Peripheral Blood Stem Cell Allografts Research Articles

Post-Transplant Cyclophosphamide Eliminates Disparity in GvHD-Free, Relapse-Free Survival and Overall Survival between 8/8 Matched and 7/8 Mismatched Unrelated Donor Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Background: Post-transplant cyclophosphamide (PTCy) has become a standard of care for graft-versus-host disease (GvHD) prophylaxis in recipients of human leukocyte antigen (HLA)-matched and mismatched unrelated donor (MMUD) allografts, generating new opportunities for successful hematopoietic cell transplantation (HCT) regardless of patient ancestry. The National Marrow Donor Program (NMDP)-sponsored 15-MMUD study, which used PTCy-based GvHD prophylaxis (PMID 3390526), demonstrated encouraging overall survival (OS) in adult patients receiving MMUD bone marrow grafts matched at ≤7/8 HLA alleles. Currently, the follow-up ACCESS study (NCT04904588) will determine if similar outcomes can be achieved using MMUD peripheral blood stem cell allografts. As part of its 5-year strategic plan, the NMDP aims to determine the extent of differences in GvHD-free, relapse-free survival (GRFS) between 8/8 and 7/8 URD allografts using PTCy and seeks to develop approaches over time to close the presumed gap in URD outcomes. Methods: The primary objective was to compare GRFS between 8/8 and 7/8 URD HCT using the Center for International Blood & Marrow Transplant Research (CIBMTR) database. After analyzing primary results, secondary objectives were added to compare GRFS, OS, and other clinical outcomes among 8/8 URD, 7/8 URD, and haploidentical-related donor (Haplo) HCT. The study included adult patients (age≥18y) with hematologic malignancies (ALL, AML, MDS) undergoing first URD or Haplo HCT between 2017-2020 using PTCy-based GvHD prophylaxis. Kaplan-Meier curves were used to estimate probability of GRFS and OS. Cox regression examined the independent effect of HLA match controlling for other clinical factors on outcomes referenced to 8/8 URD HCT. A priori clinically selected factors considered as possible confounders in the regression model included disease risk index, comorbidity risk, pre-HCT Karnofsky score, conditioning regimen intensity, graft source, donor/recipient CMV serostatus, year of HCT, donor/recipient age and race/ethnicity. Final models were stratified by factors violating the proportional hazards assumption. Factors were eliminated in a backwards fashion if p-values were >0.10 unless inclusion affected the hazard ratio (HR) of HLA match by more than 10%. Interactions were tested against a p-value of <0.01. Results: Table 1 shows demographics for the three patient cohorts: Haplo (n=2772), 8/8 URD (N=1517), and 7/8 MMUD (N=540). Notable differences among the cohorts included: 8/8 URD recipients had younger, predominantly Caucasian donors and were more likely to receive myeloablative conditioning. Haplo recipients had more donor/recipient CMV seropositivity and received more reduced intensity conditioning. Otherwise patient characteristics were similar. Contrary to our expectations, multivariable regression analysis (MVA) showed no significant differences in either GRFS or OS between recipients of 8/8 and 7/8 URD HCT at 1, 2 and 3-years post-HCT ( Figure 1). Outcomes, including relapse and NRM, between 8/8 and 7/8 URD HCT were similar irrespective of conditioning intensity. However, 8/8 URD HCT associated with lower two-year moderate/severe chronic GvHD than 7/8 URD [1.30 (1.00-1.68), p=0.049]. We next compared GRFS and OS among 8/8 and 7/8 URD and Haplo at 3y after HCT. On MVA, GRFS [HR 1.15 (1.04-1.26), p=0.005] and OS [HR 1.15 (1.03-1.29), p=0.013] were significantly better in 8/8 URD compared to Haplo HCT. Differences between 8/8 URD and Haplo appeared to be driven by significantly higher NRM [HR 1.46 (1.22-1.74), p<0.001)] and two-year moderate/severe chronic GvHD [HR 1.28 (1.07-1.54), p=0.007] in Haplo. No significant differences were seen in GRFS or OS at 3 years when comparing 7/8 URD to Haplo. Causes of death among donor types were similar with primary disease relapse/progression, infection and organ failure being the most frequent. Conclusions: Use of PTCy-based GvHD prophylaxis seems to have resolved previously observed differences in GRFS and OS between 8/8 and 7/8 URD HCT. HCT using an 8/8 URD HCT, if available, continues to be the best option for patients lacking a matched sibling donor. Further studies comparing Haplo to 7/8 URD HCT are warranted, but will require larger numbers of 7/8 URD HCT. Both mismatched donor sources substantially increase access to HCT for patients regardless of their ancestry.

A French single-center experience on allogeneic stem cell transplant cryopreservation during severe acute respiratory syndrome coronavirus 2 pandemic

Background aimsAllogeneic hematopoietic stem cell transplantation (allo-SCT) is a curative treatment for chemo-resistant hematological malignancies. Because of transport restriction imposed by the coronavirus disease 2019 pandemic, regulatory bodies and societies recommended graft cryopreservation before recipient conditioning. However, the freezing and thawing processes, including washing steps, might impair CD34+ cell recovery and viability, thereby impacting the recipient engraftment. Over 1 year (between March 2020 and May 2021), we aimed to analyze the results of frozen/thawed peripheral blood stem cell allografts in terms of stem cell quality and clinical outcomes. MethodsTransplant quality was evaluated by comparing total nucleated cells (TNCs), CD34+ cells and colony-forming unit–granulocyte/macrophage (CFU-GM)/kg numbers as well as TNC and CD34+ cell viabilities before and after thawing. Intrinsic biological parameters such as granulocyte, platelet and CD34+ cell concentrations were analyzed, as they might be responsible for a quality loss. The impact of the CD34+ cell richness of the graft on TNC and CD34 yields was evaluated by designing three groups of transplants based on their CD34 /kg value at collection: >8 × 10 6/kg, between 6 and 8 × 106/kg and <6 × 106/kg. The consequences of cryopreservation were compared in the fresh and thawed group by evaluating the main transplant outcomes. ResultsOver 1 year, 76 recipients were included in the study; 57 patients received a thawed and 19 patients a fresh allo-SCT. None received allo-SCT from a severe acute respiratory syndrome coronavirus 2–positive donor. The freezing of 57 transplants led to the storage of 309 bags, for a mean storage time (between freezing and thawing) of 14 days. For the fresh transplant group, only 41 bags were stored for potential future donor lymphocyte infusions. Regarding the graft characteristics at collection, median number of cryopreserved TNC and CD34+ cells/kg were greater than those for fresh infusions. After thawing, median yields were 74.0%, 69.0% and 48.0% for TNC, CD34+ cells and CFU-GM, respectively. The median TNC dose/kg obtained after thawing was 5.8 × 108, with a median viability of 76%. The median CD34+ cells/kg was 5 × 106, with a median viability of 87%. In the fresh transplant group, the median TNC/kg was 5.9 × 108/kg, and the median CD34+ cells/kg and CFU-GM/kg were 6 × 106/kg and 276.5 × 104/kg, respectively. Sixty-one percent of the thawed transplants were out of specifications regarding the CD34+ cells/ kg requested cell dose (6 × 106/kg) and 85% of them would have had this dose if their hematopoietic stem cell transplant had been infused fresh. Regarding fresh grafts, 15.8% contained less than 6 × 106 CD34+ cells /kg and came from peripheral blood stem cells that did not reach 6 × 106 CD34+ cells /kg at collection. Regarding the factor that impaired CD34 and TNC yield after thawing, no significant impact of the granulocyte count, the platelet count or the CD34+ cells concentration/µL was observed. However, grafts containing more than 8 × 10 6/kg at collection showed a significantly lower TNC and CD34 yield. ConclusionsTransplant outcomes (engraftment, graft-versus-host disease, infections, relapse or death) were not significantly different between the two groups.

Reduced Intensity Conditioning and Dual T-Cell Modulation Improves Gvhd Free, Relapse Free Survival in AML Patients Compared with Myeloablative Conditioning

BACKGROUND The efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in acute myeloid leukemia (AML) relies on the antileukemic effect of the conditioning regimen and the graft-versus leukemia (GVL) effect mediated by donor T-cells. Leveraging the GVL effect while reducing toxicity enables reduced intensity conditioning (RIC) to be used to older or frail patients, but may lead to higher rates of graft-versus-host disease (GVHD), impairing later quality of life. Novel T-cell modulation strategies may limit the incidence of GVHD while preserving antileukemic activity leading to better outcomes. Herein, we compare the outcomes of AML patients treated with myeloablative (MAC) and RIC regimens including patients receiving dual T-cell depletion using Anti-Thymocyte Globulin (ATG) and Post-Transplant Cyclophosphamide (PTCy). METHODS Between 2013 and 2018, 362 adults with AML in complete remission underwent allo-HSCT and were included in the study. Overall, 112 (31%) patients received MAC and 250 (69%) received RIC regimens. MAC consisted of Flu(4), Bu (4mg) and 400cGy of total body irradiation (TBI). RIC regimen consisted on Flu (4), Bu (2) and 200cGy TBI in 249 recipients and one received clofarabine/busulfan. One hundred seventy-one (68.4%) the recipients who received RIC regimen, received a novel dual T-cell depletion strategy using ATG (total dose of 4.5mg/kg in 130 patients and 2mg/kg in 41 recipients), PTCy, and cyclosporine for GVHD prophylaxis. Peripheral blood stem cell (PBSC) grafts were used in 98.9% of the recipients. Data was collected retrospectively and updated on April 2019. The cumulative incidence of GVHD was assessed accounting relapse and death as competing events. A multivariate analysis for overall survival (OS), relapse-free survival (RFS) and GVHD-Free/RFS (GFRFS) was conducted controlled by those variables found to be significant in univariate analysis. RESULTS Baseline information is summarized in Table 1. The incidence of grade II-IV and III-IV acute GVHD at day +100, and moderate/severe chronic GVHD at 1 year was respectively: 28.6%, 10.5%, and 18.4%. RIC was associated with a significantly lower cumulative incidence of clinically relevant acute and chronic GVHD (P&lt;0.05). Main outcome information is summarized in tables 1 and 2, and displayed graphically in figures A-F. With a median follow-up of 3.7 years, 68 (18.8%) recipients relapsed and 160 (44.2%) died. The 2-years OS, RFS, and GRFS were 53.8%, 50.8%, and 33.8%, respectively. OS, RFS, non-relapse mortality, and cumulative incidence of relapse were not significantly affected by regimen intensity (P&gt;0.05). However, RIC regimens were associated with superior GRFS. Forty-three (12.7%) recipients had a high Disease Risk Index (DRI). Conditioning intensity was not a significant risk factor for OS (HR 0.9; P=0.931) or RFS (HR 1; P=0.902) in this group of patients. Tables 3 and 4 show the results from multivariate analysis for OS, RFS, and GFRFS. Older patients, those with high DRI, or recipients of 9/10 matched unrelated donor (MUD) grafts had significantly worse OS and RFS. GVHD prophylaxis with dual T-cell modulation (ATG-PTCy-CsA) was the only protective parameter for a better GRFS (HR 0.5; P=0.005). CONCLUSION In AML patients, RIC with PBSC allografts and dual T-cell modulation with ATG and PTCy led to superior GRFS when compared with MAC regimens. Reduction in the cumulative incidence of clinically significant acute and chronic GVHD may be possible without compromising on the efficacy of the GVL effect. The use of this GVHD prophylaxis strategy, along with mitigation of conditioning toxicity by using RIC, may result in better quality of life. Further investigations would be done with the use of this novel GVHD prophylaxis in the setting of MAC regiments. Dual T-cell suppression leads to increased infectious complications including viral reactivations. The use of lower doses of ATG, or individualized dosing strategies based on lymphocyte count may help to further optimize this strategy. Disclosures Michelis: CSL Behring: Other: Financial Support. Mattsson:Celgene: Honoraria; Therakos: Honoraria; Gilead: Honoraria.

Evaluation of a Donor Testing Kit for the Prediction of AGVHD in Patient Receiving a Peripheral Blood Stem Cell Allograft

Evaluation of a Donor Testing Kit for the Prediction of AGVHD in Patient Receiving a Peripheral Blood Stem Cell Allograft

Successful Allogeneic Hematopoietic Cell Transplantation (HCT) with Low Toxicity and Gvhd in a Heterogeneous Cohort of Primary Immunodeficiency (PID) Patients

HCT has been used for decades as a definitive therapy for patients with PIDs. These patients often enter HCT with significant comorbidities and disease sequelae and may have limited donor options if family members are also affected, so the ability to offer HCT to all who require it remains suboptimal. Twenty-nine children and adults with various underlying PIDs received a serotherapy-free, radiation-free reduced intensity conditioning platform designed with the goals of optimizing immune reconstitution, minimizing complications such as graft-versus-host disease (GVHD), and permitting use of alternative donors. Conditioning consisted of pentostatin, low-dose cyclophosphamide and 2 days of busulfan, and GVHD prophylaxis included post-transplantation cyclophosphamide, mycophenolate mofetil, and sirolimus. All received T cell replete bone marrow or peripheral blood stem cell allografts. Patient and donor characteristics are shown in Fig 1a. Neutrophil recovery occurred at median day +17 (range 14-42). With median follow-up of 14 months (range 3-33), graft-failure-free, steroid-refractory grade 3-4 GVHD-free survival was estimated at 82% at 1 year (Fig 2). Two deaths occurred in patients with HCT-CI scores of 6 (bacterial sepsis and invasive Aspergillosis, day +44) and 8 (presumed viral encephalitis, day +110). There were 3 graft failures (1 primary, with autologous recovery on day +14 and 2 secondary on day +34 and +159). Two patients were successfully retransplanted with eventual full donor chimerism, while the third's infection was sufficiently temporized by the first transplant to make an immediate retransplant not necessary. The kinetics of donor chimerism differed between myeloid and lymphoid compartments. Most patients had complete donor myeloid chimerism by day +28 but a slower rise in donor CD3 chimerism (median 77% at day +28 to 94% at day +60) (Fig 3). GVHD rates have been low, with cumulative incidence of steroid-responsive grade 2-4 acute GVHD at 1 year of 14% (death and graft failure as competing risks) and no chronic GVHD to date. HCT-related outcomes and complications are listed in Fig 1b. Of note, BK-associated hemorrhagic cystitis occurred at high rates, but serious viral complications were infrequent. Some degree of phenotype reversal is evident in all evaluable patients. All 10 patients with lymphoma or lymphoproliferative disorder are in remission, and, of 24 engrafted survivors, only two continue to require immunoglobulin replacement beyond 6 months post-HCT. Future directions include reducing the duration of post-HCT immunosuppression to hasten improved viral control and increasing pre-HCT lymphodepletion for selected patients at high risk for graft failure. Continued long term follow up is needed to better characterize phenotype reversal, graft durability, immune reconstitution and late toxicities of the platform.

Influence of Donor Type (sibling vs matched-unrelated donor vs haplo-identical donor vs cord blood) on Outcomes after Clofarabine-Based Reduced-Intensity Conditioning Allograft for Myeloid Malignancies

Background: Recently, we have reported the good results of a clofarabine-based reduced-intensity conditioning (RIC) regimen for peripheral blood stem cell (PBSC) allografts, using either matched (Le Bourgeois, ASH 2017) or haploidentical (haplo) donors (Chevallier, ASH 2017). However, the influence of donor type in this setting is unknown.Patients and Methods: We conducted a retrospective study including all adults (≥18 yo) allografted in our department with a clofarabine-based RIC regimen for a myeloid malignancy. All types of donors were accepted, and patients received allogeneic peripheral blood stem cells (PBSC) or cord blood (CB) transplants. The aim of this study was to assess whether or not the donor type (sibling, matched unrelated (MUD), haplo or CB) impacted outcomes.Results: Between October 2009 and February 2018, 122 patients met the inclusion criteria. Donors were sibling in 36 cases, “MUD” in 55 (including one 9/10 mismatched donor), haplo in 27 and CB in 4. The sibling+MUD patients received a CloB2A1/A2 RIC regimen consisting of clofarabine 30 mg/m²/day 4 to 5 days (Clo), busulfan 3.2 mg/kg/day 2 days (B2) and 2.5mg/kg/day of rabbit anti-thymocyte globulin 1 or 2 days (A1 or A2). Haplo and CB recipients were conditioned by a Baltimore-like RIC regimen and a Minneapolis-like regimen, respectively, where fludarabine were replaced by clofarabine. All patients received cyclosporine (CsA) + mycophenolate mofetyl as GVHD prophylaxis, except sibling recipients who were given CsA alone. Haplo recipients received also 2 days of post-transplant cyclophosphamide. All non-CB patients received PBSC as source of graft.The median age of the whole cohort was 61,5 years old (range: 18-73) and the median follow-up 31 months (range: 4,5-106). All patients engrafted except 1 CB patient and 1 haplo recipient who died of infection before engraftment. All CB cases died at 1, 8, 9 and 11,5 months post-transplant, respectively (infection n=1, relapse n=2, chronic GVHD n=1). As a consequence, we thereafter compared outcomes only between the three other donor groups.There were no significant differences between sibling, MUD or haplo recipient groups in terms of gender, median age, type of disease, ELN 2010 classification for AML, status at transplant (complete remission vs active), disease risk index, donor/recipient CMV status or median graft quantity of CD34+ stem cells. The only differences were the partition of ABO compatibility, less frequent in the MUD group (42% vs sibling 69% vs haplo 67%, p=0,02) and a history of previous allograft (haplo n=7, sibling n=0, MUD n=6, p=0,005).Neutrophils (>0,5 Giga/L) and platelets (50 Giga/L) recoveries were significantly delayed in the haplo-group (19 days, vs sibling 15 vs MUD 15, p=0.0003; and 31 days vs 11 vs 12, p<0.0001).Acute grade 2-4 or 3-4 graft versus host disease (GVHD) incidences were similar between the three groups at 50% and 22% for sibling, 34,5% and 14,5% for MUD and 48% and 11% for haplo (p=0,18 for grade 2-4 and p=0,45 for grade 3-4) as well as moderate+severe chronic GVHD incidences (sibling 14%, MUD 16%, haplo 15% p=0,94).Follow-ups were similar at 34.2 (6-74), 33.7 (4.5-106) and 21.4 (7-53) months respectively for sibling, MUD or haplo donors. This was associated with similar 2-year overall survivals (OS) at 64,7% (50-83), 73,9% (62-87) and 60,2% (43-83) respectively (p=0.4) and 2-year disease-free survivals (DFS) at 57,7% (43-76), 70,9% (59-84) and 53,6% (37-77) respectively (p=0.1). Two-year GVHD-relapse free survival (GRFS) was also similar at respectively 37,9% (24-57), 54,3% (41-70) and 38,9% (23-63) (p=0.2) as well as 2-year non-relapse mortality (NRM) at 14%, 11% and 18,5% (p=0,63).When considering only AML patients, again similar 2-year survivals were observed between the three groups. OS was 71.4% (54-93) for sibling (n=21), 75.1% (62-90) for MUD (n=40) and 66.6% (46-95) for haplo (n=15, p=0.65) and DFS respectively 66,6% (49-90), 70,8% (57-87) and 66,6% (46-95 p=0.47). The same was observed for GRFS at 38% (22-65), 56% (41-75) and 40% (21-74, p=0.14) and NRM at 14%, 7,5% and 7%, p=0.34).In multivariate analysis, donor type remained independent of outcomes in this series.Conclusion: These data confirm that since no difference was observed in terms of outcomes, haplodonors represent a valid alternative for patients receiving a clofarabine-based RIC PBSC allograft for myeloid malignancies who lack a matched sibling donor. DisclosuresGastinne:Millennium/Takeda: Honoraria. Moreau:Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Acute Phase Proteins for Monitoring Hematopoietic Recovery After Early Engrafting of CD34+ Peripheral-Blood-Stem-Cells for Autografting or Allografting in Patients with Malignant Diseases.

BACKGROUND Neutropenic fever (NF) is associated with delayed engraftment after peripheral blood stem cell transplantation (PBSCT). MATERIAL AND METHODS We followed the levels of acute-phase proteins (APPs) serially in 60 patients after peripheral blood stem-cell autograft (n=39) or peripheral blood stem-cell allograft (n=21) for hematologic malignancies and germinal tumors; we then examined the correlation of those levels with the presence of fever and with markers of engraftment. RESULTS Fever (present in 60% of patients) was associated with a highly statistically significant delay in reaching conventional engraftment targets (ANC >500/μL [0.5×10^9/L]; platelets >20,000/μL [20×10^9/L]; reticulocytes >20,000/μL [20×10^9/L]) (for all associations, p<0.001). Every 4th day for 24 days, we measured the APPs levels and the number of neutrophils (ANC), platelets (PL), and reticulocytes (RET) to reach the reference values of >0.5 G/L or >1.0 G/L for ANC, >20 G/L or >50 G/L for PL, and >20 G/L for RET, respectively. The presence of NF resulted in longer time to engraft hematopoietic stem cells with ANC, PL, and PET counts statistically significant (range 0.001-0.004). The median day range for NF patients was 21.22-26.89 versus 13.88-19.13 for no NF patients. CONCLUSIONS Our results provide additional information for monitoring hematopoietic engraftment in patients following PBSCT; the presence of NF can be tracked by serial measurements in serum of three investigated APPs throughout an early phase of hematopoietic recovery.

Peripheral blood stem cell versus bone marrow transplantation: A perspective from the Acute Leukemia Working Party of the European Society forBloodand Marrow Transplantation.

Over the past decade, transplantation of peripheral blood hematopoietic cells has increased and is now the predominant graft source for related or unrelated adult allogeneic hematopoietic stem cell transplantation. At the same time, increasing numbers of patients are receiving reduced-intensity conditioning (RIC) prior to hematopoietic stem cell infusion. In prior work using smaller patient numbers and limited data, RIC peripheral blood stem cell (PBSC) transplantation was shown to be noninferior to RIC bone marrow (BM) transplantation for acute leukemia. A recent, large registry analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation showed that peripheral blood grafts result in superior outcomes compared with BM after RIC regimens for acute leukemia. The T-cell-replete PBSC allografts are associated with significant graft-versus-leukemia (GVL) benefits that are important drivers of improved leukemia-free survival and overall survival. However, an increased risk of chronic graft-versus-host disease (cGVHD) after peripheral blood grafts is concerning and long-term follow-up comparing peripheral versus BM grafts after RIC regimens is needed. Further assessment of the long-standing risks should be undertaken in an effort to better understand whether the risk of cGVHD among peripheral blood graft recipients translates into continued GVL effects and long-term remissions and cures or if it results in late morbidity and mortality.

Granulocyte Colony-Stimulating Factor–Mobilized Allografts Contain Activated Immune Cell Subsets Associated with Risk of Acute and Chronic Graft-versus-Host Disease

We defined associations among immune cell subsets in granulocyte colony-stimulating factor (G-CSF)–mobilized allografts and clinical outcomes after allogeneic hematopoietic cell transplantation (alloHCT). Fresh peripheral blood stem cell (PBSC) aliquots from 238 G-CSF–mobilized allografts were extensively characterized by immunophenotype. Subset-specific transplanted cells were correlated with acute graft-versus-host disease (aGVHD), chronic GVHD (cGVHD), malignant disease relapse, nonrelapse mortality, and overall survival. Of 238 assessable alloHCT recipients, 185 patients (78%) received reduced-intensity conditioning and 152 (64%) antithymocyte globulin-based serotherapy. Incidences of aGVHD and cGVHD were 58% and 48%, respectively. Median follow-up was 21 months (range, 1.4 to 41.1). In multivariable analyses adjusted for relevant clinical factors, allograft activated natural killer (NK) cells (CD56+CD16+CD69+CD158b+) were associated with a significantly lower risk of aGVHD (P = .0016; HR, .51; 95% confidence interval, .33 to .78), whereas late-activated HLA-DR+ CD3+ cells were associated with significantly higher aGVHD (P < .0005; HR, 2.31; 95% confidence interval, 1.55 to 3.43). In a subgroup of patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), receipt of an allograft from an older donor (≥40 years) was associated with a higher incidence of relapse (P = .0042; HR, 2.99); allograft content of early activated CD3+ cells (CD3+CD69+; P = .0024; HR, .4) and NKT cells (CD3+CD56+; P = .0006; HR, .54) were associated with a lower incidence of relapse. Presence of HLA-Bw4-80Ile+ genotype was associated with lower relapse incidence. In conclusion, activated NK cells within PBSC allografts associate with lower aGVHD risk, whereas HLA-DR+ T cells associate with higher aGVHD and cGVHD risk. NKT cells and early activated T cells are associated with lower relapse risk in AML and MDS patients. These findings may have implications in therapeutic targeting of select populations in the allograft to minimize incidence of GVHD.

High-Dose Sirolimus and Immune-Selective Pentostatin plus Cyclophosphamide Conditioning Yields Stable Mixed Chimerism and Insufficient Graft-versus-Tumor Responses.

We hypothesized that lymphoid-selective host conditioning and subsequent adoptive transfer of sirolimus-resistant allogeneic T cells (T-Rapa), when combined with high-dose sirolimus drug therapy in vivo, would safely achieve antitumor effects while avoiding GVHD. Patients (n = 10) with metastatic renal cell carcinoma (RCC) were accrued because this disease is relatively refractory to high-dose conditioning yet may respond to high-dose sirolimus. A 21-day outpatient regimen of weekly pentostatin (P; 4 mg/m(2)/dose) combined with daily, dose-adjusted cyclophosphamide (C; ≤200 mg/d) was designed to deplete and suppress host T cells. After PC conditioning, patients received matched sibling, T-cell-replete peripheral blood stem cell allografts, and high-dose sirolimus (serum trough target, 20-30 ng/mL). To augment graft-versus-tumor (GVT) effects, multiple T-Rapa donor lymphocyte infusions (DLI) were administered (days 0, 14, and 45 posttransplant), and sirolimus was discontinued early (day 60 posttransplant). PC conditioning depleted host T cells without neutropenia or infection and facilitated donor engraftment (10 of 10 cases). High-dose sirolimus therapy inhibited multiple T-Rapa DLI, as evidenced by stable mixed donor/host chimerism. No antitumor responses were detected by RECIST criteria and no significant classical acute GVHD was observed. Immune-selective PC conditioning represents a new approach to safely achieve alloengraftment without neutropenia. However, allogeneic T cells generated ex vivo in sirolimus are not resistant to the tolerance-inducing effects of in vivo sirolimus drug therapy, thereby cautioning against use of this intervention in patients with refractory cancer.

Allograft T-Cell, T-Regs, NK-Cell and B-Cell Content Influence Distinct Clinical Outcomes Following G-CSF Mobilized Hematopoietic Stem Cell Transplantation

Background: Donor grafts with more naive T cells and plasmacytoid dendritic cells were associated with improved overall survival after unrelated donor bone marrow, but not peripheral blood stem cell (PBSC) transplants (Waller, E JCO 2014). Here we present results on influence of innate and adaptive immune subsets in G-CSF mobilized allografts on incidence of acute GVHD (aGVHD) and chronic GVHD (cGVHD) in 238 patients (pts).Methods: We analyzed the absolute numbers and percentages of T, NK, NKT and B cells along with an extensive immunophenotypic characterization of their activation status in consecutive PBSC allografts obtained from sibling and unrelated donors between 2010 - 2014 and studied their association with the incidence of aGVHD and cGVHD. Wilcoxon rank sum tests were used to screen differential marker expression between those who did vs. did not develop aGVHD and similarly for cGVHD. Significant markers were evaluated in the multivariable (m.v.) setting along with known prognostic factors, including: recipient age, related vs. unrelated donor, female donor vs. not, Anti-thymocyte globulin (ATG) use (yes vs. no), and Reduced-intensity conditioning (RIC) vs. not. Cutpoints for markers were generated using recursive partitioning algorithms and evaluated in m.v. models.Results: Of the 238 alloSCT pts evaluated, most (71%) had unrelated donors, 64% received ATG, where most pts with unrelated donors received ATG (83%), and 78% received RIC. The incidence of aGVHD and cGVHD was 58% and 38% respectively. A total of 107 pts had grade II-IV aGVHD reported (71 II, 28 III, 8 IV), and 92 of 192 evaluable for cGVHD (at least 100 days of f/u) had reported cGVHD. Median follow-up in living pts was 21 months (range: 1.4 to 41.1 months). Table 1 shows dichotomized markers most influential on aGVHD. Higher absolute numbers of T cells, activated T cells, CD8+ cells, CD8+ cells expressing IL-7 receptor and CD27 were associated with higher incidence of aGVHD. Higher number of Stage 4 NK cells expressing stem cell factor receptor, and T-regs were associated with a lower incidence of aGVHD. Similar analyses were done for cGVHD (Table 2). Higher absolute numbers of activated T lymphocytes, activated B lymphocytes, KIR expressing CD3+ cells, CD8+ lymphocytes and activated NK cells were associated with higher incidence of cGVHD. When the percent of these makers in relation to total lymphocytes was evaluated regarding association with aGVHD, higher percent of T-regs (OR: 0.204, p=0.0018), effector memory T cells (OR: 0.45, p=0.024) and NKG2D positive NK cells (OR: 0.38, p=0.0008) conferred protection from aGVHD . Similar analysis for cGVHD showed higher percent of naïve CD4+ T cells conferred protection from cGVHD (OR: 0.44; p=0.0062) while higher percent of CD8+ cells (OR: 3.93; p=0.0032) and activated NK cells (OR: 2.08; p=0.024) was associated with cGVHD.Conclusions: These results show a protective role of donor T-regs, CD4+ T cells and Stage 4 NK cells from aGVHD. Additionally, higher content of activated T cells, CD8+ cells and B lymphocytes are associated with higher incidence of cGVHD. Higher content of activated NK cells seems to protect from aGVHD, but not from cGVHD. Updated results including multivariable analyses will be presented. These findings showing the influence of specific subsets in the allograft on aGVHD and cGVHD may provide opportunities for therapeutic interventions for graft engineering or pharmacologic methods for targeting specific immune subsets to decrease incidence of aGVHD and cGVHD.Table 1Univariate model results for aGVHD with dichotomized markers using cutpoints:MarkerAbsoluteORp-valueCD3+/CD5616- (T lymphocytes)3.070.0013CD3+/HLA DR+ (Activated T lymphocytes)3.260.012CD8+/CD45RA- (CD 8+ lymphocytes)2.560.012CD8+/CD27+ (Effector Memory CD8 cells)3.250.0082CD8+/CD127+ ( CD8 cells expressing IL-7 receptor)2.920.073 CD4+/CD25+/CD127-(T regs)0.430.057CD3-/CD16-/CD56+/CD117+ (Stage 4 NK cells expressing Stem cell factor receptor)0.120.0007Table 2Univariate model results for cGVHD with dichotomized markers using cutpoints:MarkerAbsoluteORp-valueCD3+/HLA DR+ (Activated T lymphocytes)4.41<0.0001CD19+/CD80+ (Activated B lymphocytes)2.440.0036CD3+/CD69+/CD158b+ (Activated T lymphocytes expressing KIR)2.810.017CD3-/CD5616+/CD69+ (Activated NK cells)2.740.0024CD3-/CD5616+/CD314+ (NKG2D positive NK cells)2.330.008 DisclosuresBlum:Celgene: Consultancy.

Secondary malignancies after allogeneic hematopoietic stem cell transplantation using reduced-intensity conditioning and outpatient conduction

BackgroundPatients given allogeneic hematopoietic stem cell transplants (HSCT) may develop secondary malignant neoplasms (SMN). Several variables have been identified but there are no data about the incidence of this complication in individuals given HSCT using reduced-intensity conditioning (RIC) methods.ObjectiveDefine the incidence of SMN in patients given HSCT using a RIC preparative regimen conducted on an outpatient basis.Materials and methodsPatients given HSCT in two institutions between October 1998 and 2012 were analyzed. To appraise the SMN appearance, those patients dead were also regarded as censored at that moment, as well as those lost to follow up and those alive at the closing of the study. 95% Confidence intervals (CI) for the survival or failure estimate were calculated with the Greenwood's method.ResultsA total of 416 allografted patients with a Karnofsky performance index of 100% were included in the study. All patients received peripheral blood stem cells allografts. The conditioning regimen was delivered as an outpatient procedure in all individuals. No patient was given radiotherapy nor antithymocyte globulin during the conditioning. Three hundred and sixty five patients (88%) were never admitted to the hospital, whereas 12% were admitted because of grade III–IV acute graft versus host disease (aGVHD), fever, or mucositis. Median survival time was 15.7 months. Survival at 6 months (95% CI): 66.4% (61.5–70.8%), at 12 months: 53.3% (48.1–58.1%), at 60 months: 30.6% (30.5–41.5%). Eight patients with a SMN were identified in the group of 416 allografted patients, SMN rates (95% CI) were: one year post graft: 1.9% (0.7–4.9%), 5 years: 3.8% (1.6–9.2%), 10 years: 6.8% (2.6–17.7%) and 13 years post-graft: 20.2% (5.5–59.2%), the cumulative probability of SMN being 6.8 at 10 years. Since the number of expected cases in the general population is 0.62, the ratio of observed to expected cases is 12.9 (P < 0.001). This figure means that the risk of developing a malignant neoplasm in allografted individuals using our method is 12.9 times higher than that in the general population. There were three non-Hodgkin's lymphomas, two M2 acute myelogenous leukemias, one hairy cell leukemia, one tongue epidermoid carcinoma, and one breast carcinoma.ConclusionsWe have found a low incidence of SMN in this group of Mexican patients allografted with the Mexican RIC method. Possible explanations for this difference are discussed, focusing on the RIC preparative regimen.

PBSCT is associated with poorer survival and increased chronic GvHD than BMT in Japanese paediatric patients with acute leukaemia and an HLA-matched sibling donor

Peripheral blood stem cells (PBSC) may be used as an alternative to bone marrow (BM) for allogeneic transplantation. Since peripheral blood stem cell bank from unrelated volunteer donor has been started in Japan, use of PBSC allografts may be increased. Therefore we surveyed the outcomes of Japanese leukemia children after PBSC and BM transplantation. This retrospective study compared the outcomes of 661 children (0-18 years) with acute lymphoblastic leukaemia (ALL) or acute myeloid leukaemia (AML) who received their first allogeneic peripheral blood stem cell transplantation (PBSCT; n = 90) or bone marrow transplantation (BMT; n = 571) from HLA-matched siblings between January 1996 and December 2007. Neutrophil recovery was faster after PBSCT than after BMT (ALL: P < 0.0001; AML: P = 0.0002), as was platelet recovery (ALL: P = 0.0008; AML: P = 0.0848). However, the cumulative incidence of chronic graft-versus-host disease (GvHD) was higher after PBSCT than after BMT (ALL: 26.0% vs. 9.9%, P = 0.0066; AML: 41.6% vs. 11.1%, P < 0.0001). The 5-year disease-free survival (DFS) was lower after PBSCT than after BMT for ALL (40.6% vs. 57.1%, P = 0.0257). The 5-year overall survival (OS) was lower after PBSCT than after BMT for ALL (42.4% vs. 63.7%, P = 0.0032) and AML (49.8% vs. 71.8%, P = 0.0163). Multivariate analysis revealed the use of PBSC was a significant risk factor for DFS and OS. PBSCT and BMT did not differ in relapse rate, acute GvHD for ALL and AML, or in DFS for AML. PBSC allografts in Japanese children engraft faster but are associated with poorer survival and increased chronic GvHD.

Influence of related donor age on outcomes after peripheral blood stem cell transplantation

The rising use of allogeneic transplantation in older recipients necessitates considering older related donors. The effect of related donor age for peripheral blood stem cell allografts (PBSC) on graft maintenance and outcomes, independent of CD34(+)cell dose, has not been well-characterized. HLA-related donors (98% siblings) underwent a uniform filgrastim-based mobilization regimen aiming to collect and infuse 5 × 10(6) CD34(+) cells/recipient kg. Donor and recipient age were modeled in multiple ways to account for the correlation, and outcomes reported by decade of donor age. The median donor and recipient ages were 52 years and 54 years, respectively. The mean CD34(+) cell dose infused was 5.6 × 10(6) CD34(+)/kg and 75% of patients received a narrow range between 4.4 and 6.6 × 10(6) CD34(+) cells/kg. Neither better PBSC mobilization nor higher CD34(+) content of allografts was significantly associated with engraftment or transplant outcomes. After adjusting for recipient age and other prognostic factors, older donor age by decade conferred a lower risk of non-relapse mortality (NRM) [hazard ratio (HR) = 0.64, 95% confidence interval (CI) 0.45-0.91, P = 0.013] and borderline improvement in overall survival (OS) (HR = 0.76, 95% CI 0.58-0.99, P = 0.045) without altering progression-free survival (PFS) (HR = 0.85, 95% CI 0.66-1.07, P = 0.18). Older donor age does not worsen outcome after matched related donor PBSC transplantation in patients receiving a narrow range CD34(+) cells. The relatively small sample size mandates that the finding of similar to improved outcomes for older related donor age must be confirmed in larger studies.

Older Sibling Donors Remain an Excellent Option: Older Donor Age and Lower CD34 Infused Do Not Adversely Impact Outcomes for Matched Sibling Peripheral Blood Stem Cell (PBSC) Transplantation

Older Sibling Donors Remain an Excellent Option: Older Donor Age and Lower CD34 Infused Do Not Adversely Impact Outcomes for Matched Sibling Peripheral Blood Stem Cell (PBSC) Transplantation

Targeted Lymphocyte Depletion: A Personalized Approach to Achieve Rapid Complete Donor Chimerism and Enhance Graft-Versus-Tumor Effects Following Reduced Intensity Allogeneic Stem Cell Transplantation for High-Risk Hematologic Malignancies.

Abstract 656Reduced intensity allogeneic stem cell transplantation (RIST) is associated with decreased transplant-related mortality (TRM), broadening the pool of patients who could potentially benefit from allogeneic cellular therapy. However, RIST historically results in mixed chimerism, has higher relapse rates and has limited efficacy in chemotherapy-refractory hematologic malignancies. In order to enhance graft-versus-tumor effects, we have developed a strategy of targeted lymphocyte depletion (TLD), which attempts to compensate for variability in host immune status and facilitate early full-donor chimerism. TLD involves the use of repetitive cycles of disease-specific conventional-dose chemotherapy to provide both tumor cytoreduction and lymphocyte depletion prior to RIST. The number of TLD cycles (0-3 maximum) is based on reaching a target CD4+ count <100 cells/μl; patients with higher pre-TLD CD4+ counts require more cycles. We employed the TLD approach in 111 patients (40 females/71 males) with median age of 50 years (range 19-71) with advanced hematologic malignancies (45% chemotherapy refractory; 60% high risk of relapse by Seattle Criteria (Kahl C et al Blood 2007). Median CD3+, CD4+, and CD8+counts at enrollment were 673 cells/μl (5-3953), 286 cells/μl (5-3888), and 277 cells/μl (1-1763) respectively. Following TLD chemotherapy, median CD3+,CD4+, and CD8+counts were 164 cells/μl (1-1496), 82 cells/μl (0-508) and 52 cells/μl (1-1195) respectively. All patients then received an identical reduced intensity conditioning regimen (fludarabine/cyclophosphamide) followed by T-cell replete HLA-matched sibling peripheral blood stem cell allografts and cyclosporine-based graft versus host disease (GVHD) prophylaxis. 109 evaluable patients demonstrated 100% engraftment; there were no late graft failures. At Day+14, median lymphocyte chimerism was 99% and median myeloid and whole blood chimerism were 100%. Patients were able to maintain chimerism as evidenced by 100% median chimerism in the myeloid, lymphoid and whole blood compartments at Day+28 and 100% median whole blood chimerism at Day +100. The cumulative incidence of grades II-IV and grades III-IV acute GVHD was 46% and 23% respectively. The cumulative incidence of chronic GVHD was 59% (15% limited, 44% extensive). One and 5-year TRM was 15% and 21% respectively. At Day +28, 38 patients had achieved a complete remission (CR) and 44 achieved partial remission (PR). Twelve additional CRs were observed at Day +100 without withdrawal of immunosuppression or donor lymphocyte infusion. Event free survival (EFS) and overall survival (OS) at one year were 49% and 66% respectively. EFS and OS at five years were 31% and 47% respectively. Of those patients alive at one year (n=73), 66% were in CR. Of those patients in CR, 58% had high risk of relapse by Seattle Criteria and 92% had not been in CR at the time of transplant (31% had stable or progressive disease). At median follow-up of 5.4 years, 65% of this subset of patients were alive and still in CR. By univariate analysis, the age of the recipient and presence of an ABO minor mismatch were significantly associated with OS (p<0.05); number of prior therapies, disease status at the time of transplant, and relapse risk by Seattle criteria were significantly associated with EFS and OS (p<0.05). The strategy of TLD provides a personalized approach to pre-transplant host immune status resulting in early full donor chimerism. Using TLD prior to RIST resulted in a high percentage of sustained complete remissions in patients with advanced hematologic malignancies. Disclosures:No relevant conflicts of interest to declare.

Targeted Lymphocyte Depletion Prior to Reduced Intensity Allogeneic Stem Cell Transplantation: A Personalized Approach to Facilitate Engraftment.

Abstract 865Reduced intensity allogeneic stem cell transplantation (RIST) is associated with decreased transplant-related mortality (TRM), broadening the pool of patients who could potentially benefit from allogeneic cellular therapy. However, RIST is typically associated with higher rates of mixed chimerism and graft rejection compared to myeloablative conditioning. Data from clinical studies have shown that the number of therapies prior to transplant, which inversely correlates with host T-cell immunity, is a statistically important predictor of graft rejection and mixed chimerism. In order to compensate for variability in host immune status and facilitate early full-donor chimerism (>95%), we developed a strategy of targeted lymphocyte depletion (TLD) which uses repetitive cycles of disease-specific conventional-dose chemotherapy to provide both tumor cytoreduction and lymphocyte depletion prior to RIST. The number of TLD cycles (0-3 maximum) was based on reaching a target CD4+ count <100 cells/μl; patients with higher pre-TLD CD4+ count required more cycles. We employed the TLD approach in 111 patients (mean age = 49 years, (19-71) with advanced hematologic malignancies. Median CD3+, CD4+, and CD8+counts at enrollment were: 673 cells/μl (5-3953), 286 cells/μl (5-3888), and 277 cells/μl (1-1763) respectively. Following TLD chemotherapy, median CD3+, CD4+, and CD8+ counts were: 164 cells/μl (1-1496), 82 cells/μl (0-508), and 52 cells/μl (1-1195) respectively. All patients then received an identical reduced intensity conditioning regimen (fludarabine/cyclophosphamide) followed by HLA-matched sibling peripheral blood stem cell allografts. All patients received cyclosporine as graft versus host disease (GVHD) prophylaxis (1) alone, (2) with methotrexate, (3) with TH2 cells, (4) with sirolimus or (5) with TH2 cells and sirolimus. Immediately prior to stem cell infusion (Day 0) median host CD3+, CD4+, and CD8+ counts were 4 cells/μl (0-69), 3 cells/μl (0-65) , and 1 cell/μl (0-44) respectively. 109 evaluable patients demonstrated 100% engraftment; there were no graft failures. At Day +14, median lymphocyte chimerism was 99% and median myeloid and whole blood chimerism were 100%. Patients were able to maintain chimerism as evidenced by median 100% chimerism in the myeloid, lymphoid and whole blood compartments at Day +28 and median 100% whole blood chimerism at Day +100. Full donor lymphocyte chimerism at Day +14 was associated with lower post-TLD CD4+ counts (p=0.012) and Day 0 CD3+, CD4+, and CD8+ counts (p<0.0005). Full donor myeloid chimerism at Day+14 and Day+28 was associated with lower Day 0 CD3+, CD4+, CD8+ counts (p<0.05). Full donor whole blood chimerism at Day +14, Day +28 and Day+100 was associated with lower Day 0 CD3+, CD4+, and CD8+ counts (p<0.05). The CD3+ and CD34+ dose contained in the allograft was associated with Day +14 lymphoid chimerism (p=0.04) and with Day +28 myeloid chimerism (p=0.03) respectively. CMV status was associated with both lymphoid and whole blood chimerism at Day +14 (p<0.05). Only lymphoid chimerism at Day+28 was associated with GVHD prophylaxis regimen (p<0.05). Patients with acute GVHD II-IV had significantly lower CD4+ counts post-TLD (p=0.01). Patients with acute GVHD III-IV had significantly lower CD4+ and CD3+ counts at Day 0 (p<0.05). These data demonstrate the tremendous variability in pre-transplant host T-cell numbers. By using the strategy of TLD, we were able to compensate for this variability while achieving levels of T-cell depletion comparable to myeloablative conditioning. We conclude that TLD provides a personalized approach to pre-transplant host immune status resulting in absence of graft rejection and rapid and full donor chimerism following RIST. Disclosures:No relevant conflicts of interest to declare.

Hematopoietic stem cell mobilization with G-CSF induces innate inflammation yet suppresses adaptive immune gene expression as revealed by microarray analysis

Granulocyte colony-stimulating factor (G-CSF) is used to boost granulocyte counts in immunocompromised patients, but its effects on the immune system may be counterproductive. We tested the hypothesis that G-CSF-mobilized peripheral blood stem cell (PBSC) products are immunologically downregulated based on gene microarray analysis. Ten peripheral blood samples from normal donors for allogeneic PBSC transplantation were obtained before and after administration of G-CSF and tested on Affymetrix Human U133 Plus 2.0 GeneChip microarrays and by flow cytometry. Significant changes in gene expression after G-CSF were reported by controlling the false discovery rate at 5%. The quantitative real-time polymerase chain reaction method was used to validate expression of representative genes. All immune cells measured, including neutrophils, monocytes, lymphocytes, and dendritic cells, were significantly increased after G-CSF. In terms of gene expression, inflammatory and neutrophil activation pathways were upregulated after G-CSF. However, adaptive immune-related gene expression, such as antigen presentation, co-stimulation, T-cell activation and cytolytic effector responses, were downregulated. Despite significant increases in lymphocytes and antigen-presenting cells, G-CSF-mobilized PBSC allografts exhibit a suppressive adaptive immune-related gene-expression profile. However, innate and inflammatory responses are elevated. Our data provides an explanation for the potentially immunosuppressive effects observed after G-CSF administration.

Comparative analysis of naïve and memory CD4 + and CD8 + T-cell subsets in bone marrow and G-CSF–mobilized peripheral blood stem cell allografts: impact of donor characteristics

Donor T cells expressing lymph node homing receptors are the foremost initiators of acute graft-vs-host disease (aGVHD), and a high proportion of CD4(+)CCR7(+) T cells in human leukocyte antigen-matched allografts has been shown to confer a high risk of aGVHD without interfering in other outcomes. Naïve, central memory (T(CM)), effector memory (T(EM)), and terminally differentiated effector memory (T(TD)) subsets, further subdivided by CD28 expression, were compared in 52 bone marrow and 37 granulocyte colony-stimulating factor-mobilized peripheral blood harvests. CCR7(+) cells (naïve and T(CM)) predominated in the CD4(+) population, whereas CD8(+) memory cells were chiefly CCR7(neg) in the grafts. Donor age, antecedent of chronic infections, and graft type were independent factors influencing graft composition. CD8(+) naïve cells negatively correlated and CD8(+) T(EM) positively correlated with age. Cytomegalovirus seropositivity was associated with more CD8(+) T(TD) and diminished CD28 expression. Toxoplasmosis seropositivity was associated with more CD4(+) T(CM) (p = 0.021). Marrow grafts comprised more CD28(+) cells within CD8(+) T(TD), but the percentage of CD4(+)CCR7(+) cells did not differ significantly between the two graft sources. Each of the four CD4(+) subsets and the percentage of CD4(+)CCR7(+) cells (p < 0.001) were correlated between graft and venous blood analyzed in 42 donors before harvest procedures. This study provides reference values for CD4(+) and CD8(+) naïve and memory subsets within allografts applicable to the healthy donor population and indicates that beforehand analysis of a whole-blood sample can help evaluating the risk of aGVHD conferred by each donor and, when possible, choosing the one conferring the lowest risk.

A high proportion of donor CD4+ T cells expressing the lymph node-homing chemokine receptor CCR7 increases incidence and severity of acute graft-versus-host disease in patients undergoing allogeneic stem cell transplantation for hematological malignancy

CC-chemokine receptor 7 (CCR7), a chemokine receptor required for transmigration into lymphoid organs, is only expressed by naive and central memory T cells. T cells with a capacity of homing into lymphoid organs can initiate acute graft-versus-host disease (GVHD) in mice and respond vigorously in vitro to alloantigens in humans, but their impact on clinical outcomes is unknown. We evaluated prospectively the distribution of naive, central memory and CCR7neg memory T-cell subsets in 39 bone marrow and 23 granulocyte colony-stimulating factor-mobilized peripheral blood stem cell allografts and investigated their impact on patient outcomes. Ranges of the relative proportions of CCR7+ cells within CD4+ and CD8+ T-cell populations were broad, but did not differ between the two sources of allografts. By multivariate analysis, high percentage of donor-derived CD4+CCR7+ T cells (>73.5%) significantly correlated with incidence, earliness of onset and severity of acute GVHD, conferring the highest adjusted hazard ratio (HR=3.9; 95% confidence interval 1.4-10.8; P=0.008) without interfering in other clinical events, especially chronic GVHD and relapse. Determination of the percentage of CD4+CCR7+ T cells in the graft provides a predictive indicator of acute GVHD. Partial depletion of this subset may reduce the risk of acute GVHD while preserving immunotherapeutic effects.