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Abstract Background: Blasts and leukemic stem cells of acute myeloid leukemia (AML) as well as several other hematologic malignancies express CD123, potentially providing a target for novel therapies. XmAb14045 (also known as SQZ622) is a potent bispecific antibody targeting both CD123 and CD3 that stimulates targeted T cell-mediated killing of CD123-expressing cells, regardless of T cell antigen specificity. It is a full-length immunoglobulin molecule designed to be dosed intermittently, in contrast to smaller constructs that are referred to as "DART" or "BiTE" bispecific antibodies that require a continuous infusion. Methods: Patients with relapsed or refractory AML, B cell acute lymphoblastic leukemia (B-ALL), blast phase chronic myelogenous leukemia, or blastic plasmacytoid dendritic cell neoplasm were eligible to enroll on this first-in-human, multicenter, open-label phase 1 dose-escalation study (XmAb14045-01) with standard 3+3 design. The primary objective was to estimate the maximum tolerated dose (MTD) or recommended dose and schedule of XmAb14045. Secondary objectives included safety, preliminary antileukemic activity, and pharmacokinetics/pharmacodynamics of XmAb14045. Treatment was administered weekly in 28 day cycles, using a weight-based dose with a single dose level in Part A and, in Part B, an initial priming dose on Day 1 followed by an escalated dose on subsequent weeks. Premedication to prevent cytokine release syndrome (CRS) was instituted as needed and included a steroid, acetaminophen, and diphenhydramine. Patients were premedicated at all XmAb14045 doses ≥0.075 µg/kg. Therapy was continued for as long as tolerated and there was continuing evidence of therapeutic benefit in the opinion of the investigator. Treatment response was assessed by the 2017 European LeukemiaNet (ELN) criteria after Cycle 1 and after each odd-numbered cycle. CRS was graded using the CRS revised grading system (Lee et al., Blood, 2014). Results: At data cut-off, 64 patients have been treated to date, 63 with relapsed/refractory AML and 1 with B-ALL. Patients had a median age of 61 years and were heavily pretreated (median of 3 prior therapies [range 1-8], including 19 [30%] who had undergone prior allogeneic stem cell transplantation). The recommended dose for Part A was 1.3 µg/kg after a single dose-limiting toxicity of Grade 4 CRS at 2.3 µg/kg; no MTD has been identified. CRS or its component symptoms was the most common treatment-emergent adverse event (TEAE). CRS episodes began within approximately 1-4 hours of the start of drug infusion and occurred in 49 of 64 patients (77%). Seven patients (11%) developed Grade ≥3 CRS, the majority of these on the first dose. There were no CRS-related deaths. Excluding CRS-related events, additional TEAEs occurring in >10% of patients included fatigue (31%), febrile neutropenia (30%), peripheral edema (30%), cough (23%), elevated hepatic transaminases (19%; all recovered without sequelae), pneumonia (17%), stomatitis (14%), hyperglycemia (13%), and sepsis (11%). No myelosuppression requiring dose modification or evidence of tumor lysis syndrome was seen. In Part A, single agent antileukemic activity was documented with a best response of CR (2) or CRi (1) in 3/13 AML patients (CR/CRi rate 23%) treated at the two highest dose levels studied to date (1.3 and 2.3 µg/kg weekly); no CR, CRi, or morphologic leukemia-free state (MLFS) responses were seen at lower doses. Antileukemic activity occurred quickly; all responders had achieved at least an MLFS response after 4 doses (1 cycle). Two responders were bridged to stem cell transplantation, and the third was ineligible for medical reasons but remains in remission at 14+ weeks after initiating therapy. Conclusions: XmAb14045 demonstrated evidence of antileukemic activity in heavily pretreated patients with relapsed/refractory AML treated in Part A at the 1.3 and 2.3 µg/kg doses administered once weekly, with a 23% CR/CRi rate. CRS was the most common toxicity but was generally manageable with premedications. The study is ongoing with further optimization of dose, schedule, and premedication regimen for CRS anticipated during accrual to dose escalation cohorts in Part B. ClinicalTrials.gov Identifier: NCT02730312 Disclosures Ravandi: Xencor: Research Funding; Abbvie: Research Funding; Amgen: Honoraria, Research Funding, Speakers Bureau; Sunesis: Honoraria; Astellas Pharmaceuticals: Consultancy, Honoraria; Abbvie: Research Funding; Seattle Genetics: Research Funding; Macrogenix: Honoraria, Research Funding; Jazz: Honoraria; Sunesis: Honoraria; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Orsenix: Honoraria; Xencor: Research Funding; Orsenix: Honoraria; Jazz: Honoraria; Bristol-Myers Squibb: Research Funding; Amgen: Honoraria, Research Funding, Speakers Bureau; Macrogenix: Honoraria, Research Funding. Foran:Xencor, Inc.: Research Funding; Agios: Research Funding. Stock:Jazz Pharmaceuticals: Consultancy. Mawad:Swedish Cancer Institute: Employment. Blum:Astellas: Consultancy; Pfizer: Consultancy; Boehringer Ingelheim: Research Funding; Forma: Research Funding; Xencor: Research Funding; Tolero: Research Funding. Saville:Xencor, Inc.: Employment, Equity Ownership. Johnson:Xencor, Inc.: Employment, Equity Ownership. Vanasse:Novartis: Employment, Equity Ownership. Ly:Xencor, Inc.: Employment, Equity Ownership. Mims:Novartis: Consultancy; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Abbvie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Abstract BACKGROUND: Recurrent mutations in isocitrate dehydrogenase 1 (IDH1) are observed in approximately 4% of patients with myelodysplastic syndrome (MDS) and have been linked with increased transformation to acute myeloid leukemia. Ivosidenib (AG-120), an oral, potent, targeted, small-molecule inhibitor of the mutant IDH1 protein (mIDH1), is a therapeutic candidate for the treatment of patients with mIDH1 MDS. Through inhibition of mIDH1, ivosidenib suppresses the production of the oncometabolite 2-hydroxyglutarate (2-HG), leading to clinical responses via differentiation of malignant cells. AIM: To report safety and efficacy data from patients with relapsed or refractory (R/R) MDS enrolled in the first-in-human, phase 1, dose escalation and expansion study of ivosidenib in patients with mIDH1 advanced hematologic malignancies (NCT02074839). METHODS: This ongoing study is evaluating the safety, maximum tolerated dose (MTD), pharmacokinetics, pharmacodynamics, and clinical activity of ivosidenib. Trial enrollment was completed on 08May2017. In dose escalation, patients received single-agent ivosidenib orally once daily (QD) or twice daily in 28-day cycles. The MTD was not reached and 500 mg QD was selected as the dose to be tested in expansion. Expansion Arm 3 enrolled patients with mIDH1 advanced hematologic malignancies, including MDS. The overall response rate (ORR) for MDS was defined as complete remission (CR) + partial remission + marrow CR. Exploratory biomarker assessments included baseline co-occurring mutations (next-generation sequencing panel for hematologic malignancies) and mIDH1 variant allele frequency (VAF) in bone marrow mononuclear cells (BEAMing Digital PCR; lower limit of detection for mIDH1, 0.02-0.04%). Here, we present safety and efficacy data for patients with MDS in expansion Arm 3 and in dose escalation whose starting dose was 500 mg QD. RESULTS: In all, 258 patients (78 in dose escalation, 180 in expansion) received ivosidenib, including 12 patients with MDS (9 from expansion and 3 from escalation) whose starting dose was 500 mg QD. Baseline characteristics for these 12 patients were: 9 men/3 women; median age, 72.5 years (range, 52-78) and 42% were ≥75 years of age; median number of prior therapies, 1 (range, 1-3). As of 10Nov2017, 7 of 12 (58.3%) patients remained on treatment and 5 (41.7%) had discontinued (one for allogeneic stem cell transplantation). The median duration of exposure to ivosidenib was 11.0 months (range, 3.3-31.1). The most common adverse events (AEs) of any grade, irrespective of causality, occurring in ≥20% of the 12 patients were back pain (n=4, 33.3%) and anemia, decreased appetite, diarrhea, dyspnea, fatigue, hypokalemia, pruritus, and rash (n=3, 25.0% each). The majority of these AEs were grade 1-2 and reported as unrelated to treatment. No AEs led to permanent discontinuation of treatment. IDH differentiation syndrome (IDH-DS) was observed in 2 of 12 (16.7%) patients; the events were grade 1 and 2, respectively. Of the 12 patients with MDS receiving ivosidenib 500 mg QD, 5 achieved CR (41.7%; 95% CI 15.2%, 72.3%) and 6 achieved marrow CR (50.0%), resulting in an ORR of 91.7% (95% CI 61.5%, 99.8%). The median durations of CR and overall response were not estimable at the time of the data cutoff. The percentages of patients who remained in CR and response at 12 months were 60.0% and 61.4%, respectively. Among 5 patients who were transfusion dependent at baseline, 4 became transfusion independent for at least 56 days on treatment. Baseline co-occurring mutations and changes in mIDH1 VAF levels on ivosidenib therapy will be presented. CONCLUSION: In patients with mIDH1 R/R MDS, ivosidenib monotherapy was well tolerated and induced durable remissions and transfusion independence. These findings support the role of ivosidenib as an effective, oral, targeted treatment for patients with mIDH1 R/R MDS. Disclosures DiNardo: Karyopharm: Other: Advisory role; Medimmune: Other: Advisory role; Celgene: Other: Advisory role; Bayer: Other: Advisory role; Agios: Consultancy, Other: Advisory role; AbbVie: Consultancy, Other: Advisory role. Watts:Jazz Pharma: Consultancy, Speakers Bureau; Takeda: Research Funding. Stein:Celgene: Consultancy; Daiichi Sankyo: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Bayer: Consultancy. de Botton:Agios: Research Funding; Celgene: Honoraria, Research Funding. Fathi:Takeda: Consultancy, Honoraria; Jazz: Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Boston Biomedical: Consultancy, Honoraria; Astellas: Honoraria; Seattle Genetics: Consultancy, Honoraria; Agios: Honoraria, Research Funding. Stein:Amgen: Speakers Bureau; Celgene: Speakers Bureau. Foran:Agios: Research Funding; Xencor, Inc.: Research Funding. Stone:AbbVie: Consultancy; Agios: Consultancy, Research Funding; Cornerstone: Consultancy; Orsenix: Consultancy; Fujifilm: Consultancy; Sumitomo: Consultancy; Pfizer: Consultancy; Celgene: Consultancy, Other: Data and Safety Monitoring Board, Steering Committee; Ono: Consultancy; Novartis: Consultancy, Research Funding; Otsuka: Consultancy; Jazz: Consultancy; Merck: Consultancy; Astellas: Consultancy; Arog: Consultancy, Research Funding; Argenx: Other: Data and Safety Monitoring Board; Amgen: Consultancy. Patel:France Foundation: Honoraria; Dava Oncology: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Tallman:Cellerant: Research Funding; BioSight: Other: Advisory board; ADC Therapeutics: Research Funding; AbbVie: Research Funding; Daiichi-Sankyo: Other: Advisory board; AROG: Research Funding; Orsenix: Other: Advisory board. Choe:Agios: Employment, Equity Ownership. Wang:Agios: Employment, Equity Ownership. Zhang:Agios: Employment, Equity Ownership. Dai:Agios: Employment, Equity Ownership. Fan:Agios: Employment, Equity Ownership. Yen:Agios: Employment, Equity Ownership. Kapsalis:Agios: Employment, Equity Ownership. Hickman:Agios: Employment, Equity Ownership. Agresta:Agios: Employment, Equity Ownership. Liu:Agios: Employment, Equity Ownership. Wu:Agios: Employment, Equity Ownership, Patents & Royalties. Attar:Agios: Employment, Equity Ownership.

Abstract Introduction: Genetic alterations at 9p24.1 resulting in overexpression of programmed death-1 (PD-1) ligands are near-universal in cHL (Roemer et al, J Clin Oncol 2016); cHL may thus be uniquely sensitive to PD-1 blockade. Nivolumab (nivo), an anti-PD-1 monoclonal antibody, was associated with an objective response rate (ORR) of 69% in relapsed/refractory (R/R) cHL after auto-HCT and irrespective of prior brentuximab vedotin (BV) in the phase 2 CheckMate 205 study (Armand et al, J Clin Oncol 2018; NCT02181738). Whether some patient (pts) can derive very long clinical benefit, whether depth of response predicts long-term outcome, whether treatment (Tx) can be interrupted in complete remission (CR), and whether the safety profile of nivo in R/R cHL changes with prolonged Tx all remain unclear. We therefore present an updated analysis of CheckMate 205, focusing on long-term efficacy and safety. Methods: This international, single-arm, multi-cohort study enrolled pts aged ≥18 y with R/R cHL after auto-HCT. Pts were BV naïve (Cohort A), had prior BV failure after auto-HCT (Cohort B), or had received BV before and/or after auto-HCT (Cohort C). Pts received nivo 3 mg/kg every 2 wk until disease progression (PD)/unacceptable toxicity. Pts in Cohort C discontinued nivo after 1 y in CR and could resume if they relapsed within 2 y of the last dose. Primary endpoint was ORR per independent radiology review committee (IRC); additional endpoints included duration of response (DOR) per IRC, progression-free survival (PFS) per IRC, overall survival (OS), and safety. Time to next Tx (TTNT: time from first dose to next systemic Tx or death) was an exploratory post-hoc analysis. Responses were assessed using International Working Group 2007 criteria. Results: In total, 243 pts were enrolled to Cohorts A (n=63), B (n=80), and C (n=100). Baseline characteristics have been previously described (Armand et al, J Clin Oncol 2018). At data cut-off, minimum follow-up was 31 mo and 49 pts (20%) were still on Tx; the most common reason for discontinuation was PD (35%). Median duration of Tx was 14 mo. ORR per IRC was 71% (65%, 71%, 75% in Cohorts A, B, C, respectively) with a best overall response (BOR) of CR in 21% (32%, 14%, 20% in Cohorts A, B, C, respectively). Among 51 pts who achieved CR, 20 had CR as the first response and 31 improved from partial remission (PR), mostly (n=28/31) within 1 year of first PR. Median time to response was 2 mo, and to CR was 4 mo. Within the first 6, 12, and 18 mo, 68%, 71%, and 71% of pts, respectively, achieved a response. Median DOR was 18 mo overall, and was 32 and 13 mo in pts with a BOR of CR and PR, respectively. Among responders, 64%, 44%, 31%, and 21% of pts had a DOR of at least 6, 12, 18, and 24 mo, respectively. Overall, 11 pts in Cohort C discontinued with persistent investigator-assessed CR; 2 reinitiated nivo due to PD. Median (95% CI) PFS per IRC among all pts was 15 (11-19) mo (Figure A), and was 17, 12 and 15 mo in Cohorts A, B, and C, respectively. Median OS was not reached in any cohort; 24-mo OS rates were 90%, 86%, and 86% in Cohorts A, B, and C, respectively, and were similar among pts in CR, PR, or with stable disease (SD; Figure B). Median TTNT was 29, 27, and 20 mo in Cohorts A, B, and C, respectively. The most common Tx-related adverse events (AEs) of any grade (G) were fatigue (24%), diarrhea (16%), and rash (12%), each <1% G3-4. Tx-related infections were reported in 15% of pts, 2% G3-4. Tx-related infusion related reactions were reported in 34 pts (14%), <1% G3-4. The most commonly reported immune-mediated AE category was rash, which was G3-4 in 4 pts (2%). In total, 26 pts (11%) experienced an AE of any cause leading to discontinuation. There were no Tx-related deaths. Conclusions: With the longest phase 2-3 study follow-up of a checkpoint inhibitor in R/R cHL to date, nivo was associated with frequent and durable responses regardless of BV Tx history. More than 1 in 5 responders remained in response ≥2 years later. With extended follow-up, additional pts achieved CR in all cohorts. Pts with CR had longer PFS than pts with PR or SD. However, pts with both PR and SD had prolonged OS, unlike pts with PD, which may suggest that clinical benefit duration is not well predicted by conventional response criteria. Nivo continued to be well tolerated, with no new safety signals. Characteristics of long-term responders will be presented. Study support: BMS. Medical writing: A Gill, Caudex, funded by BMS Figure. Figure. Disclosures Armand: Infinity: Consultancy; Affimed: Consultancy, Research Funding; Pfizer: Consultancy; Otsuka: Research Funding; Adaptive: Research Funding; Merck: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Roche: Research Funding; Tensha: Research Funding. Younes:Celgene: Honoraria; Genentech: Research Funding; Janssen: Honoraria, Research Funding; Bayer: Honoraria; Novartis: Research Funding; J&J: Research Funding; Astra Zeneca: Research Funding; BMS: Honoraria, Research Funding; Merck: Honoraria; Abbvie: Honoraria; Takeda: Honoraria; Seattle Genetics: Honoraria; Roche: Honoraria, Research Funding; Sanofi: Honoraria; Incyte: Honoraria; Curis: Research Funding; Pharmacyclics: Research Funding. Zinzani:PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Honoraria, Speakers Bureau; Celltrion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Speakers Bureau; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; SERVIER: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees. Collins:ADC Therapeutics: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Speakers Bureau; Celleron: Consultancy, Honoraria; Gilead: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Speakers Bureau; Celgene Corporation: Research Funding; BMS: Consultancy, Honoraria, Research Funding; MSD: Consultancy, Honoraria; Amgen: Research Funding. Ramchandren:Merck: Research Funding; Bristol-Myers Squibb: Consultancy; Seattle Genetics: Consultancy, Research Funding; Pharmacyclics LLC an AbbVie Company: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Cohen:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BioInvent: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Takeda: Research Funding; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees. De Boer:Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Membership on an entity's Board of Directors or advisory committees; EISA: Membership on an entity's Board of Directors or advisory committees. Kuruvilla:Lundbeck: Honoraria; Gilead: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Princess Margaret Cancer Foundation: Research Funding; Leukemia and Lymphoma Society Canada: Research Funding; Abbvie: Consultancy; Merck: Consultancy, Honoraria; Karyopharm: Honoraria; Roche: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria; Amgen: Honoraria; Celgene: Honoraria. Trněný:F. Hoffman-La Roche Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board, Research Funding; Sandoz: Honoraria; Gilead: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Abbvie: Honoraria, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Morphosys: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board. Shipp:Merck: Research Funding; Bayer: Research Funding; AstraZeneca: Honoraria; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Sacchi:Bristol-Myers Squibb: Employment, Equity Ownership. Sumbul:Bristol-Myers Squibb: Employment. Ansell:Trillium: Research Funding; Pfizer: Research Funding; Regeneron: Research Funding; Celldex: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; Merck & Co: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Takeda: Research Funding.

Abstract Background: The phase 3 double-blind, CALGB/Alliance 100104 study assessed the efficacy and safety of lenalidomide (LEN) or placebo maintenance therapy until relapse in post-autologous stem cell transplantation (ASCT) patients with newly-diagnosed multiple myeloma (NDMM). Interim analyses demonstrated superiority for LEN versus placebo for time to progression (TTP), thus meeting the primary TTP endpoint of the trial. The study was unblinded in December 2009 and, based on the TTP and overall survival (OS) benefit observed with LEN, patients in the placebo arm (who had not yet progressed) at the time of unblinding were given the option of crossing over to receive LEN. Data have been reported for a follow-up of 91 months based on the planned intention to treat (ITT) analysis, yielding a TTP hazard ratio (HR) 0.57 and an OS difference of HR 0.61 (Holstein SA, et al. Lancet Haematol. 2017;4:e431-42). Crossover to active treatment enabled patients to benefit from LEN maintenance and collection of additional efficacy and safety data; however, crossover can confound the estimates of OS for longer follow-up. We report the results of an analysis adjusted for crossover, thus aiming to provide a more accurate estimate of the survival benefit achieved with LEN maintenance therapy. Methods: Results are reported for an analysis based on an updated data cutoff, post-October 2016. The rank-preserving structural failure time model (RPSFTM) was considered the most appropriate method to adjust for crossover (Robins JM, Tsiatis AA. Commun Stat Theory Methods. 1991;20:2609-31). This method requires that the assumption that the treatment effect is the same for patients who receive LEN at randomization as those who receive LEN as crossover treatment is not violated; a landmark analysis was performed to explore this. The iterative parameter estimation (IPE; Branson M, Whitehead J. Stat Med. 2002;21:2449-63) algorithm was used as validation. Both the RPSFTM and IPE analyses assume a residual LEN effect after discontinuation (base case). Results: A total of 76 NDMM patients who had not progressed, as determined by central adjudication, crossed over from placebo to LEN and were included in the analysis. The landmark analysis of OS from the date of unblinding indicated that the treatment effect for the crossover versus the non-crossover placebo group was HR 0.57 (95% confidence interval [CI] 0.29-1.15) (Figure). This also provided a measure of the benefit of LEN maintenance in patients who started maintenance therapy after the trial-specified 90-100 day window post-ASCT (median 11.5 months post-randomization; range 3.2-51.0 months). Adjustment for crossover using the RPSFTM or IPE resulted in an increase in the relative treatment effect of LEN maintenance (vs placebo) on OS from 30.8 months for the ITT analysis (HR 0.61; 95% CI 0.47-0.81) to 40.1 months (HR 0.52; 95% CI 0.36-0.73) for the RPSFTM analysis and 38.8 months (HR 0.52; 95% CI 0.37-0.74) for the IPE analysis (Table). Results were consistent across the two methods. Discussion: This analysis was performed on an updated version of the data set reported in the Holstein article. Once we adjusted for crossover, depending on the methodology used, there was an additional gain of ~40 months of OS. Previously, a pre-planned, pooled meta-analysis of 3 studies that included CALGB/Alliance (McCarthy PL, et al J Clin Oncol. 2017;35:3279-89) indicated that the OS gain was 2.5 years; however, our analysis from the CALGB study alone shows that LEN maintenance may provide a survival benefit of > 3 years. In diseases where prolonged follow-up is required to demonstrate survival benefits, allowing patients to crossover to active treatment may be important to facilitate this. However, the results should be analyzed appropriately to enable assessment of the value of the therapy. As this analysis indicates, the value of active treatment may be underestimated if adjustment for crossover is not performed. In conclusion, the data reported here provide further insight into the survival benefits of LEN maintenance therapy post-ASCT and support guideline recommendations to offer LEN maintenance therapy to all patients post-ASCT. Support: U10CA180821, U10CA180882, U10CA180820; ClinicalTrials.gov Identifier: NCT00114101. Disclosures McCarthy: Bristol Myers Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Takeda: Consultancy, Honoraria. Richardson:Amgen: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: 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, Research Funding; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees. Cooper:Celgene: Consultancy; BresMed Health Solutions Ltd: Employment. Saunders:Celgene: Consultancy; BresMed Health Solutions Ltd: Employment. Dhanasiri:Celgene: Employment, Equity Ownership. Anderson:Bristol Myers Squibb: Consultancy; Millennium Takeda: Consultancy; C4 Therapeutics: Equity Ownership, Other: Scientific founder; Celgene: Consultancy; OncoPep: Equity Ownership, Other: Scientific founder; Gilead: Membership on an entity's Board of Directors or advisory committees. Stadtmauer:Celgene: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Takeda: Consultancy. Holstein:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Abstract Background : Treatment for relapsed multiple myeloma (MM) has evolved with the availability of many novel agents; outcomes in patients with newly diagnosed MM have improved with IMiD® agents (lenalidomide [R] or pomalidomide) and proteasome inhibitor (PI) use. Regardless of autologous stem cell transplant, many patients receive R maintenance therapy (Jagannath, Blood Adv 2018; Palumbo, N Engl J Med 2012). However, there is a lack of data describing the nature of relapse and treatment choices for patients progressing on R maintenance therapy. Recent phase III data do not evaluate these patients who are relapsed or refractory to R; current treatment guidelines do not specifically recommend second-line (2L) treatment options for these patients (Laubach, Leukemia 2016). However, phase III data show that pomalidomide in combination with bortezomib and dexamethasone improves progression-free survival (PFS) (HR 0.54; P = 0.0027) in R-exposed and refractory patients, including those with 1 prior line (Richardson, J Clin Oncol 2018). The Connect MM Registry is a US, multicenter, prospective observational cohort study designed to examine diagnostic and treatment patterns, clinical outcomes and quality of life in patients with MM. For patients who received R maintenance therapy, we describe patterns of relapse, 2L treatment choice, and outcomes. Methods : From 250 sites, transplant eligible and ineligible adult patients ≤ 60 days from MM diagnosis were enrolled (N = 3011). Patients were treated at physicians' discretion and followed up for treatment and outcomes until early discontinuation or study end. Patients who relapsed during R maintenance therapy (≤ 15 mg; assessed by treating physician), were analyzed for baseline (BL) characteristics, nature of relapse, and 2L treatment. Patients with symptoms at time of relapse were defined as the presence of ≥ 1 CRAB (hyperCalcemia, Renal failure, Anemia, and Bone disease) criterion ± 60 d from PD; absence of CRAB criteria at PD in this window was considered nonsymptomatic relapse. Primary endpoint was PFS from start of 2L; safety (serious adverse events; SAE) from start of 2L was also assessed. Logistic regression analyses on all BL factors and factors before start of 2L treatment were performed to determine covariates differentiating comparator groups. Survival outcomes were analyzed using a Cox regression after adjusting for covariates. Results : Data cutoff: 1/15/18. Of 2938 treated patients, 1102 entered 2L, 236 having received R maintenance therapy in 1L. Of those patients, 52% (n = 123) and 47% (n = 112) experienced symptoms at time of relapse and nonsymptomatic relapse, respectively (data not available for 1 patient). The top ten 2L regimens are presented in the Table. Median duration of prior maintenance therapy (367 d [IQR: 577] vs 489 d [IQR: 599]) and time from first progression to start of 2L treatment (0.3 vs 0.3 mo) did not notably differ between nature of relapse groups. Prolonged median PFS from start of 2L was observed for patients receiving triplet+ (≥ 3 agents) vs doublet (≤ 2 agents) regimens (HR: 0.72; Figure 1). PFS was better for IMiD agent + PI group compared with PI (without IMiD agents) group (HR, 0.68; Figure 2). Results of sensitivity analyses and overall survival will be presented. SAEs occurred similarly among treatment groups: 42.6% with IMiD agent + PI, 34.5% with IMiD agent (without PI), and 35.8% with PI. Conclusions: This is the first description of relapse patterns, 2L treatment choice and survival outcomes after PD on R maintenance therapy in community-based patients. Nearly equal numbers of patients had symptoms at time of relapse and nonsymptomatic relapse on R maintenance therapy. After PD on R maintenance, approximately 50% of patients switched to PI regimens without IMiD agents, 25% continued with IMiD agent + PI regimens, and 25% continued in the IMiD agents group. Our data show PFS benefit for triplet+ over doublet treatment in 2L. Patients in the IMiD agent + PI group gained survival benefits over patients in the PI group. Further characterization of the patients continuing with IMiD treatment in 2L after R maintenance therapy relapse (~ 25% of patients) are ongoing. Follow-up with recently approved agents (elotuzumab, daratumumab) and their use in 2L is limited in this analysis. These data may be used to better inform treatment choices after relapse on R maintenance therapy. Disclosures Jagannath: Celgene: Consultancy; Merck: Consultancy; Multiple Myeloma Research Foundation: Speakers Bureau; Medicom: Speakers Bureau; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy. Narang:Janssen: Speakers Bureau; Celgene: Consultancy, Speakers Bureau. Ailawadhi:Takeda: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Pharmacyclics: Research Funding; Celgene: Consultancy. Rifkin:Celgene: Consultancy; Boehringer Ingelheim: Consultancy; McKesson: Equity Ownership; EMD Serono: Consultancy; Amgen: Consultancy; Takeda: Consultancy; Sandoz: Consultancy. Terebelo:Celgene: Consultancy; Janssen: Speakers Bureau; Takeda: Speakers Bureau; Pharmacyclics: Speakers Bureau. Toomey:Celgene: Consultancy; Myriad Genetics: Speakers Bureau; Dava Oncology: Other: Travel. Durie:Takeda: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Amgen: Consultancy. Hardin:Celgene: Consultancy. Gasparetto:Janssen: Consultancy, Honoraria, Other: Travel; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel; Takeda: Honoraria; Celgene: Consultancy, Honoraria, Other: Travel, Research Funding. Wagner:EveryFit: Consultancy; Gilead: Consultancy; Janssen: Consultancy. Omel:Takeda Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Srinivasan:Celgene: Employment. Kitali:Celgene: Employment. Agarwal:Celgene Corporation: Employment, Equity Ownership. Abonour:Prothena: Research Funding; Takeda: Consultancy, Research Funding; Celgene: Consultancy, Research Funding.

Abstract Background Therapy-related myeloid neoplasm (tMN) includes t-myelodysplasia (tMDS) and t-acute myeloid leukemia (tAML) and are serious late effects of the treatment of cancer. Prognosis of tMN is poor, related to the increased frequency of adverse cytogenetics and other clinical features which predict poor response to conventional treatment. Over the last years, azacitidine (AZA) has become the standard of treatment for high risk MDS (Silverman, JCO 2002; Fenaux, Lancet Oncol 2009) and has shown efficacy in AML. AZA represents an interesting option for patients with tMN considering its safety profile and its efficacy in poor prognosis subgroups of apparently de novo MDS patients including those with monosomy 7. Most prospective trials of AZA have excluded patients with tMN. Most tMN data are retrospective or registry studies (Bally, Leuk Res 2013). This abstract presents the results of 47 t-MN patients prospectively enrolled as a specific cohort in the E1905 study. Methods E1905 study is a randomized phase 2 study from the North American Leukemia Intergroup (NCT00313586, Prebet , ASH 2010) 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). 6 cycles of treatment were planned; responding patients could receive up to 24 cycles. MDS, CMML, and AML with myelodysplasia-related changes were included. Patients with tMN were subsequently accrued as a separate cohort after amendment of the protocol. Response was assessed using IWG 2000 criteria (Cheson et al, Blood 2000); the primary endpoint of the overall trial was achievement of a normal hemogram in 25% of treated patients in either treatment arm. Results A total of 47 patients were included. Median age was 70 years (39y-83y), 45% male, and 94% of patients had ECOG PS 0-1. 29 patients could be subclassified as t-MDS and 18 as t-AML. At inclusion, median peripheral blood counts were: neutrophils 1.0 G/l, Platelets 35 G/L, Hemoglobin 9.2 g/l, peripheral blood blasts 0%, marrow blasts 14.0%. 68% of patients were RBC transfusion dependent and 40% platelet transfusion dependent. As expected, the cytogenetic evaluation showed a high frequency of unfavorable risk cytogenetics (74%) as compared to normal or intermediate risk cytogenetics (26%). Baseline characteristics were not statistically different between the 2 arms. 24 patients were treated with AZA monotherapy and 23 with AZA+entinostat. The median number of administered cycles was 4 and was significantly higher in patients treated with AZA monotherapy (6 cycles vs.3 cycles, p=0.008). 8 patients in the combination arm and 1 patient in the AZA monotherapy arm died of infection or hemorrhage before cycle 3. In an intent to treat analysis, overall response rates (CR, PR, or trilineage Hematologic improvement) were 11/24 (46%) in AZA monotherapy (95% CI 26 – 67%) and 4/23 (17%) in the combination arm (95% CI 5 – 39%, p=0.06 comparing the two arms). Median overall survival in the two arms were 12.8 months and 5.7 months (p=0.008). Conclusions In this group of very high risk patients with therapy-related myeloid neoplasms, the use of the novel 50 * 10 schedule of azacitidine monotherapy appears effective, with response rates comparable to those for patients with de novo MDS/AML treated on the same protocol (74 pts, 40% with unfavorable cytogenetics, ORR=32%, median OS=18 months). Because there are no prospective data examining the approved dose schedule of AZA (75 mg/m2/day * 7 days), it is not clear if this surprisingly high response rate derives from the current extended schedule of lower dose AZA, or would be true with standard dose AZA as well. This high response may enable many of these patients to proceed to allogeneic stem cell transplant. Entinostat combined with azacitidine at the dose and schedule applied in E1905 does not appear to be effective and tolerable as compared to azacitidine alone. Disclosures: Prebet: CELGENE: Honoraria. Off Label Use: Use of azacitidine in acute myeloid leukemia. Gore:CELGENE: Equity Ownership, Research Funding.

Abstract Introduction:The prognosis is poor for patients with follicular lymphoma (FL) who experience early relapse within 2 years of initial diagnosis and for those who are double refractory to both rituximab and chemotherapy (Casulo et al. J Clin Oncol 2015). Avadomide, a cereblon-modulating agent that promotes degradation of the hematopoietic transcription factors Aiolos and Ikaros, is being examined in this setting. Avadomide demonstrated promising clinical activity in combination with obinutuzumab or rituximab in relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL) and FL (Michot et al. Blood 2017; Ribrag et al. Blood 2017). Herein, we report FL subgroup analyses for the avadomide plus rituximab combination (Arm D) of the CC-122 DLBCL-001 study in both lenalidomide-naïve and treated patients. Methods: CC-122-DLBCL-001 (NCT02031419) is aphase Ib dose escalation/expansion study of avadomide, CC-223, and CC-292 given orally as doublets, and as triplets in combination with rituximab, as well as avadomide plus rituximab doublets, in patients with R/R DLBCL or FL after ≥1 prior line of therapy. In the dose expansion phase of the study, patients received avadomide once daily (QD) for 5 days/week (5/7 d), with a fixed dose of intravenous rituximab 375 mg/m2/cycle (28-day cycle). The study endpoints were safety, tolerability, pharmacokinetics, preliminary efficacy (overall response rate [ORR] and complete response [CR]), and blood pharmacodynamic markers of avadomide. Results: As of May 1, 2018, 37 patients with FL were enrolled in the Arm D expansion group, including 29 in cohort 1 (no prior lenalidomide) and 8 in cohort 2 (≥2 cycles of prior lenalidomide). Baseline patient characteristics were similar between the two cohorts. In the total FL population, the median age was 61 years (range, 41-81 years), 54% were male, and 46% had an Eastern Cooperative Oncology Group performance status of 1. The median number of prior systemic anticancer regimens was 3 (range, 1-8). At disease diagnosis, three patients (8%) had bulky disease (≥7 cm in single dimension) and 7 (19%) had high Follicular Lymphoma International Prognostic Index scores. Twenty-three patients (62%) were refractory to rituximab and 11 (30%) were double-refractory to rituximab and an alkylating agent. As of the data cutoff, 27 patients (71%) were ongoing and no evaluable patients had experienced a dose-limiting toxicity. The most common (≥10%) any-grade adverse events (AEs) were neutropenia (46%) and anemia (24%). Grade 3/4 AEs occurring in >1 patient were neutropenia (32%); fatigue, dizziness, and anemia (8% each); febrile neutropenia and diarrhea (5% each). Six patients (16%) experienced serious AEs related to study drugs. One patient died during the study (sepsis considered possibly related to study treatment). Avadomide dose reduction occurred in 7 (19%) patients. Among all FL patients, the ORR was 65% with 8 patients (22%) achieving a CR. Response rates appeared to be independent of prior lenalidomide treatment, with an ORR of 62% (CR=14%) in cohort 1 and an ORR of 75% (CR=50%) in cohort 2. The median follow up for progression-free survival (PFS) was 6.3 months and 49% of patients had <6 months of PFS follow up. In the total FL population, 6-month and 12-month PFS rates were 83 (95% CI, 64-93) and 66 (37-84), respectively. Conclusions: Avadomide combined with rituximab was well tolerated. AEs were generally consistent with the known safety profile of avadomide and toxicities associated with rituximab. Moreover, this combination showed promising efficacy in patients with R/R FL independent of prior treatment with lenalidomide. These findings support the role of avadomide plus an anti-CD20 antibody as a novel chemotherapy-free treatment for this difficult to treat patient population. Disclosures Nastoupil: TG Therappeutics: Research Funding; Karus: Research Funding; Novartis: Honoraria; Merck: Honoraria, Research Funding; Juno: Honoraria; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Research Funding; Spectrum: Honoraria; Genentech: Honoraria, Research Funding. Ribrag:Amgen: Research Funding; Roche: Honoraria, Other: travel; epizyme: Consultancy, Honoraria; MSD: Honoraria; Infinity: Consultancy, Honoraria; NanoString Technologies: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Other: travel; Servier: Consultancy, Honoraria; pharmamar: Other: travel; Gilead: Consultancy, Honoraria; Incyte Corporation: Consultancy; argenX: Research Funding. Chavez:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Humanigen: Consultancy; Merck: Research Funding; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Speakers Bureau. Witzig:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Andorsky:AstraZeneca: Consultancy; Genentech: Consultancy; Celgene: Research Funding; CTI BioPharma: Consultancy, Research Funding. Corradini:Janssen: Honoraria, Other: Lecturer; Amgen: Honoraria, Other: Advisory Board & Lecturer; Gilead: Honoraria, Other: Advisory Board & Lecturer; Celgene: Honoraria, Other: Advisory Board & Lecturer; Roche: Honoraria, Other: Advisory Board & Lecturer; Takeda: Honoraria, Other: Advisory Board & Lecturer; Sanofi: Honoraria, Other: Advisory Board & Lecturer; Novartis: Honoraria, Other: Advisory Board & Lecturer; Abbvie: Honoraria, Other: Advisory Board & Lecturer; Sandoz: Other: Advisory Board. Flinn:ArQule: Research Funding; Agios: Research Funding; TG Therapeutics: Research Funding; Calithera: Research Funding; BeiGene: Research Funding; Verastem: Consultancy, Research Funding; Janssen: Research Funding; Curis: Research Funding; Pharmacyclics: Research Funding; Incyte: Research Funding; Trillium: Research Funding; Forty Seven: Research Funding; Kite: Research Funding; Pfizer: Research Funding; Verastem: Research Funding; Novartis: Research Funding; Genentech: Research Funding; Merck: Research Funding; Portola: Research Funding; Takeda: Research Funding; Seattle Genetics: Research Funding; Constellation: Research Funding; Forma: Research Funding; Celgene: Research Funding; Gilead: Research Funding; Infinity: Research Funding. Sangha:Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Lilly: Honoraria, Membership on an entity's Board of Directors or advisory committees; Lundbeck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; BI: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees. Uttamsingh:Celgene Corporation: Employment, Equity Ownership. Hagner:Celgene Corporation: Employment, Equity Ownership. Gandhi:Celgene Corporation: Employment, Equity Ownership. Chen:Celgene Corporation: Employment, Equity Ownership. Hege:Mersana: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; SITC: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Employment, Equity Ownership, Patents & Royalties: multiple; Arcus Biosicences: Membership on an entity's Board of Directors or advisory committees. Pourdehnad:Celgene Corporation: Employment, Equity Ownership. Kuruvilla:Celgene: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Lundbeck: Honoraria; BMS: Consultancy, Honoraria; Abbvie: Consultancy; Merck: Consultancy, Honoraria; Amgen: Honoraria; Seattle Genetics: Consultancy, Honoraria; Karyopharm: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Princess Margaret Cancer Foundation: Research Funding; Leukemia and Lymphoma Society Canada: Research Funding.

Abstract Introduction: The phase 2 CheckMate 205 study (NCT02181738) of nivolumab (nivo) has demonstrated high objective response rates (ORRs), durable efficacy, prolonged overall survival (OS), and an acceptable safety profile in patients (pts) with relapsed/refractory classical Hodgkin lymphoma (R/R cHL) after failure of autologous hematopoietic cell transplantation (auto-HCT) irrespective of prior brentuximab vedotin (BV) treatment (Armand et al, J Clin Oncol 2018). Atypical response patterns have been observed with checkpoint inhibitors, and clinical benefits may be experienced by pts who are treated beyond progression (TBP) as defined by conventional criteria (Cheson et al, Blood 2016; Younes et al, Ann Oncol 2017). Stable reductions in tumor burden without symptoms of active disease were seen in pts TBP in CheckMate 205, suggesting that pts might continue to derive clinical benefits from nivo beyond disease progression. As TBP was an option for some pts in CheckMate 205, we report here updated outcomes of those pts. Methods: This single-arm, multicenter study enrolled pts (age ≥18 y) with R/R cHL after failure of auto-HCT into 3 cohorts (A: BV naïve; B: BV after auto-HCT; C: BV before and/or after auto-HCT). Nivo was administered at 3 mg/kg IV every 2 wk until disease progression or unacceptable toxicity (or after 1 year in complete response [CR] for cohort C). Response was assessed by 2007 International Working Group (IWG) criteria. A protocol amendment allowed pts with stable performance status and perceived clinical benefit to be TBP per investigator assessment. Tumor burden after initial progression was assessed; exploratory analyses included OS and time to next therapy (TTNT). Pts TBP were further categorized as PD-1 resistant (failure to achieve CR/partial response [PR] during initial treatment with nivo or CR/PR with subsequent progressive disease [PD] ≤90 d of response) and non-resistant pts (CR/PR followed by PD >90 d from response). Results: At data cutoff, 130 pts had PD, among whom 80 (62%) were TBP, and 50 (38%) were not (non-TBP). Demographics of pts TBP and non-TBP were similar to the overall study population, although more pts TBP had ECOG performance status of 0 at baseline (59% vs 36%) and stage IV disease at diagnosis (30% vs 22%), but fewer had B symptoms at baseline (23% vs 30%). In pts TBP vs non-TBP, the cause of initial progression was new lesions in 50 (63%) vs 23 (46%), increased total tumor burden in 17 (21%) vs 11 (22%), and non-target lesion progression in 19 (24%) vs 4 (8%) (pts could have multiple reasons for progression). ORR prior to progression was similar between TBP (54%) and non-TBP (64%) pts. At data cutoff, the median (range) doses of nivo given beyond progression was 11 (1-64) and median TBP duration was 5 (95% CI: 3, 7) mo. Nine (11%) pts TBP remained on treatment compared with 2 (4%) non-TBP. The most common reason for discontinuation was further disease progression in 55 (69%) and 28 (56%) pts TBP and non-TBP, respectively. The majority of pts TBP (37/67 evaluable pts) had stable or reduced target lesion tumor burden and most had sustained further reduction compared with the burden presented at the time of disease progression (Figure). There was no discernible difference in the response to TBP between PD-1 resistant vs non-resistant pts. Median OS for pts TBP was not reached; 1- and 2-yr OS (95% CI) was 94% (85, 97) and 87% (77, 93), respectively. Median TTNT was 20 (95% CI: 14, 24) mo for all pts TBP. Treatment-related adverse events (TRAEs) occurred in 50% of pts after progression vs 68% prior to progression. The most common TRAEs reported after progression were fatigue (8%) and increased lipase (6%). Treatment-related serious AEs after progression were reported in 2 (3%) pts: aspartate aminotransferase increase (n=1) and hypercalcemia (n=1). No deaths occurred in pts TBP. Conclusions: Among pts treated beyond investigator-assessed progression, most commonly due to development of new lesions, continued reductions in tumor burden were observed in a majority with further nivo treatment irrespective of prior PD-1 resistance status. Nivo continued to be well tolerated during TBP with no new safety signals. Pts who have stable performance status despite progression according to conventional criteria may derive continued clinical benefit from TBP. Future work will focus on identifying subsets of pts TBP who may benefit the most from continued nivo treatment. Study support: BMS. Disclosures Cohen: Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BioInvent: Consultancy; Bristol-Myers Squibb: Research Funding; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Kuruvilla:Leukemia and Lymphoma Society Canada: Research Funding; BMS: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Princess Margaret Cancer Foundation: Research Funding; Seattle Genetics: Consultancy, Honoraria; Lundbeck: Honoraria; Gilead: Consultancy, Honoraria; Celgene: Honoraria; Amgen: Honoraria; Karyopharm: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy; Merck: Consultancy, Honoraria. Ansell:Celldex: Research Funding; Takeda: Research Funding; Pfizer: Research Funding; LAM Therapeutics: Research Funding; Merck & Co: Research Funding; Affimed: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding. Younes:Abbvie: Honoraria; J&J: Research Funding; Roche: Honoraria, Research Funding; Merck: Honoraria; Curis: Research Funding; Janssen: Honoraria, Research Funding; Novartis: Research Funding; Pharmacyclics: Research Funding; Takeda: Honoraria; BMS: Honoraria, Research Funding; Seattle Genetics: Honoraria; Sanofi: Honoraria; Bayer: Honoraria; Celgene: Honoraria; Astra Zeneca: Research Funding; Incyte: Honoraria; Genentech: Research Funding. Trněný:Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; F. Hoffman-La Roche Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board, Research Funding; Gilead: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Morphosys: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Sandoz: Honoraria; Abbvie: Honoraria, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board. Ramchandren:Bristol-Myers Squibb: Consultancy; Merck: Research Funding; Seattle Genetics: Consultancy, Research Funding; Pharmacyclics LLC an AbbVie Company: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Collins:BMS: Consultancy, Honoraria, Research Funding; MSD: Consultancy, Honoraria; Celgene Corporation: Research Funding; Amgen: Research Funding; Takeda: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria; ADC Therapeutics: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria, Speakers Bureau; Celleron: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Speakers Bureau. Zinzani:Astra Zeneca: Speakers Bureau; PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; PFIZER: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; MSD: Honoraria, Speakers Bureau; Takeda: Membership on an entity's Board of Directors or advisory committees; SERVIER: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celltrion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TG Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees. De Boer:EISA: Membership on an entity's Board of Directors or advisory committees; MSD: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding. Shipp:Merck: Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Honoraria; Bayer: Research Funding. Sacchi:Bristol-Myers Squibb: Employment, Equity Ownership. Sy:Bristol-Myers Squibb: Employment. Armand:Otsuka: Research Funding; Affimed: Consultancy, Research Funding; Infinity: Consultancy; Pfizer: Consultancy; Merck: Consultancy, Research Funding; Adaptive: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Roche: Research Funding; Tensha: Research Funding.

Abstract Abstract 2859 Introduction: Patients with chronic lymphocytic leukemia who relapse following purine-analog or bendamustine-based treatments have a poor prognosis. These patients have limited therapeutic options and novel agents with alternative mechanisms of action are needed. In phase 1 and 2 trials, escalating dose regimens of the immunomodulatory agent lenalidomide demonstrated promising activity with relapsed/refractory CLL. Of interest, the data indicate that superior efficacy might be achieved by a starting dose above 2.5 mg daily lenalidomide. A phase 2 trial (CLL-009 study) was developed to investigate the safety of different starting doses of lenalidomide followed by a step-wise dose escalation as tolerated in relapsed/refractory CLL. Methods: In this ongoing trial, eligible subjects with relapsed/refractory CLL who have received at least 1 prior treatment regimen are being enrolled. Subjects are randomized 1 :1 :1 to receive a double-blinded starting dose of 5 mg, 10 mg, or 15 mg oral lenalidomide on days 1–28 of each 28-day cycle. The primary objectives are to determine the safety and efficacy of the different lenalidomide starting doses of 5 mg, 10 mg or 15 mg daily, followed by an intra-patient escalation up to a maximum of 25 mg daily using a Bayesian approach. Based on individual patient tolerability, the daily lenalidomide dose can be escalated every 28 days by 5 mg increments. Dose reductions also occur in 5 mg increments; however, dose levels below 5 mg sequentially include 2.5 mg and 1.25 mg daily. Tumor lysis syndrome (TLS) prophylaxis, comprised of oral hydration and allopurinol 300 mg/day is initiated at least 3 days prior to starting study drug and for a minimum of the first 3 treatment cycles. This adaptive design trial is considering joint efficacy and toxicity outcomes to stop randomization of less promising arms. Accrual to a starting dose arm will be stopped if unacceptable toxicities and/or high progression rate are observed in that arm. A total of 90 subjects will be enrolled in the study. Results: To date, 51 subjects with a median age of 63 years (range 39–78) have been enrolled. Subjects to date are primarily male (65%) and Caucasian (84%), and slightly more than half (53%) are ≥ 65 years old. Cytogenetic data is available for 42 subjects; 10 have del(11q), 8 have del(17p), and 24 have del(13q). Overall, 31 subjects had at least one cytogenetic deletion. Based on the Binet and Rai staging systems: 3 (6%), 10 (20%) and 15 (29%) of subjects are stage A, B and C, respectively; and, 6 (12%), 7 (14%) and 7 (14%) subjects are low, intermediate or high-risk disease, respectively. For 3 (6%) subjects the Binet/Rai staging is currently unknown. The most common hematological grade 3/4 adverse events (AEs) thus far include neutropenia (41% of patients) and thrombocytopenia (24%). The most common non-hematological grade 3/4 AEs include fatigue (12%) and tumor flare (12%). Only 1 subject (2%) experienced tumor lysis syndrome of grade 1. Over half of the subjects (53%) remain on therapy; 24 (47%) subjects have discontinued treatment. The longest subject has completed 17 cycles, and remains on study medication. The most common reasons for study discontinuation include disease progression (n = 8) and AEs (n = 10). To date, 20 subjects (54% of eligible patients) have successfully dose escalated above their respective starting double blinded dose level, including 3, 3, 2 and 12 subjects undergoing 4, 3, 2, and 1 dose escalations, respectively. As 14 patients are still in the first cycle of the study, a total of 20 subjects have had no dose level reduction or escalations. The average duration of treatment is 4.34 cycles, and the median number of cycles is 3. Efficacy evaluations are completed monthly after 3 months of study drug treatment. By investigator assessment, 34 subjects have been evaluated to date, including 1 (3%) complete response, 12 (35%) partial response, 7 (21%) stable disease, 10 (29%) progressive disease and 4 (12%) not evaluable. Conclusion: The independent Data Monitoring Committee, as of March 24, 2011 (N=41), recommended that accrual into all three treatment arms should continue as planned, suggesting all three starting doses were tolerated. To date, the ORR is 38% (13/34 evaluable subjects), and 54% of subjects (20/37) have dose escalated at least once. In this relapsed/refractory CLL population lenalidomide appears active, and completion of accrual will hopefully demonstrate the appropriate starting dose. Disclosures: Wendtner: Celgene: Consultancy, Honoraria, Research Funding. Off Label Use: lenalidomide in cll. Goldberg:Celgene: Honoraria, Research Funding, Speakers Bureau. Bloor:Celgene: Honoraria, Research Funding. Stilgenbauer:Celgene: Consultancy, Honoraria, Research Funding. Cymbalista:Roche: Research Funding; Mundipharma: Honoraria; Genzyme: Honoraria. Kipps:Celgene: Consultancy, Research Funding; Abbott Industries: Research Funding; Genentech: Research Funding; Gilead Sciences: Consultancy, Research Funding; Igenica: Membership on an entity's Board of Directors or advisory committees. Purse:Celgene: Employment, Equity Ownership. Zhang:Celgene: Employment, Equity Ownership. Mei:Celgene: Employment.

Abstract Abstract 824 There is no standard therapy for MM relapsing after autologous hematopoietic cell transplantation (AHCT). A second AHCT can result in additional progression-free survival (PFS). Nonmyeloablative/reduced intensity conditioning (NST/RIC) allogeneic transplantation (AlloHCT) has the advantages of a tumor-free graft and the potential of a graft-versus-myeloma (GVM) effect. Few studies have compared second AHCT vs. NST/RIC AlloHCT. We compared the outcome of second AHCT or NST/RIC AlloHCTafter relapse from prior AHCT in patients with MM reported to the CIBMTR from 1995–2008. Recipients of planned tandem transplants, AlloHCT for graft failure or second malignancies and myeloablative alloHCT were excluded. 137 patients underwent second AHCT and 152 underwent NST/RIC AlloHCT (32 HLA-identical sibling and 120 unrelated donor). The table below illustrates clinical characteristics and patient outcomes. AlloHCT recipients were significantly younger (median 53 years [yrs] of age vs. 56 yrs in the AHCT cohort (p < 0.001). The groups were similar in Karnofsky performance score (KPS) and gender. Conditioning regimens differed between groups. In the AHCT cohort, 85% were melphalan based. In the NST/RIC alloHCT cohort, 38% received melphalan + other drugs and 24% received total body irradiation +/− other drugs but no melphalan (p <0.001). Time from 1st to 2nd transplant was significantly shorter for the AlloHCT cohort (30 vs. 23 months, p = 0.014). Acute graft-versus-host disease (GVH) was 35% at 60 days while chronic GVHD was 44% at 36 months.Patient CharacteristicsAutologousAllogeneicP-valueNumber of patients137152Age at 2nd transplant, median (range), years56 (28–65)53 (32–65)0.001*Gender Male84 (61)90 (59)0.720Karnofsky Score pre-transplant ≥90%68 (50)76 (50)0.884Time from 1st to 2nd transplant, months, median (range)30 (6–122)23 (6–78)0.014* 6–24 months44 (32)78 (51)0.001* >24 months93 (68)74 (49)OutcomesTreatment-related Mortality (TRM)12 months2 (1–5)13 (8–19)<0.001*60 months4 (2–8)15 (10–21)<0.001*Relapse/Progression12 months51 (43–58)72 (64–79)<0.001*36 months82 (76–88)80 (73–86)0.655Progression-free survival12 months47 (40–54)15 (10–21)<0.001*36 months13 (9–19)6 (3–10)0.038*Overall Survival (OS)12 months83 (77–89)51 (42–58)<0.001*36 months46 (37–54)20 (14–27)<0.001*60 months29 (21–38)9 (5–15)<0.001**Significant difference The most common cause of death in both cohorts was progression of MM. On multivariate analysis risk of death was higher for alloHCT (HR 2.38, p < 0.001), KPS < 90 (HR 1.96, p < 0.001), and year of transplant (2004 or earlier, HR 1.77, p = < 0.001). AlloHCT was associated with significantly higher risk of TRM (HR 7.14, p < 0.001). Durie-Salmon Stage III was associated with a higher risk of relapse (HR 2.70, 95% CI: 1.93–3.80, P<0.001) and treatment failure in the alloHCT group (HR 3.05, 95% CI: 2.20–4.22, p < 0.001). We conclude that patients with MM who underwent NST/RIC alloHCT after AHCT failure experienced higher TRM and lower probability of survival compared with those who received second AHCT. Because genetic risk data were not available for these patients, we cannot exclude the possibility that the alloHCT population was a higher risk population. Despite this limitation, our data demonstrate that the value of alloHCT after relapse from prior AHCT is limited. Disclosures: No relevant conflicts of interest to declare.