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Background: Patients ≥55 years of age with rel/ref AML who have failed to achieve complete remission (CR) after standard induction & salvage therapies do not routinely undergo allogeneic hematopoietic cell transplantation (HCT) due to inability to receive myeloablative conditioning and lack of efficacy. With the advent of recently approved targeted therapies (e.g. venetoclax, IDH inhibitors) more patients achieve CR, however durable responses in heavily pre-treated patient populations remain unsatisfactory with very few patients being transplanted. The SIERRA (Study of Iomab-B in Elderly Relapsed or Refractory AML) trial is a prospective, randomized, phase 3 trial designed to address this unmet need. We present the preliminary analysis of the first 50% of patients and analyze the proportion of patients who fail standard chemo and targeted therapies that can then successfully undergo HCT with Iomab-B-based conditioning. Study continues to enroll (N=150), primary end-point durable CR of ≥180 days. Methods: Eligible patients are ≥ 55 years with rel/ref AML (≥5% blasts), adequate organ function, and related/unrelated 8/8 HLA-matched donors. Patients are randomized (1:1) to receive Iomab-B followed 12-14 days later by reduced intensity conditioning (fludarabine(FLU)/TBI) and HCT, or to conventional care (CC). CC patients may receive investigator's choice of salvage therapy, including newly approved targeted agents such as venetoclax, IDH Inhibitors and may proceed to standard HCT if they achieve CR. If patients do not achieve CR, the study allows cross-over (CO) to Iomab-B with HCT. Results: Preliminary data are available from the first 75 patients enrolled on the SIERRA trial. Median age of 64 years (range: 55-77). All patients had active measurable disease (Table 1). Patients in this trial were heavily pretreated with 85% failing ≥2 induction therapies and 33% failing targeted therapies. Molecular and cytogenetics was 68% adverse risk. (NCCN, v1.2018) Following therapeutic dose of Iomab-B as a single agent, there was significant reduction of circulating blasts by day 3 (99%, p<0.0001), and peripheral blasts became undetectable by day 8 prior to FLU. All patients transplanted on the Iomab-B arm with data available showed median days to engraftment of ANC at 14 (range: 9-22) and platelets at 16 (range: 4-30) (Table 1). After randomization, 82% (31/38) patients in the CC arm failed salvage therapy and did not proceed to standard HCT. Significantly, 32% (12/38) of these patients received targeted therapy. 73% (8/11) of the patients receiving venetoclax with HMA or cytarabine did not adequately respond and did not proceed to standard HCT, 45% (5/11) crossed over to Iomab-B and received HCT. Following standard chemotherapies, 85% (22/26) were evaluated for CO. In total, 63% (19/30) received Iomab-B and HCT. The most common reason preventing crossover was disease progression. All crossover (Iomab-B) patients showed similar engraftment (Table 1). CC patients showed increased incidence of febrile neutropenia with grade 3 prior to CO evaluation or HCT, compared to Iomab-B patients prior to HCT (CC: 34%, Iomab-B: 8%). Iomab-B administration was generally well-tolerated with no grade 4 and 1 grade 3 infusion reaction. There were no Iomab-B-related deaths or 100 day non-relapse transplant related mortality deaths in patients on the Iomab-B arm (Table 1). Conclusion: 100% of the patients receiving HCT on the Iomab-B arm engrafted, despite a median of 29% BM blasts pre-Iomab-B. 82% of the patients on the CC arm failed to be eligible for standard of care transplant, including a high percentage of those receiving targeted therapies. On the CC arm, 63% of eligible patients crossed over to Iomab-B/HCT with robust engraftment despite a median of 35% BM blasts pre-Iomab-B. The incidence of grade 3 febrile neutropenia was higher in patients treated on the conventional care arm with salvage therapy vs. those treated on the Iomab-B arm prior to HCT. In conclusion, despite advanced age, active disease and heavily pre-treated patients, 68% (50/74) of all patients enrolled in the SIERRA trial were able to undergo HCT after reinduction and targeted conditioning with Iomab-B. These results show significant improvements in the current rates of transplantation in this patient population. This SIERRA trial is currently enrolling. For full study details see www.sierratrial.com or clinicaltrials.gov (NCT02665065). Disclosures Gyurkocza: Actinium Pharmaceuticals: Research Funding. Nath:Astellas: Consultancy; Actinium: Consultancy; Daiichi Sankyo: Consultancy. Stiff:Amgen: Research Funding; Gamida-Cell: Research Funding; Incyte: Research Funding; Unum: Research Funding; Cellectar: Research Funding; Gilead/Kite Pharma: Consultancy, Honoraria, Research Funding. Tomlinson:Actinium Pharmaceuticals, Inc: Other: Travel Support. Abhyankar:Incyte: Speakers Bureau; Therakos: Other: Consulting, Speakers Bureau. Hari:AbbVie: Consultancy, Honoraria; Cell Vault: Equity Ownership; Sanofi: Honoraria, Research Funding; Spectrum: Consultancy, Research Funding; Amgen: Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Research Funding; Janssen: Consultancy, Honoraria; Kite: Consultancy, Honoraria. Al-Kadhimi:Seattle Genetics: Other: Stocks; Celldex Biotech: Other: Stocks. Foran:Agios: Honoraria, Research Funding. Orozco:Actinium Pharmaceuticals: Research Funding. Van Besien:Miltenyi Biotec: Research Funding. Sabloff:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas Pharma Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; ASTX: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi Canada: Research Funding. Kebriaei:Pfizer: Honoraria; Kite: Honoraria; Jazz: Consultancy; Amgen: Research Funding; Pfizer: Honoraria; Kite: Honoraria; Jazz: Consultancy; Amgen: Research Funding. Levy:Takeda (Millennium Pharmaceuticals): Consultancy. Lazarus:Adaptive Biotechnologies: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria, Speakers Bureau; Actinium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Teva Pharmaceuticals: Speakers Bureau; Biosight: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; AstraZeneca: Honoraria, Speakers Bureau; Bristol Myers Squibb: Honoraria, Speakers Bureau; Pluristem Therapeutics, Inc: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; CSL Behring: Consultancy; Genentech: Speakers Bureau. Giralt:Novartis: Consultancy; Actinium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Amgen: Consultancy, Research Funding; Kite: Consultancy; Miltenyi: Research Funding; Takeda: Consultancy, Research Funding; Johnson & Johnson: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy. Berger:Actinium Pharmaceuticals, Inc: Employment, Equity Ownership. Reddy:Actinium Pharmaceuticals: Employment. Pagel:Pharmacyclics: Consultancy; AstraZeneca: Consultancy; Gilead Sciences: Consultancy.

Abstract Background: Patients ≥55 years of age with active, relapsed or refractory acute myeloid leukemia (R/R AML) who have failed standard induction therapies most often receive salvage therapy with a wide variety of agents, but very few achieve remission. These patients do not routinely undergo allogeneic hematopoietic cell transplantation (HCT) due to lack of efficacy using a standard HCT approach. The SIERRA trial is a prospective, randomized, phase 3, open-label, ongoing multicenter trial designed to address this significant unmet need in R/R AML. This trial compares Iomab-B, an 131I-radiolabeled anti-CD45 antibody as targeted conditioning prior to HCT against standard conventional care therapies with an accrual goal of 150 patients. We have performed a preliminary safety analysis, validating the initial feasibility of this multi-center trial. Methods: Eligible patients are ≥ 55 years of age with active, R/R AML, adequate organ function, and related/unrelated matched donor. Patients are randomized (1:1 ratio) to receive dosimetry directed Iomab-B followed 12 days later by HCT with fludarabine 30 mg/m2 x 3 days and 2 Gy of total body irradiation as transplant conditioning, or to a Conventional Care (CC) arm. Patients randomized to CC, may receive investigator's choice of salvage induction chemotherapy including approved targeted agents as well as Venetoclax (in combination with a hypomethylating agent) and proceed to standard HCT if they achieve complete remission (CR). If patients do not achieve CR, the study allows optional cross-over to the Iomab-B arm, evaluated between days 28-42 after CC therapy. The primary efficacy endpoint for the study is durable complete remission (dCR) of 6 months. The secondary efficacy objective is to evaluate overall survival at 1 year. Results: Forty patients have been enrolled to date and data are available for 38 patients (19 = Iomab-B, 19 = CC) as of July 5th, 2018. The median age was 63 years (range: 55-76). All patients had active disease at the time of enrollment with median bone marrow (BM) blasts of 30% in the Iomab-B arm and 47% in the crossover arm prior to receiving Iomab-B (Table 1). Of the patients in the CC arm, 88% did not achieve a CR and 65% of those crossed-over to receive Iomab-B. The most common reason preventing crossover was declining performance status. Time to HCT was not increased in the crossover patients receiving Iomab-B compared to those that underwent a standard of care transplant after achieving CR (median 65 vs 75 days), while the Iomab-B arm patients were transplanted at a median of 27 days after randomization. Iomab-B therapy was well-tolerated with no grade 3 or 4 infusion-related reactions reported. The median activity of Iomab-B was 626 mCi (range: 397-1027). All patients randomized to Iomab-B (N=13) engrafted, with median days to engraftment of ANC at 13 (range: 9-22) and platelets at 17 (range: 13-26). All patients who received Iomab-B after crossover (N=9) also engrafted with time to engraftment similar to patients initially randomized to the Iomab-B arm (Table 1). Donor chimerism (≥95%), within 100 days after HCT, was found in 9 of 10 patients in the Iomab-B arm and 8 of 9 patients in those that crossed over to receive Iomab-B, with two patient exceptions having mixed donor chimerism at day 28. A preliminary safety analysis for all randomized patients on either study arm showed the most frequent non-hematologic adverse events ≥ grade 3 occurring in >10% patients were febrile neutropenia (34.2%), stomatitis (15.8%), malnutrition (13.2%), epistaxis, sepsis, hypotension, hypobilirubinemia and fatigue (all 10.5%). There were no Iomab-B-related deaths. Interpretation: Preliminary safety analysis demonstrates the feasibility of delivering targeted conditioning with Iomab- B for HCT in R/R AML patients who have active disease and a high BM blast burden (median: ≥ 30%) prior to transplantation. All patients who received Iomab-B, including those crossed over after failing to achieve CR on CC salvage therapy, engrafted ANC within 13 days, despite active disease prior to transplant. In addition, the time to HCT from randomization was not increased in patients receiving Iomab-B after cross-over compared to those who underwent standard of care HCT after achieving CR on the CC arm. This study is currently enrolling and for full study details see www.sierratrial.com or clinicaltrials.gov (NCT02665065). Disclosures Tomlinson: Foundation Medicine: Consultancy. Foran:Xencor, Inc.: Research Funding; Agios: Research Funding. Chen:Bellicum Pharmaceuticals: Research Funding. Levy:Takeda (Millennium Pharmaceuticals, Inc.): Consultancy. Lazarus:Pluristem Ltd.: Consultancy. Berger:Actinium Pharmaceuticals: Employment, Equity Ownership. Reddy:Actinium Pharmaceuticals: Employment, Equity Ownership; Pharmacyclics: Employment. Pagel:Pharmacyclics, an AbbVie Company: Consultancy; Gilead: Consultancy.

Abstract Abstract 906 Background: Single-arm Phase 2 trials of DF in the treatment of severe VOD/MOF post-SCT demonstrated a complete response (CR) in 36–46% of patients (pts). A subsequent Phase 3 trial enrolling pts with more severe VOD (28%/24% with ventilator/dialysis dependence at study entry vs 5%/7%) demonstrated a CR of 24% compared to 9% in a matched Historical Control (HC); p=0.0148; Richardson ASH 2009). Given the life-threatening nature of VOD/MOF, DF was made available in the United States through a Treatment IND protocol (T-IND) in December 2007 to gather additional safety and response data. Methods: Pts were required to have a diagnosis of VOD based upon Baltimore criteria (total bilirubin ≥ 2.0 mg/dL with ≥ 2 of the following: hepatomegaly, ascites or 5% weight gain) with MOF (either renal and/or pulmonary failure). Pts without a Baltimore diagnosis could enroll with biopsy-proven evidence of VOD. Eligibility criteria were expanded to permit patients with late onset VOD (VOD diagnosed after 21 days (d) or VOD/MOF after 28d post-SCT). Key exclusion criteria included clinically significant bleeding or need for >1 pressor to maintain BP. CR was defined as bilirubin < 2 mg/dL + resolution of MOF. Mortality was assessed at D+100. DF was given at 6.25 mg/kg IV q6h (25 mg/kg/d); treatment duration was recommended for at least 21d. Results: This interim analysis is based on 104 pts enrolled between14Dec2007-29Sep2009 and treated at 36 institutions. Most sites (n=23) enrolled only 1–2 pts. Nearly all pts (n=98) had undergone prior SCT; 6 had prior chemotherapy only; and 29 pts had late onset VOD post-SCT. Of the SCT pts, 69 pts enrolled in the T-IND met eligibility criteria for the original Phase 3 trial. Baseline demographics included median age 17 years (range 0.1 – 66); 59% male; and 16% with prior SCT. The most common diagnosis was leukemia (30% AML; 22% ALL; 7% other leukemia). The majority of pts had undergone allogeneic SCT (88%) with conditioning consisting of cyclophosphamide (76%), busulfan (42%) and/or TBI (41%). Mean onset of VOD post-SCT was 17 days. At entry, 20% of pts were dialysis dependent; 28% were ventilator dependent. Mean number of days of DF administration was 20 (range 2–88). Of the 104 pts, 36 (35%) achieved a CR by D+100. For the various sub-populations, the CR by D+100 rate was 24% for pts with late-onset VOD (n=29); 35% for those pts undergoing SCT (n=98); and 39% for the 69 pts who matched the entry criteria for the Phase 3 trial. Comparison of this group of 69 pts to the Phase 3 HC showed a statistically improved outcome (p=0.0007). Similar to the Phase 3 results, the CR rate was higher in pts who were not on dialysis/ventilator at study entry (41% vs 23%). Although children had previously been noted to have a higher CR rate in prior studies, the CR rate in the T-IND was similar in children compared to adults (35% and 34%, respectively). Overall D+100 mortality rate equaled 61% (n=104). Comparing the 69 pts who met Phase 3 entry criteria, D+100 mortality was 58% (p=0.0465 compared to the HC using Kaplan Meier estimates by log-rank analysis). Toxicity proved manageable: 11 pts experienced a total of 13 drug-related AEs including pulmonary hemorrhage (n=5), GI hemorrhage (n=3), hypotension (n=2), rectal hemorrhage, cerebral hemorrhage and pulmonary alveolar hemorrhage (1 pt each). Overall, 10% of pts experienced a drug-related toxicity that led to discontinuation. Similar to the observation of decreased GvHD in pediatric pts undergoing SCT who received prophylactic DF compared to best supportive care, the incidence of all grade GvHD was relatively low (8%). Conclusions: In 104 pts with severe VOD/MOF enrolled at 36 US institutions, use of DF demonstrated a 35% CR by D+100. Comparing those pts who met criteria for the Phase 3 trial to the HC used in that study, D+100 CR and survival were significantly improved in this study population. DF-associated toxicities are consistent with prior studies. Following an amendment in 30Sep2009, entry criteria for the T-IND study were expanded to permit enrollment of pts without SCT (VOD post chemotherapy) as well as pts without MOF to evaluate earlier intervention. Analysis of this group will be performed separately. Enrollment into the T-IND study continues. Disclosures: Richardson: Gentium: Membership on an entity's Board of Directors or advisory committees. Massaro:Gentium: Consultancy. Hannah:Gentium: Consultancy. Iacobelli:Gentium: Employment.

INTRODUCTION: Histologic remission is associated with superior long-term clinical outcomes in ulcerative colitis (UC). VARSITY, the first head-to-head comparison of biologic agents in UC (NCT02497469; EudraCT 2015-000939-33), showed superior clinical remission and endoscopic improvement at Week 52 with vedolizumab (VDZ), a gut-selective, humanized, α 4 β 7 integrin monoclonal antibody, vs adalimumab (ADA), a systemic, human, anti-tumor necrosis factor (anti-TNF) monoclonal antibody. 1 Both VDZ and ADA were generally safe and well-tolerated. 1 This analysis compared histologic improvements with VDZ vs ADA in VARSITY. METHODS: Patients with moderately to severely active UC were randomized 1:1 to active VDZ intravenous (IV) infusions (300 mg)/placebo subcutaneous (SC) injections or placebo IV/active ADA SC (160/80/40 mg). Prespecified histologic exploratory endpoints included histologic remission (Geboes score < 2 or Robarts Histopathology Index [RHI] score < 3) and minimal histologic disease activity (Geboes score < 3.2 or RHI score < 5) at Week 14 and Week 52. Histologic remission was also assessed based on previous anti-TNF use. RESULTS: A total of 769 patients received ≥1 dose of VDZ (n = 383) or ADA (n = 386). Median (range) duration of exposure was 477 (127, 630) days for VDZ and 420 (71, 454) days for ADA. Mean (standard deviation) baseline histologic disease activity was similar between groups (Geboes: VDZ, 15.0 [4.92]; ADA, 15.1 [5.03]; RHI: VDZ, 19.5 [8.74]; ADA, 19.6 [8.89]). Histologic remission induced by VDZ at Week 52 was greater than with ADA in the overall (Geboes or RHI), anti-TNF naïve (Geboes or RHI), and anti-TNF failure (RHI only) groups (Table 1). Histologic remission at Week 14 favored VDZ over ADA, with larger differentiation when using RHI (Table 1). VDZ also outperformed ADA in achieving minimal histologic disease activity at Weeks 14 and 52 (Table 1). CONCLUSION: VARSITY showed that use of VDZ, compared with ADA, achieved higher rates of histologic remission and minimal histologic disease activity at Weeks 14 and 52 in patients with moderately to severely active UC. These data support the use of VDZ over ADA in UC.

INTRODUCTION: VARSITY is the first head-to-head trial comparing the efficacy and safety of 2 biologic therapies, vedolizumab (VDZ) and adalimumab (ADA), in patients with moderately to severely active ulcerative colitis (UC). We previously reported significantly higher rates of clinical remission (31.3% vs 22.5%; P = 0.0061) and endoscopic improvement (39.7% vs 27.7%; P = 0.0005) at Week (Wk) 52 with VDZ vs ADA. 1 METHODS: VARSITY was a phase 3b, randomized, double-blind, double-dummy, active-controlled study (NCT02497469; EudraCT 2015-000939-33). Here we report the predefined, exploratory endpoints of early clinical response and clinical remission (defined in the Table 1) within the first 14 wks, as well as durable clinical remission (patients in clinical remission at Wk 14 and Wk 52). RESULTS: A total of 769 patients received ≥1 dose of VDZ (n = 383) or ADA (n = 386). Baseline characteristics were comparable between the 2 groups. A trend for separation in clinical response started to emerge at Wk 6 favoring VDZ vs ADA. Clinical response at Wk 14 favored VDZ vs ADA (257 [67.1%] vs 177 [45.9%]; treatment difference 21.2%). More patients achieved clinical remission at Wk 14 on VDZ vs ADA (102 [26.6%] vs 82 [21.2%]; treatment difference 5.3%). Patients on VDZ achieved higher rates of durable clinical remission (70 [18.3%] vs 46 [11.9%]); laboratory results correlated with these findings. Post hoc analyses showed a larger mean (standard deviation) change of C-reactive protein (CRP) from baseline to Wk 14 (−32.88 [155.77] nmol/L VDZ vs −3.35 [260.81] nmol/L ADA) and to Wk 52 (−50.87 [174.76] nmol/L VDZ vs −37.21 [169.17] nmol/L ADA) in favor of VDZ. Greater mean declines in fecal calprotectin (FCP) levels were seen in patients on VDZ compared with ADA (Wk 14: −1,551.3 [6,236.70] mg/kg VDZ vs −1,167.6 [4,647.67] mg/kg ADA; Wk 52: −2,187.3 [7,440.42] mg/kg VDZ vs −1,846.6 [4,560.55] mg/kg ADA). CONCLUSION: Patients on VDZ had numerically higher rates of both clinical response and clinical remission by Wk 14 compared with ADA. Patients on VDZ also achieved higher rates of durable clinical remission compared with ADA. CRP and FCP results correlated with these findings. These data on early clinical response and clinical remission, as well as durable remission, further support the use of VDZ over ADA in patients with moderately to severely active UC.

Objective Vedolizumab is a gut-selective antibody to α 4 β 7 integrin for the treatment of ulcerative colitis (UC) and Crohn's disease (CD). We report an integrated summary of the safety of vedolizumab. Design Safety data (May 2009–June 2013) from six trials of vedolizumab were integrated. Adverse events were evaluated in patients who received ≥1 dose of vedolizumab or placebo and were reported as exposure-adjusted incidence rates as the number of patients experiencing the event per 100 person-years (PYs) of exposure. Predictors of serious infection were assessed using a Cox proportional hazards model. Results In total, 2830 patients had 4811 PYs of vedolizumab exposure (median exposure range, 1–1977 days). No increased risk of any infection or serious infection was associated with vedolizumab exposure. Serious clostridial infections, sepsis and tuberculosis were reported infrequently (≤0.6% of patients). No cases of progressive multifocal leucoencephalopathy were observed. Independent risk factors for serious infection in UC were prior failure of a tumour necrosis factor α antagonist (HR, 1.99; 95% CIs 1.16 to 3.42; p=0.0122) and narcotic analgesic use (HR, 2.68; 95% CI 1.57 to 4.58; p=0.0003), and in CD were younger age (HR, 0.97; 95% CI 0.95 to 0.98; p<0.0001), corticosteroid (HR, 1.88; 95% CI 1.35 to 2.63; p=0.0002) or narcotic analgesic use (HR, 2.72; 95% CI 1.90 to 3.89; p<0.0001). Investigator-defined infusion-related reactions were reported for ≤5% of patients in each study. Eighteen vedolizumab-exposed patients (<1%) were diagnosed with a malignancy. Conclusions Vedolizumab has a favourable safety profile with low incidence rates of serious infections, infusion-related reactions and malignancies over an extended treatment period. Trial registration number NCT01177228, NCT00619489 , NCT00783718 , NCT00783692 , NCT01224171 , NCT00790933 .