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Abstract Abstract 2687 Background: Patients with early stage (Stages I, II) diffuse large B cell (DLBCL) have been traditionally treated with either CHOP x6 alone or with CHOP followed by involved field external beam radiotherapy (IFRT). With the demonstration of the superiority of rituximab CHOP (RCHOP) in advanced stage DLBCL, RCHOP has been adopted as the chemoimmunotherapy standard of care in early stage disease with or without IFRT. Radioimmunotherapy (RIT) has the advantage of delivering high-energy, short path length radiation in a targeted approach using an anti-CD20 antibody as the carrier. Thus, radiation is potentially targeted to microscopic sites outside of known disease. Goals: To evaluate the complete response (CR) rate and functional CR rate (CR or CRu/PR and PET negative) to a treatment regimen of RCHOP followed by 90Y-ibritumomab tiuxetan (Zevalin, Spectrum Pharmaceuticals) radioimmunotherapy (RIT); only patients not achieving PET negative status after RIT were to be given IFRT. The study goal was to achieve a functional CR rate of ≥75%. Patients and Methods: Eligible patients were those with new, untreated Stages I or II DLBCL as determined by standard CT scanning, adequate blood counts, creatinine and bilirubin <2.0 mg/dl, cardiac ejection fraction >45%, and a performance status 0–2. Stage I patients were required to have ≥1 adverse risk factor (≥60 years, bulky disease, elevated LDH or PS2). Patients received standard RCHOP21 × 2 cycles and then were restaged. Patients in CR received 2 additional cycles; those in PR or CRu received 4 additional cycles. At end of RCHOP a PET scan was repeated and centrally reviewed; those with a PR or functional CR proceeded to Zevalin RIT 0.4 mCi/kg (maximum 32 mCi) within 12 weeks of the last RCHOP. Patients were restaged 12 weeks post-RIT; PET negative patients were observed without maintenance; PET positive patients received 30Gy involved field radiation and then were restaged. Descriptive statistics were used to summarize the patient characteristics, treatment and response. The Kaplan-Meier method was used to estimate failure rates. Results: Between Dec 2004 and Nov 2008, 62 patients were enrolled; after pathology review 53 were considered eligible. 42% (22/53) patients were stage I/IE; 58% (31/53) were stage II/IIE. 57% (30/53) received 6 cycles of RCHOP; 40% (21/53) received 4 cycles; and 2 patients received 1 and 2 cycles, respectively. After immunochemotherapy, 79% (42/53) were in functional CR and 19% (10/53) PR; 1 was unevaluable. Of the 53 eligible patients who completed RCHOP therapy 91% (48/53) proceeded to RIT. After RIT, 87% (46/53; 95% CI: 75–95) were in CR/CRu and 89% (47/53; 95% CI:77–96%) were in functional CR. One patient proceeded to IFRT. The median follow-up is now 4.3 years. Seven (13%) of patients have had tumor progression but only 2 have died (1 of disease). At 4 years, 88% of patients remain progression free and 98% remain alive (Fig 1,2). The median has not been reached for either PFS or OS. There has been one case of myelodysplastic syndrome. Conclusions: Combination immunochemotherapy and RIT is an active regimen for patients with early stage DLBCL. Nearly all patients will achieve functional CR without the requirement of IFRT. The regimen of RCHOP and RIT for early stage DLBCL is worthy of further study. Disclosures: Witzig: Spectrum: Membership on an entity's Board of Directors or advisory committees, Research Funding, uncompensated Other. Off Label Use: Use of Zevalin in treating patients with Stage I-II DLBCL. Kahl:Roche: Consultancy; Genentech: Consultancy, Research Funding. Horning:Genentech: Employment; Roche: Equity Ownership.

Abstract Abstract 415 Background: The ability to cure patients (pts) with advanced Hodgkin's Lymphoma (HL) with combination chemotherapy (CC) (MOPP and variants, ABVD and variants) represented a major milestone in oncology research, and CC became a paradigm for other malignancies. Further, the rationale for combined modality therapy (CMT) (radiation (RT) and CC) in HL evolved based on the high frequency of relapse in initially involved sites. As response rates and survival improved, newer treatments such as the combined modality Stanford V regimen were developed to shorten the duration of chemotherapy, add RT to sites of disease and reduce toxicity while maintaining or improving the cure rate. Indeed, the Stanford V regimen was tested and validated in a Phase II co-operative group trial (E1492) (J Clin Oncol 2000; 18:972). In order to investigate this approach against “standard” therapy, we conducted a randomized Phase III Intergroup trial of ABVD vs. the Stanford V regimen for patients with locally extensive or advanced HL. Objectives: The trial was designed to detect a 33% reduction in the failure free survival (FFS) hazard rate with Stanford V compared with ABVD, which corresponds to a difference in five-year FFS of 64% vs. 74%. Method: Patients with locally extensive (defined as clinical Ann Arbor Stage I-IIA/B and bulky mediastinal disease (BMD) (mass > 1/3 maximum intrathoracic diameter on standing postero-anterior chest x-ray or >/−10 cm on computerized tomography) or advanced (Ann Arbor Stage III or IV) HL were randomized to receive either ABVD × 6–8 cycles (C) (51% had 6 C, 35% had 8 C, 14% had <6 C) + 36 Gy (only in pts with BMD) or Stanford V × 12 weeks (95% had 12 weeks) + 36 Gy (for sites >5cm or for macroscopic splenic disease). The log-rank test was used to compare FFS for all eligible patients stratified on extent of disease (locally extensive vs. advanced), and number of International Prognostic Factor Project (IPFP) risk factors (0–2 vs. 3–7). An extended Cox model was also used to address non-proportional hazard between the two arms. Results: 854 pts enrolled from April, 1999 to June, 2006 and 812 were eligible for analysis. 404 pts were randomized to ABVD and 408 to Stanford V. Median age was 33 yrs in both arms (range 16–83). 53% were men and 47% women; 4% had Stage I, 31% had Stage II, 39% had Stage III and 25% had Stage IV disease by Ann Arbor criteria. 35% of pts on ABVD and 35% on Stanford V had BMD. Three % of pts had nodular lymphocyte predominant HL, 77% of pts had nodular sclerosis HL, 14% had mixed cell HL. Age, stage, pathology and risk factors (0–2 vs. 3–7) were similar in both arms. In total, 65% were IPFP score 0–2 and 33% were 3–6. Response rate. There was no difference in response rates (RR) between the two arms (ABVD=72% CR+ CCR, 7.7% PR, 7.9% SD; Stanford V= 69 % CR +CCR, 7% PR and 10 % SD. 8% were not evaluable for response on ABVD and 9% on Stanford V. Toxicity was similar in both groups. The most frequent Grade 3 + 4 toxicity was neutropenia, and was similar between the 2 groups (76% Grade 3 + 4 in ABVD and 70% Grade 3+ 4 in Stanford V). Grade 5 toxicity was <1% in both groups. There was, however, more Grade 3 lymphopenia in Stanford V (78% vs. 42%, p< 0.0001) and more Grade 3 +4 sensory neuropathy in Stanford V (10%) than in ABVD (3%) (p< 0.0001). A total of 26 second primary cancers developed, 12 after ABVD and 14 after Stanford V (p=NS). FFS and OS. For 812 eligible patients, with a median follow up of 5.25 years, 5-year FFS was 73% for ABVD and 71% for Stanford V (p=0.29 by log rank) (Figure left); 5-year OS was 88% for ABVD and 87% for Stanford V (p=0.87 by log-rank, HR=0.97, 95% CI: 0.65 to 1.44) (Figure right) indicating no significant difference in either FFS or OS between the 2 arms. Conclusion: In the largest Phase III intergroup trial of HL in North America, there was no significant difference in RR, FFS, OS, and 5-year toxicity when ABVD (+ RT for BMD) is compared with Stanford V (+RT for nodal sites >5 cm and macroscopic splenic disease). There was more Grade 3 lymphopenia (p< 0.0001) and more Grade 3 + 4 sensory neuropathy (p< 0.0001) on Stanford V. Thus ABVD (plus RT for BMD) remains the standard of care because Stanford V did not meet the objective of 33% improvement in FFS. For some patients, Stanford V, when given as described with RT, remains an acceptable alternative. Disclosures: Friedberg: Genentech: Honoraria. Blum:Seattle Genetics: Research Funding; Novartis: Research Funding; Celgene: Research Funding. Horning:Genentech: Employment.

Abstract Abstract 416 Background: Standard therapy for locally extensive Hodgkin Lymphoma (HL) defined as stage I/II with bulky mediastinal disease [mediastinal mass ratio (MMR) > than 1/3 of the chest diameter on standing postero-anterior chest x-ray or 10 cm on computerized tomography] is combined modality therapy (CMT). E2496 was a North American intergroup, randomized phase III study comparing ABVD versus the Stanford V regimen for patients with locally extensive and advanced stage HL. In this subgroup analysis we compare two CMT approaches, ABVD + radiotherapy (RT) and the Stanford V regimen, in patients with stage I/II bulky mediastinal HL. Methods: Patients with stage I/II HL bulky mediastinal disease were randomized to receive chemotherapy (CT) on either Arm A (ABVD × 6–8 cycles administered q 28 days) or Arm B (12 weeks of Stanford V, administered weekly). Two-3 weeks after completion of chemotherapy, modified involved field RT was delivered at 36 Gy to the mediastinum to patients on ABVD as well as Stanford V. Patients on Stanford V also received involved field RT to any other sites >5 cm at diagnosis. The primary endpoint was failure free survival (FFS) defined as the time to either progression/relapse or death. The log-rank test was used to compare FFS and OS (overall survival) for all eligible patients. Results: Of the 812 eligible patients with advanced HL enrolled on the study 267 had locally advanced bulky mediastinal disease: 136 on ABVD and 131 on Stanford V. Patient characteristics between the two randomized groups were well matched with a median age of 30 years and 86% had stage II disease. On ABVD 61% of patients received 6 cycles, 29% 8 cycles of CT and 77% required some dose modification. In Stanford V 97% completed the assigned 12 weeks of CT and 76% required some dose modification. 82% received RT per protocol in ABVD versus 88% in Stanford V. The overall response (CR+PR) was 82% in ABVD and 86% in Stanford V. At a median follow-up of 5.47 years, there are 19 failures and 6 deaths in the ABVD group and 25 failures with 9 deaths in the Stanford V group. We failed to detect statistically significant differences between ABVD +RT and Stanford V for FFS (5y 85% versus 77% p=0.13, HR=1.56 95% CI (0.87, 2.88) and OS (5y 95% versus 92% p=0.31, HR=1.69 95% CI (0.60, 4.75). No difference in hematologic toxicity was observed between the two arms. Evaluation of pulmonary function and patterns of failure are pending. Conclusions: For stage I/II patients with bulky mediastinal disease, CMT with either ABVD +RT or the Stanford V regimen results in high cure rates and is highly effective. ABVD for 6–8 cycles plus 36 Gy RT remains the US standard of care. Longer follow up is required to assess RT related late effects. Future research efforts should focus on risk stratification to identify; a) the 15–20% of patients destined to relapse after standard therapy and evaluate treatment intensification strategies and b) the 80–85% of patients who are cured with standard therapy and determine whether a subset can achieve the same excellent outcomes with a reduction or elimination of radiation. Planned US cooperative group trials will address these questions, using ABVD as the chemotherapy backbone in conjunction with interim PET imaging for risk stratification. Disclosures: Blum: Seattle Genetics: Research Funding; Novartis: Research Funding; Celgene: Research Funding. Horning:Genentech: Employment.

Abstract Background: Retinoblastoma (RB) is the most frequent pediatric retinal tumor. In the present study, to elucidate chemoresistance mechanisms and identify potential biomarkers in RB, we utilized RNA sequencing (RNAseq) technological platforms to reveal transcriptome profiles and identify any differentially expressed genes (DEGs) between an etoposide drug-resistant subline (Y79/EDR) and parental Y79 cells. Methods: To test whether Y79/EDR cells showed resistance to antineoplastic agents for RB, we treated the cells with etoposide, carboplatin and vincristine and analyzed them with a Cell Counting Kit-8 (CCK-8). Y79/EDR and parental Y79 cells were used for RNAseq and bioinformatics analysis to enable a genome-wide review of DEGs between the two lines using the DESeq R package (1.10.1). Then, DEG enrichment in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways was analyzed with KOBAS software. Next, real-time quantitative reverse transcription polymerase chain reaction (real time QRT-PCR) and cytotoxicity assays were performed to experimentally and functionally validate the identified candidate biomarkers. Results: Y79/EDR cells showed resistance to etoposide, carboplatin and vincristine at different concentrations. In total, 524 transcripts were differentially expressed in Y79/EDR cells based on analysis of fragments per kilobase of transcript per million fragments mapped (FPKM); among these, 57 genes were downregulated and 467 genes were upregulated in Y79/EDR cells compared to parental Y79 cells. We selected candidate DEGs, including ARHGAP9 , HIST1H4H , RELN , DDIT4 , HK2 , STC1 and PFKFB4, for mRNA expression validation with real time QRT-PCR assays and found that the expression levels determined by real time QRT-PCR were consistent with the RNAseq data. Further studies involving downregulation of ARHGAP9 with a specific siRNA showed that ARHGAP9 altered the cellular sensitivity of Y79 cells to etoposide and carboplatin. Conclusion: Our initial findings provided a genomic view of the transcription profiles of etoposide-induced acquired resistance in RB. Follow-up studies indicated that ARHGAP9 might be a chemoresistance biomarker in RB, providing insight into potential therapeutic targets for overcoming acquired chemoresistance in RB. These findings can aid in understanding and overcoming chemoresistance during treatment of RB in the clinic.

Abstract Abstract 589 Background: The initial results of this intergroup trial with median follow-up of 3.5 years (yrs) were previously reported (J Clin Oncol 24:3121, 2006). We present updated results with median follow-up of 9.4 yrs from induction therapy randomization, and 9.0 yrs from maintenance randomization. Methods: 632 patients (pts), age >60 yrs, with DLBCL were randomized to CHOP+rituximab 375 mg/m2 IV, administered Day -7, -3, and two days before cycles 3/5/7 (if given) (R-CHOP), versus CHOP, for two cycles beyond best response for 6–8 cycles total. Pts were stratified by the International Prognostic Index (IPI) (<3 vs >3). 415 pts responding to R-CHOP or CHOP were then randomized to maintenance rituximab 375 mg/m2 weekly times 4, every 6 months for 2 yrs starting 4 weeks after the last chemotherapy (MR, n=207), or observation (OBS, n=208). Results are presented for the 546 (267 R-CHOP; 279 CHOP) pts for induction, and 352 (174 MR; 178 observation) evaluable, centrally reviewed, maintenance pts. Failure-free survival (FFS) was the primary endpoint. The stratified weighted Cox regression was used to remove the effect of MR in comparing induction treatment, and stratified log-rank test used to assess maintenance effect. Results: Baseline characteristics and response to induction were balanced. 9-yr FFS and OS) are 35% and 44% for R-CHOP, and 25% and 37% for CHOP. Compared with CHOP, R-CHOP significantly prolonged FFS (p=.008), but not OS (p=.11). Pts were categorized into low-risk (LR) and high-risk (HR) groups according to their IPI (<3 or 33) (LR, n=217; HR, n=327). A significant difference in the effect of induction therapy was observed for high-risk patients only for FFS (p=0.02, HR=0.61, 95% CI, 0.51 to 0.93) but not for OS. MR significantly prolonged FFS (log-rank p=0.018, HR=0.71, 95%CI, 0.54 to 0.94), but not OS (p=0.44, HR=0.89, 95%CI, 0.65 to 1.20). A significant interaction between maintenance and induction therapies was observed in that MR significantly prolonged FFS after CHOP (p=0.003, HR=0.56, 95%CI, 0.38 to 0.82), but not after R-CHOP (p=0.89, HR=0.97, 95% CI, 0.64 to 1.47). There was no OS difference with MR after CHOP (p=0.19, HR=0.76, 95% CI. 0.50 to 1.15) or R-CHOP (p=0.77, HR=1.07, 95% CI, 0.68 to 1.68). Median time to failure after maintenance randomization following CHOP+MR was 9.5 yrs vs 2.0 yrs for CHOP+OBS (p=0.003) and following R-CHOP+MR was 8.5 yrs vs 7.5 yrs for R-CHOP+OBS (p=NS). Proportionately more treatment failures occurred within 2 yrs after CHOP+OBS (73%) compared to CHOP+MR (47%), p=0.01. In contrast, the proportion of failures within 2 yrs was similar for R-CHOP+OBS (38%) and R-CHOP+MR (36%), p=NS. Conclusions: Initial R-CHOP therapy, as compared with CHOP, resulted in improved DFS and FFS for older DLBCL pts. MR after CHOP, but not after R-CHOP, significantly prolonged time to failure but did not prolong OS. However, FFS was 42% at 9 yrs among R-CHOP responders, with or without MR. Future treatment strategies should build upon these findings in this older patient population, often with significant co-morbidities. Disclosures: Morrison: merck: Consultancy, Membership on an entity's Board of Directors or advisory committees; celgene: Consultancy, Speakers Bureau; amgen: Consultancy, Speakers Bureau; genentech: Speakers Bureau; pfizer: Speakers Bureau. Fisher:roche: Consultancy. Horning:Genentech: Employment.

Abstract Background: Venous thromboembolism (VTE) is an important cause of morbidity and mortality in patients with hematologic malignancies (HMs). The national burden of inpatient VTE in patients with HMs is not known. Methods: We used the National Inpatient Sample (NIS), one of the largest publicly-available inpatient dataset in United States (U.S.), which represents a 20% stratified random sample of discharges from all hospitals, excluding rehabilitation and long-term acute care hospitals. The NIS is drawn from all States participating in Healthcare Cost and Utilization Project, representing more than 95 percent of the U.S. population. Discharge weights are used to generate national estimates. Patients with HMs were identified using ICD9 codes published by NIS and VTE was defined by ICD9 codes 451 - 453 and 415.1. Annual rates of inpatient VTE were calculated from 1993 to 2012 by HM type. Multivariate odds of inpatient VTE was determined by logistic regression controlling for confounders (age, sex, Charlson co-morbidity index, metastasis, chemotherapy, transfusion of blood products, major operating room procedure, primary hypercoagulable state, disseminated intravascular coagulation, heparin induced thrombocytopenia and thrombosis, antiphospholipid syndrome, obesity and calendar year). The malignancies with non-specific designation (e.g. unspecified leukemia) or with less than 1000 patients (weighted number) were excluded from results. Results: 8.42million hospitalized patients (weighted number) with HMs were identified, and 335,240had VTE (3.98%). In patients with HMs, rates of inpatient VTE increased from 2.59% to 5.22% between 1993 and 2012 (p<0.01). A detailed analysis of VTE rates for various HMs is presented in Table 1. The HMs with highest odds of inpatient VTE are peripheral T-cell lymphoma (PTCL), anaplastic large cell lymphoma (ALCL) and primary central nervous system (CNS) lymphoma (OR 1.56, 1.53, and 1.39, p<0.05) as compared to all other HM. Among leukemias, hairy cell leukemia had higher odds of VTE (OR 1.19, p<0.05). The HMs with the least odds of VTE were acute lymphoid leukemia, chronic monocytic leukemia and plasma cell leukemia (OR 0.65, 0.66 and 0.71, p<0.05). The HMs with the highest rates of VTE were PTCL, large cell lymphoma and ALCL (6.96%, 6.35% and 6.27%). The HMs with lowest rate of VTE were megakaryocytic leukemia, acute lymphoid leukemia and acute monocytic leukemia (1.42%, 2.04%, and 2.73%). Conclusions: Our study provides national estimates of inpatient VTE in HM, which are increasing over the last 20 years. Certain HMs have higher rates and odds of VTE as compared to others. Identification of these differences provides valuable information for the use of prophylaxis in HM with high risk of VTE. Table 1. Multivariate Odds and Rates of Inpatient Venous Thromboembolism in Patients with Hematologic Malignancies (Total weighted N = 8.42 million) Hematologic malignancy Inpatient VTE rate (%) Adjusted OR (95% CI) of inpatient VTE compared to all other HM Hodgkin's disease Hodgkin's disease - lymphocyte rich 3.86 1.15 (0.82 - 1.61) Hodgkin's disease - nodular sclerosing 4.04 1.3 (1.18 - 1.43) Hodgkin's disease - mixed cellularity 4.02 1.22 (0.89 - 1.68) Hodgkin's disease - lymphocyte depleted 3.88 1.14 (0.73 - 1.77) Non-hodgkin's lymphoma Nodular lymphoma 4.89 1.2 (1.13 - 1.28) Mycosis fungoides 4.83 1.25 (1.16 - 1.35) Sezary's disease 3.99 1.08 (0.72 - 1.62) Peripheral t-cell lymphoma 6.96 1.56 (1.32 - 1.85) Burkitt's lymphoma 3.44 1.05 (0.97 - 1.15) Marginal zone lymphoma 5.57 1.07 (0.91 - 1.26) Mantle cell lymphoma 4.91 1.03 (0.92 - 1.15) Primary CNS lymphoma 6.18 1.39 (1.18 - 1.64) Anaplastic large cell lymphoma 6.27 1.53 (1.21 - 1.94) Large cell lymphoma 6.35 1.36 (1.22 - 1.51) Sarcoma Myeloid sarcoma 4.24 1.14 (0.9 - 1.44) Myeloma and leukemia Multiple myeloma 4.57 1.14 (1.1 - 1.18) Plasma cell leukemia 2.85 0.71 (0.5 - 1) Lymphoid leukemia - acute 2.04 0.65 (0.61 - 0.69) Lymphoid leukemia - chronic 3.43 0.76 (0.73 - 0.78) Myeloid leukemia - acute 3.71 0.97 (0.93 - 1) Myeloid leukemia - chronic 2.93 0.72 (0.68 - 0.76) Monocytic leukemia - acute 2.73 0.75 (0.59 - 0.96) Monocytic leukemia - chronic 2.74 0.66 (0.44 - 0.98) Erythrocytic leukemia - acute 2.95 0.81 (0.5 - 1.32) Megakaryocytic leukemia 1.42 0.48 (0.23 - 1.02) Hairy cell leukemia 4.72 1.19 (1.07 - 1.32) Disclosures No relevant conflicts of interest to declare.

Abstract Background: Despite advances in chemotherapy, R/R HL remains a significant clinical problem with over 1,000 primarily young lives lost annually. HL is a unique tumor in which a small number of malignant Hodgkin Reed-Sternberg (HRS) cells propagate an immunosuppressive microenvironment that augments HRS growth and survival. We hypothesized that immune checkpoint inhibitor therapy could activate the tumor immune microenvironment, while the CD30 expressing HRS cells could be targeted by brentuximab vedotin (BV), thereby overcoming tumor cell resistance and deepening clinical responses. E4412 is a phase 1 ECOG-ACRIN sponsored study of the combination of BV and the checkpoint inhibitors ipilimumab (IPI) and nivolumab (NIVO) in patients with relapsed/refractory (R/R) Hodgkin lymphoma (HL). Here we report the data on the patients treated with BV + IPI, the first cohort of the study. Methods: Patients with biopsy proven R/R HL were treated with BV 1.8mg/kg and two escalating doses of IPI: 1 mg/kg or 3mg/kg. After safety was determined an expanded cohort was treated with BV 1.8mg/kg IV and IPI 3mg/kg IV. The schedule consisted of BV administered every 21 days for 16 cycles and IPI every 21 days x 4 doses and thereafter every 3 months for up to a year. Dose limiting toxicity (DLT) was defined for purposes of dose escalation within the first cycle of therapy. Patients are followed for toxicity up to 30 days beyond their last treatment. Results: As of 7/2015 19 of 23 planned patients have been treated with BV + IPI. We report the data on the full dose escalation population (13 patients: Dose level 1 (6), Dose level 2 (7)). The median age was 33 years (range: 20-49). Seven patients were male. Patients were heavily pretreated with a median of 4 prior therapies (2-13). Fourpatients had prior treatment with BV; 8 patients had prior SCT (7 autologous, 1 allogeneic). Safety: Overall the regimen of BV + IPI was extremely well tolerated with no DLTs noted during dose escalation. Toxicities considered at least possibly related to drug during any cycle of treatment are shown according to grade in Table 1. The most common treatment related adverse events were: diarrhea, rash, and peripheral sensory neuropathy. Other AEs of interest included: alopecia, transaminitis, and uveitis. Grade 3 and 4 treatment related adverse events (AEs) included: Dose level 1: one grade 3 infusion reaction, which led to a protocol amendment to include premedication, no further grade 3 infusion reactions were noted; Dose level 2: one each: grade 3 rash, vomiting, and peripheral sensory neuropathy, and one grade 4 thrombocytopenia in patient with pre-existing thrombocytopenia. Response: For the 12 evaluable patients, the overall response (ORR) for the combination of BV + IPI was 67% with a complete response (CR) rate of 42% (5 of 12 patients). An additional 2 patients had stable disease (SD) giving a clinical benefit rate of 83%. Three of 5 of the CRs occurred at dose level 1 (1mg dose of IPI). The median progression free survival (PFS) is 0.74 years with a median follow-up of 0.66 years. Conclusion: In this first reported study of the combination of checkpoint inhibitor and ADC, toxicity was low, primarily grades 1 and 2. In a heavily pretreated patient population, 33% of whom had had prior BV and 67% of whom were s/p ASCT, the ORR of 67% and CR rate of 42% suggests a potential deepening of response compared to monotherapy. More than half of these CRs occurred at 1mg of IPI suggesting that in combination with ADC, low doses of immune stimulation may be highly active. Optimization of this combination strategy is planned with ongoing accrual to cohorts receiving BV + NIVO, and BV + IPI + NIVO. Data will be updated to include the full BV + IPI cohort by the time of the annual meeting. Table 1. Common and Immune Toxicities Toxicity Type Dose Level 1 (n=6) Dose Level 2 (n=7) Grade Grade 1,2 3 4 5 1,2 3 4 5 (n) (n) (n) (n) (n) (n) (n) (n) Fatigue 5 - - - 3 - - - Fever 1 - - - 3 - - - Pain 2 - - - 3 - - - Alopecia 2 - - - 1 - - - Pruritus 1 - - - 2 - - - Rash maculo-papular 4 - - - 2 1 - - Diarrhea 4 - - - 4 - - - Dyspepsia 2 - - - 1 - - - Nausea 6 - - - 4 - - - Vomiting 3 - - - 2 1 - - Papulopustular rash 1 - - - 1 - - - Alanine aminotransferase increased 3 - - - 3 - - - Aspartate aminotransferase increased 3 - - - 2 - - - Platelet count decreased - - - - - - 1 - Anorexia 3 - - - - - - - Headache 2 - - - 2 - - - Peripheral sensory neuropathy 5 - - - 4 1 - - Dry eye 2 - - - - - - - Uveitis 1 - - - - - - - Cough 2 - - - 1 - - - Disclosures Diefenbach: Molecular Templates: Research Funding; Immunogen: Consultancy; Celgene: Consultancy; Idera: Consultancy; Jannsen Oncology: Consultancy; Gilead: Equity Ownership, Research Funding, Speakers Bureau; Incyte: Research Funding; Genentech: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding. Off Label Use: Presentation will discuss the experimental use of the checkpoint inhibitor Ipilimumab in relapsed/refractory Hodgkin lymphoma.. Cohen:Celgene: Consultancy; Millennium: Consultancy; Pharmacyclics: Consultancy; Seattle Genetics: Consultancy; BMS: Research Funding; Janssen: Research Funding. Robertson:Eli Lilly: Equity Ownership. Fenske:Pharmacyclics: Honoraria; Seattle Genetics: Honoraria; Millennium/Takeda: Research Funding; Celgene: Honoraria. Kahl:Roche/Genentech: Consultancy; Seattle Genetics: Consultancy; Millennium: Consultancy; Cell Therapeutics: Consultancy; Celgene: Consultancy; Infinity: Consultancy; Pharmacyclics: Consultancy; Juno: Consultancy. Ansell:Bristol-Myers Squibb: Research Funding; Celldex: Research Funding.

Abstract Abstract 2906 Poster Board II-882 Background: The World Health Organization (WHO) classification system recognizes indolent SM (ISM) as an entity characterized by low systemic mast cell (MC) burden but frequent skin involvement. The WHO system also recognizes 2 provisional ISM sub-variants: smoldering SM (SSM) and bone marrow (BM) mastocytosis (BMM). The two are respectively characterized by increased systemic MC burden (presence of ≥ 2 ‘B-findings') and BM MC infiltration in the absence of skin or multiorgan visceral lesions. The prognostic relevance of this sub-classification remains unclear. Methods: The study population was drawn from a larger cohort of 342 adult SM patients (Blood. 2009 Jun 4;113(23):5727). Clinical data and BM histology were reviewed, and the diagnosis of ISM and its subclassification confirmed per the 2008 WHO proposal. The primary objectives of the study were to: (i) describe the clinical characteristics of a large cohort of ISM patients, within the context of the WHO classification; (ii) evaluate the prevalence of molecular and cytogenetic abnormalities; (iii) evaluate whether ISM subclassification is prognostically relevant on the basis of survival and risk of transformation to acute leukemia or aggressive SM (ASM). Results: (i) Clinical characteristics: 159 ISM patients were evaluated (69 males; median age 49 years, range 19-84); 22 (14%) had SSM, 36 (23%) BMM, and 101 (63%) ‘ISM-other' (ISMo). By definition, ‘B-findings' were absent in BMM patients. ‘B-findings' in SSM (and ISMo) patients was as follows: hepatosplenomegaly and/or lymphadenopathy 91% (21%), BM MC >30% or serum tryptase level >200ng/mL 68% (8%), and hypercellular BM or dysmyelopoiesis without cytopenias 50% (2%). SSM patients were older (p<0.01) and more frequently displayed constitutional symptoms (p<0.01), and anemia (p<0.01). MC mediator-release symptoms (p=0.01), including anaphylaxis (p<0.01), were more frequent in BMM. The following MC-mediators were studied: serum tryptase (57%), beta prostaglandin F2alpha (45%), urine methylhistamine (32%), and urine histamine (21%) – significant differences were noted amongst the ISM subgroups with the following relationship: SSM>ISMo>BMM (p<0.01). (ii) Molecular and cytogenetic abnormalities: Complete karyotype information was available for 55 patients; only 1 patient (with ISMo) had an abnormal karyotype. Fifty nine patients were screened for KITD816V and JAK2V617F; JAK2V617F was universally absent, and distribution of KITD816V was not significantly different amongst the ISM subgroups: SSM (100%), BMM (92%), and ISMo (69%). (iii) Survival and risk of disease transformation: At a median follow of 27 months (range <1-417), 26 deaths were recorded (ISMo 14, SSM 10, and BMM 2), and the combined median survival was 198 months: ISMo 301 months, SSM 120 months, and BMM (not reached) (p<0.01; Figure). Transformation to acute leukemia and ASM was seen in 1 patient (SSM) and 3 patients (2 SSM and 1 ISMo), respectively. Conclusions: Among WHO-defined ISM patients, SSM is associated with significantly shorter survival whereas BMM and ISMo are prognostically similar. If these observations are confirmed by others, consideration may be given to classifying SSM as a distinct subcategory of SM, instead of a sub-variant of ISM as it currently stands. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: Induction therapy with daunorubicin (Dauno) & cytarabine (Ara-C) [DA] has been the standard of care for eligible older adults (age ≥ 60 years) with newly diagnosed acute myeloid leukemia (AML) for over 2 decades. Single agent Clofarabine (CLO) induction & consolidation (Consol.) therapy has demonstrated important clinical activity in this age group in large phase II studies. Lower induction mortality (IM) & similar reported complete remission rate (CR) & overall survival (OS), as well as notable activity in those with higher risk disease features [including unfavorable cytogenetics, therapy-related AML (t-AML) & prior antecedent hematologic disorder (AHD)] raises the possibility that a non-Ara-C-based regimen could achieve similar or superior OS with lower toxicity. Methods: We performed a randomized United States Intergroup Phase III trial of single agent CLO [30mg/m2 x 5 days induction; 20 mg/m2 re-induction (if indicated) & 2 cycles Consol.] vs. standard DA therapy [Dauno 60mg/m2 D1-3 & Ara-C 100mg/m2 D1-7 induction x 1-2 cycles; 2 cycles Consol. with Ara-C (1.5g/m2 Q12hrs D1-6 age 60-69; once daily if age 70+)] in patients (pts) age ≥ 60 yrs with newly diagnosed AML. Patients with serum creatinine >1.0 (or GFR <60 mL/min) and those with AML-M3 and ECOG performance status >3 (PS>2 if age 70+ yrs) were excluded. Randomization was stratified by age (60-69 vs. 70+), t-AML, & AHD. Pts with HLA-matched donor were eligible for allogeneic transplantation (AlloHCT) after induction, and those completing Consol. were eligible for randomization #2 (R#2) to maintenance decitabine [20mg/m2 x 3D, monthly x 1 year] versus observation. With a target accrual of 747, E2906 was powered to determine non-inferiority [and possible superiority] of CLO vs. standard DA, and primary endpoint was OS. A weighted statistical analysis was performed to account for confounding impact of R#2. AlloHCT patients were censored at transplant in this analysis. Responses & cytogenetics were confirmed centrally and OS & CR rates were monitored by an independent Data Safety Monitoring Committee (DSMC) at pre-specified time points. Results: As of Feb 23, 2015, 727 pts were randomized. Median age was 68 years (range 60-86); 57% were male, and 38% were age ≥70 yrs. Treatment arms are well balanced for all baselineclinical & AML characteristics, & 30% had unfavorable cytogenetics. Of 659 with complete treatment information reported, 30.4% on DA vs. 40.1% on CLO received 2 cycles of induction (p=0.006). Median follow-up of surviving patients is 7.6 months. Table 1. shows early treatment results (CR, toxicity) for the 686 pts randomized as of Dec 23, 2014 (2 months prior to study end, & excluding 90 with ongoing response evaluation). DA CLO p-value CR/CRi 43.8% 42.8% p=0.87 30-day mortality 8.5% 7.9% p=0.89 60-day mortality 14.9% 13.1% p=0.58 Gr 4-5 Non-Heme Tox.Induction 27% 19% p=0.02 Gr 4-5 Non-Heme Tox.Consol. 20% 7% p=0.001 374 pts have died (174, DA; 200, CLO) & significantly inferior OS was observed for CLO vs. DA [Hazard Ratio (HR) 1.41 (95% CI 1.12-1.78)] (Fig. 1). Planned subgroup analyses were performed (Table 2) demonstrating significant differences in OS after CLO for patients age 60-69 yrs, without AHD, & with intermediate risk cytogenetics; but not for those with Unfav. Cytogen. (Fig. 2) or t-AML. Based on the primary weighted analysis, DSMC recommended suspension of new accrual to E2906 on Feb 23, 2015 & all active patients on CLO were transitioned to DA Arm. Table 2.NHR CLO/Standard (95% CI)*Weighted OS7271.41 (1.12-1.78)Unweighted OS7271.23 (1.00-1.50)Age 60-694491.48 (1.10-1.99)Age 70+2781.34 (0.93-1.93)Intermed. Risk Cytogen.3781.77 (1.27-2.47)Unfav. Risk Cytogen.2160.96 (0.65-1.43)No AHD6041.46 (1.13-1.89)AHD1231.22 (0.74-2.00)De novo AML6271.52 (1.18-1.96)Therapy-related AML1000.94 (0.54-1.61) Conclusions: Despite similar CR & IM, OS after single agent CLO is inferior to standard DA therapy for pts age ≥60 years with newly diagnosed AML who are fit for intensive therapy, and DA remains the standard of care. However no difference in OS was observed after CLO in some pre-specified high risk AML subgroups. R#2 & AlloHCT arms continue in E2906 for pts already enrolled. Embedded prospective minimal residual disease study at CR is being performed to identify pts at higher risk after CLO & DA. Figure 1. Weighted Kaplan-Meier Curves for OS Figure 1. Weighted Kaplan-Meier Curves for OS Figure 2. Unfavorable Cytogenetics OS by Therapy Figure 2. Unfavorable Cytogenetics OS by Therapy Disclosures Off Label Use: Use of clofarabine in AML, and maintenance therapy with decitabine in AML. Claxton:Medimmune: Research Funding; BMS: Consultancy; Astellas: Research Funding; Cyclacel: Research Funding; Merck: Research Funding; Ambit: Research Funding. Levine:Loxo Oncology: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Foundation Medicine: Consultancy. Altman:Seattle Genetics: Consultancy; BMS: Consultancy; Spectrum: Consultancy; Astellas: Consultancy; Ariad: Consultancy; Novartis: Consultancy. Al-Kali:Novartis: Research Funding.

Abstract Background: acquisition of somatic mutations including JAK2V617F or MPLW515L/K results in constitutive activation of JAK-STAT signaling that commonly characterizes myeloproliferative disorders (MPD). JAK2 is the central signaling mediator for most hematopoietic cytokines in this signaling pathway. Hypothesis: small molecule JAK2 inhibitors may have a therapeutic role in MPD regardless of JAK2 mutation status. Methods: We studied effects of the JAK2 inhibitor, TG101209, in a cell-free kinase assay, relevant cell lines, an in vivo phosphorylation assay, and primary cells from MPD patients carrying JAK2V617F or MPLW515L/K mutations. Results: in a cell-free kinase assay, TG101209 inhibited JAK2 potently (IC50=6nM) and displayed selectivity relative to JAK3, ABL, and VEGFR2 kinases (IC50=170nM, 820nM, and 150nM, respectively). In cell proliferation assays, TG101209 inhibited JAK2-expressing Ba/F3 cells (IC50=280nM) and JAK2V617F-homozygous human erythroleukemia (HEL) cells (IC50=300nM), but not BCR-ABL-carrying K562 cells (IC50>2μM). At 24 hours, TG101209 (600nM) induced apoptosis of HEL cells but not K562 cells (40% and 5%, respectively). SCID mice injected intravenously with Ba/F3-JAK2V617F cells developed significant disease burden including massive splenomegaly due to tumor infiltration (day 12). We observed marked decrease in STAT5 phosphorylation in splenic tumors 5 hours after administration of 2 oral doses of TG101209 (50 mg/kg) in this in vivo model. Based on the above data, we plated patient-derived CD34+ cells in methylcellulose (0nM, 300nM, and 600nM TG101209) with and without cytokines. We studied 2 controls and 9 MPD patients: PV=5 (all JAK2V617F+) and AMM=4 (3 were MPLW515L/K+) for colony number, colony size, and colony mutation burden, under each assay condition. TG101209 inhibited overall colony growth from MPD patients (IC50=300–600nM), and it preferentially suppressed growth of mutant colonies relative to wild type in both of 2 MPLW515K+ patients (AMM1 and AMM2) and in 3 of 5 JAK2V617+ patients (PV1-PV3) (Table). Conclusions: TG101209 potently inhibits cell growth that is dependent on constitutive JAK-STAT signaling. Furthermore, for MPD patient-derived cells, TG101209 preferentially suppresses growth of progenitors carrying JAK-activating mutations (MPLW515K>JAK2V617F>MPLW515L). Hence, our data supports the strategy of targeting aberrant JAK-pathway signaling in MPD as a viable therapeutic approach. Patient Mutation IC50 (nM) No Drug (% colonies mutation-positive) TG101209 (% colonies mutation-positive) Erythroid Myeloid Erythroid Myeloid Erythroid Myeloid Normal WT 1000 600 n/a PV1 JAK2V617F ~600 300–600 82 90 36 70 PV2 JAK2V617F ~300 70 55 60 20 PV3 JAK2V617F NA 20 30 30 0 PV4 JAK2V617F >600 ~600 7 10 17 10 PV5 JAK2V617F ~300 300–600 64 92 82 100 AMM1 MPLW515K <300 ~300 100 90 0 20 AMM2 MPLW515K 300–600 ~300 100 90 25 36 AMM3 MPLW515L 300–600 300–600 100 100 92 90 AMM4 WT >600 300–600 n/a