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Abstract Background: Pev (TAK-924/MLN4924), a novel investigational NAE inhibitor, enhances the anti-leukemic effects of aza in AML cell lines and murine xenografts (Smith et al, Blood 2011). Single-agent pev activity was confirmed in relapsed/refractory AML pts (Swords et al, Br J Haematol 2015). This open-label, multi-center, dose-escalation study (NCT01814826) investigated pev + aza in treatment-naïve older AML pts. Dose-limiting toxicities (DLTs)includedG2 hyperbilirubinemia and G4 AST elevation (n=1 each) at pev 30 mg/m2. The maximum tolerated dose (MTD) for the combination was pev 20 mg/m2 + aza 75 mg/m2 (Swords et al, ASH 2014).We present updated safety/efficacy results for the MTD cohort (fully enrolled). Methods: Primary objectives included safety and tolerability assessments of pev + aza in addition to defining the MTD. Secondary objectives included pharmacokinetics (PK) and disease response assessments. Treatment-naïve pts ≥60 yrs unlikely to benefit from standard induction therapy (defined by ≥1 of: antecedent hematologic disease; known adverse cytogenetic risk; ECOG PS 2; ≥75 yrs), received pev 20 or 30 mg/m2 IV on d 1, 3 and 5, + fixed-dose aza (75 mg/m2 IV/SC) on d 1-5, 8 and 9, every 28 d until disease progression or unacceptable toxicity. Adverse events (AEs) were assessed per NCI-CTCAE v4.03; response per IWG criteria for AML. Bone marrow samples were collected at screening to assess cytogenetic risk (CALGB) and mutation profile; serial samples for PK analysis were drawn in cycle 1. Results: Demographics:As of May 17 2016, 61 pts (median age 75 yrs [range 61-89]; 54% male; 77% ECOG PS 0/1, 23% ECOG PS 2; 57% de novo, 43% secondary AML; median marrow blasts 36% [range 5-92]) had received pev 20 mg/m2, of whom 48% had intermediate-, 30% adverse-, and 3% favorable-risk cytogenetics. Safety/PK: Pts received a median of 4 cycles (range 1-33), and 23/61 pts (38%) received ≥6 cycles of pev + aza. The most common AEs were constipation (46%), nausea (44%), fatigue (43%), and anemia (39%). Fifty pts (82%) experienced ≥G3 AEs; the most frequent (≥15%) were anemia, febrile neutropenia (each 28%), thrombocytopenia (21%), neutropenia (18%), and pneumonia (15%). ≥G3 AST/ALT elevations were reported in 5% of pts. Forty-one pts (67%) experienced serious AEs; the most frequent (≥10%) were febrile neutropenia, neutropenia (each 25%), and pneumonia (11%). Two pts discontinued due to pev related toxicity (G3 febrile neutropenia). There were 11 on-study deaths unrelated to study therapy. In the MTD expansion phase (n=55), 2 pts experienced DLTs of transient G3/4 transaminase elevations, and were successfully re-challenged following dose reduction to remain on study. Pev PK was not altered by the addition of aza. Responses: Overall response rate (ORR) in 52 response-evaluable pts was 60% (18CR, 5CRi, 8PR; Figure 1), with a median duration of remission of 8.3 mos (95% CI: 5.75, 12.06); 19/31 (61%) responses occurred within the first 2 cycles.Of the 23 pts with CR/CRi, 14 had responses lasting ≥4 cycles, 2 went on to have allogeneic stem cell transplant, 9 had intermediate-, 7 adverse-, and 1 favorable-risk cytogenetics. ORR was: 64% (14/22; 7CR, 3CRi, 4PR) vs 57% (17/30; 11CR, 2CRi, 4PR) for pts with low- (<30%) vs high- (≥30%) marrow blasts; 58% (18/31; 11CR, 3CRi, 4PR) vs 62% (13/21; 7CR, 2CRi, 4PR) for de novo vs secondary AML pts; 61% (14/23; 8CR, 1CRi, 5PR) vs 50% (8/16; 5CR, 2CRi, 1PR) for intermediate- vs adverse-risk cytogenetic pts; 83% (19/23; 14CR, 2CRi, 3PR) vs 41% (12/29; 5CR, 3CRi, 4PR) for pts who received ≥6 cycles vs <6 cycles of aza, respectively. Responses were seen in pts with typically refractory disease; 7/11 pts with TP53 mutations achieved either a CR/CRi (n=3) or PR (n=4); 4 stayed on study for >10 cycles. After a median follow-up of 16.4 mos, 6-mo survival was 52%. Median overall survival was: 7.0 mos for the MTD cohort; 8.5 vs 5.2 mos for pts with low- (<30%) vs high- (≥30%) marrow blasts (Figure 2); 5.6 vs 11.2 mos for de novo vs secondary AML pts (Figure 3); and 16.1 vs 5.3 mos for pts aged 65-74 vs ≥75 yrs, respectively. Conclusion: Pev + aza was well tolerated. Response rates and durable remissions were observed with limited additional toxicity beyond what is expected for aza alone. The timing and frequency of responses suggests benefit from the addition of pev compared to aza alone (Dombret et al, Blood 2015). At the time of writing, a randomized phase 2 study in low-blast AML/high-risk myelodysplastic syndromes is ongoing. Disclosures Coutre: Janssen: Consultancy; Pharmacylics, LLC, an AbbVie Company: Consultancy, Research Funding; AbbVie: Research Funding. Zeidner:Tolero: Research Funding; Merck: Research Funding; Takeda: Research Funding; Otsuka: Consultancy; Agios: Honoraria. Foran:medscape: Honoraria; Millennium Pharmaceuticals, Inc.: Research Funding; novartis: Honoraria; pfizer: Honoraria; karyopharm: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. Cruz:Millennium Pharmaceuticals, Inc.: Honoraria; Millennium Pharmaceuticals, Inc.: Speakers Bureau. Erba:Novartis: Consultancy, Speakers Bureau; Celator: Research Funding; Daiichi Sankyo: Consultancy; Celgene: Consultancy, Speakers Bureau; Juno: Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding; Pfizer: Consultancy; Seattle Genetics: Consultancy, Research Funding; Incyte: Consultancy, DSMB, Speakers Bureau; Amgen: Consultancy, Research Funding; Agios: Research Funding; Sunesis: Consultancy; Gylcomimetics: Other: DSMB; Astellas: Research Funding; Ariad: Consultancy; Jannsen: Consultancy, Research Funding. Berdeja:Abbvie, Acetylon, Amgen, Bluebird, BMS, Calithera, Celgene, Constellation, Curis, Epizyme, Janssen, Karyopharm, Kesios, Novartis, Onyx, Takeda, Tragara: Research Funding. Tam:Millennium Pharmaceuticals, Inc.: Consultancy. Vardhanabhuti:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Dobler:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Faessel:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Dash:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Sedarati:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Dezube:Millennium Pharmaceuticals Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment, Equity Ownership. Savona:Takeda: Research Funding; Amgen Inc.: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; Sunesis: Research Funding; Ariad: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees.

Abstract Background: The incidence of secondary Acute Lymphoblastic leukemia (sALL) after a preceding first primary solid organ malignancy (1M) is not well defined. We undertook a Surveillance Epidemiology and End Results (SEER)-based analysis to describe the occurrence of sALL among adult patients with a history of common 1M's. We also evaluated differences in sALL survival on the basis of age, the site and extent of 1M, and for evidence of any underlying racial/ethnic disparity. Methods: The SEER-18 database (1973-2011) was interrogated for the current study. All confirmed cases of ALL (ICD-O-3 codes: 9811, 9812, 9814-18, 9826-28, 9835-37) in adult patients (age ≥18 years) were identified. De novo ALL vs. sALL was determined by using the SEER variable ‘First Malignant Primary Indicator'. 1M prior to the diagnosis of ALL was identified by merging all SEER databases together by patient ID number. Those with 1M stage of ‘in situ'; sALL cases reported <2 months after the diagnosis of 1M; and those with “unknown” information on 1M (n=471) were excluded. Standard race/ethnicity categories were used. Latency interval (time from diagnosis of 1M to sALL) was calculated for all patients. Overall survival (OS) was calculated as the interval from diagnosis to death, or censored at date of last contact, December 31st 2011, or 5 years after diagnosis, whichever came first. A proportional hazards Cox regression model was performed to evaluate the impact of sALL and latency on OS, adjusting for age at diagnosis, race/ethnicity, marital status, birthplace, SEER registry site, and year of diagnosis. All statistical tests were two-sided and utilized the SAS software (v9.4) with a two-sided significance level of 0.05. Results: A total of n=8,398 adult patients with primary ALL (1ALL) and n=414 with sALL were identified. Patient characteristics were significantly different between 1ALL & sALL (Table). Males comprised 49.8% of sALL patients as compared to 58% with 1ALL. Age at diagnosis of ALL was also significantly different, with 55.5% of sALL patients being ≥65 years as compared to 51.4% of 1ALL observed in the 18-44 years age group. Non-Whites comprised 27.3% of sALL and 40.4% of 1ALL, with Hispanics having the most differential distribution of 13.3% and 24.6%, respectively in the two groups. Distribution of sALL patients by latency from 1M is shown in Table. The majority of sALL patients had a diagnosis of local/regional (rather than advanced stage) 1M (Table). sALL patients had a significantly inferior OS when compared to 1ALL (HR 1.211, 95%CI 1.079-1.359) (Median OS 14 months vs. 18 months, Figure). sALL cases with longer latency interval (>5 year) appeared to have better median OS compared to shorter latency intervals, but this difference was not statistically significant (p=0.53). Conclusion: We have performed the largest population-based analysis identifying sALL after 1M, demonstrating that sALL patients are older and have significantly worse OS than 1ALL. We noted a lower relative incidence of sALL in Hispanics as compared with 1ALL, while the converse was true for Whites. Although detailed treatment data (specifically with respect to chemotherapeutic agents) is not available in SEER, it is possible that treatment for local/regional 1M - presumably adjuvant in nature - may be associated with the risk of sALL. Further analyses are required and are ongoing to confirm the relative incidence after specific 1M's, and the impact of both specific treatment modalities and the era of treatment for 1M on risk of developing sALL. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures No relevant conflicts of interest to declare.

Abstract Background CD19, a B cell-specific marker, is expressed in the majority of patients with B-lineage leukemia and non-Hodgkin lymphoma. SGN-CD19A is a novel antibody-drug conjugate (ADC) composed of a humanized anti-CD19 monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin F (MMAF) via a maleimidocaproyl linker. Methods This first-in-human, phase 1, open-label, dose-escalation study is investigating the safety, tolerability, pharmacokinetics, and antitumor activity of SGN-CD19A in adult and pediatric patients with relapsed or refractory B-cell leukemia or highly aggressive lymphoma (NCT 01786096). Eligible patients must have B-cell acute lymphoblastic leukemia (B-ALL) or lymphoma (B-LBL), Burkitt leukemia or lymphoma, and be relapsed or refractory to at least 1 prior systemic regimen. A modified continual reassessment method is used for dose allocation and maximum tolerated dose (MTD) estimation for both pediatric and adult patients. The study is evaluating 2 schedules of IV SGN-CD19A administration: weekly (Days 1 and 8 of 21-day cycles; 0.3-4.5 mg/kg) or every 3weeks (q3week; 0.5-6 mg/kg). Results To date, 49 patients with relapsed or refractory leukemia (n=40) or lymphoma (n=9) have been treated. Median age of adult (n=38) and pediatric patients (n=11) was 37 and 11 years (range, 18-74 and 1-16), respectively. Patients received a median of 2 prior therapies (range 1-9); 14 patients (29%) previously received an allogeneic stem cell transplant. On the weekly schedule, 39 patients (28 adult, 11 pediatric) have been treated, and the median number of cycles is 2.5 (adults; range, 1-12) or 1 (pediatric; range, 1-4). On the q3week schedule, 10 adult patients have been treated, and the median number of cycles is 2.5 (range, 1-4) to date. Six patients remain on study treatment (3 on each schedule), and enrollment is ongoing. The toxicity profiles were similar across both dosing schedules (0.3-2.3 mg/kg weekly and 4-5 mg/kg q3week) and across adult and pediatric patients. The most frequently reported drug-related AEs included pyrexia, nausea, chills, vomiting, blurred vision, and dry eye. Frequent infusion-related reactions were observed early in the study, and recommendation for premedication was instituted. Ocular events were also observed and treated with ophthalmic steroids; steroid eye drop prophylaxis was instituted with each dose. Corneal findings consistent with superficial microcystic keratopathy were observed in 13 adult patients (34%) and in 1 pediatric patient (9%). Grade 3/4 corneal AEs have been observed in 4 adult patients; the majority of these events have resolved or improved to Grade 1 or 2. Steroid eye drop prophylaxis has reduced the incidence of Grade 3/4 events at this interim analysis. Three DLTs were observed: acidosis in a pediatric patient at 1 mg/kg weekly, cytokine release syndrome in an adult patient at 2 mg/kg weekly, and asymptomatic Grade 4 AST elevation in an adult patient at 5 mg/kg q3week. MTD has not yet been determined. SGN-CD19A ADC pharmacokinetic profiles indicate target-mediated drug disposition in patients with leukemia. Plasma ADC exposures generally increased with doses and were lower than those in patients with lymphoma. To date, no objective responses were observed in 9 efficacy-evaluable pediatric patients or in 3 adult patients with Burkitt lymphoma/leukemia. However, in efficacy-evaluable adult patients with B-ALL/B-LBL, objective responses were observed in 6 of 25 patients treated on the weekly schedule (3 CR, 2 CRp, 1 PR), and in 4 of 8 patients treated on the q3week schedule (2 CR, 2 CRp). Of 8 B-ALL patients with CR/CRp, 6 were MRD negative. Conclusions MTDs have not yet been identified, and dose escalation continues on weekly and q3week schedules. SGN-CD19A has been generally well tolerated. At this interim analysis, objective responses were observed in 30% (10 of 33) of heavily pretreated adult B-ALL/B-LBL patients dosed weekly or q3week. Evidence of activity in relapsed/refractory patients and lack of overlapping toxicities suggest opportunities for combination with conventional anti-leukemic therapies in lymphoblastic malignancies. Disclosures Fathi: Ariad: Consultancy; Exelixis: Research Funding; Takeda pharmaceuticals International Co.: Research Funding; Seattle Genetics, Inc.: Consultancy, Research Funding. Off Label Use: SGN-CD19A is an investigational agent being studied in patients with B-cell malignancies. SGN-CD19A is not approved for use. . Chen:Seattle Genetics, Inc.: Consultancy, Research Funding, Speakers Bureau, Travel expenses Other. Trippett:OSI Pharmaceuticals: Research Funding; Seattle Genetics, Inc.: Research Funding. O'Brien:Seattle Genetics, Inc.: Research Funding. DeAngelo:Seattle Genetics, Inc.: Research Funding. Shah:Pharmacyclics: Consultancy; SWOG: Consultancy; Celgene: Consultancy, Speakers Bureau; NCCN: Consultancy; Seattle Genetics, Inc.: Research Funding; Janssen: Consultancy. Cooper:Seattle Genetics, Inc.: Research Funding. Foran:Seattle Genetics, Inc.: Research Funding. Hale:Seattle Genetics, Inc.: Research Funding. Pressey:Seattle Genetics, Inc.: Research Funding. Silverman:Seattle Genetics, Inc.: Research Funding. Tibes:Seattle Genetics, Inc.: Research Funding. Kim:Bayer: Consultancy; Eli Lily: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding. Albertson:Seattle Genetics, Inc.: Employment, Equity Ownership. Sandalic:Seattle Genetics, Inc.: Employment, Equity Ownership. Zhao:Seattle Genetics, Inc.: Employment, Equity Ownership. Borate:Genoptix: Consultancy; Seattle Genetics, Inc.: Research Funding.

Abstract 5-azacitidine (5-AZA) is standard of care in the first-line setting for higher-risk patients with Myelodysplastic Syndrome (MDS). However, 40-50% of patients are refractory to 5-AZA and most responders ultimately demonstrate disease progression within 2 years, often progressing to AML. For patients refractory to 5-AZA, 2-year survival probability is low (15%). Thus, there is a need for more effective initial and second-line therapies for patients with higher-risk MDS. The Inhibitors of Apoptosis (IAP) Proteins are a family of molecules that suppress apoptotic cell death. Expression of IAPs is dysregulated in MDS, suggesting a potential path for therapeutic intervention. SMAC (second mitochondrial activator of caspases) is an IAP antagonist, resulting in caspase activation, inhibition of NF-kB and increased apoptosis. Birinapant is a potent bivalent SMAC mimetic with improved tolerability and therapeutic index compared to other SMAC mimetics. This Phase Ib/2a study was designed primarily to determine the MTD and recommended Phase 2 dose and schedule of birinapant in combination with 5-AZA in patients with higher-risk MDS who are naïve or have relapsed or are refractory to 5-AZA. To date, 11 patients have been enrolled in the Phase 1b portion of the study, including 7 with IPSS classification high-risk MDS (5 male, 2 female; median age 75, range 64-82) and 4 with intermediate-risk MDS (2 male, 2 female; median age 72.5, range 65-84). All patients received standard 5-AZA, administered via either intravenous (IV) or subcutaneous (SC) routes, at 75 mg/m2 for 7 days of a 28-day cycle in combination with birinapant. Birinapant was administered IV twice weekly (Days 1 and 4) for either 3 of 4 weeks or 4 of 4 weeks per 28-day cycle at a dose of 13 mg/m2. No cycle 1 dose-limiting toxicities have been observed. Adverse events ≥ Grade 2 observed in two or more patients and judged to be related to treatment were rash/pruritis (Grade 2, 2 patients), thrombocytopenia (Grade 4, 2 patients) and neutropenia (Grade 4, 1 patient; Grade 3, 1 patient). Two SAEs, Grade 3 abdominal soft tissue necrosis with abdominal pain in the area of subcutaneous injections of 5-AZA, and Grade 3 cellulitis were judged to be related to treatment. These local injection site reactions/cellulitis were more severe than usually expected with SC 5-AZA, suggesting an on target pharmacodynamic (TNF mediated) localized synergistic effect in skin, but were not observed with IV administration. Both occurred after cycle 1 and were not considered DLTs. Data showing inhibition of NF-kB, a downstream pro-survival molecule activated by IAPs, in circulating blast cells from patients treated with birinapant at a dose of 13 mg/m2 twice weekly for 3 weeks out of 4, suggests that birinapant is pharmacologically active at this dosing schedule. Based on these and other pharmacodynamic data, despite not determining the formal MTD, the Phase 2 dosing regimen has been established as birinapant administered at 13 mg/m2 IV twice weekly for 3 weeks of a 28-day cycle in combination with 5-AZA at 75 mg/m2 by IV infusion for 7 days of a 28-day cycle. Although not a primary endpoint, evidence of clinical activity in 5-AZA resistant/refractory patients was observed in 2 of 11 patients to date, with an additional good clinical response in a 5-AZA naive high-risk MDS/CMML patient. One patient with prior 5-AZA-refractory MDS (cytogenetics: hypodiploid and +11q) showed bone marrow (BM) blast count reduction from 25% to 2% after 1 cycle of 5-AZA/birinapant treatment. Another patient with MDS (cytogenetics: +X; +19; +21) refractory to single-agent 5-AZA showed BM blast count reduction from 21% to 7% after 2 cycles. A third patient with treatment-naïve MDS/CMML-2 (cytogenetics: 46, XY, inv(6)(p11.2q15), t(6;21)(q21;q22) ) who had received prior hydroxyurea demonstrated BM blast count reduction from 17% to 2% after 3 cycles and underwent hematopoietic stem cell transplant. Several patients remain on study and are in active follow-up. This Phase 1b trial provide data for an acceptable safety profile of the first combination of a SMAC mimetic (birinapant) administered with IV 5-AZA. Early signs of clinical activity including in 5-AZA naïve and refractory patients were observed. These results provide rationale for a randomized Phase 2 study comparing birinapant in combination with 5-AZA against 5-AZA alone in the first-line setting for patients with higher-risk MDS. Disclosures Borthakur: Tetralogic Pharmaceuticals: Research Funding. Foran:TetraLogic Pharmaceuticals: Research Funding. Wang:Tetralogic Pharmaceuticals: Research Funding. Rakkar:Tetralogic Pharmaceuticals: Research Funding. Hager:Tetralogic Pharmaceuticals: Research Funding. Frey:Tetralogic Pharmaceuticals: Research Funding. Andreeff:TetraLogic Pharmaceuticals: Research Funding. Carter:Tetralogic Pharmaceuticals: Research Funding. Minderman:Tetralogic Pharmaceuticals: Research Funding. Russell:Tetralogic Pharmaceuticals: Employment. Tibes:Tetralogic Pharmaceuticals: Research Funding.

Abstract Background Follicular lymphoma (FL) is an indolent non-Hodgkin lymphoma (NHL) with heterogeneous outcomes and remains largely incurable. Immunochemotherapy (IC) continues to be the standard therapy backbone in the frontline and relapsed settings, though novel agents are increasingly used and investigated. Lenalidomide is an immunomodulatory molecule with known single-agent activity in relapsed lymphoma. It is also active in the frontline setting and has been reported to be effective and tolerated in upfront combination regimens in FL (Fowler et al, Lancet Oncol. 2014, 15(12):1311-8). Here we report our experience with frontline use of R2CHOP (lenalidomide in combination with R-CHOP) in patients with FL. Methods A phase 1/2 study of R2CHOP was conducted in NHL patients with primarily diffuse large B-cell lymphoma (DLBCL). While the phase 2 study was focused on DLBCL patients, treatment-naive patients with stage II-IV, histologically-confirmed FL (grades 1, 2, and 3a) meeting criteria for therapy were eligible for the phase 1 part of the study. Additionally, FL patients were identified in the phase 2 portion of the study after central pathology review. These patients were allowed to complete therapy and were followed accordingly. Treatment consisted of 6 cycles of R2CHOP with lenalidomide given on days 1-10 and R-CHOP given in 21-day cycles. All patients received pegfilgrastim and aspirin (if not on anticoagulation) along with other supportive measures per provider discretion. Primary objectives were safety assessment and efficacy. Results Ten patients with FL (3 had grade 1, 3 had grade 2, and 4 had grade 3a) were enrolled in the R2CHOP phase 1/2 study at Mayo Clinic. One patient was in the phase 1 arm at dose level 2 (lenalidomide 20 mg/d) and 9 patients were in the phase 2 arm (lenalidomide 25 mg/d). The mean age was 60.8 years (range: 41-82). Eight out of ten patients were male; 5/10 had ECOG performance status of 0; 5/10 had an IPI score of intermediate or higher. All patients completed 6 cycles of planned treatment. One patient required lenalidomide dose adjustment due to toxicity. There were no lenalidomide dose interruptions. The overall response rate (ORR) was 100% and the complete response (CR) rate defined by PET imaging was 90%. Eight out of ten remain progression-free and 9/10 are alive at a median follow-up of 4.6 years (range: 2.1-5.3). Estimated progression-free survival (PFS) at 5 years was 79% (95% CI: 56-100%). The main toxicity was reversible myelosuppression with 80% treatment-related hematologic grade 3 or higher adverse events (AEs) (leukopenia 80%, neutropenia 80%, thrombocytopenia 40%, anemia 20%, transaminitis 20%). Rate of nonhematologic grade 3 or higher AEs was 20% (fatigue 10%, pneumonia 10%). Conclusions Frontline therapy with R2CHOP in patients with untreated FL appears to be effective and associated with acceptable toxicity. The observed PET-based CR rate and PFS were promising in this cohort. Whether R2CHOP is superior to lenalidomide/rituximab alone or standard bendamustine/rituximab will require randomized studies. Figure Estimated PFS in FL patients treated with upfront R2CHOP. Figure. Estimated PFS in FL patients treated with upfront R2CHOP. Disclosures Reeder: Celgene: Research Funding; Novartis: Research Funding; BMS: Research Funding; Millennium: Research Funding. Foran:novartis: Honoraria; Millennium Pharmaceuticals, Inc.: Research Funding; pfizer: Honoraria; karyopharm: Honoraria; medscape: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. Nowakowski:Bayer: Consultancy, Research Funding; Morphosys: Research Funding; Celgene: Research Funding.

Abstract Background: Approximately 1,000 acute promyelocytic leukemia (APL) patients are diagnosed in the US annually. APL has the highest cure and early mortality rates of all acute leukemias. The availability of all trans-retinoic acid (ATRA) in 1995 and arsenic trioxide in 2000 has further improved the overall survival (OS). However, whether there is uniform improvement in OS across demographic subgroups and if sooner time-to-treatment (TTT) reduces early mortality are unknown. We used the National Cancer Data Base (NCDB), a nationwide oncology registry covering 70% of the US cancer population to answer these questions. Methods: We identified patients with APL diagnosed from 1998-2011 using ICD-O-3 code 9866. Survival functions were estimated using the Kaplan-Meier method and 30-day mortality was estimated as 1-survival at 30 days. We compared OS according to demographic subgroups (gender, age [18-40, 41-64, and >65 years], race [White, Black, Native American, Asian/Pacific Islander, and other], and ethnicity) across years of diagnosis (Period [P] 1: 1998-2001, P2: 2002-2006, and P3: 2007-2011). For 30-day mortality, we compared the rates according to demographic subgroups and time periods and determined the effect of TTT (days from APL diagnosis to ATRA and/or chemotherapy). For this analysis we included only patients treated within 30 days of diagnosis and those diagnosed from 2003 to 2011. TTT was grouped as 0, 1, 2, or >3 days. We used mixed-effects logistic regression model to obtain odds ratio comparing treatment delays. Our model accounted for multiple subjects per facility with a random intercept and was adjusted for gender, Charlson-Deyo score, and year of diagnosis. Results: Characteristics: There were 8,084 APL patients in our study. The median age at diagnosis was 51 (24% were older than 65) years and 50% were females. White race (85%) was the most common, followed by black (11%) and Asian (3%). Twelve percent were Hispanic in origin. Slightly more patients (54.8%) were treated in academic centers. Thirty seven percent had either Medicaid or Medicare insurance. OS: Race had no impact on OS, although Asians had a trend towards improved OS (P=0.06). Both females and young age affected OS favorably (P <0.0001). In general, OS improved over the three time periods (P=0.002). Across Periods 1-3, we observed significant improvement in OS among the males (P=0.03), 18-40 (P=0.035) and 41-64 (P=0.005) age groups, Whites (P=0.012), and non-Spanish/Hispanics (P=0.002), but not among their counterparts. 30-day mortality rate: Age above 65 years was associated with highest 30-day mortality (33%). Similarly male gender had statistically significant higher 30-day mortality (shown in the Figure). There was no statistically significant difference among Periods 1-3. As expected, untreated patients had an increased risk of death versus treated (HR=1.9, confidence interval 1.7-2.1). TTT: A third (33.5%) of the patients was treated within two days of APL diagnosis. TTT was not independently associated with lower 30-day mortality rate (shown in the Table). Presence of disseminated intravascular coagulopathy (DIC) data was not available to analyze. Conclusions: From 1998-2011, the OS of APL continued to improve but not uniformly across demographic subgroups. In contrast, the 30-day mortality did not improve in the same time period. Both Age above 65 and male gender predicted worse 30-day mortality and OS. Our study did not find a favorable association between shorter TTT and lower 30-day mortality rate. Our study was not able to study these findings among different risk groups. Disclosures Al-Kali: Celgene: Research Funding. Tibes:TetraLogic Pharmaceuticals: Research Funding.

Abstract Background: The results of the primary endpoint of the E2906 North American Intergroup phase 3 trial - demonstrating significantly inferior OS after single agent clofarabine versus standard intensive daunorubicin & cytarabine induction and consolidation - strongly support the use of intensive therapy for patients age ≥60 years with newly-diagnosed AML who are fit for treatment. This result was achieved despite similar CR rates (including CRi - CR with incomplete blood count recovery) and similar early (30- & 60-day) induction mortality between study arms, raising the question as to the importance of achieving CR as an endpoint. Therefore, we performed a follow-up analysis to address the factors that contribute to early mortality, the necessity for 2nd induction cycle to achieve CR, and to assess the survival impact of the quality of remission. Methods: E2906 design, study population and results for the primary objective were reported previously (ASH 2015, abstr. #217a). We performed this updated analysis to evaluate clinical risk factors for early mortality and re-induction, and to assess the impact of response quality on OS. Univariate comparisons were made with Fisher's exact test (category) and t-test (continuous variable), and logistic regression models were used to examine risk factors associated with early mortality, and with requiring a 2nd cycle of induction therapy. We performed a landmark analysis (beginning Day 60 after initiation of therapy) to determine the impact of response quality (CR/CRi, morphologic leukemia-free-state (MLFS), and treatment failure - i.e. residual/refractory AML) on OS. Survival comparisons were performed with log-rank test. Results: A total of n=727 patients were registered to E2906, the median age is 68 years (range 60-86) and the median follow-up of surviving patients is now 18.3 months. Adjusting for treatment, cytogenetic risk group, FAB subtype, WBC count, and secondary AML, increasing age (p=0.06) and performance status (PS) >1 (p=0.05) were associated with 30-day mortality and only PS >1 (p=0.06) with 60-day mortality. Treatment arm (p=0.003), adverse cytogenetic risk group (p=0.02), increasing age (p=0.03) and baseline WBC <10K (p=0.03) were each independently associated with higher risk of receiving 2nd cycle induction, but there was no difference in CR/CRi (44.2% vs. 42.2%, p=0.58) or in median OS (13.8 versus 12.0 months, p=0.11) for those receiving 1 vs. 2 induction cycles, respectively. We next performed a landmark analysis (day 60, n=608 evaluable patients) to evaluate OS in relation to the quality of response (Table). We observed an advantage in achieving CR and CR/CRi, although the benefit of CRi diminished greatly after 12 months, and OS after MLFS appeared more similar to treatment failure (Figure, p<0.001). The relative adverse impact of CRi and MLFS (vs. CR) was most pronounced for patients treated with clofarabine, where median OS was shorter for those achieving CRi (12.2m vs. 22.6m standard therapy, p=0.007) and MLFS (6.6m vs. 13.4m standard therapy, p=0.15). Conclusion: This follow-up analysis confirms the importance of CR regardless of the number of cycles of induction therapy required to achieve remission, and identifies risk factors associated with early mortality and with requiring re-induction. At longer follow-up the OS after CRi appears to be inferior to true CR, particularly after clofarabine. We hypothesize that this may be due to higher rates of minimal residual disease in CRi, and studies to determine this are being performed. MLFS is not associated with a better overall survival than frank treatment failure (i.e. residual disease) and therefore its value as a response category is uncertain. These results highlight the role of standard intensive remission induction therapy with the intent of achieving CR, which remains the standard of care for fit older adults. Table. Table. Figure 1. Figure 1. Disclosures Foran: karyopharm: Honoraria; novartis: Honoraria; medscape: Honoraria; Millennium Pharmaceuticals, Inc.: Research Funding; pfizer: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. Melnick:Janssen: Research Funding. Altman:Novartis: Honoraria; BMS: Honoraria; Janssen: Honoraria; Syros: Honoraria. Al-Kali:Novartis: Research Funding; Celgene: Research Funding.

Abstract Background Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells in the peripheral blood, bone marrow, lymph nodes, and spleen. This is due to a combined effect of deferred apoptosis with slow, but persistent proliferation of malignant cells. In CLL, tumor-sustaining homeostasis is critically maintained by the ubiquitin proteasome system. The proteasome mediates degradation of various transcription factors such as TP53 as well as upholding a balance between the anti and pro apoptotic proteins of the BCL2 family. Previous studies have demonstrated that the clinical course of the disease is negatively associated with malfunctioning apoptotic pathways that result in increased levels of BCL2. Thus, identification and correction of defects that affect programmed cell death offer therapeutic vantage to reset and engage cell death pathways in CLL. Aim Examination of the anti-CLL properties of the investigational agent MLN2238 (Millennium Pharmaceuticals, Inc., Cambridge, MA) and its ability to inhibit the proteasomal machinery; induce CLL cell death and downregulate BCL2. MLN2238 activity was also investigated in conjunction with anti-CLL therapies such as fludarabine and dexamethasone along with the BH3 mimetic BCL2 inhibitor, AT-101 (Ascenta Pharmaceuticals, Malvern, PA). Methods CLL cells with >90% CD19+ tumor population were obtained from 28 patients with a confirmed diagnosis of CLL. Proteasomal activity was measured using synthetic fluorogenic peptide substrates. Apoptosis was measured by annexin-v/PI staining, and mitochondrial membrane permeability (MOMP) was assessed using TMRM followed by flow cytometry. Protein profiles were ascertained by western blot. Results MLN2238 inhibited the chymotrypsin-like proteasomal activity by more than 90% (p<0.005) in all patient samples without altering PSMB5 protein levels. Moderate to minimal inhibitory effect on caspase-like and trypsin-like proteasomal activities, respectively, was also noted. CLL cells showed a concentration dependent decrease in viability in response to treatment with MLN2238 at an IC50 of 50 nM. MLN2238 treated cells underwent apoptosis in a dose dependent manner with a median dose effect (cell death) observed in 42% of cells at 25 nM (range 10% - 54%) and 60% of cells at a 50 nM concentration (range, 25% - 73%). PARP-1 and caspase-3 cleavage along with an increase in MOMP was also noted after CLL cells were treated with MLN2238; however, apoptosis was only partially blocked by the pan-caspase inhibitor z-VAD.fmk. BCL2 downregulation was dose-dependent and was observed as early as 12 hours. We sought to determine whether directly disrupting BCL2 function with AT-101 could enhance the anti-CLL effects of MLN2238. When used at sub-IC50 concentrations, AT1-10 synergized with MLN2238 to induce CLL cell death. Synergy was also observed when MLN2238 was paired with the cytotoxic agent fludarabine, whereas the combination of MLN2238 and dexamethasone resulted in additive anti-CLL activity. Conclusion While PI have made an important impact in various B cell cancers, their role in CLL has not been well established. We investigated preclinically, a novel PI and noted that targeting the proteasome with MLN2238 resulted in lethal events in CLL cells, which were further enhanced by disruption of the BCL2 prosurvival pathway. Moreover, proteasome disruption sensitized CLL cells to the cytotoxic effect of fludarabine, an important therapeutic in CLL. These data provides the mechanistic basis for evaluation of MLN2238 in CLL through rationale design of drug combination strategies based on CLL biology. We would like to acknowledge the Leukemia and Lymphoma Society (A.C.-K. is a Leukemia and Lymphoma Scholar in Clinical Research) for their ongoing support. We are also grateful to Mary Ella Mahoney Davidson (Millennium Pharmaceuticals) for providing logistical support. Disclosures: Foran: Celgene: Research Funding.

Abstract INTRODUCTION Recurrent somatic mutations in the metabolic enzymes isocitrate dehydrogenase 1 and 2 (IDH1/2) confer gain-of-function activity in cancer cells, resulting in accumulation of the oncometabolite, D-2-hydroxyglutarate (2-HG). High levels of 2-HG result in epigenetic changes and impaired cellular differentiation. IDH mutations have been identified in multiple solid tumors and hematologic malignancies. Approximately 6-10% and 9-13% of adults with acute myeloid leukemia (AML) carry mutations in IDH1 (mIDH1) or IDH2 (mIDH2), respectively. AG-120 is a first-in-class, oral, potent, reversible, selective inhibitor of the IDH1 mutant enzyme under evaluation in multiple ongoing single agent and combination clinical trials [NCT02074839, NCT02073994, NCT02632708, NCT02677922]. This is the first report of IDH1 mutation clearance assessed by variant allele frequency (VAF) analysis using next-generation sequencing (NGS) in patients treated on the dose escalation portion of the first-in-human phase 1 study [NCT02074839]. METHODS Patients with advanced mIDH1-positive hematologic malignancies received AG-120 as a single agent orally once daily (QD) or twice daily (BID) continuously in 28-day cycles. Primary objectives were determination of safety, maximum tolerated dose (MTD), and selection of a dose schedule for expansion cohorts and future studies. Secondary objectives included clinical activity assessed by investigators using modified 2003 International Working Group Criteria in AML. Determination of mIDH1 VAF was performed using the FoundationOne® Heme test on mononuclear cells from the bone marrow or peripheral blood at screening and subsequent time points on study. This NGS assay reports IDH1 mutations for samples with VAF ≥1%, with median coverage 500X. Patients with IDH1 mutational clearance (IDH1-MC) were defined as having mIDH1 at baseline and at least one on-study sample with no reported mIDH1. RESULTS Seventy-eight patients were treated in the dose escalation portion, which is now closed to enrollment. As of the data cut-off of May 12, 2016, the median duration on treatment was 3.2 months and 9 (11.5%) patients remain on treatment, with an additional 8 (10.3%) patients transitioned to stem cell transplant. Doses ranged from 300-1200 mg QD with 1 cohort at 100 mg BID. Though the MTD was not reached, the recommended phase 2 dose was determined to be 500 mg QD. The majority of adverse events (AEs) were grade 1 and 2, the most common (≥30%) being diarrhea, fatigue, and nausea; the most common grade ≥3 AEs (≥15%) were febrile neutropenia, anemia, leukocytosis and pneumonia. The most common serious AEs were febrile neutropenia (16.7%) and pneumonia (12.8%). The overall response rate (ORR) was 38.5% (n=30), with 17.9% (n=14) achieving a complete remission (CR). Longitudinal mIDH1 VAF data were available for 51 patients; of these, 22% (n=11) achieved a CR. IDH1-MC was observed in 27.3% (3/11) patients who achieved CR (Figure 1). In contrast, only 1/40 patients who did not achieve CR experienced IDH1-MC. This occurred in a patient with an initially low mIDH1 VAF who had clinical progression despite IDH1-MC (Figure 1, bottom right). In all 3 patients with CR who achieved IDH1-MC, an initial increase in mIDH1 VAF, or early peak, was observed prior to IDH1-MC, suggesting that early clonal expansion might have occurred as part of the mechanism of action of AG-120. CONCLUSION This is the first demonstration that treatment with single agent AG-120 can result in mIDH1 clearance as determined by NGS. Further analysis of the mutational profiles is planned. AG-120, a potent, selective, oral inhibitor of mIDH1 continues to demonstrate a well-tolerated safety profile in patients with advanced hematologic malignancies, and induced objective single-agent durable responses. The data continue to support the efficacy and safety of single agent AG-120 and provide evidence that the underlying biology of the disease is altered by treatment. Figure 1. VAF analysis using FoundationOne® Heme NGS assay in 4 AML patients with IDH1-MC treated with AG-120 Figure subscript: Y-axis is mIDH1 VAF, x-axis is days on treatment. Text indicates investigator-assessed clinical response. CR, complete remission; CRi, CR with incomplete neutrophil recovery; CRp, CR with incomplete platelet recovery; R/R, relapsed/refractory; SD, stable disease; PD, progressive disease; *post-transplant sample Figure 1. VAF analysis using FoundationOne® Heme NGS assay in 4 AML patients with IDH1-MC treated with AG-120. / Figure subscript: Y-axis is mIDH1 VAF, x-axis is days on treatment. Text indicates investigator-assessed clinical response. CR, complete remission; CRi, CR with incomplete neutrophil recovery; CRp, CR with incomplete platelet recovery; R/R, relapsed/refractory; SD, stable disease; PD, progressive disease; *post-transplant sample Disclosures DiNardo: Daiichi Sankyo: Other: advisory board, Research Funding; Novartis: Other: advisory board, Research Funding; Abbvie: Research Funding; Celgene: Research Funding; Agios: Other: advisory board, Research Funding. de Botton:Novartis: Consultancy; Agios: Consultancy, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Servier: Consultancy; Pierre Fabre: Consultancy. Stein:Agios: Other: advisory board; Celgene: Other: advisory board; Novartis: Other: advisory board. Roboz:Cellectis: Research Funding; Agios, Amgen, Amphivena, Astex, AstraZeneca, Boehringer Ingelheim, Celator, Celgene, Genoptix, Janssen, Juno, MEI Pharma, MedImmune, Novartis, Onconova, Pfizer, Roche/Genentech, Sunesis, Teva: Consultancy. Pollyea:Alexion: Other: advisory board; Pfizer: Other: advisory board, Research Funding; Ariad: Other: advisory board; Glycomimetics: Other: DSMB member; Celgene: Other: advisory board, Research Funding. Fathi:Bexalata: Other: Advisory Board participation; Agios Pharmaceuticals: Other: Advisory Board participation; Seattle Genetics: Consultancy, Other: Advisory Board participation, Research Funding; Merck: Other: Advisory Board participation; Celgene: Consultancy, Research Funding. Altman:Syros: Honoraria; BMS: Honoraria; Janssen Pharmaceuticals: Honoraria; Novartis: Honoraria. Flinn:Janssen: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Gilead Sciences: Research Funding; ARIAD: Research Funding; RainTree Oncology Services: Equity Ownership. Foran:novartis: Honoraria; Millennium Pharmaceuticals, Inc.: Research Funding; karyopharm: Honoraria; medscape: Honoraria; pfizer: Honoraria; boehringer ingelheim: Research Funding; agios: Research Funding; Cellerant: Research Funding. Pigneux:Sunesis: Consultancy, Honoraria; Agios: Consultancy, Honoraria. Kantarjian:ARIAD: Research Funding; Bristol-Myers Squibb: Research Funding; Amgen: Research Funding; Pfizer Inc: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding. Liu:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Attar:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Sacolick:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Yen:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Hurov:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Choe:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Wu:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Stone:Amgen: Consultancy; Sunesis Pharmaceuticals: Consultancy; Pfizer: Consultancy; Roche: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy; Celator: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy; Novartis: Consultancy; Jansen: Consultancy; ONO: Consultancy; Juno Therapeutics: Consultancy; Merck: Consultancy; Seattle Genetics: Consultancy; Xenetic Biosciences: Consultancy.

Abstract Background: The proteasome is an established and druggable target for the treatment of plasma cell-related malignancies including Waldenstrom macroglobulinemia (WM). WM cells as a consequence of high immunoglobulin production and increased B-cell receptor (BCR) mediated proliferation upregulate proteasome activity. Additionally, microenvironmental influence mediated through BCR signaling directly influences Bcl-2 and its BH3 family members, supporting tumor cell survival. Indeed, WM patients derive significant clinical benefit from proteasome-inhibitor (PI) based therapy with agents such as bortezomib and carfilzomib. However, resistance to PI develops over time and for these patients the optimal choice and sequence of therapy has yet to be determined. Using our WM models of PI-resistance we interrogated molecular events within the BCR and Bcl-2 pathways to determine therapeutic potential of targeting these crucial pathway in PI-resistance. Materials & Methods: WM cell lines (BCWM.1 and MWCL-1) and carfilzomib-resistant (CR) subclones (BCWM.1/CR and MWCL-1/CR) were used in experiments. Gene-expression and long-noncoding (LNC) RNA analysis was performed (Arraystar) and validated by real-time PCR. Bortezomib, carfilzomib, ABT199 and ibrutinib were purchased from Sellekchem. Results: To determine the functional impact of BCR and Bcl-2 signaling in PI-resistance, as well as therapeutic sensitivity of PI-resistant cells to their inhibitors (ibrutinib, ABT-199, respectively), we established and characterized WM cell lines resistant to carfilzomib. BCWM.1/CR cells showed approximately 20-fold resistance to carfilzomib (IC50 = 92.75nM) and MWCL-1/CR cells approximately 10-fold resistance (Fig. 1A). Both CR clones also displayed some cross-resistance to bortezomib. Gene expression and LNC-RNA profiling demonstrated several changes between carfilzomib-resistant vs. sensitive WM cells. Analysis of proteasome-related mRNA revealed downregulation of PSMB5, PSMB1, PSMB2 and PSMB8. Similarly, profiling of BCR-associated genes demonstrated decreased expression of several components, including BTK and SPI1. This observation functionally manifested as reduced sensitivity to the BTK-inhibitor ibrutinib, wherein CR cells displayed 1.5 - 2 fold growth resistance to ibrutinib on 72hr MTS assay. Next we examined the expression of Bcl-2 family members in CR cells. Intriguingly, we observed that Bcl-2 and Mcl-1 were significantly downregulated but XIAP (inhibitor of apoptosis) was significantly increased in CR cells vs. wildtype WM cells- both at transcriptional and translational levels. This suggested that upon acquisition of CR, a transcriptional shift towards XIAP occurs to accommodate sustained therapeutic stress from carfilzomib and maintain steady antiapoptotic composure. To test if the PI-resistant cells have moved away from their survival dependence on Bcl-2, we treated CR cells to increasing concentrations of the Bcl-2-specific inhibitor, ABT199, and as anticipated, CR cells displayed reduced apoptosis in presence of ABT199 compared to wildtype WM cells (32% annexin-V staining vs. 50%, respectively) (Fig. 1B). Conclusions: Our study sheds insight into the differential drivers of PI-resistance particularly towards carfilzomib, in WM cells. We demonstrate that acquisition of CR is associated with downregulation of Bcl-2 and Mcl-1, which is countered by upregulation of XIAP- an event that renders CR cells resistant to ABT199 (as it targets only Bcl-2). Likewise, downregulation of BCR-related components in CR cells was associated with reduced sensitivity towards ibrutinib. These observations suggest that acquisition of resistance to PI such as carfilzomib can impact future treatment with agents such as ibrutinib or ABT199. Our preclinical models provide rationale or early sequencing of ibrutinib or ABT199 in therapeutic planning of WM patients prior to induction of PI resistance. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.