia relapse/persistence. Adhesion of AML cells to BM stroma is dependent on the CXCR4 receptor binding to its ligand CXCL12. High levels of CXCR4 expression correlate with poor survival in AML. It is postulated that blocking the CXCL12/CXCR4 axis will dislodge AML cells from the protective microenvironment and, when combined with chemotherapy, may improve the response to therapy. BL-8040 (BKT140) is a short peptide which inhibits the binding of CXCR4 to CXCL12, resulting in mobilization of leukemic blasts from the BM to the peripheral blood (PB). BL-8040 has strong affinity for the CXCR4 receptor with long receptor occupancy and as a single agent induces differentiation and apoptosis of leukemia cells in preclinical models. A clinical trial assessing the safety and efficacy of BL-8040 in combination with cytarabine (Ara-C) for the treatment of relapsed/refractory AML patients was recently completed (NCT01838395). Here we report results from correlative studies done on samples from patients who participated in this trial. Objective: To assess BL-8040 single agent anti leukemia effects in relapsed/refractory AML. Method: Patients received a once daily SC dose of BL-8040 monotherapy on days 1-2 followed by the same dose of BL-8040 plus Ara-C (1.5g/m2 for patients ≥60; 3g/m2 for patients <60) per day on days 3-7. Six dose levels of BL-8040 (0.5 - 2.0 mg/kg) were tested. PD parameters such as mobilization of leukemic blasts and induction of differentiation and apoptosis were assessed after monotherapy with BL-8040 using frequent PB sampling and BM aspirates at baseline and on day 3 prior to Ara-C administration. Results: 45 patients (including 3 receiving compassionate use BL-8040) with a median age of 61 yrs were treated. The majority of patients had poor risk disease with 24% secondary AML and 17% with prior allogeneic stem-cell transplantation. Most patients were heavily pretreated with 19% relapsing after a short first remission (CR1 ≤12 months), 17% had ≥2 relapses and 45% refractory to 1-2 inductions. The CR+CRi rate was 38% in subjects receiving BL-8040 dose ≥1.0 mg/kg (n=39). Ongoing follow-up (FU) of responding patients (expansion phase; N=19) shows median EFS of 9.3 months (range 4.3-12.8 months). At the time of this analysis 10/19 patients are alive with a FU range of 0.96 - 12.8 months. FACS analysis revealed that BL-8040 monotherapy triggered an average 4.3-fold increase of immature AML blasts (CD45+Low/CD34+/CD117+/HLA-DR+) in PB (i.e., mobilization). Response to treatment was associated with more robust mobilization of AML blasts following BL-8040 monotherapy (responders 9.5 vs non-responders 1.7 fold median). Preferential mobilization of AML blasts over normal cells (4.7 fold vs. 1.4 fold, respectively) was confirmed by FISH analysis in a subset of patients with informative cytogenetic abnormalities. Induction of granulocytic differentiation of immature leukemia progenitors (2.5 fold) in the BM following BL-8040 monotherapy was noted. Finally, induction of AML blasts apoptosis (40% increase) by BL-8040 alone was evident by FACS in day 3 (pre-araC) bone marrow biopsies. Conclusions: The data demonstrate that sustained blockade of the CXCR4-CXCL12 axis with BL-8040 is safe and well tolerated and when given in combination with Ara-C improves the response rate achieved historically with Ara-C alone. In addition, treatment with BL-8040 as a single agent rapidly and efficiently induces mobilization, differentiation and cell death of AML blasts. This selective effect on chemotherapy-resistant cells may be translated into reduction of residual disease arguing for incorporation into front-line trials and such studies are ongoing. Disclosures Foran: Millennium Pharmaceuticals, Inc.: Research Funding; medscape: Honoraria; karyopharm: Honoraria; pfizer: Honoraria; novartis: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. DiPersio:Incyte Corporation: Research Funding. Peled:Biokine Therapeutics: Employment. Abraham:Biokine Therapeutics Ltd: Employment. Pereg:BioLineRx Ltd: Employment. Vainstein:BioLineRx Ltd.: Employment. Oberkovitz:BioLineRx Ltd.: Employment. Aharon:BioLineRx Ltd.: Employment. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding.