ALBERT

Description: Disease relapse remains the major cause of treatment failure following hematopoietic transplantation for AML/MDS. A major goal is to develop more effective antileukemic regimens without excessive toxicity. Busulfan (Bu)-fludarabine (Flu) is a widely used preparative regimen. We demonstrated that targeting a relatively high busulfan systemic exposure pharmacokinetic (PK) dose adjustment was superior to fixed busulfan dosing. Clofarabine (Clo) has improved antileukemic activity compared to fludarabine. We previously reported a phase I/II study of different dosing combinations of busulfan with Flu and Clo; the best results were obtained with Bu with Flu 10 mg/m2 and Clo 30 mg/m2 daily for four daily doses. We performed a phase III randomized controlled trial to determine if Flu/Clo/Bu improved progression free survival compared to the Flu/Bu regimen. Busulfan was given with PK dose adjustment AUC 6000 mM x min for age

Description: INTRODUCTION More active high-dose regimens are needed for non-Hodgkin’s (NHL) and Hodgkin’s lymphomas (HL), where standard BEAM offers poor results in refractory or poor-risk relapsed tumors. We previously developed a regimen of infusional gemcitabine with busulfan and melphalan (Gem/Bu/Mel), exploiting the synergy between gemcitabine and alkylators based on inhibition of DNA damage repair. Gem/Bu/Mel was safe and highly active against refractory lymphomas (Nieto, BBMT 2012). To further increase its activity we combined it in preclinical experiments with SAHA, which induces relaxation of the chromatin and renders DNA more accessible to DNA-targeting agents. Concurrent exposure to SAHA and Gem/Bu/Mel resulted in markedly increased apoptosis and cytotoxicity in refractory B- and T-NHL lines, with increased PARP1 cleavage and γ-H2AX reflecting increased DNA damage (Valdez, Exp Hematol 2012). SAHA has a dose-response effect in refractory lymphoma lines up to clinically achievable levels with doses of 1,000 mg, higher than its usual dose. We wished to clinically study the concurrent combination of SAHA and Gem/Bu/Mel in refractory NHL and HL. Methods Patients ages 12-65 with refractory lymphomas and adequate end-organ function were eligible for this dose-finding study of SAHA combined with Gem/Bu/Mel. SAHA was given on days -8 to -3 at 200-1,000 mg PO daily (levels 1-11), preceding all chemotherapy. Gemcitabine was given as a loading dose of 75 mg/m2 followed by infusion at a fixed dose rate of 10 mg/m2/min over 3.5 (levels 1-5), 4 (level 6) or 4.5 hours (levels 7-11) on days -8 and -3. Each gemcitabine dose was immediately followed by the corresponding dose of busulfan or melphalan. After a test dose on day -10, busulfan was given from days-8 to -5 targeting a daily AUC of 4,000. Melphalan was infused at 60 mg/m2/day on days -3 and -2. ASCT was on day 0. Patients with CD20+ tumors received rituximab (375 mg/m2) on days +1 and +8. Dose limiting toxicities (DLT) were defined as any G4-5 nonhematological organ toxicity, or as G3 skin or G3 mucositis lasting 〉3 days at peak severity. Dose escalation followed a Bayesian design targeting a maximal DLT probability of 20%. Results Between 10/11 and 6/13, 66 patients were enrolled with DLCL, HL and T-NHL (Table 1). SAHA was escalated up to 1,000 mg PO daily, combined with full doses of Gem/Bu/Mel without encountering DLTs. There were no treatment-related deaths. The toxicity profile was manageable, including mucositis (48% G2, 31% G3), skin (11% G2, 3% G3), self-limited transaminase elevation (30% G2, 6% G3), and self-limited elevation of bilirubin not associated to VOD (22% G2, 16% G3). There were no cardiac, pulmonary, renal or CNS toxicities. There was no QT prolongation detected after SAHA. Neutrophils and platelets engrafted promptly at median days +10 (range, 8-13) and +12 (range, 8-55), respectively. This toxicity profile is undistinguishable from the one we previously described with Gem/Bu/Mel. Activity and patient outcomes at median follow-up of 8 months (1-23) are shown on Table 2 and Figures: Conclusions Concurrent administration of SAHA with high-dose GemBuMel is feasible up to a daily dose of SAHA of 1,000 mg, with no increased toxicities compared to Gem/Bu/Mel alone. Early results indicate that SAHA/Gem/Bu/Mel is highly active in refractory or poor-risk relapsed HL and DLCL and warrants further study in earlier disease stages. Longer follow-up is needed to confirm these findings. Disclosures: Nieto: Otsuka Pharmaceuticals: Research Funding. Off Label Use: Vorinostat not approved for DLCL or Hodgkin's lymphoma. Qazilbash:Otsuka Pharmaceuticals: Research Funding. Andersson:Otsuka Pharmaceuticals: Research Funding.

Description: INTRODUCTION: More active high-dose regimens are needed for refractory or poor-risk relapsed non-Hodgkin's (NHL) and Hodgkin's lymphomas (HL), where standard BEAM offers unsatisfactory results. We previously developed a regimen of infusional gemcitabine with busulfan and melphalan (Gem/Bu/Mel), pursuing the inhibition by gemcitabine of DNA damage repair (Nieto et al, BBMT 2012). Since vorinostat induces chromatin relaxation and facilitates access of chemotherapy to DNA, we combined it with Gem/Bu/Mel, which resulted in a safe and markedly synergistic regimen (Nieto et al, BBMT 2015). Still, the addition of vorinostat to GemBuMel induced upregulation of DNA methyltransferase (DNMT) in lymphoma cells, which could be abrogated preclinically by azacitidine, further increasing tumor-cell kill (Valdez et al, Exp Hematol 2012). These observations led us to study the clinical combination of azacitidine with vorinostat/Gem/Bu/Mel. METHODS: Patients ages 12-65 with refractory or poor-risk relapsed lymphomas and adequate end-organ function were eligible. Azacitidine was given on days -8 to -3 at 15-35 mg/m2/day IV (levels 1-3), followed by vorinostat (1,000 mg PO daily, days -8 to -3), gemcitabine (loading dose of 75 mg/m2 followed by infusion at 10 mg/m2/min over 4.5 hours, days -8 and -3), busulfan (target daily AUC of 4,000, days -8 to -5) and melphalan (60 mg/m2/day, days -3 and -2). ASCT was on day 0. Patients with CD20+ tumors received rituximab (375 mg/m2) on day -9. Dose limiting toxicities (DLT) were defined as any G4-5 nonhematological organ toxicity, or as G3 skin or G3 mucositis lasting 〉3 days at peak severity. Dose escalation of azacitidine followed a Bayesian design targeting a maximal DLT probability of 25%. We assessed DNMT-3B levels by Western blot in peripheral blood mononuclear cells drawn at baseline and days -5 and -1 in 8 patients treated at the MTD. RESULTS: Between 11/13 and 6/15, 60 patients were enrolled: 25 DLBCL (10 double hit), 21 HL, 8 T-NHL (3 PTCL, 2 ALCL, 1 AITL, 1 NK/T, 1 panniculitis-like), 4 follicular NHL and 2 mantle cell (Table 1). Table 1. Patient population. Median age (range) 41 (16-65) Primary induction failure / high-risk/refractory relapse 28% / 62% Bulky lesions at relapse/PD 58% Secondary IPI (DLBCL): 0-1 / 〉1 44% / 56% LDH at relapse/PD (DLBCL): High / Normal 50% / 50% Median # prior chemotherapy lines (range) 3 (2-7) Prior xRT 17% PET+ at HDC 32% Status at HDC: 68% CR, 25% PR, 7% unresponsive Patients were treated at levels 1-3, with the MTD of azacitidine established at level 1 (15 mg/m2/day). The DLT was mucositis, observed at the following frequencies: level 1 (N=37): 16%, level 2 (N=18): 28%, level 3 (N=5): 40%. One patient died from early RSV pneumonia at level 3. The toxicity profile at the MTD was manageable: mucositis (40% G2, 32% G3), self-limited transaminitis (16% G2, 16% G3), self-limited elevation of bilirubin not associated with VOD (19% G2, 22% G3) and dermatitis (13% G2). There were no cardiac, pulmonary, renal or CNS toxicities. Neutrophils and platelets engrafted promptly at median days +9 (7-11) and +12 (8-64), respectively. This toxicity profile is identical to the one seen with Gem/Bu/Mel and vorinostat/Gem/Bu/Mel. DNMT-3B levels in PBMNC decreased from baseline to day -1 by a median 58% (19-80%) in 7/8 pts. Response assessment and patient outcomes at median follow-up of 11 months (2-21) at are shown on Table 2 and Figures: Table 2. Activity/outcomes. ORR CR % EFS % OS DLBCL 78% 44% 68% 86% HL 86% 86% 81% 100% T-NHL 100% 100% 87.5% 87.5% CONCLUSIONS: Azacitidine/vorinostat/Gem/Bu/Mel is feasible, with no increased toxicities compared to Gem/Bu/Mel ± vorinostat, and highly active in refractory or poor-risk relapsed HL and NHL. This regimen warrants further study. Figure 1. Figure 1. Disclosures Off Label Use: Azacitidine, vorinostat, gemcitabine, busulfan, melphalan: Use at high doses for lymphoma. . Alousi:Therakos, Inc: Research Funding. Andersson:Otsuka Research and Development, Inc.: Consultancy.

Description: 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) 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/CR11 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.

Description: The combination of IV Bu and Flu is an effective and well-tolerated HCT conditioning regimen for patients with advanced acute leukemia. However, relapse remains the main reason for treatment failure. We combined two nucleoside analogues Flu and Clo, and showed cytotoxic synergy when combined with Bu, first in pre-clinical models, and subsequently in a randomized clinical study (Andersson BBMT 2011). We selected the optimized regimen from Andersson et al, and combined with escalating doses of the histone deacetylase inhibitor vorinostat in attempts to augment disease control without increasing toxicity. Herein, we describe our initial experience with this novel regimen for patients with advanced acute leukemia or MDS undergoing allogeneic HCT. Methods: Vorinostat (200mg to 1200mg) was escalated in cohorts of 3 patients, and administered 1 hour prior to the fixed regimen of Flu 10 mg/m2 followed by Clo 40 mg/m2 followed by Bu. The nucleoside analogs were infused over 1 hour once daily for 4 days, followed on each day by Bu, infused over 3 hours to a pharmacokinetically targeted daily area under the curve (AUC) of 5500 μMol-min ± 5%. Dilantin was given for seizure prophylaxis. GVHD prophylaxis was based on tacrolimus andmini-MTX, with the addition of rabbit anti-thymocyte globulin (4 mg/kg total dose) for unrelated donor transplants. The presence of minimal residual disease (MRD) was determined by multiparameter flow cytometry. Results: 21 patients (7 AML, 14 ALL) with median age 43 years (range 19-60) received an allogeneic matched sibling (n=10) or unrelated donor (n=11) HCT in CR1 (n=13), CR2 (n=1), primary induction failure (n=5), or relapse (n=2). Twelve patients had MRD or overt disease present at time of HCT. Ten patients had high-risk karyotype defined by t(9;22) (n=3), t(4;11) (n=2), complex (n=2), or del 5 or 7 (n=3). Median time from diagnosis to HCT was 5 months (range 3-48). Median time to ANC 〉 0.5 x 109/L and platelets 〉 20 x 109/L were 11 (range 10-15) and 12 days (5-30), respectively. Excluding grade 1 toxicities, the most commonly reported toxicities were nausea with maximum grade 2 (71%), followed by grade 2 or 3 mucositis (64%). Grade 2 or 3 reversible elevation of liver function tests was noted in 54% of pts, including 1 case of reversible VOD. No renal toxicities were noted. Two patients with prior systemic treatment for acute GVHD died of infections (disseminated adenovirus and E.coli sepsis). Ten patients achieved CR and clearance of MRD by day +30 after HCT; one patient had progressive disease and on patient died before disease restaging. Eighteen patients achieved 100% donor chimerism at 30 days following HCT, 2 patients remain with mixed chimerism by 100 day assessment following HCT, and 1 patient died before assessment. The incidence of grades II-IV acute GVHD is 43% and chronic extensive GVHD among 18 evaluable patients is 24%. With a median follow-up of 10 months among surviving patients (1-22), overall and progression-free survival at 6 months is 95% and 71%, respectively. Early results suggest excellent disease control in MRD negative patients (Figure). Conclusion: The Vorinostat-Flu-Clo-Bu combination is well-tolerated and did not add appreciable toxicity in these patients with high-risk leukemia. Longer follow-up is needed to better assess disease control. Figure Figure. Disclosures Ciurea: Spectrum Pharmaceuticals: Other: Advisory Board; Cyto-Sen Therapeutics: Equity Ownership. Patel:Ziopharm Oncology: Equity Ownership, Patents & Royalties; Intrexon: Equity Ownership, Patents & Royalties.

Description: 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.

Description: Background :Relapse remains a major cause of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT), especially in patients with high-risk acute myeloid leukemia (AML). Therefore, how to eradicate the minimal residual disease and prevent of relapse are of great importance to improve the outcome of allo-HSCT for these high risk AML patients. M ethods :We retrospectively investigated decitabine (DAC) as part of a modified Bu-Cy regimen for high-risk AML patientsundergoing allo-HSCT. Fifty-nine patients received DAC (20 mg/m2/d,i.v.) for 5 days, followed by modified Bu-Cy (DAC group). A control (CON) of 177 patients (pair-matched 1:3) received modified Bu-Cy only. Results:Median follow-up was 402 (85-1504) days. There was no difference in graft versus-host disease occurrence. Treatment-related mortality (day 100) was 0% (DAC) and 6.2% (CON). The DAC group had better 2-year overall survival (OS, 77% versus 64%, P=0.018) and leukemia-free survival (LFS, 73% versus 56%, P=0.007). The differences were more substantial among patients with active disease: OS, 83% (DAC) versus 47% (CON), P=0.01 and LFS, 77% (DAC) versus 34% (CON), P=0.002. Median time to relapse was 187 days (DAC) versus 86 days (CON) and two-year relapse rates were 10% (DAC) and 49% (CON) for patients with active disease. Patients with cytogenetic monosomy 7 or 7q- abnormality responded better. Conclusions: Our data indicate that novel conditioning regimen containing DAC may be an effective and well-tolerated strategy and confer a subgroup-specific survival advantage in high-risk AML patients undergoing allo-HSCT. Disclosures No relevant conflicts of interest to declare.

Description: Background: Reduced intensity conditioning regimen (RIC) extends allogeneic hematopoietic cell transplantation (HCT) to older patients and patients with comorbidities. Compared to myeloablative (MA) conditioning, RIC has higher rate of relapse but lower rate of non-relapse mortality (NRM), resulting in similar survival. BMT CTN is conducting a prospective study to compare these two approaches. To further improve survival for older patients, a MA regimen with low NRM is needed. Timed sequential therapy (TST), giving two courses of chemotherapy 1 week apart, has higher antileukemic effect in in-vitro and in-vivo in studies of patients with AML, including phase 3 studies. We hypothesized that MA dose of busulfan delivered per principles of TST enhances antileukemic effect without increasing toxicity. We therefore designed a study to test safety of two MA schedules of busulfan targeting busulfan exposure (AUC) of 16000 μmol.min and 20000 μmol.min. AUC of 20000 μmol.minis close to total average drug exposure achieved with IV busulfan fixed dose of 12.8mg/kg. Methods: Patients were randomized to receive total busulfan exposure of 16,000 μmol.min(16K) or 20,000 μmol.min( 20K). Patients received IV busulfan 80 mg/m2 per day on day -13 and -12 in outpatient clinic, fludarabine 40 mg/m2 day x 4 (day -6 to -3) and IV busulfanx 4 (day -6 to -3). Busulfan was dosed to achieve target AUC of 16K or 20K based on pharmacokinetic studies done on day -13 and day -6. GVHD prophylaxis was Tacrolimus (day -2 onwards) and mini dose methotrexate-5mg/m2 on day 1, 3, 6, and 11. Stem cells were infused on day 0. Primary endpoint of the study was to compare 100 day non-relapse mortality in two arms with stopping rules built in for safety. Patients with hematological malignancies were eligible for the study if they had adequate organ function and 8/8 matched related or unrelated donor. We enrolled patients on this study who were suitable for RIC. When the study began, upper age limit for eligibility was 70 years, but this was increased to 75 years during the course of the study as safety was established. Fisher’s exact test was used to compare toxicity and NRM rates between arms. Cox proportional hazards regression was used to estimate the effects of clinical variables on overall survival. Results: 97 patients were enrolled on the study until the DSMB stopped the randomization and permitted continued accrual onto the higher dose arm with busulfan AUC of 20,000 μmol.min. 49 were randomized to busulfan AUC of 16K and 48 to 20K. For all patients, median age was 60 (18-75) years. 3 (2%) patients were less than 40 years of age, 12 (12%) 40-49, 33 (34%) 50-59, 39 (40%) 60-69, and 10 (10%) 70-79 years. 53 patients had AML/MDS, 24 CML/MPD, 16 myeloma, and 4 lymphoid malignancies. Based on revised disease risk index, 3 had low risk, 53 intermediate risk, 35 high risk, and 6 very high risk disease. Donor was related for 43 and unrelated for 54. Comorbidity scores were 0 in 23, 1-2 in 24, and ≥ 3 in 50. With a median follow up of 9.2 months (range 1.8-24) in surviving patients, 100 day NRM was similar in two groups, 4% in 16K and 6% in 20K (p=0.68). Maximum toxicity per patient was not significantly different between arms (Table 1, p=0.37). The 1-year unadjusted survival rates (95% CI) in combined disease risk indexes low and intermediate vs high and very high were 67 (50-79)% and 38 (19-57)%, respectively for all 97 patients. Multivariable Cox regression analysis for overall survival showed increased risk of death for older age (HR 1.05; p=0.03), comorbidity 3 and higher (HR 1.89 p=0.08), and high or very high risk index (HR 2.04; p= 0.05). After also accounting for donor relation and cell type, Bu AUC of 20k showed improved overall survival and a 50% reduction in the risk of death (HR 0.50, P= 0.058). Table 1. Maximum grade of toxicity per patient, N (Row %) MaximumGrade per Patient AUC=16k AUC=20k Total p-value 5 7 (54%) 6 (46%) 13 0.37 4 6 (50%) 6 (50%) 12 3 23 (44%) 29 (56%) 52 2 11 (73%) 4 (27%) 15 1 2 (40%) 3 (60%) 5 Total Patients 49 48 97 Conclusion: Myeloablative timed sequential busulfan regimen is safe in older patients and patients with comorbidities. The regimen with busulfan AUC of 20,000 μmol.min appears promising and needs to be studied further. Disclosures Popat: Otsuka: Research Funding. Off Label Use: Busulfan.