Genome-wide transcription factor-binding maps reveal cell-specific changes in the regulatory architecture of human HSPCs.

Hematopoietic stem and progenitor cells (HSPCs) rely on a complex interplay among transcription factors (TFs) to regulate differentiation into mature blood cells. A heptad of TFs (FLI1, ERG, GATA2, RUNX1, TAL1, LYL1, LMO2) bind regulatory elements in bulk CD34+ HSPCs. However, whether specific heptad-TF combinations have distinct roles in regulating hematopoietic differentiation remains unknown. We mapped genome-wide chromatin contacts (HiC, H3K27ac, HiChIP), chromatin modifications (H3K4me3, H3K27ac, H3K27me3) and 10 TF binding profiles (heptad, PU.1, CTCF, STAG2) in HSPC subsets (stem/multipotent progenitors plus common myeloid, granulocyte macrophage, and megakaryocyte erythrocyte progenitors) and found TF occupancy and enhancer-promoter interactions varied significantly across cell types and were associated with cell-type-specific gene expression. Distinct regulatory elements were enriched with specific heptad-TF combinations, including stem-cell-specific elements with ERG, and myeloid- and erythroid-specific elements with combinations of FLI1, RUNX1, GATA2, TAL1, LYL1, and LMO2. Furthermore, heptad-occupied regions in HSPCs were subsequently bound by lineage-defining TFs, including PU.1 and GATA1, suggesting that heptad factors may prime regulatory elements for use in mature cell types. We also found that enhancers with cell-type-specific heptad occupancy shared a common grammar with respect to TF binding motifs, suggesting that combinatorial binding of TF complexes was at least partially regulated by features encoded in DNA sequence motifs. Taken together, this study comprehensively characterizes the gene regulatory landscape in rare subpopulations of human HSPCs. The accompanying data sets should serve as a valuable resource for understanding adult hematopoiesis and a framework for analyzing aberrant regulatory networks in leukemic cells.

Germline mutations in mitochondrial complex I reveal genetic and targetable vulnerability in IDH1-mutant acute myeloid leukaemia.

The interaction of germline variation and somatic cancer driver mutations is under-investigated. Here we describe the genomic mitochondrial landscape in adult acute myeloid leukaemia (AML) and show that rare variants affecting the nuclear- and mitochondrially-encoded complex I genes show near-mutual exclusivity with somatic driver mutations affecting isocitrate dehydrogenase 1 (IDH1), but not IDH2 suggesting a unique epistatic relationship. Whereas AML cells with rare complex I variants or mutations in IDH1 or IDH2 all display attenuated mitochondrial respiration, heightened sensitivity to complex I inhibitors including the clinical-grade inhibitor, IACS-010759, is observed only for IDH1-mutant AML. Furthermore, IDH1 mutant blasts that are resistant to the IDH1-mutant inhibitor, ivosidenib, retain sensitivity to complex I inhibition. We propose that the IDH1 mutation limits the flexibility for citrate utilization in the presence of impaired complex I activity to a degree that is not apparent in IDH2 mutant cells, exposing a mutation-specific metabolic vulnerability. This reduced metabolic plasticity explains the epistatic relationship between the germline complex I variants and oncogenic IDH1 mutation underscoring the utility of genomic data in revealing metabolic vulnerabilities with implications for therapy.

RUNX1-mutated families show phenotype heterogeneity and a somatic mutation profile unique to germline predisposed AML.

First reported in 1999, germline runt-related transcription factor 1 (RUNX1) mutations are a well-established cause of familial platelet disorder with predisposition to myeloid malignancy (FPD-MM). We present the clinical phenotypes and genetic mutations detected in 10 novel RUNX1-mutated FPD-MM families. Genomic analyses on these families detected 2 partial gene deletions, 3 novel mutations, and 5 recurrent mutations as the germline RUNX1 alterations leading to FPD-MM. Combining genomic data from the families reported herein with aggregated published data sets resulted in 130 germline RUNX1 families, which allowed us to investigate whether specific germline mutation characteristics (type, location) could explain the large phenotypic heterogeneity between patients with familial platelet disorder and different HMs. Comparing the somatic mutational signatures between the available familial (n = 35) and published sporadic (n = 137) RUNX1-mutated AML patients showed enrichment for somatic mutations affecting the second RUNX1 allele and GATA2. Conversely, we observed a decreased number of somatic mutations affecting NRAS, SRSF2, and DNMT3A and the collective genes associated with CHIP and epigenetic regulation. This is the largest aggregation and analysis of germline RUNX1 mutations performed to date, providing a unique opportunity to examine the factors underlying phenotypic differences and disease progression from FPD to MM.

The mutational burden of therapy-related myeloid neoplasms is similar to primary myelodysplastic syndrome but has a distinctive distribution.

Therapy-related myeloid neoplasms (T-MN) are poorly characterized secondary hematological malignancies following chemotherapy/radiotherapy exposure. We compared the clinical and mutational characteristics of T-MN (n = 129) and primary myelodysplastic syndrome (P-MDS, n = 108) patients. Although the somatic mutation frequency was similar between T-MN and P-MDS patients (93% in both groups), the pattern was distinct. TP53 mutations were more frequent in T-MN (29.5 vs. 7%), while spliceosomal complex mutations were more common in P-MDS (56.5 vs. 25.6%). In contrast to P-MDS, the ring sideroblasts (RS) phenotype was not associated with better survival in T-MN, most probably due to genetic association with TP53 mutations. SF3B1 was mutated in 96% of P-MDS with ≥15% RS, but in only 32% T-MN. TP53 mutations were detected in 92% T-MN with ≥15% RS and SF3B1 wild-type cases. Interestingly, T-MN and P-MDS patients with "Very low" or "Low" Revised International Prognostic Scoring System (IPSS-R) showed similar biological and clinical characteristics. In a Cox regression analysis, TP53 mutation was a poor prognostic factor in T-MN, independent of IPSS-R cytogenetics, disease-modifying therapy, and NRAS mutation. Our data have direct implications for T-MN management and provide evidence that, in addition to conventional disease parameters, mutational analysis should be incorporated in T-MN risk stratification.

Genomic subtyping and therapeutic targeting of acute erythroleukemia.

Acute erythroid leukemia (AEL) is a high-risk leukemia of poorly understood genetic basis, with controversy regarding diagnosis in the spectrum of myelodysplasia and myeloid leukemia. We compared genomic features of 159 childhood and adult AEL cases with non-AEL myeloid disorders and defined five age-related subgroups with distinct transcriptional profiles: adult, TP53 mutated; NPM1 mutated; KMT2A mutated/rearranged; adult, DDX41 mutated; and pediatric, NUP98 rearranged. Genomic features influenced outcome, with NPM1 mutations and HOXB9 overexpression being associated with a favorable prognosis and TP53, FLT3 or RB1 alterations associated with poor survival. Targetable signaling mutations were present in 45% of cases and included recurrent mutations of ALK and NTRK1, the latter of which drives erythroid leukemogenesis sensitive to TRK inhibition. This genomic landscape of AEL provides the framework for accurate diagnosis and risk stratification of this disease, and the rationale for testing targeted therapies in this high-risk leukemia.

A phase II study of a modified hyper-CVAD frontline therapy for patients with adverse risk diffuse large B-cell and peripheral T-cell non-Hodgkin lymphoma.

To improve complete remission (CR) rates by reducing toxicity and enhancing delivery, we created a modified hyper-CVAD/MA regimen (cyclophosphamide, vincristine, doxorubicin, dexamethasone/methotrexate, cytarabine) by reducing the cytarabine dose (3 g/m2 to 2 g/m2) and number of cycles (eight to six). We conducted a phase II trial in the pre-rituximab era in the intermediate-high international prognostic index (IPI) (≥2) de novo diffuse large B-cell lymphoma (DLBCL) and peripheral T-cell lymphoma (PTCL) (ACTRN12605000105640). CR rates were compared with reported IPI-stratified rates. Sixty-three patients (n = 26 PTCL; n = 37 DLBCL) were evaluated; median follow-up of 30 months. CR rates for PTCL and DLBCL patients were 46% and 49%, respectively, similar with reported CR rates with CHOP-like chemotherapy (p = .6). Of the patients, 51 (81%) experienced ≥1 unplanned hospital admission; only 41 (65%) completed six cycles. The cytarabine modifications did not prevent significant toxicity. Modified hyper-CVAD/MA resulted in similar outcomes to CHOP-like chemotherapy in aggressive lymphomas and was associated with significant toxicity.

Prospective, Randomized, Double-Blind, Phase III Clinical Trial of Anti-T-Lymphocyte Globulin to Assess Impact on Chronic Graft-Versus-Host Disease-Free Survival in Patients Undergoing HLA-Matched Unrelated Myeloablative Hematopoietic Cell Transplantation.

Purpose Several open-label randomized studies have suggested that in vivo T-cell depletion with anti-T-lymphocyte globulin (ATLG; formerly antithymocyte globulin-Fresenius) reduces chronic graft-versus-host disease (cGVHD) without compromising survival. We report a prospective, double-blind phase III trial to investigate the effect of ATLG (Neovii Biotech, Lexington, MA) on cGVHD-free survival. Patients and Methods Two hundred fifty-four patients 18 to 65 years of age with acute leukemia or myelodysplastic syndrome who underwent myeloablative HLA-matched unrelated hematopoietic cell transplantation (HCT) were randomly assigned one to one to placebo (n =128 placebo) or ATLG (n = 126) treatment at 27 sites. Patients received either ATLG or placebo 20 mg/kg per day on days -3, -2, -1 in addition to tacrolimus and methotrexate as GVHD prophylaxis. The primary study end point was moderate-severe cGVHD-free survival. Results Despite a reduction in grade 2 to 4 acute GVHD (23% v 40%; P = .004) and moderate-severe cGVHD (12% v 33%; P < .001) in ATLG recipients, no difference in moderate-severe cGVHD-free survival between ATLG and placebo was found (2-year estimate: 48% v 44%, respectively; P = .47). Both progression-free survival (PFS) and overall survival (OS) were lower with ATLG (2-year estimate: 47% v 65% [ P = .04] and 59% v 74% [ P = .034], respectively). Multivariable analysis confirmed that ATLG was associated with inferior PFS (hazard ratio, 1.55; 95% CI, 1.05 to 2.28; P = .026) and OS (hazard ratio, 1.74; 95% CI, 1.12 to 2.71; P = .01). Conclusion In this prospective, randomized, double-blind trial of ATLG in unrelated myeloablative HCT, the incorporation of ATLG did not improve moderate-severe cGVHD-free survival. Moderate-severe cGVHD was significantly lower with ATLG, but PFS and OS also were lower. Additional analyses are needed to understand the appropriate role for ATLG in HCT.

Red cell alloimmunization is associated with development of autoantibodies and increased red cell transfusion requirements in myelodysplastic syndrome.

Up to 90% of patients with a myelodysplastic syndrome require red blood cell transfusion; nevertheless, comprehensive data on red cell alloimmunization in such patients are limited. This study evaluates the incidence and clinical impact of red cell alloimmunization in a large cohort of patients with myelodysplastic syndrome registered in the statewide South Australian-MDS registry. The median age of the 817 patients studied was 73 years, and 66% were male. The cumulative incidence of alloimmunization was 11%. Disease-modifying therapy was associated with a lower risk of alloimmunization while alloimmunization was significantly higher in patients with a revised International Prognostic Scoring System classification of Very Low, Low or Intermediate risk compared to those with a High or Very High risk (P=0.03). Alloantibodies were most commonly directed against antigens in the Rh (54%) and Kell (24%) systems. Multiple alloantibodies were present in 49% of alloimmunized patients. Although 73% of alloimmunized patients developed alloantibodies during the period in which they received their first 20 red cell units, the total number of units transfused was significantly higher in alloimmunized patients than in non-alloimmunized patients (90±100 versus 30±52; P<0.0001). In individual patients, red cell transfusion intensity increased significantly following alloimmunization (2.8±1.3 versus 4.1±2.0; P<0.0001). A significantly higher proportion of alloimmunized patients than non-alloimmunized patients had detectable autoantibodies (65% versus 18%; P<0.0001) and the majority of autoantibodies were detected within a short period of alloimmunization. In conclusion, this study characterizes alloimmunization in a large cohort of patients with myelodysplastic syndrome and demonstrates a signficant increase in red cell transfusion requirements following alloimmunization, most probably due to development of additional alloantibodies and autoantibodies, resulting in subclinical/clinical hemolysis. Strategies to mitigate alloimmunization risk are critical for optimizing red cell transfusion support.

A Phase 2/3 Multicenter, Randomized, Open-Label Study to Compare the Efficacy and Safety of Lenalidomide Versus Investigator's Choice in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma.

Purpose: Randomized, multicenter, open-label, phase 2/3 trial investigating lenalidomide versus investigator's choice (IC) in relapsed/refractory diffuse large B-cell lymphoma (DLBCL).Experimental Design: Patients with DLBCL who received ≥2 prior therapies were stratified by DLBCL subtype [germinal center B-cell (GCB) vs. non-GCB; determined by immunohistochemistry (IHC)] and then randomized 1:1 to lenalidomide (25 mg/day, 21 days of 28-day cycle) or IC (gemcitabine, rituximab, etoposide, or oxaliplatin). Crossover to lenalidomide was permitted for IC-treated patients with radiologically confirmed progressive disease. The primary endpoint was overall response rate (ORR). Progression-free survival (PFS), overall survival, and subtype analysis [GCB vs. activated B-cell (ABC)] using gene expression profiling (GEP) were exploratory endpoints.Results: Stage 1: 102 DLBCL patients (by IHC: non-GCB, n = 54; GCB, n = 48) received ≥1 dose of lenalidomide or IC. Hematologic treatment-emergent adverse events with lenalidomide versus IC included neutropenia (42.6%; 36.4%), anemia (33.3%; 47.3%), thrombocytopenia (24.1%; 43.6%), and leukopenia (5.6%; 12.7%), respectively. Overall, lenalidomide-treated patients had an ORR of 27.5% versus 11.8% in IC (ORRs were similar regardless of IHC-defined DLBCL subtype). Median PFS was increased in patients receiving lenalidomide (13.6 weeks) versus IC (7.9 weeks; P = 0.041), with greater improvements in non-GCB patients (15.1 vs. 7.1 weeks, respectively; P = 0.021) compared with GCB (10.1 vs. 9.0 weeks, respectively; P = 0.550).Conclusions: The clinical benefit of lenalidomide monotherapy in DLBCL patients was more evident in the non-GCB subtype. Exploratory analyses suggest that this preferential benefit was more pronounced in the GEP-defined ABC population, demonstrating a need for additional studies of lenalidomide in DLBCL using GEP subtyping. Clin Cancer Res; 23(15); 4127-37. ©2017 AACR.

Idarubicin Dose Escalation During Consolidation Therapy for Adult Acute Myeloid Leukemia.

Purpose Higher doses of the anthracycline daunorubicin during induction therapy for acute myeloid leukemia (AML) have been shown to improve remission rates and survival. We hypothesized that improvements in outcomes in adult AML may be further achieved by increased anthracycline dose during consolidation therapy. Patients and Methods Patients with AML in complete remission after induction therapy were randomly assigned to receive two cycles of consolidation therapy with cytarabine 100 mg/m2 daily for 5 days, etoposide 75 mg/m2 daily for 5 days, and idarubicin 9 mg/m2 daily for either 2 or 3 days (standard and intensive arms, respectively). The primary end point was leukemia-free survival (LFS). Results Two hundred ninety-three patients 16 to 60 years of age, excluding those with core binding factor AML and acute promyelocytic leukemia, were randomly assigned to treatment groups (146 to the standard arm and 147 to the intensive arm). Both groups were balanced for age, karyotypic risk, and FLT3-internal tandem duplication and NPM1 gene mutations. One hundred twenty patients in the standard arm (82%) and 95 patients in the intensive arm (65%) completed planned consolidation ( P < .001). Durations of severe neutropenia and thrombocytopenia were prolonged in the intensive arm, but there were no differences in serious nonhematological toxicities. With a median follow-up of 5.3 years (range, 0.6 to 9.9 years), there was a statistically significant improvement in LFS in the intensive arm compared with the standard arm (3-year LFS, 47% [95% CI, 40% to 56%] v 35% [95% CI, 28% to 44%]; P = .045). At 5 years, the overall survival rate was 57% in the intensive arm and 47% in the standard arm ( P = .092). There was no evidence of selective benefit of intensive consolidation within the cytogenetic or FLT3-internal tandem duplication and NPM1 gene mutation subgroups. Conclusion An increased cumulative dose of idarubicin during consolidation therapy for adult AML resulted in improved LFS, without increased nonhematologic toxicity.

Dynamic assessment of RBC-transfusion dependency improves the prognostic value of the revised-IPSS in MDS patients.

RBC-transfusion dependency (RBC-TD) is an independent prognostic factor for poor overall survival (OS) in the WHO classification-based prognostic scoring system (WPSS) for MDS patients. However, WPSS did not include cytopenia, whereas revised International Prognostic Scoring System (IPSS-R) did not include RBC-TD. Thus, neither of these prognostic scoring systems incorporates both cytopenia and RBC-TD. We aimed to test whether RBC-TD adds prognostic value to the IPSS-R. We analyzed MDS patients not treated with disease-modifying therapy, and enrolled in SA-MDS Registry (derivation cohort; n = 295) and Dusseldorf registry (Germany; validation cohort; n = 113) using time-dependent Cox proportional regression and serial landmark analyses. In the derivation cohort, RBC-TD patients had inferior OS compared to RBC transfusion-independent (RBC-TI) patients (P < 0.0001) at 6- (18 vs. 64 months), 12- (24 vs. 71 months), and 24-months (40 vs. 87 months). In a Cox proportional regression analysis, RBC-TD was an independent adverse prognostic marker in addition to age, sex, and IPSS-R variables (P < 0.0001). A prognostic index (PI) was derived using these Cox-proportional regression model variables. In the validation cohort, this PI classified patients into four prognostic groups with significantly different OS (P < 0.001) as in the derivation cohort. In conclusion, multivariate analysis by Cox proportional hazards regression and serial landmark analyses clearly demonstrates that development of RBC-TD at any time during the course of MDS is associated with poor OS, independent of IPSS-R. This study demonstrates that dynamic assessment of RBC-TD provides additional prognostic value to IPSS-R and should be included in treatment decision algorithms for MDS patients.

Early treatment intensification with R-ICE and 90Y-ibritumomab tiuxetan (Zevalin)-BEAM stem cell transplantation in patients with high-risk diffuse large B-cell lymphoma patients and positive interim PET after 4 cycles of R-CHOP-14.

In the treatment of diffuse large B-cell lymphoma, a persistently positive [18F]fluorodeoxyglucose positron emission tomography (PET) scan typically carries a poor prognosis. In this prospective multi-center phase II study, we sought to establish whether treatment intensification with R-ICE (rituximab, ifosfamide, carboplatin, and etoposide) chemotherapy followed by 90Y-ibritumomab tiuxetan-BEAM (BCNU, etoposide, cytarabine, and melphalan) for high-risk diffuse large B-cell lymphoma patients who are positive on interim PET scan after 4 cycles of R-CHOP-14 (rituximab, cyclophosphamide, doxorubicin, and prednisone) can improve 2-year progression-free survival from a historically unfavorable rate of 40% to a rate of 65%. Patients received 4 cycles of R-CHOP-14, followed by a centrally-reviewed PET performed at day 17-20 of cycle 4 and assessed according to International Harmonisation Project criteria. Median age of the 151 evaluable patients was 57 years, with 79% stages 3-4, 54% bulk, and 54% International Prognostic Index 3-5. Among the 143 patients undergoing interim PET, 101 (71%) were PET-negative (96 of whom completed R-CHOP), 42 (29%) were PET-positive (32 of whom completed R-ICE and 90Y-ibritumomab tiuxetan-BEAM). At a median follow up of 35 months, the 2-year progression-free survival for PET-positive patients was 67%, a rate similar to that for PET-negative patients treated with R-CHOP-14 (74%, P=0.11); overall survival was 78% and 88% (P=0.11), respectively. In an exploratory analysis, progression-free and overall survival were markedly superior for PET-positive Deauville score 4 versus score 5 (P=0.0002 and P=0.001, respectively). Therefore, diffuse large B-cell lymphoma patients who are PET-positive after 4 cycles of R-CHOP-14 and who switched to R-ICE and 90Y-ibritumomab tiuxetan-BEAM achieved favorable survival outcomes similar to those for PET-negative R-CHOP-14-treated patients. Further studies are warranted to confirm these promising results. (Registered at: ACTRN12609001077257).

Targeting sphingosine kinase 1 induces MCL1-dependent cell death in acute myeloid leukemia.

Acute myeloid leukemia (AML) is an aggressive malignancy where despite improvements in conventional chemotherapy and bone marrow transplantation, overall survival remains poor. Sphingosine kinase 1 (SPHK1) generates the bioactive lipid sphingosine 1-phosphate (S1P) and has established roles in tumor initiation, progression, and chemotherapy resistance in a wide range of cancers. The role and targeting of SPHK1 in primary AML, however, has not been previously investigated. Here we show that SPHK1 is overexpressed and constitutively activated in primary AML patient blasts but not in normal mononuclear cells. Subsequent targeting of SPHK1 induced caspase-dependent cell death in AML cell lines, primary AML patient blasts, and isolated AML patient leukemic progenitor/stem cells, with negligible effects on normal bone marrow CD34+ progenitors from healthy donors. Furthermore, administration of SPHK1 inhibitors to orthotopic AML patient-derived xenografts reduced tumor burden and prolonged overall survival without affecting murine hematopoiesis. SPHK1 inhibition was associated with reduced survival signaling from S1P receptor 2, resulting in selective downregulation of the prosurvival protein MCL1. Subsequent analysis showed that the combination of BH3 mimetics with either SPHK1 inhibition or S1P receptor 2 antagonism triggered synergistic AML cell death. These results support the notion that SPHK1 is a bona fide therapeutic target for the treatment of AML.

KB004, a first in class monoclonal antibody targeting the receptor tyrosine kinase EphA3, in patients with advanced hematologic malignancies: Results from a phase 1 study.

EphA3 is an Ephrin receptor tyrosine kinase that is overexpressed in most hematologic malignancies. We performed a first-in-human multicenter phase I study of the anti-EphA3 monoclonal antibody KB004 in refractory hematologic malignancies in order to determine safety and tolerability, along with the secondary objectives of pharmacokinetics (PK) and pharmacodynamics (PD) assessments, as well as preliminary assessment of efficacy. Patients were enrolled on a dose escalation phase (DEP) initially, followed by a cohort expansion phase (CEP). KB004 was administered by intravenous infusion on days 1, 8, and 15 of each 21-day cycle in escalating doses. A total of 50 patients (AML 39, MDS/MPN 3, MDS 4, DLBCL 1, MF 3) received KB004 in the DEP; an additional 14 patients were treated on the CEP (AML 8, MDS 6). The most common toxicities were transient grade 1 and grade 2 infusion reactions (IRs) in 79% of patients. IRs were dose limiting above 250mg. Sustained exposure exceeding the predicted effective concentration (1ug/mL) and covering the 7-day interval between doses was achieved above 190mg. Responses were observed in patients with AML, MF, MDS/MPN and MDS. In this study, KB004 was well tolerated and clinically active when given as a weekly infusion.

Distinct evolution and dynamics of epigenetic and genetic heterogeneity in acute myeloid leukemia.

Genetic heterogeneity contributes to clinical outcome and progression of most tumors, but little is known about allelic diversity for epigenetic compartments, and almost no data exist for acute myeloid leukemia (AML). We examined epigenetic heterogeneity as assessed by cytosine methylation within defined genomic loci with four CpGs (epialleles), somatic mutations, and transcriptomes of AML patient samples at serial time points. We observed that epigenetic allele burden is linked to inferior outcome and varies considerably during disease progression. Epigenetic and genetic allelic burden and patterning followed different patterns and kinetics during disease progression. We observed a subset of AMLs with high epiallele and low somatic mutation burden at diagnosis, a subset with high somatic mutation and lower epiallele burdens at diagnosis, and a subset with a mixed profile, suggesting distinct modes of tumor heterogeneity. Genes linked to promoter-associated epiallele shifts during tumor progression showed increased single-cell transcriptional variance and differential expression, suggesting functional impact on gene regulation. Thus, genetic and epigenetic heterogeneity can occur with distinct kinetics likely to affect the biological and clinical features of tumors.

Filgrastim-Stimulated Bone Marrow Compared with Filgrastim-Mobilized Peripheral Blood in Myeloablative Sibling Allografting for Patients with Hematologic Malignancies: A Randomized Canadian Blood and Marrow Transplant Group Study.

In adult hematopoietic cell transplantation (HCT), filgrastim-mobilized peripheral blood (G-PB) has largely replaced unstimulated marrow for allografting. Although the use of G-PB results in faster hematopoietic recovery, it is also associated with more chronic graft-versus-host disease (cGVHD). A potential alternative allograft is filgrastim-stimulated marrow (G-BM), which we hypothesized may be associated with prompt hematopoietic recovery but with less cGVHD. We conducted a phase 3, open-label, multicenter randomized trial of 230 adults with hematologic malignancies receiving allografts from siblings after myeloablative conditioning to compare G-PB with G-BM. The primary endpoint was time to treatment failure, defined as a composite of extensive cGVHD, relapse/disease progression, and death. With a median follow-up of 36 months (range, 9.6 to 48), comparing G-BM with G-PB, there was no difference between the 2 arms with respect to the primary outcome of this study (hazard ratio [HR], .91; 95% confidence interval [CI], .68 to 1.22; P = .52). However, the cumulative incidence of overall cGVHD was lower with G-BM (HR, .66; 95% CI, .46 to .95; P = .007) and there was no difference in the risk of relapse or progression (P = .35). The median times to neutrophil recovery (P = .0004) and platelet recovery (P = .012) were 3 days shorter for recipients allocated to G-PB compared with those allocated to G-BM, but there were no differences in secondary engraftment-related outcomes, such as time to first hospital discharge (P = .17). In addition, there were no graft failures in either arm. This trial demonstrates that, compared with G-PB, the use of G-BM allografts leads to a significantly lower rate of overall cGVHD without a loss of the graft-versus-tumor effect and comparable overall survival. Our findings suggest that further study of this type of allograft is warranted.