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High-dose chemotherapy and autologous stem-cell transplant (HDC/ASCT) is standard treatment for chemosensitive relapsed classical Hodgkin lymphoma, although outcomes of high-risk relapse (HRR) patients remain suboptimal. We retrospectively analyzed all HRR classical Hodgkin lymphoma patients treated with HDC/ASCT at our institution between 01/01/2005 and 12/31/2019. HRR criteria included primary refractory disease/relapse within 1 year, extranodal extension, B symptoms, requiring more than one salvage line, or positron emission tomography (PET)-positive disease at ASCT. All patients met the same ASCT eligibility criteria. We treated 501 patients with BEAM (n=146), busulphan/melphalan (BuMel) (n=38), gemcitabine( Gem)/BuMel (n=189) and vorinostat/Gem/BuMel (n=128). The Gem/BuMel and vorinostat/Gem/BuMel cohorts had more HRR criteria and more patients with PET-positive disease at ASCT. Treatment with brentuximab vedotin (BV) or anti-PD1 prior to ASCT, PET-negative disease at ASCT, and maintenance BV increased over time. BEAM and BuMel predominated in earlier years (2005-2007), GemBuMel and BEAM in middle years (2008-2015), and vorinostat/GemBuMel and BEAM in later years (2016-2019). The median follow-up is 50 months (range, 6-186). Outcomes improved over time, with 2-year progressionfree survival (PFS)/overall survival (OS) rates of 58%/82% (2005-2007), 59%/83% (2008-2011), 71%/94% (2012-2015) and 86%/99% (2016- 2019) (P

Despite low nonrelapse mortality (NRM) at day 100 after allogeneic hematopoietic cell transplantation (HCT), NRM at 1 year remains substantial. In this study, we retrospectively analyzed 199 patients who were treated on a phase II clinical trial assessing safety and efficacy of myeloablative fractionated busulfan and fludarabine conditioning regimen for hematologic malignancies. The goal of the study was to identify factors associated with NRM occurring between days 101 and 365 post-HCT and generate a hypothesis for future studies to reduce the risk of NRM at 1 year. We found that a vast majority (83%) of patients who experienced NRM between days 101 and 365 had prior grade II-IV acute graft-versus-host disease (GVHD), which was the leading cause of death either by itself (33.3%) or complicated by infections (37.5%). In multivariate analysis, grade II-IV acute GVHD (hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.3–6.6, p = 0.01) was the only significant predictor of NRM between days 101 and 365. Measures to reduce the risk of acute GVHD could lower the risk of NRM at 1 year and improve overall survival.

Background A myeloablative conditioning regimen can be safely given to older patients and those with comorbidities without increasing nonrelapse mortality (NRM) by fractionating the dose of intravenous busulfan. How this approach compares in efficacy with traditional, nonfractionated, lower dose regimens is unknown. Methods Outcomes were compared in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome who received either myeloablative, fractionated busulfan (f-Bu) dosed to achieve an area under the curve of 20,000 μmol per minute (f-Bu20K) over 2 weeks (n = 84) or a standard, nonfractionated, lower busulfan dose regimen of 16,000 μmol per minute (Bu16K) over 4 days (n = 78). Both groups also received fludarabine 40 mg/m2 intravenously for 4 days. Graft-versus-host disease prophylaxis was tacrolimus and methotrexate. Patients in the Bu16K group who had unrelated donors also received antithymocyte globulin. The primary endpoint was progression-free survival. Results Roughly one-half of the patients were aged >65 years, approximately 40% had poor-risk cytogenetics, approximately 40% of those with AML were not in complete remission, and approximately 40% had a comorbidity index >3. At 2 years, progression-free survival was significantly improved in the f-Bu20K group compared with the Bu16K group (45% vs 24%, respectively; hazard ratio [HR], 0.6; 95% CI, 0.4-0.8; P = .004). This was because of a significant reduction in progression (34% vs 59%, respectively; HR, 0.5; 95% CI, 0.3-0.8; P = .003) without any increase in NRM (21% vs 15%, respectively; HR, 1.4; 95% CI, 0.7-3; P = .3), which resulted in improved overall survival (51% vs 31%, respectively; HR, 0.6; 95% CI, 0.3-0.9; P = .01). Conclusions A myeloablative, fractionated busulfan regimen reduces relapse and improves survival without increasing NRM in older patients with AML and myelodysplastic syndrome.

Busulfan is given in the conditioning regimens preceding hematopoietic stem cell transplantation (HSCT), and plasma levels can be monitored. A targeted, individualized systemic exposure (SE) dose can be achieved by calculating the area under the plasma concentration versus time curve (AUC). The objective of this study was to determine a cutoff value for safety for the AUC for busulfan plasma levels in patients undergoing HSCT. A total of 149 consecutive HSCT patients were studied. After an oral test dose of busulfan, we set target doses of 4000, 5000, or 6000 µMol⸱min/day, and analyzed the AUC of oral or intravenous Bu. These patients were compared with 53 historical control subjects who had received myeloablative conditioning regimen without busulfan pharmacokinetic monitoring. Using a test dose and the administration route had no impact on the sinusoidal obstructive syndrome (SOS) incidence, transplant-related mortality or 1-year overall survival. However, patients receiving busulfan at doses set up at AUC > 5000 had an increased risk to develop SOS after HSCT (hazard ratio 3.39, p = 0.034, 95% CI 1.09-10.52). Adjusting the busulfan dose according to SE levels target dose during conditioning is associated with lower rates of oral severe mucositis and SOS. A cutoff of 5000 µMol⸱min is safe and does not impair survival.

Patients with severe thalassemia commonly have a survival that is significantly shorter than that of the general population. Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the only established treatment that is potentially curative, but it is limited by the availability of donors and the medical condition of the patient. To expand the donor pool to include haploidentical related donors, we introduced a program consisting of a pharmacologic pretransplant immune suppression phase (PTIS) and 2 courses of dexamethasone and fludarabine, followed by pretransplant conditioning with fludarabine-i.v. busulfan and post-transplant graft-versus-host disease (GVHD) prophylaxis with cyclophosphamide, tacrolimus, and mycophenolate mofetil. We transplanted 83 consecutive transfusion-dependent patients with thalassemia (median age, 12 years; range, 1 to 28 years) with a minimum follow-up of 6 months (median, 15 months; range, 7 to 53 months); the 3-year projected overall and event-free survival is over 96%, and there have been no secondary graft failures. Of the first 31 patients, we had 2 graft failures, both of them occurring in patients with extremely high titers of anti-donor-specific HLA antibodies (anti-DSAs), but after adjusting the PTIS to include bortezomib and rituximab for patients with high titers of anti-DSAs and using pharmacologic dose guidance for busulfan, we had no graft failures in the last 52 patients. Six (7%) of 83 patients developed severe GVHD. We conclude that this is a safe and efficacious approach to allogeneic SCT in thalassemia, yielding results comparable to those available for patients with fully matched donors.

Background Immune reconstitution of T cells has been proven to be a protective factor against cytomegalovirus (CMV) reactivation in patients post-hematopoietic stem cell transplant. Recently, more evidence has suggested that natural killer (NK) cells also play role in the protection against CMV reactivation in these patients. Methods CMV-specific T cells and CMV-reactive NK cells from pediatric patients undergoing hematopoietic stem cell transplant were examined by flow cytometry. These cells were defined as cells producing interferon gamma (IFNγ) upon stimulation with CMV antigens. Results This study demonstrated that NK cells reactive to CMV do exist in pediatric patients after stem cell transplant. These cells vigorously responded to stimulation with CMV peptides (pp65 and IE1) and to a lesser extent to CMV whole lysate by secretion of IFNγ. Patients with CMV reactivation tended to have less CMV-reactive NK cells than those without. Conclusion Reconstitution of CMV-reactive NK cells, together with CMV-specific T cells, may play a role in the control of CMV infections in patients after stem cell transplant.

Background: Myeloablative conditioning can be given safely to older patients by simply administering busulfan over a longer period (fractionated busulfan regimen) than the standard four-day regimen (Popat et al Lancet Haematology 2018). This longer duration of conditioning regimen allows addition of targeted agents like Venetoclax, which may be synergistic with conditioning chemotherapy and may further improve disease control with this regimen. We therefore added Venetoclax to our ongoing prospective clinical trial with f-Bu-Flu-Cladribine conditioning (NCT02250937). After enrolling 83 patients, the study was amended and venetoclax was added for the next 33 patients. Here we report the safety and preliminary efficacy of venetoclax and fractionated busulfan regimen. Methods: Between 2/2019 and 3/2021, 33 patients with AML (n=21) or MDS (n=10) up to 70 years of age with adequate organ function and 8/8-HLA matched related or unrelated donor were enrolled on a prospective trial. The conditioning regimen was f-Bu to target an area under the concentration vs time curve (AUC) of 20,000 ± 12% μmol.min given over a period of 2-3 weeks. The first two doses of busulfan (80 mg/m2 IV each) were administered either consecutively (days -13 and -12) or with further fractionation, one week apart (days -20 and -13) on outpatient basis. Then, inpatient fludarabine 10 mg/m 2, and cladribine 10 mg/m 2 were given followed by Bu on days -6 to -3. Venetoclax 400mg daily was given from day -22 to -3. Azoles were avoided during this period. GVHD prophylaxis was PTCy 50mg/kg on days 3 and 4 and tacrolimus from day 5. Results: The median age was 59 years (range, 23-69); High or very high disease risk index was present in 21%; Comorbidity index score of >3 was present in 45%; Donor was a sibling in 39%; and peripheral blood stem cells was the graft source in 100%. The median follow up was 8 months. At 1-year, overall survival was 84% (95% confidence interval, 71-100), progression-free survival 77% (64-94), relapse 13% (1-25), and non-relapse mortality 10% (0-20) [Table 1, Figure 1]. Incidence of acute GVHD grade 2-4 was 28% (12-43) and grade 3-4 acute GVHD was 3% (0-9) at day 100. All patients engrafted. The median time to neutrophil engraftment was 15 days (13 -19) and median time to platelet engraftment was 23 days (11-85). Full donor chimerism at day 30 was noted in 76%. Common grade 3 or 4 toxicity were neutropenic fever (58%), mucositis (18%) and pulmonary toxicity in 21%. Conclusion: Venetoclax can be safely added to the fractionated busulfan regimen. Early data on efficacy appear promising. Figure 1 Figure 1. Disclosures Popat: Bayer: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding. Mehta: CSLBehring: Research Funding; Syndax: Research Funding; Incyte: Research Funding; Kadmon: Research Funding. Hosing: Nkarta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Gulbis: EUSA Pharma: Other: Advisory board participation. Rezvani: AvengeBio: Other: Scientific Advisory Board ; Pharmacyclics: Other: Educational grant, Research Funding; GemoAb: Other: Scientific Advisory Board ; Navan Technologies: Other: Scientific Advisory Board; Bayer: Other: Scientific Advisory Board ; Caribou: Other: Scientific Advisory Board; Takeda: Other: License agreement and research agreement, Patents & Royalties; Virogin: Other: Scientific Advisory Board ; GSK: Other: Scientific Advisory Board ; Affimed: Other: License agreement and research agreement; education grant, Patents & Royalties, Research Funding. Qazilbash: Bristol-Myers Squibb: Other: Advisory Board; Oncopeptides: Other: Advisory Board; Amgen: Research Funding; Angiocrine: Research Funding; NexImmune: Research Funding; Biolline: Research Funding; Janssen: Research Funding. Kadia: Cure: Speakers Bureau; Novartis: Consultancy; Dalichi Sankyo: Consultancy; Cellonkos: Other; Ascentage: Other; Genfleet: Other; Sanofi-Aventis: Consultancy; Genentech: Consultancy, Other: Grant/research support; Astellas: Other; Liberum: Consultancy; BMS: Other: Grant/research support; Amgen: Other: Grant/research support; Aglos: Consultancy; Pfizer: Consultancy, Other; AstraZeneca: Other; AbbVie: Consultancy, Other: Grant/research support; Pulmotech: Other; Jazz: Consultancy. Konopleva: Calithera: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding; Ascentage: Other: grant support, Research Funding; Cellectis: Other: grant support; Ablynx: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Rafael Pharmaceuticals: Other: grant support, Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; AstraZeneca: Other: grant support, Research Funding; Stemline Therapeutics: Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; Forty Seven: Other: grant support, Research Funding; Sanofi: Other: grant support, Research Funding; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; KisoJi: Research Funding. Shpall: Axio: Consultancy; Magenta: Consultancy; Novartis: Consultancy; Bayer HealthCare Pharmaceuticals: Honoraria; Adaptimmune: Consultancy; Navan: Consultancy; Takeda: Patents & Royalties; Novartis: Honoraria; Affimed: Patents & Royalties; Magenta: Honoraria.

Background: Myeloablative conditioning can be given safely to older patients by simply administering busulfan (Bu) over a longer period (fractionated (f)-Bu) with fludarabine (Flu) than the standard four-day regimen. (Popat et al Lancet Haematology 2018). We added thiotepa (Thio) to this f-Bu/Flu regimen in patients with haploidentical (haplo) donors to promote engraftment and to reduce relapse. With encouraging results, Thio was then added in matched unrelated (MUD) and sibling (MSD) donor recipients also. However, the optimal doses of Thio and Bu were undefined. To further optimize the regimen, we tested two different f-Bu/Flu/Thio regimens in parallel prospective cohorts: (a) higher dose Bu with lower dose Thio, and (b) lower dose Bu with a higher dose Thio. Patients were enrolled on these cohorts based on age and co-morbidity index (HCT-CI). Herein, we report on the safety and preliminary efficacy of these regimens (NCT02861417). Methods: Patients 60 years with HCT-CI 3, or >60 years with HCT-CI >2, or >70 years irrespective of HCT-CI received f-BU to target AUC of 16,000 with Thio 5mg/kg (Bu16K/Thio5; Cohort 2). In both cohorts, the first two doses of Bu (80 mg/m2 IV each) were given as outpatient on days -20 and -13. The last four Bu doses were given as inpatient following each dose of Flu 40 mg/m2 on days -6 through -3. Thio was given on day -7. GVHD prophylaxis was post-transplant cyclophosphamide (PTCy) 50mg/kg on days 3 and 4, tacrolimus and MMF. Results: 66 patients were enrolled - 25 in cohort 1 and 41 in cohort 2, with a median age 60 years (range, 22-69) vs 62 years (range, 30-74), respectively (P=0.14). Diagnoses were AML/MDS (64% vs 54%), CML/MPD (24% vs 22%), ALL (12% vs 22%) and 1 myeloma; P=0.24. Most had intermediate disease risk index (80% vs 73%, P=0.57); median HCT-CI was 1 (range, 0-6) vs 3 (range, 0-9); P Primary graft failure occurred in 1 patient in cohort 1 and none in cohort 2. The median time to neutrophil engraftment was 17.5 days (range, 14-26) vs 18 days (range, 12-26); P=0.12, respectively; platelet engraftment > 20K was 30 days in both groups; P=0.75. Median donor chimerism at day 30 was 100% in both groups. The incidence of acute GVHD grade III-IV was 4% vs 5%; P=0.88 at day 100; extensive chronic GVHD at 1 year was 13% vs 10%; P=0.83. At 1-year overall survival was 72% vs 78%; P=0.95; relapse was 12% each; non-relapse mortality was 20% vs 17%; P=0.97 [Table 1, Fig 1]. Common grade >3 toxicities were neutropenic fever (64% vs 42%; P=0.13), bacterial infection (44% vs 34%; P=0.45), nausea (12% vs 2%; P=0.15), mucositis (8% vs 5%; P=0.63), pneumonitis (12% vs 7%; P=0.67), hemorrhagic cystitis (8% vs 5%) and sinusoidal obstructive syndrome (8% vs 2.4%). Conclusion: In this population of older patients and/or high co-morbidities, both myeloablative regimens with f-Bu/Flu with thiotepa and PTCy were well tolerated and led to low NRM, low risk of relapse and encouraging survival. Although both regimens led to similar outcomes, the f-Bu/Flu/Thio regimen with Bu16K and thiotepa 5 mg/kg dose may be preferred as this was used in patients who were older and/or had high co-morbidities. Figure 1 Figure 1. Disclosures Popat: Bayer: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding. Mehta: CSLBehring: Research Funding; Kadmon: Research Funding; Syndax: Research Funding; Incyte: Research Funding. Hosing: Nkarta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Rezvani: Caribou: Other: Scientific Advisory Board; Virogin: Other: Scientific Advisory Board ; AvengeBio: Other: Scientific Advisory Board ; GSK: Other: Scientific Advisory Board ; Bayer: Other: Scientific Advisory Board ; Navan Technologies: Other: Scientific Advisory Board; GemoAb: Other: Scientific Advisory Board ; Takeda: Other: License agreement and research agreement, Patents & Royalties; Pharmacyclics: Other: Educational grant, Research Funding; Affimed: Other: License agreement and research agreement; education grant, Patents & Royalties, Research Funding. Qazilbash: Oncopeptides: Other: Advisory Board; Janssen: Research Funding; Bristol-Myers Squibb: Other: Advisory Board; NexImmune: Research Funding; Amgen: Research Funding; Angiocrine: Research Funding; Biolline: Research Funding. Shpall: Affimed: Patents & Royalties; Adaptimmune: Consultancy; Novartis: Consultancy; Magenta: Consultancy; Magenta: Honoraria; Axio: Consultancy; Takeda: Patents & Royalties; Navan: Consultancy; Novartis: Honoraria; Bayer HealthCare Pharmaceuticals: Honoraria.

Busulfan is used in myeloablative schemes for hematopoietic stem cell transplantation (HSCT), with monitoring of dosage through the area under the curve (AUC) of the drug plasma concentration (µMol min). In this study, we compared the complete pharmacokinetics of busulfan administered orally (Bu-Oral) and intravenously (Bu-IV). We evaluated 40 patients who underwent HSCT with different types of conditioning regimens. After one dose, in the Bu-Oral group (n = 21), the median AUC was 1174 µMol min (799-4000), reaching a median of 4440 µMol min (3428-7181.5) during conditioning in 24 h. In the Bu-IV group (n = 19), it was 1244.8 µMol min (1001.2-2021), reaching 5598.0 µMol min (3102-8818) during conditioning in 24 h. Measuring plasma concentration of Bu in patients undergoing HSCT is important, regardless of the formulation, and the inclusion of a pre-HSCT test can predict the optimal dose during conditioning. Pharmacokinetics of the oral administration of busulfan, as well as clearance, are extremely variable, and this can potentially compromise the clinical results of the treatment since it makes it difficult to predict clinical results.

Summary Background Retrospective studies suggest that conditioning therapy with busulfan plus melphalan could result in longer progression-free survival compared with melphalan alone in patients with multiple myeloma undergoing autologous haemopoietic cell transplantation (auto-HCT). We aimed to test this hypothesis in a randomised trial. Methods The primary objective of the study was to compare progression-free survival with conditioning of busulfan plus melphalan with melphalan alone in patients with multiple myeloma. Patients with newly diagnosed multiple myeloma who were eligible for cell transplantation, aged 70 years or younger, with at least stable disease, were randomly assigned (1:1) to treatment. Patients received either busulfan plus melphalan, with a test dose of busulfan 32 mg/m2 followed by pharmacokinetically adjusted doses on days −7, −6, −5, and −4 to achieve a target daily area under the curve (AUC) of 5000 mmol-minute and melphalan 70 mg/m2 per day on days −2 and −1 (total melphalan dose 140 mg/m2), or a melphalan dose of 200 mg/m2 on day −2. Randomisation was performed via a Clinical Trial Conduct Website at the University of Texas MD Anderson Cancer Center. The accrual is complete and final results are presented here. The study is registered with ClinicalTrials.gov , number NCT01413178 . Findings Between Oct 12, 2011, and March 22, 2017, 205 patients were assessed for eligibility and randomly assigned to treatment. The primary analysis of progression-free survival was measured in 202 patients who received treatment: 104 patients in the busulfan plus melphalan group and 98 patients in the melphalan alone group. 90 days after auto-HCT, 102 (98%) of 104 patients given busulfan plus melphalan and 95 (97%) of 98 patients given melphalan alone achieved partial response or better. The median follow-up in the busulfan plus melphalan group was 22·6 months (IQR 15·2–47·1) and 20·2 months (IQR 8·8–46·6) in the melphalan alone group. Median progression-free survival was 64·7 months (32·9–64·7) with busulfan plus melphalan versus 43·5 months (19·9–not estimated) with melphalan alone (hazard ratio 0·53 [95% CI 0·30–0·91]; p=0·022). There were no treatment-related deaths by day 100 in either group. Grade 2–3 mucositis was observed in 77 (74%) of 104 patients in the busulfan plus melphalan group versus 14 (14%) of 98 patients in the melphalan alone group. Interpretation These findings, if confirmed in other ongoing studies, suggest that busulfan plus melphalan could replace melphalan alone as the conditioning regimen for auto-HCT in patients with newly diagnosed myeloma. Funding This study was funded in part by the National Institutes of Health (NIH) through MD Anderson's Cancer Center Support Grant ( CA016672 ).

Summary Allogeneic stem cell transplantation is now part of standard care for acute leukaemia. To reduce toxicity of the pretransplant conditioning regimen, intravenous busulfan is usually used as a preparative regimen for acute leukaemia patients undergoing allogeneic stem cell transplantation. Systemic busulfan exposure, characterized by the area under the plasma concentration versus time curve, AUC, is strongly associated with clinical outcome. An AUC that is too high is associated with severe toxicities, whereas an AUC that is too low carries increased risks of recurrence of disease and failure to engraft. Consequently, an optimal AUC-interval needs to be determined for therapeutic use. To address the possibility that busulfan pharmacokinetics and pharmacodynamics vary significantly with patients’ characteristics, we propose a tailored approach to determine optimal covariate-specific AUC-intervals. To estimate these personalized AUC-intervals, we apply a flexible Bayesian non-parametric regression model based on a dependent Dirichlet process and Gaussian process. Our analyses of a data set of 151 patients identified optimal therapeutic intervals for AUC that varied substantively with age and whether the patient was in complete remission or had active disease at transplant. Extensive simulations to evaluate the dependent Dirichlet process–Gaussian process model in similar settings showed that its performance compares favourably with alternative methods. We provide an R package, DDPGPSurv, that implements the dependent Dirichlet process–Gaussian process model for a broad range of survival regression analyses.

Context Fractionated busulfan/fludarabine (Bu-Flu) myeloablative conditioning yields low non-relapse mortality (NRM) in older patients and those with comorbidities after matched sibling (MSD) or unrelated (MUD) donor transplant (HCT). [Popat et al, Lancet Haematology 2018]. This has not been tested in haploidentical patients, and safety of post-transplant cyclophosphamide (PTCy) GVHD prophylaxis with this approach is unknown; both aims were assessed in the current trial. Objective Primary objective/endpoints were safety/NRM. Design Open label, non-randomized, phase II. Participants Eligibility criteria included any hematologic malignancy, age Interventions Patients received busulfan 80 mg/m2 i.v. either on days -13 and -12 (n=45) or with further fractionation (days -20 and -13; n=10) and fludarabine 40 mg/m2 i.v. plus busulfan (days -6 to -2) dosed to achieve target AUC 20,000 pmol/min per pharmacokinetic studies. Haploidentical patients received thiotepa 5 mg/kg i.v on day -7. GVHD prophylaxis included PTCy 50 mg/kg i.v. and tacrolimus. Haploidentical and later MUD recipients also received mycophenolate mofetil. Results Fifty-five patients were enrolled between 08/2016 and06/2018; median follow-up was 37.6 months (range, 25.3–47.8). Diagnoses were AML/MDS (n=30), CML/MPN (n=9), ALL (n=6), and lymphoma/myeloma (n=10). Donors were haploidentical (n=26, 47%), MUD (n=18, 33%), or MSD (n=11, 20%) with PB (n=33, 60%) or BM graft. DRI was intermediate/high (n=50, 91%); 40% (n=22) had HCT-CI >3. There was no graft failure. Median time to neutrophil and platelet engraftment was 17 days (range, 13–39) and 25 days (range, 11–167). Day 100 NRM was 16.4% (95% CI 6.5–26.2%) and 24.6% (12.6–36.6%) at 3-years. Day 100 grade II–IV and III–IV acute GVHD was 38.2% (95% CI 25.2–51.2%) and 9.1% (95% CI 1.4–16.8%), 3-year chronic GVHD (all extensive) was 15.2% (95% CI 5.3–25.1%). Relapse was 25.5% (95% CI 13.8–37.1%), PFS 50% (95% CI 38.1–65.6%), OS 60.7% (95% CI 48.7–75.6%). Conclusions Myeloablative fractionated Bu-Flu with PTCy is safe and effective in MSD, MUD, and haploidentical HCT. It appears to reduce the severe acute/chronic GVHD without an apparent increase in relapse.

Relapse is the major cause of mortality in patients with acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Effective preventive intervention in high-risk AML may be crucial. In this study, we investigated the clinical efficacy and safety of low dose decitabine (DAC) as part of a modified Busulfan-Cyclophosphamide (Bu-Cy) regimen for high-risk AML patients undergoing allo-HSCT to reduce relapse rate. Fifty-nine patients received DAC (20 mg/m2/d, i.v.) for 5 days, followed by modified Bu-Cy (DAC group). A matched-pair control (CON) group of 177 patients (matched 1:3) received modified Bu-Cy only. The differences were more substantial among patients with active disease: 2-year OS, 80.7% (DAC) versus 43.5% (CON), P = 0.011 and 2-year LFS, 64.9% (DAC) versus 39.2% (CON), P = 0.024. Median time to relapse was 8 months (DAC) versus 5 months (CON) for the entire groups and 6.5 months (DAC) versus 3.5 months (CON) for patients with active disease. In summary, our data indicated that the conditioning regimen containing low dose DAC may confer a survival advantage in high-risk AML patients with active disease undergoing allo-HSCT, and a prospective randomized trial is warranted to confirm these observations.

BACKGROUND: Optimal conditioning regimen for older patients with myelofibrosis undergoing allogeneic hematopoietic cell transplantation (HCT) is not known. Likewise, role of dose intensity is not clear. METHODS: We conducted a non-randomized prospective phase II trial using low-dose, later escalated to high-dose (MAC) busulfan with fludarabine (Bu-Flu) in myelofibrosis patients up to 74 years. First 15 patients received intravenous busulfan 130 mg/m(2)/day on days −3 and −2 (“low dose”); 31 received high dose – either 100 mg/m(2)/day (days −5 to −2; n=4) or pharmacokinetic-guided area under the curve of 4,000 μmol.min (days −5 to −2; n=27). Primary endpoint was day 100 non-relapse mortality (NRM). FINDINGS: Median age was 58 years (interquartile range (IQR) 53–63). Dynamic international prognostic scoring system (DIPSS)-plus was intermediate (n=28) or high (n=18). Donors were related (n=19) or unrelated (n=27). Cumulative incidence of NRM was 9.7% (95% confidence interval (CI) 0-20.3) at day 100 and at 3 years in the high dose, while it was 0% in the low dose group at day 100, and increased to 20% (95% CI 0-41.9) at 3 years. With a median follow up of 5.1 years (IQR 3.8–6), 3-year relapse was 32.3% (95% CI 15.4-49.1) in high dose versus 53.3% (95% CI 26.6-80.1) in low dose; event-free survival was 58% (95% CI 43-78%) versus 27% (95% CI 12-62%), and overall survival was 74% (95% CI 60-91%) versus 60% (95% CI 40-91%) respectively. In multivariate analysis, high dose busulfan had a trend towards lower relapse (Hazard ratio (HR) 0.44, 95% CI, 0.18-1.07, p=0.07), with no impact on NRM. INTERPRETATION: Intensifying Bu-Flu regimen using pharmacokinetic-monitoring appears promising in reducing relapse without increasing non-relapse mortality. FUNDING: The study was supported partly by Otsuka pharmaceutical and partly by the Cancer Center Support Grant (NCI Grant P30 CA016672). TRIAL REGISTRATION: ClinicalTrials NCT00475020

Summary Background Haemopoietic stem-cell transplantation (HCT) conditioning regimens that can reduce risk of relapse without increasing non-relapse mortality are needed. We aimed to test the safety of timed-sequential delivery of low-dose versus high-dose myeloablative busulfan in older patients and patients with comorbidities. Methods This non-stratified, open-label, randomised phase 2 trial was done at The University of Texas MD Anderson Cancer Center (Houston, TX, USA). Patients with haematological cancers aged between 5 and 75 years were eligible to participate in the study. Patients who had HIV or uncontrollable infections were excluded. Eligible patients were randomly assigned (1:1 by a computer-generated programme in block sizes of four) to receive a total intravenous busulfan dose to achieve an area under the curve of 16 000 μmol/min (16K group) or 20 000 μmol/min (20K group) on the basis of pharmacokinetic analysis, plus intravenous fludarabine 40 mg/m2 for 4 days. The investigators and the research nurses were masked to the block size to conceal allocation. The primary outcome was day 100 non-relapse mortality. All analyses were by modified intention to treat, including only patients who received at least one dose of the study drug. No interim analyses were planned and accrual is complete. This study is registered with ClinicalTrials.gov, number NCT01572662. Findings Between April 18, 2012, and Dec 9, 2015, 98 patients were enrolled. 49 patients were randomly assigned to the 16K group and 49 to the 20K group, one of which was removed from the study before starting the intervention. Median age was 60 years (IQR 54–67). 50 (52%) patients had an HCT-specific comorbidity index score of 3 or more, and 41 (42%) had a high or very high Disease Risk Index score. Day 100 non-relapse mortality was 4% (95% CI 0–10) in the 16K group and 6% (0–13) in the 20K group (p=0·65). Infection was the most common grade 3–5 toxicity in both the 20K group (25 [52%] of 48 patients) and the 16K group (24 [49%] of 49 participants). Mucositis (nine [19%] of 48 patients vs three [6%] of 49 patients), idiopathic pneumonia syndrome (nine [19%] of 48 patients vs two [4%] of 49 patients), and culture-negative neutropenic fever (16 [33%] of 48 patients vs eight [16%] of 49 patients) were more common in the 20K group than in the 16K group. Interpretation Myeloablative doses of busulfan administered in a timed-sequential manner with fludarabine is associated with low non-relapse mortality in older patients and patients with comorbidities. Additional studies are required to show whether this approach can reduce the risk of relapse. Funding Cancer Center Support Grant (US National Cancer Institute, National Institutes of Health).

Combination of drugs that target different aspects of aberrant cellular processes is an efficacious treatment for hematological malignancies. Hypomethylating agents (HMAs) and inhibitors of poly(ADP-ribose) polymerases (PARPis) and histone deacetylases (HDACis) are clinically active anti-tumor drugs. We hypothesized that their combination would be synergistically cytotoxic to leukemia and lymphoma cells. Exposure of AML and lymphoma cell lines to the combination of the PARPi niraparib (Npb), the HMA decitabine (DAC) and the HDACi romidepsin (Rom) or panobinostat (Pano) synergistically inhibited cell proliferation by up to 70% via activation of the ATM pathway, increased production of reactive oxygen species, decreased mitochondrial membrane potential, and activated apoptosis. Addition of the DNA alkylating agents busulfan (Bu) and/or melphalan enhanced the anti-proliferative/cytotoxic effects of the triple-drug combination. [Npb+DAC+Rom] significantly increased the level of chromatin-bound PARP1 and DNMT1 and caused acetylation of DNA repair proteins, including Ku70, Ku80, PARP1, DDB1, ERCC1 and XPF/ERCC4. This three-drug combination down-regulated the components of the nucleosome-remodeling deacetylase (NuRD) complex, which is involved in DNA-damage repair. Addition of Bu to this combination further enhanced these effects on NuRD. The trapping of PARP1 and DNMT1 to chromatin, acetylation of DNA repair proteins, and down-regulation of NuRD may all have increased double-strand DNA break (DSB) formation as suggested by activation of the DNA-damage response, concomitantly resulting in tumor cell death. Similar synergistic cytotoxicity was observed in blood mononuclear cells isolated from patients with AML and lymphoma. Our results provide a rationale for the development of [Npb+DAC+Rom/Pano] combination therapies for leukemia and lymphoma patients.

Compared to reduced-intensity conditioning regimen, myeloablative conditioning (MAC) for hematopoietic stem cell transplantation (HCT) reduces relapse but is avoided in older patients because of higher non-relapse mortality (NRM). To meet the need for a myeloablative regimen for older patients, we developed a novel fludarabine and busulfan MAC regimen. We fractionated the dose of busulfan and gave it for 6 days over a 2-week period and demonstrated the feasibility and safety of this approach. However, the disease-specific efficacy of this regimen is not known. The purpose of this study was to estimate the efficacy of fractionated busulfan regimen by estimating diseases specific survival outcomes. The conditioning regimen consisted of busulfan and fludarabine. On days −13 and −12 before HCT, patients received 80 mg/m2 busulfan intravenously (IV) daily in an outpatient clinic. Additional chemotherapy was administered during inpatient treatment from day −6 through day −3, including fludarabine 40 mg/m2 and busulfan IV once daily. The dosing of busulfan was determined from pharmacokinetic analyses to achieve for the course a target area under the curve of 20,000 ± 12% μmol/min, which is close to the average exposure of myeloablative dose of busulfan. One hundred fifty patients with high-risk hematological malignancies up to 75 years were enrolled in this prospective phase II study. The objective was to evaluate NRM, relapse, survival, the rates of graft-versus-host disease (GVHD), and long-term complications. The median age of the patient population was 61 years (interquartile range, 55-67). The most common diagnoses were acute myeloid leukemia (AML; N = 59 [39.3%]), myelodysplastic syndrome (MDS; n = 29 [19.3%]), and myelofibrosis (MF; N = 22 [14.7%]). Most had an unrelated donor (n = 93 [62%]) and received peripheral blood graft (n = 110 [73.3%]). Over half had an HCT-specific comorbidity index of ≥3 (n = 79 [52.7%]). The median follow-up among survivors was 43.4 months (interquartile range, 38.9-50.4). In patients with AML in complete remission, MDS, and myelofibrosis, 3-year overall survival was 66.7% (95% confidence interval [CI], 50.2-88.5%), 43.6% (95% CI, 28.6-66.4%), and 59.1% (95% CI, 41.7-83.7%) respectively. The cumulative incidence of NRM was 22% (15.3%-28.7%), extensive chronic GVHD was 27% (95% CI, 20-34%), bronchiolitis obliterans was 4.7% (95% CI, 1.3-8.1%), and secondary malignancy was 8.7% (95% CI, 4.1-13.2%) at 3 years. Lengthening the duration of busulfan (fractionation) permits safe delivery of myeloablative conditioning in older patients, leading to prolonged survival. © 2021 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

The combination of gemcitabine (Gem), busulfan (Bu), and melphalan (Mel) is a promising regimen for autologous stem-cell transplantation (SCT) for lymphomas. To further improve the efficacy of [Gem + Bu + Mel], we added poly(ADP-ribose) polymerase (PARP) inhibitor olaparib (Ola). We hypothesized that Ola would inhibit the repair of damaged DNA caused by [Gem + Bu + Mel]. Exposure of J45.01 and Toledo cell lines to IC10-20 of individual drug inhibited proliferation by 6-16%; [Gem + Bu + Mel] by 20-27%; and [Gem + Bu + Mel + Ola] by 61-67%. The synergistic cytotoxicity of the four-drug combination may be attributed to activation of the DNA-damage response, inhibition of PARP activity and DNA repair, decreased mitochondrial membrane potential, increased production of reactive oxygen species, and activation of the SAPK/JNK stress signaling pathway, all of which may enhance apoptosis. Similar observations were obtained using mononuclear cells isolated from patients with T-cell lymphocytic leukemia. Our results provide a rationale for undertaking clinical trials of this drug combination for lymphoma patients undergoing SCT.

The establishment of long-lived pathogen-specific T cells is a fundamental property of the adaptive immune response. However, the mechanisms underlying long-term persistence of antigen-specific CD4+ T cells are not well-defined. Here we identify a subset of memory CD4+ T cells capable of effluxing cellular toxins, including rhodamine (Rho), through the multidrug efflux protein MDR1 (also known as P-glycoprotein and ABCB1). Drug-effluxing CD4+ T cells were characterized as CD161+CD95+CD45RA-CD127hiCD28+CD25int cells with a distinct chemokine profile and a Th1-polarized pro-inflammatory phenotype. CD4+CD161+Rho-effluxing T cells proliferated vigorously in response to stimulation with anti-CD3/CD28 beads and gave rise to CD161- progeny in vitro. These cells were also capable of self-renewal and maintained their phenotypic and functional characteristics when cultured with homeostatic cytokines. Multidrug-effluxing CD4+CD161+ T cells were enriched within the viral-specific Th1 repertoire of healthy donors and patients with acute myeloid leukemia (AML) and survived exposure to daunorubicin chemotherapy in vitro. Multidrug-effluxing CD4+CD161+ T cells also resisted chemotherapy-induced cytotoxicity in vivo and underwent significant expansion in AML patients rendered lymphopenic after chemotherapy, contributing to the repopulation of anti-CMV immunity. Finally, after influenza vaccination, the proportion of influenza-specific CD4+ T cells coexpressing CD161 was significantly higher after 2 years compared with 4 weeks after immunization, suggesting CD161 is a marker for long-lived antigen-specific memory T cells. These findings suggest that CD4+CD161+ T cells with rapid efflux capacity contribute to the maintenance of viral-specific memory T cells. These data provide novel insights into mechanisms that preserve antiviral immunity in patients undergoing chemotherapy and have implications for the development of novel immunotherapeutic approaches.

We investigated the long-term safety and disease control data obtained with i.v. busulfan (Bu) combined with clofarabine (Clo) in patients with acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (HSCT). A total of 107 patients, median age 38 years (range, 19 to 64 years) received a matched sibling donor (n = 52) or matched unrelated donor (n = 55) transplant for ALL in first complete remission (n = 62), second complete remission (n = 28), or more advanced disease (n = 17). Nearly one-half of the patients had a high-risk cytogenetic profile as defined by the presence of t(9;22) (n = 34), t(4;11) (n = 4), or complex cytogenetics (n = 7). Clo 40 mg/m2 was given once daily, with each dose followed by pharmacokinetically dosed Bu infused over 3 hours daily for 4 days, followed by hematopoietic cell infusion after 2 days of rest. The Bu dose was based on the drug clearance as determined by a test Bu dose of 32 mg/m2. The target daily area under the curve was 5500 µmol/min for patients aged 59 years. With a median follow-up of 3.3 years among surviving patients (range, 1 to 5.8 years), the 2-year progression-free survival (PFS) for patients undergoing HSCT in first complete remission (CR1), second complete remission (CR2), or more advanced disease was 62%, 34%, and 35%, respectively. The regimen was well tolerated, with nonrelapse mortality (NRM) of 10% at 100 days and 31% at 2 years post-HSCT. The incidence of grade II-IV and III-IV acute graft-versus-host disease (GVHD) was 35% and 10%, respectively; 18% patients developed extensive chronic GVHD. The 2-year overall survival (OS) for patients undergoing HSCT in CR1, CR2, or more advanced disease was 70%, 57%, and 35%, respectively. Among 11 patients aged >59 years treated with reduced-dose Bu in CR1 (n = 7) or CR2 (n = 4), 4 remain alive and disease-free, with a median follow-up of 2.6 years (range, 2 to 4.7 years). Only the presence of minimal residual disease at the time of transplantation was associated with significantly worse PFS and OS in multivariate analysis. Our data indicate that the Clo-Bu combination provides effective disease control while maintaining a favorable safety profile. OS and NRM rates compare favorably with those for traditional myeloablative total body irradiation-based conditioning regimens.

Background Most PMBCL pts are cured with frontline chemoimmunotherapy ± RT. Data are scant regarding the role of HDC/ASCT for R/R PMBCL, and the benefit of RT administered peri-HDC/ASCT. Our institutional approach has focused on developing potentially more active HDC regimens, and on consideration of post-ASCT consolidation RT, especially for pts who had not achieved a CR at the time of HDC. Methods We retrospectively analyzed all patients (pts) with R/R PMBCL treated with HDC/ASCT at MDACC between 01/01/2000-12/31/2019. All pts underwent similar standard pre-SCT evaluation and met eligibility criteria as per our institutional guidelines. Response assessment differed over time and included CT and gallium scan (N=9) and PET/CT (N=49). Cox proportional hazards regression models evaluated the associations of the specific HDC regimen and clinical covariates of interest with EFS and OS. Results 58 pts received HDC/ASCT with BEAM-rituximab (N=36) or rituximab/gemcitabine/busulfan/melphalan ± vorinostat (R-GemBuMel) (n=22) (Table 1). The R-GemBuMel group included more pts pretreated with >2 lines of therapy than the R-BEAM group (55% vs. 28%, p=0.025), had fewer pts in CR (41% vs. 69%, P=0.01) and more pts in PD/SD at ASCT (32% vs. 3%, P=0.01). Prior RT at a median 44 (36-48) Gy was administered to 29 pts (20 R-BEAM, 9 R-GemBuMel, P=0.27). Nineteen pts (89% not in CR at SCT) who had not previously received full doses of RT received post-SCT RT (6 after BEAM, 13 after R-GemBuMel, P There were 2 treatment-related deaths in the R-BEAM arm, none in the R-GemBuMel arm. At median follow-up of 69.1 months (interquartile range, 36.5-85.2), the EFS rates were 57.6% (overall), 67.6% (R-GemBuMel) and 52.7% (R-BEAM) (Figure 1a). Their respective OS rates were 69.3%, 81.1% and 63.9% (Figure 1b). On multivariable Cox regression analyses, R-GemBuMel (vs. R-BEAM) (HR=0.29, p=0.05), and 1 organ involved (vs. >1) (HR 0.28, p=0.009) were associated with improved EFS, whereas older age (HR= 1.08 per year above median, p=0.005), refractory disease (SD/PD) at SCT (vs. CR/PR) (HR 5.44, p=0.01) correlated with worse EFS. Likewise, R-GemBuMel (HR= 0.16, p=0.03) and 1 organ involved (HR=0.17, p=0.004) significantly resulted in improved OS, whereas older age (HR= 1.11, p=0.002), and refractory (SD/PD) disease at SCT (HR= 21.27, p=0.001) correlated with worse OS. Neither sex nor disease status (primary refractory vs. relapse) nor No. prior lines (2 vs. >2) nor pre-SCT RT nor post-SCT RT correlated significantly with EFS or OS. Conclusions HDC/ASCT for R/R PMBCL pts, with post-SCT RT for pts with active disease at SCT, results in favorable long-term results. R-GemBuMel ± vorinostat seems to improve EFS and OS compared to R-BEAM. Disclosures Alousi: Incyte: Honoraria, Research Funding; Therakos: Research Funding; Alexion: Honoraria. Hosing:NKARTA Inc.: Consultancy. Kebriaei:Amgen: Other: Research Support; Ziopharm: Other: Research Support; Kite: Other: Served on advisory board; Pfizer: Other: Served on advisory board; Jazz: Consultancy; Novartis: Other: Served on advisory board. Popat:Bayer: Research Funding; Novartis: Research Funding. Qazilbash:Angiocrine: Research Funding; Bioline: Research Funding; Janssen: Research Funding; Bioclinica: Consultancy; Amgen: Research Funding. Shpall:Zelluna: Membership on an entity's Board of Directors or advisory committees; Adaptimmune: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Magenta: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Licensing Agreement. Champlin:Takeda: Patents & Royalties; Genzyme: Speakers Bureau; Cytonus: Consultancy; Omeros: Consultancy; Actinium: Consultancy; Johnson and Johnson: Consultancy; DKMS America: Membership on an entity's Board of Directors or advisory committees. Nieto:Affimed: Consultancy, Other: Grant Support; Novartis: Other: Grant Support; Astra Zeneca: Other: Grant Support; Secura Bio: Other: Grant Support.

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. Fludarabine (Flu) with IV Busulfan (Bu) recently has replaced TBI- and double alkylator regimens in pretransplant conditioning because of its improved safety. Post-transplant relapse is still a major concern. Clofarabine (Clo) has improved antileukemic activity compared with Flu, and cell line studies indicated that Flu and Clo with Bu may be synergistic and superior to Flu alone with Bu. We previously conducted a phase II study of different combinations of Flu and Clo with Bu; the best results were obtained with Flu 10 mg/m2 and Clo 30 mg/m2 daily, with Bu, in four daily doses. We then performed a phase III randomized controlled trial comparing Flu-Clo-Bu (FCB) with our standard Flu-Bu regimen. Busulfan was given with PK-guided dosing to an average daily AUC of 6000 mM-min for age ≤60 and 4000 mM-min for patient ages 61-70. GVHD prophylaxis was tacrolimus-mini methotrexate. Unrelated donor recipients received low-dose rabbit ATG, total dose of 4 mg/kg. Patients aged 3-70 with intermediate or high risk AML or MDS, with PS>70% and adequate organ function were eligible if they had an HLA identical related or 9/10 or 10/10 matched unrelated donor. There was no restriction for preexisting comorbid conditions. Patients were stratified based on disease status, complete remission (CR) vs. no CR (NCR). 250 patients were randomized; 120 received FCB and 130 got Flu-Bu. 95 had a matched sibling, 155 a matched unrelated donor. Median age was 51 yrs. 181 had AML, 69 MDS, and 92 (37%) had poor risk cytogenetics. 133 patients were in remission; 117 had active disease. Comorbidity indices (HCT-CI) varied from 0-10 and were evenly distributed between the groups. Performance status was >90% in 88%. All evaluable patients (n=249) achieved engraftment. 95 (38%) developed grade 2 and 16 (6%) grade 3-4 acute GVHD, while 93 (39%) got chronic GVHD. The median progression-free survival (PFS) for the FCB group was 39.3 mos and for the Flu-Bu group was 28.1 mos. There was a significantly lower risk of progression with FCB (p=0.025), but this benefit was offset by a higher risk of NRM (p=0.018) (Fig. a). There was no significant difference in PFS for patients in CR, but [NCR age ≤60 years] patients had median PFS of 28 mos with FCB vs. 8 mos with Flu-Bu (Fig. b). For patients age > 60 years, FCB yielded a median PFS ~25 mos compared with 6 mos with Flu-Bu (Fig. c). Additional analysis revealed that NCR patients with a low HCT-CI (0-2) benefited more from FCB than from Flu-Bu. The overall survival (OS) for the (NCR, HCT 0-2) group was also longer with FCB than with Flu-Bu (Fig. d). A Bayesian regression analysis including treatment-covariate interactions showed that most of the benefit of FCB was seen in this subgroup, while patients with HCT scores of ≥3 were less likely to benefit overall from FCB due to higher TRM with FCB. Our trial demonstrates the safety of the FCB regimen in patients with HCT 0-2 and better disease control with FCB compared with Flu-Bu in NCR patients. Patients with ≥3 comorbid conditions are at increased risk for TRM associated with FCB, somewhat offsetting the antileukemic benefit. Thus, clinical application of FCB should take CR status and performance status into account, and also include a personalized assessment of the risk for treatment-related complications based on the nature and number of preexisting comorbid conditions. Finally, age did not play a role for the use of FCB; it can be safely utilized in appropriate patients up to 70 years of age, and can be expected to yield better disease control. Figure Disclosures Alousi: Therakos: Research Funding; Incyte: Honoraria, Research Funding; Alexion: Honoraria. Bashir:Amgen: Other: Advisory Board; Purdue: Other: Advisory Board; KITE: Other: Advisory Board; Takeda: Other: Advisory Board, Research Funding; Celgene: Research Funding; Acrotech: Research Funding; StemLine: Research Funding. Ciurea:Kiadis Pharma: Current equity holder in publicly-traded company, Research Funding. Hosing:NKARTA Inc.: Consultancy. Kebriaei:Pfizer: Other: Served on advisory board; Ziopharm: Other: Research Support; Novartis: Other: Served on advisory board; Amgen: Other: Research Support; Kite: Other: Served on advisory board; Jazz: Consultancy. Oran:Celgene: Consultancy; ASTEX: Research Funding; Arog Pharmaceuticals: Research Funding. Rezvani:Pharmacyclics: Other: Educational grant; Formula Pharma: Membership on an entity's Board of Directors or advisory committees; Adicet Bio: Membership on an entity's Board of Directors or advisory committees; GemoAb: Membership on an entity's Board of Directors or advisory committees; Virogen: Membership on an entity's Board of Directors or advisory committees; Affimed: Other: Educational grant; Takeda: Other: Licensing agreement. Shah:BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding; GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy. Shpall:Adaptimmune: Membership on an entity's Board of Directors or advisory committees; Zelluna: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: Licensing Agreement; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Magenta: Membership on an entity's Board of Directors or advisory committees. Parmar:Cellenkos Inc.: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Popat:Bayer: Research Funding; Novartis: Research Funding. Nieto:Secura Bio: Other: Grant Support; Astra Zeneca: Other: Grant Support; Novartis: Other: Grant Support; Affimed: Consultancy, Other: Grant Support. Champlin:Omeros: Consultancy; Takeda: Patents & Royalties; Actinium: Consultancy; DKMS America: Membership on an entity's Board of Directors or advisory committees; Cytonus: Consultancy; Genzyme: Speakers Bureau; Johnson and Johnson: Consultancy. OffLabel Disclosure: The use of fludarabine and clofarabine is not approved by the FDA in pretranpslant conditioning therapy.

Background: We started a randomized phase II trial [NCT01572662] that compared the safety of two myeloablative fractionated ("timed-sequential") busulfan with fludarabine (Bu-Flu) conditioning regimens: one with a lower dose of busulfan (area under the curve [AUC] of 16 000 μmol.min; 16K arm) and one with a higher dose (AUC of 20 000 μmol.min; 20K arm). After 49 patients were treated on the 16K group and 48 patients on the 20K group, the randomization was stopped as the higher dose arm was found to be as safe as the lower dose arm. The outcomes of those patients were previously reported, with the primary endpoint of interest being day 100 non-relapse mortality (NRM). The trial then continued enrolment as a single-arm study with increased accrual onto the higher dose arm. The current paper reports long-term outcomes of a total of 150 patients treated on the higher dose arm with an extended median follow-up of over 3.5 years. Methods: Patients with hematological malignancies up to 75 years of age were included. Bu dosing was determined on the basis of pharmacokinetic (PK) analyses conducted after day -13 and day -6 dose to achieve target AUC 20 000 ± 12% μmol.min (20K arm). On days −13 and −12, patients received 80 mg/m2 Bu IV daily as outpatient. Then, Flu 40 mg/m2 and Bu IV once daily were given as inpatient from day −6 though −3. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus from day −2 and methotrexate on days 1, 3, 6, and 11. Results: The median age was 61 years (interquartile range, 55-67); most were males (91; 61%) had an unrelated donor (n=93, 62%) and received peripheral blood graft (n=110, 73.3%). The most common diagnoses were acute myeloid leukemia (AML) and myelodysplastic syndrome (n = 88, 58.7%). Among AML, 41% (n=24) were in CR, 44% (n=26) had primary induction failure and 15% (n=9) had relapsed disease without attaining CR before HCT. Over half had HCT-Specific Comorbidity Index (HCT-CI) >3 (n=79, 52.7%). Estimated relapse, NRM, and overall survival (OS) were 40% (95% confidence interval (CI), 32.1%-47.9%), 22% (95% CI, 15.3%-28.7%), and 49.1% (95% CI, 41.7%-57.8%) at 3 years [Table]. The highest relapse rate at 3 years was noted in patients with myeloma (70.6%), followed by MDS (51.7%), and lymphoma (46.2%), while it was the lowest in myelofibrosis (13.6%). Among AML patients not in CR, the rate of relapse was not higher than those who were in CR (37.1% and 41.7%, respectively at 3 years). NRM at 3 years ranged from 7.7% (lymphoma) to 37.1% (AML, not in CR). Lymphoma patients had the lowest NRM (7.7%) and the best OS (69.2%) at 3 years, while AML patients not in CR had the highest NRM (37.1%) and the lowest OS (31.4%) [Figure]. Patients with HCT-CI 0-2 had lower NRM (14.1%; 95% CI, 5.9%-22.3%) and better OS (57.2%; 95% CI, 46.7%-70.1%) than those with HCT-CI > 3 (NRM: 29.1%; 95% CI, 19%-39.2% & OS: 41.7%; 95% CI, 32.2%-54.2%). Day 100 cumulative incidence of grade II-V acute GVHD was 38% (95% CI, 30.2%-45.8%), grade III-IV was 11.3% (95% CI, 6.2%- 16.4%). At 3 years, cumulative incidence of extensive chronic GVHD was 27% (95% CI, 20%-34%), bronchiolitis obliterans was 4.7% (95% CI, 1.3%-8.1%), and secondary malignancies was 8.7% (95% CI, 4.1%-13.2%). Conclusion: The fractionated myeloablative Bu-Flu conditioning regimen is well tolerated and leads to acceptable risk of NRM, relapse and long term survival in older patients, those with high risk disease and high comorbidities. Acknowledging the high risk study population, the long term outcomes, although acceptable, provide a framework to further improve upon. Modifications of this fractionated Bu-Flu regimen to further enhance its efficacy (with the addition of other chemotherapy agents) while reducing the toxicity and risk of NRM (with an inclusion of novel GVHD prophylaxis regimens) are currently being investigated. Disclosures Mehta: Incyte: Research Funding; Kadmon: Research Funding; CSL Behring: Research Funding. Alousi:Therakos: Research Funding; Alexion: Honoraria; Incyte: Honoraria, Research Funding. Bashir:Celgene: Research Funding; Amgen: Other: Advisory Board; KITE: Other: Advisory Board; Purdue: Other: Advisory Board; Takeda: Other: Advisory Board, Research Funding; Acrotech: Research Funding; StemLine: Research Funding. Hosing:NKARTA Inc.: Consultancy. Kebriaei:Novartis: Other: Served on advisory board; Amgen: Other: Research Support; Jazz: Consultancy; Kite: Other: Served on advisory board; Ziopharm: Other: Research Support; Pfizer: Other: Served on advisory board. Oran:Celgene: Consultancy; Arog Pharmaceuticals: Research Funding; ASTEX: Research Funding. Qazilbash:Angiocrine: Research Funding; Amgen: Research Funding; Bioclinica: Consultancy; Bioline: Research Funding; Janssen: 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; Johnson and Johnson: Consultancy; Actinium: Consultancy; Cytonus: Consultancy; Omeros: Consultancy; Genzyme: Speakers Bureau; DKMS America: Membership on an entity's Board of Directors or advisory committees. Popat:Bayer: Research Funding; Novartis: Research Funding.

Background We previously reported that conditioning with Bu-Mel results in significantly longer PFS compared to Mel alone in patients with newly diagnosed multiple myeloma ([NDMM] Lancet Haematol 2019). Here we report the outcomes of the high-risk patients (based on chromosomal abnormalities as defined by IMWG) enrolled in this trial. Methods The primary objective was to compare PFS in NDMM patients who undergo auto-HCT with Bu-Mel versus Mel conditioning. Transplant eligible patients were randomly assigned (1:1) to treatment. Patients in Bu-Mel arm received test dose Bu 32 mg/m2 followed by PK adjusted Bu to achieve a target AUC of 5000 microMol-minute (days -7 to -4) and Mel 70 mg/m2 on days -2 and -1. Patients in Mel arm received Mel 200 mg/m2 on day -2. Results Sixty-two patients (Bu-Mel, n=32; Mel, n=30) were identified. Median age at transplant was 61 yrs in the Bu-Mel and 60 yrs in the Mel arm. Sixteen (50%) and 18 (60%) patients were male in the Bu-Mel and the Mel arm, respectively. The R-ISS stage was I in 6 (22%), II in 17 (63%), and III in 4 (15%) of 27 patients in the Bu-Mel arm versus I in 8 (38%), II in 9 (43%), and III in 4 (19%) of 21 patients in the Mel arm, p=0.39. There was no significant difference in the HCT-CI score, induction therapy, response to induction, number of patients receiving maintenance therapy, and other patients, disease, or treatment characteristics between the two treatment groups. The median time to neutrophil engraftment (ANC ≥500) was 11 days and 12 days in the Bu-Mel and Mel arms, respectively, p=0.002. The median time to platelet engraftment (platelet count ≥20K without transfusion support) was 10 days and 12.5 days in the Bu-Mel and Mel arms, respectively, p Conclusion Conditioning therapy with Bu-Mel before auto-HCT yields significantly longer PFS in high-risk myeloma patients compared with Mel alone. Longer follow-up is needed to characterize any OS benefit.

We hypothesized that IV Busulfan (Bu) dosing could be safely intensified through pharmacokinetic (PK-) dose guidance to minimize the inter-patient variability in systemic exposure (SE) associated with body-sized dosing, and this should improve outcome of AML/MDS patients undergoing allogeneic stem cell transplantation (allo-HSCT). To test this hypothesis, we treated 218 patients (median age 50.7 years, male/female 50/50%) with fludarabine (Flu) 40 mg/m2 once daily ×4, each dose followed by IV Bu, randomized to 130 mg/m2 (N=107) or PK-guided to average daily SE, AUC of 6,000 µM-min (N=111), stratified for remission-status, and allo-grafting from HLA-matched donors. Toxicity and graft vs. host disease (GvHD) rates in the groups were similar; the risk of relapse or treatment-related mortality remained higher in the fixed-dose group throughout the 80-month observation period. Further, PK-guidance yielded safer disease-control, leading to improved overall and progression-free survival, most prominently in MDS-patients and in AML-patients not in remission at allo-HSCT. We conclude that AML/MDS patients receiving pretransplant conditioning treatment with our 4-day regimen may benefit significantly from PK-guided Bu-dosing. This could be considered an alternative to fixed dose delivery since it provides the benefit of precise dose delivery to a predetermined SE without increasing risk(s) of serious toxicity and/or GvHD.

Gemcitabine (Gem), busulfan (Bu) and melphalan (Mel) are used for hematopoietic stem cell transplantation (HSCT). To further improve their efficacy, a preclinical study on their synergism with the HDAC inhibitor panobinostat (Pano) and the BCL2 inhibitor venetoclax/ABT199 was performed. Multiple myeloma (MM) cell lines MM.1R and MC/CAR were exposed to ~IC(20) levels of the drugs. Synergistic cytotoxicity was observed in cells exposed to the 5-drug combination as indicated by combination indexes < 1, supported by ~86% inhibition of proliferation and ~84% annexin V-positivity in MM.1R and ~58% inhibition of proliferation and ~46% annexin V-positivity in MC/CAR cells. Activation of the DNA-damage response and apoptosis were suggested by a modest increase in the phosphorylation of ATM and its substrates, significant cleavage of PARP1, caspase 3 and HSP90, DNA fragmentation, mitochondrial membrane depolarization and reactive oxygen species production. The 5-drug combination significantly decreased the levels of PI3K, AKT, mTOR, RAPTOR, P-P70S6K, and eIF2α with concomitant increase in the P-AMPK and its substrate Tuberin/TSC2, suggesting that the mTOR signaling pathway was compromised. Endoplasmic reticulum (ER) stress through activation of the unfolded protein response (UPR) was also observed as suggested by an increase in the level of calnexin, BiP/GRP78, ERO1-Lα, and PDI, which may relate to venetoclax-mediated inhibition of BCL2 in the ER. This is the first report on the effects of venetoclax-containing regimen on UPR. These results provide a rationale to propose a clinical trial on using (Gem+Bu+Mel+Pano+Venetoclax) as part of a conditioning regimen for MM patients undergoing auto-HSCT.

Background Pharmacokinetics (PK) is the study of the absorption, distribution, metabolism, and excretion of drugs. Many chemotherapeutic agents have a sensitive PK index, in which a small margin in blood concentrations is the difference between nontherapeutic, therapeutic, and adverse outcomes. Objectives This article will provide an overview of evidence-based approaches to the collection of PK samples, monitoring of PK levels, and the resulting management of patients undergoing PK testing. Methods A case study involving busulfan, an alkylating agent used in the pre-stem cell transplantation setting, will highlight the cross-contamination of samples while a drug is being infused through a central venous catheter with PK sample collection from a proximal peripherally inserted central catheter. The influence of false elevations in drug concentrations on PK-guided dose adjustments will also be emphasized. Findings Imprecise blood collections or cross-contamination of samples may lead to inaccurate drug concentration results and, subsequently, undesired low or high drug dosage calculations.

// Benigno C. Valdez 1 , Yang Li 1 , David Murray 2 , Jonathan E. Brammer 1 , Yan Liu 1 , Chitra Hosing 1 , Yago Nieto 1 , Richard E. Champlin 1 , Borje S. Andersson 1 1 Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA 2 Department of Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada Correspondence to: Benigno C. Valdez, email: bvaldez@mdanderson.org Keywords: HDAC inhibitors, drug transporter, combination therapy, lymphoma, pre-transplant regimen Received: May 05, 2016 Accepted: August 11, 2016 Published: August 24, 2016 ABSTRACT HDAC inhibitors, DNA alkylators and nucleoside analogs are effective components of combination chemotherapy. To determine a possible mechanism of their synergism, we analyzed the effects of HDAC inhibitors on the expression of drug transporters which export DNA alkylators. Exposure of PEER lymphoma T-cells to 15 nM romidepsin (Rom) resulted in 40%-50% reduction in mRNA for the drug transporter MRP1 and up to ~500-fold increase in the MDR1 mRNA within 32-48 hrs. MRP1 protein levels concomitantly decreased while MDR1 increased. Other HDAC inhibitors − panobinostat, belinostat and suberoylanilide hydroxamic acid (SAHA) − had similar effects on these transporters. The protein level of MRP1 correlated with cellular resistance to busulfan and chlorambucil, and Rom exposure sensitized cells to these DNA alkylators. The decrease in MRP1 correlated with decreased cellular drug export activity, and increased level of MDR1 correlated with increased export of daunorubicin. A similar decrease in the level of MRP1 protein, and increase in MDR1, were observed when mononuclear cells derived from patients with T-cell malignancies were exposed to Rom. Decreased MRP1 and increased MDR1 expressions were also observed in blood mononuclear cells from lymphoma patients who received SAHA-containing chemotherapy in a clinical trial. This inhibitory effect of HDAC inhibitors on the expression of MRP1 suggests that their synergism with DNA alkylating agents is partly due to decreased efflux of these alkylators. Our results further imply the possibility of antagonistic effects when HDAC inhibitors are combined with anthracyclines and other MDR1 drug ligands in chemotherapy.

Novel approaches to pre-transplant conditioning are needed to improve treatment of advanced T-cell malignancies. We investigated the synergism of fludarabine (Flu), clofarabine (Clo), busulfan (Bu), and romidepsin (Rom) in T-cell lines and patient-derived cell samples. [Flu+Clo+Bu+Rom] had combination indexes of 0.4-0.5 at ∼50% cytotoxicity in PEER and SUPT1 cells, suggesting synergism. Drug exposure resulted in histone modifications, DNA-damage response (DDR), increased reactive oxygen species (ROS), decreased glutathione (GSH) and mitochondrial membrane (MM) potential, and apoptosis. Similar activation of DDR and apoptosis was observed in patient samples. The PI3K-AKT-mTOR, NFκB, Raf-MEK-ERK, JAK-STAT and Wnt/β-catenin pro-survival pathways were inhibited by the 4-drug combination. The SAPK/JNK stress pathway was activated. A novel finding was the down-regulation of the drug transporter MRP1. We propose the following mechanisms of synergism: Flu, Clo and Rom induce histone modifications and chromatin remodeling, exposing DNA to Bu alkylation; the increased production of ROS, due to drug-mediated stress response and decreased GSH, damages the MM causing leakage of pro-apoptotic factors; down-regulation of MRP1 increases intracellular Bu concentration and exacerbates the DDR; and inhibition of multiple survival pathways. Our results provide the basis for a clinical trial to evaluate [Flu+Clo+Bu+Rom] as part of conditioning regimen for refractory T-cell malignancy patients undergoing stem cell transplantation.

Background More active high-dose chemotherapy (HDC) regimens are needed for refractory lymphomas. The authors previously combined infusional gemcitabine with busulfan and melphalan (Gem/Bu/Mel) pursuing DNA damage repair inhibition. Subsequently, they combined Gem/Bu/Mel with vorinostat, which facilitates chemotherapy access to DNA. The resulting regimen was safe and synergistic. However, vorinostat induced DNA methyltransferase up-regulation, which could be preclinically abrogated by azacitidine, increasing tumor-cell kill. Those observations led to a clinical combination of azacitidine with vorinostat/Gem/Bu/Mel. Methods Patients ages 12 to 65 years with refractory or poor-risk relapsed lymphomas were eligible. They received intravenous azacitidine on days -11 through -3 at doses from 15 to 35 mg/m(2) daily (dose levels 1-3), followed by oral vorinostat (1000 mg once daily on days -11 through -3), gemcitabine (2775 mg/m(2) over 4.5 × 2), busulfan (at an area under the receiver operating characteristic curve of 4000 daily × 4), and melphalan (60 mg/m(2) × 2). Patients who had tumors that were positive for CD20 (cluster of differentiation 20; B-lymphocyte antigen) received rituximab on day -9. Results In total, 60 patients were enrolled, including 26 with diffuse large B-cell lymphoma (DLBCL) (10 double hit/double expressors), 21 with Hodgkin lymphoma, 8 with T-cell lymphoma, and 5 with other B-cell lymphomas. The median patient age was 41 years (range, 16-65 years), patients had received a median of 3 prior lines of chemotherapy (range, 2-7 lines of chemotherapy); and 32% of tumors were positive on positron emission tomography studies at the time of HDC. Two patients died from treatment complications (respiratory syncytial virus pneumonia and sepsis, respectively). The maximum tolerated dose of azacitidine was encountered at dose level 1 (15 mg/m(2) daily). The toxicity profile (mainly mucositis and dermatitis) was manageable and was identical to that of vorinostat/Gem/Bu/Mel. Neutrophils and platelets engrafted promptly. At a median follow-up of 15 months (range, 8-27 months), the event-free and overall survival rates were 65% and 77%, respectively, among patients with DLBCL; 76% and 95%, respectively, among patients with Hodgkin lymphoma; and 88% for both among patients with T-cell lymphoma. Conclusions Double epigenetic modulation of Gem/Bu/Mel with azacitidine/vorinostat is feasible and highly active in patients with refractory/poor-risk relapsed lymphomas, warranting further evaluation. Cancer 2016. © 2016 American Cancer Society. Cancer 2016;122:2680-2688. © 2016 American Cancer Society.

Thalassemia free survival after allogeneic stem cell transplantation (SCT) is about 80–90% with either matched related or unrelated donors. However, the probability of finding a HLA-compatible donor is less than 50%. We explored the use of a mismatched related (“Haplo-”) donor. All patients received two courses of pre-transplant immunosuppression therapy (PTIS) with fludarabine (Flu) and dexamethasone (Dxm) to facilitate engraftment. After two courses of PTIS, a reduced-toxicity conditioning regimen of rabbit anti-thymocyte globulin (ATG), Flu, and IV Busulfan (Bu) was given followed by T-cell replete peripheral blood progenitor cells (PBPC). GVHD prophylaxis consisted of cyclophosphamide (Cy) on days SCT +3 and +4 (Post-Cy), and on day SCT +5 tacrolimus or sirolimus was started together with a short course of mycophenolate mofetil. Thirty-one patients underwent haplo-SCT. Their median age was ten years (range, 2 to 20 years). Twenty-nine patients engrafted with 100% donor chimerism. Two of three patients with high titers of donor-specific anti-HLA antibodies suffered primary graft failure. Median time to neutrophil engraftment was 14 days (range, 11 to 18 days). Five patients developed mild to moderate, reversible veno-occlusive disease, while nine patients developed acute GVHD grade II, that quickly responded to steroid therapy. Only five patients developed limited chronic GVHD. Projected overall and event-free survival rates at two years are 95% and 94%, respectively. The median follow up time is 12 months (range; 7 to 33 months). This haplo-SCT protocol may yield excellent outcomes for thalassemia patients, and provide a treatment option for patients lacking a HLA-matched donor.

Background: Recent approval of ruxolitinib (rux) for steroid refractory graft versus host disease (GvHD) has revolutionized the field and provided tremendous choice for the patients. However, the side effects including thrombocytopenia leads to dug discontinuation and intolerance. We have previously shown that adoptive therapy with cord blood (CB) derived T regulatory (Treg) cells can prevent and treat GvHD. We hypothesized that the addition of CB Treg therapy to rux based therapy can augment overall efficacy. Methods: CellTrace Violet suppression assay was performed to evaluate the suppressor function of CB Treg cells in the presence or absence of rux. Xenogenic GvHD mouse model was utilized where the NSG mice underwent sublethal irradiation on day -1 followed by injection of 1x107 donor peripheral blood (PB) mononuclear cells (MNCs) on day 0. Oral rux at 1 mg daily was fed continuously to the mice in the presence or absence of 1x107 CB Treg cells, tagged with CellTrace Violet dye, administered on days +4, +7, +11, +18. Mice were followed every other day for weight, GvHD score and survival. Serial blood draws were performed to analyze for cell compartment and cytokine assays. Results: We examine whether the addition of rux impacts the suppressor function of CB Treg cells. Varying concentration of rux including 0.01, 0.05, 0.1 and 0.5 µM were added at 24, 48 and 96 hours of the cell suppression assay. The addition of rux 0.05 µM at 48 hours of the cell suppression culture led to a restoration of poor cell function (Figure A). Lowest GVHD score was reported in the rux+CB Treg combination arms at day +14 when compared to rux alone or CB Treg alone arm which (Figure B) translated into a superior survival in the rux +CB Treg arm (Figure C). Furthermore, an increase in the hemoglobin level (Figure D) and the platelet count (Figure E) was demonstrated in the rux+CB Treg arm. Addition of rux led to longer persistence of the injected CB Treg cells on day 14 (data not shown) which correlated with the increase in the plasma level of the pro-Treg cell signaling markers including IL-7 (Figure F) and IL-15 (Figure G). A decrease in the IL-4 production supported the increased Treg cell function (Figure H). A synergistic suppression of inflammatory cytokines including IL-17 (Figure I) and IL1A (Figure J) was evident in the rux+CB Treg arm. Conclusion: The combination of CB Tregs with ruxolitinib leads to improved overall survival, decreased inflammatory cytokines and improved hematologic parameters. Such combination should be explored in a clinical setting Figure Disclosures Sadeghi: Cellenkos Inc.: Current Employment. Parmar:Cellenkos Inc.: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Context: Standard scoring systems prognosticate outcomes of MF at diagnosis and at allogeneic transplantation. Thorough evaluation of pre-transplant characteristics can point to appropriate mitigation strategies to improve outcomes. Objective: To evaluate the impact of individual components of standard scoring systems, along with factors previously reported in the literature, on transplant outcomes in patients with MF. Design: 65 consecutive patients transplanted for MF with a myeloablative regimen (details below) during 2007-2019 at the MD Anderson Cancer Center, were identified; associations between factors of interest and outcomes were evaluated. Median follow-up for survivors was 35.6 months. Patients: At transplant, median age was 61 years (range, 27-73); 42% were transfusion-dependent; 31% had secondary MF; and 53% of the patients were intermediate-2 while 42% were high-risk by DIPSS-plus. Interventions: Conditioning was Fludarabine 40 mg/m2 daily for 4 days, each dose followed by one daily dose of PK-guided IV Busulfan to an average daily AUC of 4,000 μM-min, or total course AUC of 16,000 μM-min. GvHD prophylaxis was tacrolimus and mini-methotrexate, patients with an unrelated donor received rabbit-antithymocyte globulin at a dose of 4-7.5 mg/kg. Outcomes: Overall survival (OS), non-relapse mortality (NRM), and cumulative incidence of relapse. Results: One-year and 3-year rates for OS were 78% and 65%, for relapse were 21% and 27%, and for NRM were 16% and 20%, respectively. Multivariable analysis (HR [95%CI]) showed a significant increase in risk of death for time from diagnosis to transplantation > 12 months (vs. ≤12 months; 3.01 [1.05-8.60], p=0.040), HCT-CT ≥ 3 (vs. 12 months (vs. ≤12 months; 7.20 [0.96-53.94], p=0.055). Increased risk of relapse was associated with age > 65 years at transplant (vs. ≤65 years; 2.77 [1.05-7.31], p=0.039), with a trend towards higher risk of relapse for patients with time to transplantation > 12 months (vs. ≤12 months; 4.50 [0.91-22.18], p=0.06). Conclusions: Time from diagnosis to transplant > 12 months was associated with worse OS with a trend towards worse NRM and relapse. Among DIPSS-components, only age and peripheral blood blasts ≥ 1 were associated with worse outcomes in this study. Analyses supported in part by the Cancer Center Support Grant (NCI Grant P30 CA016672)

e19520 Background: Scoring systems, such as DIPSS-plus, prognosticate outcomes of myelofibrosis (MF) at diagnosis and at transplant. In this study, we evaluated the impact of individual components of these scoring systems, along with other factors previously reported to significantly prognosticate transplant outcomes in patients with MF. Methods: We identified 65 consecutive patients conditioned uniformly with Fludarabine(40 mg/m2X4days)/Busulfan(AUC-4000X4days) and ATG(MUD), tacroliumus and methotrexate for GVHD prophylaxis for allo-SCT during 2007-2019 at MD Anderson Cancer Center, USA. Associations between factors of interest and overall survival(OS), cumulative-incidence-of-relapse(relapse) and non-relapse mortality(NRM) were evaluated. Results: At transpant, median age was 61(range = 27-73) years; 42% were transfusion-dependent, 31% had secondary MF and 53% patients were intermediate2 and 42% were high-risk by DIPSS-plus. Forty percent of the 35 patients who had 28-gene panel tested had atleast one high-molecular-risk mutation, per MIPSS. Median follow-up for survivors was 35.6 months(range = 0.5-123). One-year and 5-year rates for OS were 78% and 51%, for relapse were 21% and 30%, and for NRM were 16% and 28%, respectively. Our multivariate analysis shows the following significant prognostic factors: HCT-CI > 3[hazard ratio(95% CI):5.63(1.48-21.27)p = 0.011], peripheral-blood blasts≥5%[5.98(1.33-26.89)p = 0.020] and prior splenectomy[6.41(1.83-22.47)p = 0.004] were associated with worse OS. Matched-unrelated donor[4.07 (1.38-12.08)p = 0.011) and mismatched-unrelated donor[7.36 (1.36-39.83)p = 0.021] versus matched-related donor as well as peripheral blasts≥5%[4.10(1.00-16.83)p = 0.05] were associated with worse NRM. Diagnosis to transplant duration > 12months[5.81(1.33-25.420)p = 0.020] was associated with higher relapse. Presence of 2 or more poor-risk mutations [6.39(1.35-30.21)p = 0.019] predicted higher relapse on univariate analysis and was not included in multivariate analysis(as data was available in 35 patients only). Conclusions: Of the IPSS-components used at diagnosis, only peripheral-blood blasts(at threshold ≥5%) was associated with worse outcome(OS and NRM). Unrelated-donor source was associated with higher NRM. Diagnosis to transplant duration > 12months predicted higher relapse. The effect of mutations needs to be validated in a bigger study.

Background Myeloablative conditioning can be given safely to older patients by simply administering busulfan over a longer period (fractionated busulfan regimen) than the standard four day regimen. (Popat et al Lancet Haematology 2018). Subsequently, we added post-transplant cyclophosphamide (PTCy) GVHD prophylaxis to our fractionated regimen with a hypothesis that it will reduce GVHD and improve outcomes. Herein, we report the results of our retrospective analysis comparing outcomes of patients with AML who received fractionated busulfan myeloablative conditioning and PTCy versus standard tacrolimus (Tac) and methotrexate (Mtx) GVHD prophylaxis. Methods Patients with AML between 18-70 years of age with adequate organ function and 8/8-HLA matched related or unrelated donor, who were treated on 4 consecutive protocols using fractionated busulfan were included in the analysis. All patients received two fixed doses of busulfan 80mg/m2 as outpatient either on days -13 and -12, or on days -20 and-13 followed by busulfan on day -6 to -3 dosed to achieve target area under the curve (AUC) of 20,000 mol/min for the whole course based on pharmacokinetic studies. Fludarabine ± cladribine were given on day -6 to -3. GVHD prophylaxis was PTCy 50mg/kg on days 3 and 4 and Tac ± mycophenolate mofetil in PTCy cohort (n=53), or standard Tac+ Mtx (n=53). Patients in both the cohorts were matched 1:1 by propensity score. Results Baseline characteristics were similar between the PTCy and Tac/Mtx cohorts. The median age was 60 (range, 18-70) and 58 (range, 24-70) years, respectively, (P=0.3). Forty-nine percent were in CR, and 30% had comorbidity index >3 in each arm. Similar proportion of patients had ELN adverse risk in both arms (43% vs 40%, respectively P=0.7). The median follow up was 19 months (range, 3-36) in the PTCy and 46 months (range, 14-73) in Tac/Mtx cohort. Overall survival at 2-year was 78% vs 58% (P=0.03), non-relapse mortality was 6% vs 13% (P=0.2), incidence of grade 3-4 acute GVHD at 1-year was 6% vs 19% (P=0.07) and chronic GVHD at 2-year was 10% vs 29% (P=0.03) [Table 1 and figure 1]. The median time to neutrophil engraftment was prolonged by 3 days (15 vs 12 days; P Conclusion As compared to Tac/Mtx, PTCy-based GVHD prophylaxis not only reduced severe acute GVHD and chronic GVHD, but also improved overall survival in AML patients up to the age of 70 years who received myeloablative fractionated busulfan conditioning. Prospective randomized trial is warranted to validate these findings.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for patients with multiple myeloma, as it provides a graft-versus-myeloma effect alongside a myeloma-free graft. Although reduced-intensity conditioning regimens decrease nonrelapse mortality (NRM), there is a paucity of data with regard to the ideal conditioning regimen in myeloma. We conducted a retrospective comparison of 3 different preparative regimens used for allo-HCT for multiple myeloma at our institution in recent clinical trials: busulfan/fludarabine (BuFlu), fludarabine/melphalan 100 mg/m2 (FM100), and fludarabine/melphalan 140 mg/m2 (FM140). NRM, progression-free survival (PFS) at 3 years, and overall survival (OS) at 3 years were the primary endpoints. Secondary endpoints included time to engraftment, and the incidence of grades II through IV acute graft-versus-host disease and chronic graft-versus-host disease. A total of 73 patients received allo-HCT with these regimens. NRM at 3 years was seen in 3 (21%), 5 (28%), and 6 (24%) patients in the BuFlu, FM100, and FM140 groups, respectively. Three-year PFS in the BuFlu, FM100, and FM140 groups was 16% (hazard ratio [HR], 1.2; 95% confidence interval [CI], 0.6 to 2.1), 26% (HR, 0.6; 95% CI, 0.3 to 1.2), and 11% (reference), respectively. Three-year OS in the BuFlu, FM100, and FM140 groups was 39% (HR, 1.1; 95% CI, 0.5 to 2.2), 43% (HR, 0.7; 95% CI, 0.3 to 1.4), and 32% (reference), respectively. High-risk cytogenetics and relapsed disease prior to allo-HCT were found to be independent predictors of inferior OS on multivariate analysis, with a HR of 2.1 (P = .02) and 2.6 (P = .004), respectively. In contrast, the preparative regimen did not emerge as a predictor of PFS or OS. Durable clinical remission can be achieved in 11% to 25% of patients with multiple myeloma with the use of allo-HCT without any significant difference in the safety or efficacy of the conditioning regimen. High-risk cytogenetics and relapsed disease prior to transplant were associated with inferior PFS and OS.

Conditioning regimens contribute significantly to outcomes following allogeneic stem cell transplantation (allo-SCT). Reduced-intensity conditioning (RIC) regimens provide lower toxicity at the cost of reduced efficacy compared with myeloablative conditioning (MAC) regimens. However, because pre-transplant prognostic variables often determine the conditioning regimen, studies of RIC vs. MAC have been inconclusive. We present a retrospective analysis of 242 acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) patients, 112 of whom were in 56 pairs matched using propensity scores, to account for variation that may confound clinical outcomes. The uniform conditioning regimens consisted of fludarabine with pharmacokinetic (PK)-guided intravenous busulfan (Bu). The RIC and MAC regimens were dosed at the average daily area under the concentration-vs-time curve (AUC) of 4000 µMol min and 5000–6000 µMol min, or total course AUC of 16,000 µMol min and 20,000–24,000 µMol min, respectively; PK-guided dosing removes overlap in systemic Bu exposure. When patients’ data were propensity-matched, there was a trend toward significantly increased full donor chimerism and decreased chronic graft vs. host disease in RIC, and no significant differences in progression free survival and overall survival between RIC and MAC. Our results also elucidate the efficacy of PK-guided-dosing in the setting of allo-SCT for AML and MDS.

We conducted a prospective phase 2 trial of gemcitabine, busulfan and melphalan (Gem/Bu/Mel) with autologous stem cell transplantation (ASCT) in patients with primary refractory or poor-risk relapsed Hodgkin lymphoma (HL) (ie, extranodal relapse or within 1 year of frontline therapy). The trial was powered to detect an improvement in 2-year progression-free survival (PFS) from a historical 50% using a BEAM regimen (carmustine/etoposide/cytarabine/melphalan) to 65%. We compared the study population with all other concurrent patients who were eligible for the trial but instead received the BEAM regimen at our center. No patient received post-ASCT maintenance therapy. The Gem/Bu/Mel trial enrolled 80 patients with a median age of 31 years, 41% with primary refractory HL and 59% with relapsed HL (36% extranodal relapses), and 30% with positron emission tomography (PET)-positive lesions at ASCT. The concurrent BEAM (n = 45) and Gem/Bu/Mel cohorts were well balanced except for higher rates of bulky relapse and PET-positive tumors in the Gem/Bu/Mel cohort. There were no transplantation-related deaths in either cohort. At a median follow-up of 34.5 months (range, 26 to 72 months), Gem/Bu/Mel was associated with better 2-year PFS (65% versus 51%; P = .008) and overall survival (89% versus 73%; P = .0003). In conclusion, our data show that Gem/Bu/Mel is safe, in this nonrandomized comparison yielding improved outcomes compared with a concurrently treated and prognostically matched cohort of patients with primary refractory or poor-risk relapsed HL receiving BEAM.

Background Myeloablative conditioning (MA) reduces relapse as compared to reduced intensity (RIC), [Scott BL JCO 2017]. But it is avoided in older patients and those with comorbidities due to high non-relapse mortality (NRM), whose outcomes remain dismal. A CIBMTR study of AML patients ≥60 years (100% CR1) showed NRM of 32-34%, relapse rate of 33-37%, progression free survival (PFS) of 31-34% and overall survival (OS) of 34-36% at 2 years. [McClune. JCO 2010] A prospective trial in AML (≥60 years, 100% CR1) showed better 2-year PFS (42%) and OS (48%). [Devine. JCO 2015] Herein, we report the results of MA HCT using timed-sequential (TS) busulfan (Bu) in 71 AML patients up to age 73. Methods Patients received intravenous Bu in TS manner targeted to achieve an area under the curve of 16,000-20,000 μmol.min, with fludarabine (flu) 40 mg/m2 intravenously for four days. Results Median age was 64 years (range, 29-73). Donor was HLA matched unrelated (n=45, 63%) or related (n=26, 27%). Most received peripheral blood graft (n=46, 65%). Only 26% (n=18) had MRD-negative CR1/2 at HCT; others had MRD-positive CR1/2 (13%, n=9), primary induction failure (PIF; 45%, n=32) or relapsed disease (16%, n=11). Nearly half (47%) had the European LeukemiaNet (ELN) adverse risk disease. More than half (55%) had HCT-CI ≥ 3. Median follow-up was 40 months (range, 21-63). The cumulative incidences of grade II-IV and III-IV acute GVHD at day 100 were 39% (95% CI, 28-51%) and 10% (95% CI, 3-17%), respectively and extensive chronic GVHD at 1 year was 20% (95% CI, 10-29%). NRM was 6% (95% CI, 0-11%) at day 100 and 24% (95% CI, 14-34%) at 2 years. At 2 years, relapse was 28% (95% CI, 3-53%) in the CR/MRD-negative group vs 48% (95% CI, 34-62%) in others; progression-free survival (PFS) was 78% (95% CI, 61-99.6%) vs 25% (95% CI, 16-40%) and overall survival (OS) was 78% (95% CI, 61-99.6%) vs 33% (95% CI, 22-48%), respectively. [Fig 1a] Two year OS was was 67% (95% CI 51-87%) in the CR group, irrespective of MRD [Fig 1b]. In multivariate analysis (MVA) adjusted for covariates higher dose Bu vs lower dose [HR 0.39, 95% CI 0.18-0.85, p=0.02] was the only significant predictor of lower relapse risk. In MVA adjusted for age, Bu dose and ELN risk, not being in CR/MRD-negative state was the only predictor of significantly inferior PFS [HR 3.2, 95% CI, 1.3-8.2, p=0.01]. For OS, MVA adjusted for age, Bu dose and ELN risk, HCT-CI ≥3 [HR 1.98, 95% CI, 1-3.9, p=0.05] and not being in CR/MRD-negative state [HR, 2.7, 95% CI 0.98-7.2, p=0.05] were associated with higher mortality. Conclusion Our outcomes of MA HCT in an extremely high risk older population are promising especially in CR patients, whose outcomes approach that of younger patients. This was achieved by delivering Bu in TS manner which minimized toxicity and potentially increased efficacy. This approach warrants further investigation.

Background Post transplant cyclophosphamide (PTCy), tacrolimus, and MMF GvHD prophylaxis makes transplantation from haploidentical donors feasible without T cell depletion. In matched donor transplant recipients, cumulative incidences of grades II-IV acute, grades III-IV acute, and chronic GVHD were 51%, 15%, and 14%, respectively when single agent PTCy was used (Kanakry et al JCO 2014 32:3497-3505). However; as a single agent it was inferior to tacrolimus and methotrexate in another study (Alousi etal BBMT 2015, 906-912). We therefore hypothesized that addition of tacrolimus to PTCy may be needed to prevent severe acute GVHD and improve transplant outcomes. Methods All patients with AML undergoing first allogeneic transplant from matched sibling or at least 9/10 matched unrelated donor between 1/1/2011 to 4/30/2018 were eligible for this retrospective study if they received a melphalan or timed sequential busulfan (course AUC 20,000 umol/min) based conditioning regimen. GVHD prophylaxis consisted of tacrolimus and methotrexate 5mg/m2 on day 1, 3, 6, and 11 in the Tac/MTX cohort (n=140); and cyclophosphamide 50mg/kg given on days 3 and 4 and tacrolimus in the PTCy cohort (n=76). Results Patient characteristics were similar in both cohorts except that patients in PTCy cohort were younger with a median age of 59 years versus 63.5 years (P Outcomes and results of univariate analysis are summarized in Table1. Conclusion Tacrolimus and PostCy based GVHD prophylaxis reduces severe GVHD and improves survival.

More active high-dose regimens are needed for refractory/poor-risk relapsed lymphomas. We previously developed a regimen of infusional gemcitabine/busulfan/melphalan, exploiting the synergistic interaction. Its encouraging activity in refractory lymphomas led us to further enhance its use as a platform for epigenetic modulation. We previously observed increased cytotoxicity in refractory lymphoma cell lines when the histone deacetylase inhibitor vorinostat was added to gemcitabine/busulfan/melphalan, which prompted us to clinically study this four-drug combination. Patients ages 12 to 65 with refractory diffuse large B cell lymphoma (DLCL), Hodgkin (HL), or T lymphoma were eligible. Vorinostat was given at 200 mg/day to 1000 mg/day (days -8 to -3). Gemcitabine was infused continuously at 10 mg/m(2)/minute over 4.5 hours (days -8 and -3). Busulfan dosing targeted 4000 μM-minute/day (days -8 to -5). Melphalan was infused at 60 mg/m(2)/day (days -3 and -2). Patients with CD20(+) tumors received rituximab (375 mg/m(2), days +1 and +8). We enrolled 78 patients: 52 DLCL, 20 HL, and 6 T lymphoma; median age 44 years (range, 15 to 65); median 3 prior chemotherapy lines (range, 2 to 7); and 48% of patients had positron emission tomography-positive tumors at high-dose chemotherapy (29% unresponsive). The vorinostat dose was safely escalated up to 1000 mg/day, with no treatment-related deaths. Toxicities included mucositis and dermatitis. Neutrophils and platelets engrafted promptly. At median follow-up of 25 (range, 16 to 41) months, event-free and overall survival were 61.5% and 73%, respectively (DLCL) and 45% and 80%, respectively (HL). In conclusion, vorinostat/gemcitabine/busulfan/melphalan is safe and highly active in refractory/poor-risk relapsed lymphomas, warranting further evaluation. This trial was registered at ClinicalTrials.gov (NCI-2011-02891).

Chimerism testing after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) represents a promising tool for predicting disease relapse, although its precise role in this setting remains unclear. We investigated the predictive value of T lymphocyte chimerism analysis at 90 to 120 days after allo-HSCT in 378 patients with AML/MDS who underwent busulfan/fludarabine-based myeloablative preparative regimens. Of 265 (70%) patients with available T lymphocyte chimerism data, 43% of patients in first or second complete remission (CR1/CR2) at the time of transplantation had complete (100%) donor T lymphocytes at day +90 to +120 compared with 60% of patients in the non-CR1/CR2 cohort (P = .005). In CR1/CR2 patients, donor T lymphocyte chimerism ≤ 85% at day +90 to +120 was associated with a higher frequency of 3-year disease progression (29%; 95% confidence interval [CI], 18% to 46% versus 15%; 95% CI, 9% to 23%; hazard ratio [HR], 2.1; P = .04). However, in the more advanced, non-CR1/CR2 cohort, mixed T lymphocyte chimerism was not associated with relapse (37%; 95% CI, 20% to 66% versus 34%; 95% CI, 25% to 47%; HR, 1.3; P = .60). These findings demonstrate that early T lymphocyte chimerism testing at day +90 to +120 is a useful approach for predicting AML/MDS disease recurrence in patients in CR1/CR2 at the time of transplantation.

Busulfan (Bu) is an alkylating agent with a limited therapeutic margin and exhibits inter-patient variability in pharmacokinetics (PK). Despite decades of use, mechanisms of Bu PK-based drug-drug interactions (DDIs), as well as the negative downstream effects of these DDIs, have not been fully characterized. Areas covered: This article provides an overview of Bu PK, with a primary focus on how known and potentially unknown drug metabolism pathways influence Bu-associated DDIs. In addition, pharmacogenomics of Bu chemotherapy and Bu-related DDIs observed in the stem cell transplant clinic (SCT) are summarized. Finally the increasing importance of Bu therapeutic drug monitoring is highlighted. Expert opinion: Mechanistic studies of Bu metabolism have shown that in addition to GST isoenzymes, other oxidative enzymes (CYP, FMO) and ABC/MDR drug transporters likely contribute to the overall clearance of Bu. Despite many insights, results from clinical studies, especially in polypharmacy settings and between pediatric and adult patients, remain conflicting. Further basic science and clinical investigative efforts are required to fully understand the key factors determining Bu PK characteristics and its effects on complications after SCT. Improved TDM strategies are promising components to further investigate, for instance DDI mechanisms and patient outcomes, in the highly complex SCT treatment setting.

Drug interactions may dictate the failure or success of a treatment. Patients undergoing hematopoietic stem cell transplantation (HSCT) are exposed to various types of drugs, and understanding how these drugs interact is of the utmost importance. The pharmacokinetics of busulfan, melphalan, and cyclophosphamide, drugs commonly used for HSCT, are known to be affected by a variety of other drugs with differing molecular structures. We hypothesized that these structurally unrelated drugs affect the transport of DNA-alkylating agents. To test this hypothesis, we developed a flow cytometry assay that used 5-carboxyfluorescein diacetate acetoxymethyl ester, which is cleaved by nonspecific intracellular esterases to 5-carboxyfluorescein (5-CF), a fluorescent ligand for the drug transporter MRP1. A decreased 5-CF efflux in the presence of a test compound suggests competitive inhibition. We demonstrated that chlorambucil, 4-hydroperoxycyclophosphamide, ketoconazole, ethacrynic acid, everolimus, and sirolimus strongly inhibited 5-CF efflux in lymphoma and leukemia cell lines. The efflux of these drugs partially depends on the glutathione (GSH) level, and their cytotoxicity is synergistic with inhibited GSH synthesis. This is consistent with the hypothesis that their GSH-conjugated products are ligands of a common cellular drug transporter. Our results may explain clinical observations on the effects of various drugs on the pharmacokinetics and pharmacodynamics of alkylating agents, and the assay may be used to deduce interaction mechanisms of drugs transported by a common system.

Purpose The clinical safety and efficacy of intravenous busulfan and fludarabine (IV Bu/Flu) myeloablative conditioning as well as graft-versus-host disease (GVHD) prophylaxis with high-dose, post-transplantation cyclophosphamide (PTCy) have been demonstrated independently in several single-institutional studies. We hypothesized that combining these two promising approaches in a multi-institutional study of human leukocyte antigen (HLA) -matched bone marrow transplantation would provide low rates of severe acute and chronic GVHD, low toxicity, and effective disease control. Patients and Methods Ninety-two adult patients (median age, 49 years; range, 21 to 65 years) with high-risk hematologic malignancies were enrolled at three centers (clinical trial No. NCT00809276). Forty-five patients received related allografts, and 47 received unrelated allografts. GVHD prophylaxis was solely with PTCy at 50 mg/kg/day on post-transplantation days +3 and +4. Results The cumulative incidences of grades 2 to 4 acute, grades 3 to 4 acute, and chronic GVHD were 51%, 15%, and 14%, respectively. Nonrelapse mortality (NRM) at 100 days and 1 year were 9% and 16%, respectively. With a median follow-up period of 2.2 years, the 2-year disease-free survival (DFS) and overall survival (OS) rates were 62% and 67%, respectively. Donor relatedness did not affect NRM, DFS, or OS. Patients in complete remission (CR) without evidence of minimal residual disease (MRD) had markedly better DFS (80%) and OS (80%) than patients in CR with MRD or with active disease at the time of transplantation (DFS, P = .0005; OS, P = .019). Conclusion This multi-institutional study demonstrates that PTCy can be safely and effectively combined with IV Bu/Flu myeloablative conditioning and confirms PTCy's efficacy as single-agent, short-course GVHD prophylaxis for both acute and chronic GVHD after bone marrow transplantation from HLA-matched donors.

Background: Myeloablative conditioning can be given safely to older patients by simply administering busulfan over a longer period (fractionated busulfan regimen) than the standard four day regimen. (Popat et al Lancet Haematology 2018). Subsequently, we added post-transplant cyclophosphamide (PTCy) GVHD prophylaxis to our fractionated regimen with a hypothesis that it will reduce GVHD and improve outcomes. Herein, we report the results of our retrospective analysis comparing outcomes of patients with AML who received fractionated busulfan myeloablative conditioning and PTCy versus standard tacrolimus (Tac) and methotrexate (Mtx) GVHD prophylaxis. Methods: Patients with AML between 18-70 years of age with adequate organ function and 8/8-HLA matched related or unrelated donor, who were treated on 4 consecutive protocols using fractionated busulfan were included in the analysis. All patients received two fixed doses of busulfan 80mg/m2 as outpatient either on days -13 and -12, or on days -20 and-13 followed by busulfan on day -6 to -3 dosed to achieve target area under the curve (AUC) of 20,000 mol/min for the whole course based on pharmacokinetic studies. Fludarabine ± cladribine were given on day -6 to -3. GVHD prophylaxis was PTCy 50mg/kg on days 3 and 4 and Tac ± mycophenolate mofetil in PTCy cohort (n=53), or standard Tac+ Mtx (n=53). Patients in both the cohorts were matched 1:1 by propensity score. Results: Baseline characteristics were similar between the PTCy and Tac/Mtx cohorts. The median age was 60 (range, 18-70) and 58 (range, 24-70) years, respectively, (P=0.3). Forty-nine percent were in CR, and 30% had comorbidity index >3 in each arm. Similar proportion of patients had ELN adverse risk in both arms (43% vs 40%, respectively P=0.7). The median follow up was 19 months (range, 3-36) in the PTCy and 46 months (range, 14-73) in Tac/Mtx cohort. Overall survival at 2-year was 78% vs 58% (P=0.03), non-relapse mortality was 6% vs 13% (P=0.2), incidence of grade 3-4 acute GVHD at 1-year was 6% vs 19% (P=0.07) and chronic GVHD at 2-year was 10% vs 29% (P=0.03) [Table 1 and figure 1]. The median time to neutrophil engraftment was prolonged by 3 days (15 vs 12 days; P Conclusion: As compared to Tac/Mtx, PTCy-based GVHD prophylaxis not only reduced severe acute GVHD and chronic GVHD, but also improved overall survival in AML patients up to the age of 70 years who received myeloablative fractionated busulfan conditioning. Prospective randomized trial is warranted to validate these findings. Disclosures Popat: Bayer: Research Funding; Incyte: Research Funding; Jazz: Consultancy. Bashir:Imbrium: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Kite: 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; StemLine: Research Funding; Acrotech: Research Funding; Celgene: Research Funding. Ciurea:Kiadis Pharma: Membership on an entity's Board of Directors or advisory committees, Other: stock holder; MolMed: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Research Funding. Kebriaei:Kite: Honoraria; Pfizer: Honoraria; Amgen: Research Funding; Jazz: Consultancy. Nieto:Astra-Zeneca: Research Funding; Affimed: Consultancy; Affimed: Research Funding; Novartis: Research Funding. Oran:Astex pharmaceuticals: Research Funding; AROG pharmaceuticals: Research Funding. Qazilbash:Genzyme: Other: Speaker; Amgen: Consultancy, Other: Advisory Board; Autolus: Consultancy; Bioclinical: Consultancy. Molldrem:M. D. Anderson & Astellas Pharma: Other: Royalties. Champlin:Johnson and Johnson: Consultancy; Actinium: Consultancy; Sanofi-Genzyme: Research Funding.

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 Patients aged 3-70 with intermediate or high risk AML or MDS, with PS>60% and adequate organ function were eligible if they had an HLA identical related or 9/10 or 10/10 matched unrelated donor. Patients were randomized to receive either Flu/Bu or Flu/Clo/Bu as the preparative regimen and stratified based on disease status, in complete remission (CR) or not in CR (NCR). 250 patients were entered; 130 received Flu/Bu, 120 Flu/Clo/Bu. 95 had a matched sibling, 155 a matched unrelated donor. Median age was 51 yrs. 181 had AML, 69 MDS. Poor risk cytogenetics was present in 37%. 133 patients were in remission; 117 had active disease. Comorbidity index was 90% in 88%. 249 patients achieved engraftment. 41% had grade 2 and 6% grade 3-4 acute GVHD. 93 patients developed chronic GVHD. The Kaplan Meier 3-year PFS was 0.52 (95%CI: 0.44 - 0.62) for Flu/Clo/Bu and 0.48 (95%CI: 0.41 - 0.58) for Flu/Bu (P=0.44). For the Flu Bu group, 52 patients progressed and 16 died with nonrelapse mortality (NRM). For the Flu/Clo Bu group, 32 progressed and 27 died with NRM. There was a significantly lower risk of progression with Flu/Clo/Bu (p=0.025), but a significantly higher risk of NRM (p=0.018). There was no difference in PFS for patients in CR, but there was a trend for improved PFS (p=0.17) with a significantly reduced risk of relapse (p=0.002) for patients over age 60 who were not in CR. In conclusion, Flu/Clo/Bu reduced the risk of relapse but had greater NRM compared to Flu/Bu. In patients over age 60 who were not in remission at transplant, there was a reduced risk of relapse and a trend towards improved PFS. Figure Disclosures Champlin: Johnson and Johnson: Consultancy; Actinium: Consultancy; Sanofi-Genzyme: Research Funding. Popat:Bayer: Research Funding; Incyte: Research Funding; Jazz: Consultancy. Oran:Astex pharmaceuticals: Research Funding; AROG pharmaceuticals: Research Funding. Ciurea:Kiadis Pharma: Membership on an entity's Board of Directors or advisory committees, Other: stock holder; MolMed: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Research Funding. Kebriaei:Pfizer: Honoraria; Kite: Honoraria; Amgen: Research Funding; Pfizer: Honoraria; Jazz: Consultancy; Kite: Honoraria. Bashir:Imbrium: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Kite: 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; StemLine: Research Funding; Acrotech: Research Funding; Celgene: Research Funding. Nieto:Astra-Zeneca: Research Funding; Novartis: Research Funding; Affimed: Research Funding; Affimed: Consultancy. Qazilbash:Bioclinical: Consultancy; Amgen: Consultancy, Other: Advisory Board; Autolus: Consultancy; Genzyme: Other: Speaker. OffLabel Disclosure: Clofarabine and fludarabine for hematopoietic transplantation