Abstract: Background: Hematopoietic cell transplantation (HCT) is an integral part of the treatment of multiple myeloma (MM). While autologous stem cell transplantation (auto-HCT) is most commonly used, the duration of response is typically finite. Allogeneic HCT (allo-HCT) can provide prolonged survival in some patients, given the added benefit of the graft-versus-myeloma effect. However, long-term data is needed to show this improvement. Method: We retrospectively reviewed a cohort of 37 consecutive patients with newly diagnosed MM who received allo-HCT as part of consolidation therapy between 1994 to 2016. Results: The median age was 54 years (range, 32 to 68), and 54% were male. The Revised International Staging System (R-ISS) stages were I, II, III, and unknown in 27%, 38%, 11%, and 24% of patients, respectively. High-risk cytogenetics (IMWG definition) was identified in 22% of patients. The median time from diagnosis to allo-HCT was 8.8 months (range; 3.3 to 34.3). For induction treatment, fourteen patients (38%) received a combination of immunomodulatory drug (IMiD) plus proteasome inhibitor (PI), sixteen patients (43%) received either IMiD or PI in combination with other agents, and seven patients (19%) did not receive either an IMiD or PI. Twenty-seven (73%) patients received auto-HCT before allo-HCT. Thirty-four (92%) patients received allo-HCT as part of various clinical trials. Median time from auto-HCT to allo-HCT was 4 months (2.5 to 27.3). Prior to allo-HCT, 1 (3%) patient was in complete remission (CR), 18 (48.5%) were in very good partial remission (VGPR), and 18 (48.5%) were in partial remission (PR). Twenty-three (62%) patients received non-myeloablative (NMA) conditioning, 10 (27%) reduced-intensity (RIC), and 4 (11%) myeloablative conditioning (MAC). The graft source was matched unrelated (MUD) in 16% and matched sibling donor (MRD) in 84% of patients. Ten (27%) patients received maintenance therapy after allo-HCT, including bortezomib (n=2), thalidomide (n=2), ixazomib (n=2), and lenalidomide (n=4). The median days to neutrophil and platelet engraftment was 12 (ANC ≥500/µL_ range; 10 to 59) and 13 (platelet count ≥20K/µL _range; 9 to 70), respectively. The cumulative incidence (CI) of non-relapse mortality (NRM) was 16% at 1-year and 19% at 3-years after allo-HCT. There was no difference in NRM between MAC or NMA/RIC conditioning. The overall response rate (PR or better) was 97%, with a 54% stringent CR+CR rate. The incidence of grade I-IV acute graft-versus-host disease (GVHD) was 35%, while chronic GVHD was seen in 62%. Causes of death were deemed to be disease-related in 8 patients, treatment-related in 11 patients, and 1 unknown. The median follow-up in surviving patients was 12.6 years (range; 2.8 to 15.8 years). The 3, 5, and 10-year actuarial overall survival (OS) rates were 70%, 56%, and 47%, respectively (Figure 1A). The 3, 5, and 10-year actuarial progression-free survival (PFS) rates were 66%, 50%, and 36%, respectively (Figure 1B). At the last follow up, 46% (n=17) of patients were alive in the entire cohort, 65% (n=11) of which survived for longer than 10-years from transplant. Sixteen percent (n=6) remained alive and in continued remission for more than 10 years from transplant, one-third of whom received maintenance treatment post allo-HCT. The longest ongoing remission was 15.8 years in this cohort. Conclusion: Allo-HCT may result in durable ( & gt;10 years) remission in a number of MM patients when performed early in the disease course. Larger studies would help identify the patients who would benefit the most, given the risk of graft-versus-host disease after allo-HCT. Disclosures Popat: Bayer: Research Funding; Novartis: Research Funding. Kebriaei:Pfizer: Other: Served on advisory board; Kite: Other: Served on advisory board; Amgen: Other: Research Support; Jazz: Consultancy; Novartis: Other: Served on advisory board; Ziopharm: Other: Research Support. Oran:Celgene: Consultancy; ASTEX: Research Funding; Arog Pharmaceuticals: Research Funding. Hosing:NKARTA Inc.: Consultancy. Manasanch:Adaptive Biotechnologies: Honoraria; GSK: Honoraria; Sanofi: Honoraria; BMS: Honoraria; Takeda: Honoraria; Quest Diagnostics: Research Funding; Merck: Research Funding; JW Pharma: Research Funding; Novartis: Research Funding; Sanofi: Research Funding. Lee:Amgen: Consultancy, Research Funding; Genentech: Consultancy; Regeneron: Research Funding; Daiichi Sankyo: Research Funding; Sanofi: Consultancy; GlaxoSmithKline: Consultancy, Research Funding; Genentech: Consultancy; Takeda: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Kaufman:Karyopharm: Honoraria; Bristol Myers Squibb: Research Funding; Janssen: Research Funding. Patel:Precision Biosciences: Research Funding; Takeda: Consultancy, Research Funding; Cellectis: Research Funding; Janssen: Consultancy, Research Funding; Poseida: Research Funding; Oncopeptides: Consultancy; Nektar: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding. Orlowski:Founder of Asylia Therapeutics, Inc., with associated patents and an equity interest, though this technology does not bear on the current submission.: Current equity holder in private company, Patents & Royalties; STATinMED Research: Consultancy; Sanofi-Aventis, Servier, Takeda Pharmaceuticals North America, Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Laboratory research funding from BioTheryX, and clinical research funding from CARsgen Therapeutics, Celgene, Exelixis, Janssen Biotech, Sanofi-Aventis, Takeda Pharmaceuticals North America, Inc.: Research Funding; Amgen, Inc., AstraZeneca, BMS, Celgene, EcoR1 Capital LLC, Forma Therapeutics, Genzyme, GSK Biologicals, Ionis Pharmaceuticals, Inc., Janssen Biotech, Juno Therapeutics, Kite Pharma, Legend Biotech USA, Molecular Partners, Regeneron Pharmaceuticals, Inc.,: Honoraria, Membership on an entity's Board of Directors or advisory committees. Thomas:Ascentage: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; X4 Pharma: Research Funding; Pharmacyclics: Other: Advisory Boards; Xencor: Research Funding; Genentech: Research Funding. Shpall:Takeda: Other: Licensing Agreement; Magenta: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Adaptimmune: Membership on an entity's Board of Directors or advisory committees; Zelluna: Membership on an entity's Board of Directors or advisory committees. Champlin:Takeda: Patents & Royalties; Actinium: Consultancy; Johnson and Johnson: Consultancy; Omeros: Consultancy; Cytonus: Consultancy; DKMS America: Membership on an entity's Board of Directors or advisory committees; Genzyme: Speakers Bureau. Qazilbash:Bioclinica: Consultancy; Amgen: Research Funding; Angiocrine: Research Funding; Bioline: Research Funding; Janssen: Research Funding. Bashir:Celgene: Research Funding; Amgen: Other: Advisory Board; Purdue: Other: Advisory Board; Takeda: Other: Advisory Board, Research Funding; Acrotech: Research Funding; StemLine: Research Funding; KITE: Other: Advisory Board.

Abstract: Background: Delayed platelet recovery and secondary thrombocytopenia, defined as a drop in platelet count not due to disease relapse after initial platelet recovery, occur in 5-25% of patients after hematopoietic cell transplantation (HCT) and indicate adverse prognosis. Platelet transfusion to prevent bleeding remains a mainstay of therapy and role of thrombopoietic agents is not known. Eltrombopag, a non-peptide small molecule, thrombopoietin receptor agonist, is licensed for use in refractory ITP and aplastic anemia. In this phase II randomized double blind placebo controlled study, we investigated the safety and efficacy of eltrombopag for post HCT thrombocytopenia. Methods: Patients 35 days or more after HCT were eligible for the study if they had 1) platelet count ≤ 20 x 109/l sustained for 7 days or if they were platelet transfusion dependent, and 2) neutrophil count ≥ 1.5 x 109/l with or without G-CSF in the previous 7 days. Patients were excluded if they had abnormal liver function tests (ALT ≥ 2.5 ULN, or Bilirubin 〉 2mg/dl) or had prior venous thrombosis. Patients were randomized to receive placebo or eltrombopag using a Bayesian adaptive algorithm in which the probability of randomization to each arm was based upon the ongoing response rate. Eltrombopag was started at a dose of 50mgs and escalated every 2 weeks to 75mgs, 125 mgs and 150mgs if platelet count was 〈 50 x 109/l. The primary endpoint was platelet count at end of the treatment (8 weeks). A patient was considered responsive if platelet count was ≥ 30 x 109/l. The primary endpoint was evaluated by calculating the Bayesian posterior probability in each arm that the response rate was higher than the other arm. A Beta (0.4, 1.6) prior distribution was assumed for each arm. Given the observed study data, the probability of response in each arm was calculated and the probability that Eltrombopag is superior was computed. Results: Sixty patients were randomized to eltrombopag (n=42) or placebo (n=18) and received at least one dose of drug. 7 patients had an autograft and 53 patients had an allograft. Donor was related for 22 and unrelated for 31 patients. Stem cell source was peripheral blood in 36 patients, bone marrow in 23 patients and cord blood in 1 patient. There were no significant differences in patient characteristics between the 2 treatment arms. The probability that the response rate in the Eltrombopag arm is superior to the response rate in the placebo arm was 0.75, given the observed data. The protocol required this probability to be 〉 0.975 to declare a winner; thus, the results are inconclusive. Fifteen (36%) of patients in eltrombopag arm responded compared to 5 (28%) of patients in placebo arm. A 95% credible interval for response in the Eltrombopag arm is 22% to 50%, and a 95% credible interval for response in the placebo arm is 11% to 48%. 37 patients completed all 8 weeks of therapy; however, all patients (n=60) who received at least one dose of study treatment were included in the intention to treat evaluation of this endpoint. A secondary objective was to compare proportion of patients achieving a platelet count ≥ 50 x 109/l. Response rate was higher in the eltrombopag arm for this endpoint as well: 9 (21.4%) patients achieved success compared with 0 (0%) patients in the placebo arm (p=0.0466; Fisher's exact test). OS, PFS, relapse rate, and non-relapse mortality were similar in two arms. Conclusion: Eltrombopag improves platelet count in patients with post-transplant thrombocytopenia. Disclosures Kim: Eli Lilly: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Bayer: Consultancy.

Abstract: INTRODUCTION: More active high-dose regimens are needed for refractory or poor-risk relapsed Hodgkin's lymphomas (HL), where BEAM offers poor results. Post-BEAM maintenance treatment with brentuximab vedotin (BV) x 48 weeks has recently been shown in the AETHERA trial to prolong progression-free survival (PFS) compared to placebo (2-year PFS 63% vs. 51%). We previously developed a regimen of infusional gemcitabine combined with busulfan and melphalan (Gem/Bu/Mel) pursuing inhibition by Gem of DNA damage repair. The encouraging results we saw in HL patients led us to conduct a phase 2 trial of Gem/Bu/Mel in HL patients at high risk of post-ASCT relapse. METHODS: HL patients ages 12-65 with ≥1 of the following criteria were eligible: Persistent active disease after 1st-line chemotherapy, CR1 〈 1 year, or extranodal disease at relapse/PD. Gem was administered as a loading dose of 75 mg/m2 followed by infusion at a fixed dose rate of 10 mg/m2/min over 4.5 hours on days -8 and -3 (total daily dose of 2,775 mg/m2). Each Gem infusion was immediately followed by the corresponding dose of Bu or Mel. Bu was administered intravenously from days-8 to -5 targeting a daily AUC of 4,000. Mel was infused at 60 mg/m2/day on days -3 and -2. ASCT was on day 0. Post-HDC involved field radiotherapy (IFRT) was considered to lesions 〉 5 cm at the time of HDC or persistently PET+ at the 1-month post-HDC evaluation. The trial had 80% power to detect a 2-year PFS increase from 50% to 65%.The concurrent BEAM cohort included all patients eligible for this trial who received BEAM off study due to no financial coverage for ASCT in a trial or patient/physician preference. RESULTS: Eighty patients were enrolled on study between 6/11-04/15 (Table 1). There was no transplant-related mortality (TRM). The toxicity profile was manageable, including mucositis (49% G2, 40% G3), skin (22% G2, 11% G3), self-limited transaminase elevation (30% G2, 19% G3), and hyperbilirubinemia (24% G2, 19% G3) with no cases of VOD. There was 1 case of G2 pneumonitis and none of cardiac, renal or CNS toxicity. Neutrophils and platelets engrafted at median days +10 (8-12) and +12 (9-21), respectively. Eight patients received post-HDC IFRT to mediastinum ± neck ± sternum at 30.6-39.6 Gy, starting on median day +42 (41-53) post-HDC, which was well tolerated. No patients received maintenance BV. Table 1. Patient characteristics Variable Study file (N=80) Concurrent BEAM cohort (N=31) P Median age (range) 31 (13-65) 39 (23-65) 0.02 Primary refractory / poor-risk relapse 41% / 59% 37% / 63% 0.6 # prior relapses 1 80% 70% 0.3 〉 1 20% 30% Median # prior chemotherapy lines (range) 2 (2-6) 2 (2-7) 0.3 Prior disease-free interval (months) 〈 6 56% 60% 0.7 6-12 24% 17% 〉 12 20% 23% Prior xRT 21% 27% 0.6 Relapse within prior xRT field 10% 3% 0.4 Extranodal relapse/PD 36% 53% 0.08 B symptoms at relapse/PD 11% 10% 0.8 Bulky relapse (any lesion 〉 5 cm) 39% 17% 0.02 # risk factors (primary refract/CR1 〈 1 yr, extranodal relapse, or B symptoms) 1 74% 77% 0.2 2 26% 17% 3 0% 6% Prior BV % 14% 25% 0.1 CR 36% 50% 0.1 PR 36% 0% No response (NR) 26% 50% PET+ at HDC 32% 7% 0.003 Status at HDC: CR/ PR / NR 68% / 24% / 8% 93% / 7% / 0% 0.01 At median follow-up of 33 mo (4-50) there have been 25 relapses following Gem/Bu/Mel, at median 6 (2-22) mo post-HDC (only 3 relapses after 12 mo). On univariate analyses, PET+ at HDC and primary refractoriness correlated with worse EFS (Table 2). On multivariate analyses, PET+ was an independent adverse predictor. Table 2. Prognostic analyses Variable Univariate analyses Multivariate analyses 2-yr EFS P HR (95% CI) P Yes No PET+ 37% 82% 0.00008 3.8 (1.7-8.9) 0.001 Primary refractory 51.5% 81% 0.006 2.2 (0.9-5.1) 0.06 〉 1 relapse 50% 73% 0.08 B symptoms 55.6% 70.4% 0.2 Bulky relapse 67% 72% 0.2 Extranodal 67% 72% 0.4 The BEAM cohort included 31 patients treated between 06/11-04/15 (Table 1) with no BV maintenance. There were fewer cases of PET+ tumors at HDC (P=0.003) and of bulky relapses (P=0.02) than the Gem/Bu/Mel file, but was matched for the other risk factors. It had no TRM. Despite a higher number of PET+ tumors at HDC, the Gem/Bu/Mel file had significantly superior 2-year PFS (65% vs. 51%, P=0.03) and 2-year OS (95.5% vs. 70%, P=0.001) than the BEAM cohort. CONCLUSIONS: Gem/Bu/Mel without maintenance BV was safe and effective in patients with refractory or poor-risk relapsed HL, with comparable results to those from the AETHERA trial using BEAM and maintenance BV. A randomized trial is necessary to compare Gem/Bu/Mel and BEAM. Figure 1. Figure 1. Disclosures Off Label Use: Gemcitabine, busulfan and melphalan are not FDA approved at high doses for Hodgkin's lymphoma. Alousi:Therakos, Inc: Research Funding. Andersson:Otsuka Research and Development, Inc.: Consultancy. Fanale:Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Research Funding; Infinity: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Research Funding; Genentech: Research Funding; Medimmune: Research Funding; Novartis: Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Molecular Templates: Research Funding; ADC Therapeutics: Research Funding; Onyx: Research Funding; Gilead: Research Funding.

Abstract: Romidepsin is a cyclic molecule that inhibits histone deacetylases. It is Food and Drug Administration-approved for treatment of cutaneous and peripheral T-cell lymphoma, but its precise mechanism of action against malignant T cells is unknown. To better understand the biological effects of romidepsin in these cells, we exposed PEER and SUPT1 T-cell lines, and a primary sample from T-cell lymphoma patient (Patient J) to romidepsin. We then examined the consequences in some key oncogenic signaling pathways. Romidepsin displayed IC 50 values of 10.8, 7.9 and 7.0 n m in PEER, SUPT1 and Patient J cells, respectively. Strong inhibition of histone deacetylases and demethylases, increased production of reactive oxygen species and decreased mitochondrial membrane potential were observed, which may contribute to the observed DNA-damage response and apoptosis. The stress-activated protein kinase/c-Jun N-terminal kinase signaling pathway and unfolded protein response in the endoplasmic reticulum were activated, whereas the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) and β-catenin pro-survival pathways were inhibited. The decreased level of β-catenin correlated with the upregulation of its inhibitor SFRP1 through romidepsin-mediated hypomethylation of its gene promoter. Our results provide new insights into how romidepsin invokes malignant T-cell killing, show evidence of its associated DNA hypomethylating activity and offer a rationale for the development of romidepsin-containing combination therapies.