Reduced-intensity Conditioning Stem Cell Transplantation Research Articles

Analysis of Survival Gains in Myelodysplastic Syndromes after a Decade of the Modern Treatment Paradigm

Introduction:The treatment of myelodysplastic syndromes (MDS) changed after the approval of lenalidomide in 2005, and 2 hypomethylating agents (HMA): azacitidine in 2004 and decitabine in 2006. Erythropoietin-stimulating agents (ESA) and reduced intensity conditioning stem cell transplantation (RIC-SCT) also became more widely utilized around that period. Analyses evaluating potential overall survival (OS) improvements in MDS since 2007 across different cancer registries have shown conflicting results. ‘Real-world’ survival trends are important to measure the true impact of these treatments outside clinical trials, especially as MDS treatment innovations may not reach all patients. We assessed the temporal change in OS and cancer-specific survival (CSS) of MDS patients in the US over the decade before (2001 - 2006) and after modern treatment options were established (2007 - 2016).Methods:Adult subjects diagnosed with MDS between 2001 and 2016 were identified in Surveillance, Epidemiology, and End Results (SEER), and categorized in 2 groups based on year of diagnosis: 2001 - 2006 (cohort 1) and 2007 - 2016 (cohort 2). MDS histologic risk was classified into low, intermediate, and high, using International Classification of Diseases for Oncology 3 rd Edition (ICD-O-3) codes. Cause of death (COD) reported to State registries (SEER recode) was used to determine CSS, defined as death from MDS or acute myeloid leukemia. Only cases with histologic confirmation of ICD-O-3 codes and complete follow up records were analyzed. Kaplan-Meier estimation was used to summarize unadjusted OS distribution. To assess the association of cohort 2 with OS and CSS gains, follow up duration was restricted to a maximum of 5 years in both cohorts and survival analysis was performed using multivariable Cox-proportional hazards regression model adjusting for age, sex, race, ethnicity, MDS risk, and geographic location.Results:We included a total of 42,217 patients with MDS, 13,633 (30.8%) in Cohort 1 (2001 - 2006) and 30,584 (69.2%) in Cohort 2 (modern treatment era). Subjects in cohort 2 were slightly older (mean age 73.8 vs 73.2 years, p<0.001) and included more males (58.6% vs 56.3%, p<0.001). Cohort 1 included more subjects with low MDS histologic risk (27.8% vs 17.2%) and fewer subjects with high MDS risk (18.4% vs 20.5%) (Table 1). Median OS for low, intermediate, and high risk MDS were 44 months (95%CI, 41.5 - 46.5), 27 months (95%CI, 25.7 - 28.3) and 10 months (95%CI, 9.3 - 10.7) in cohort 1, and 48 months (95%CI 45.9 - 50.1), 26 months (95%CI 25.3 - 26.7) and 11 months (95%CI 10.6 - 11.4) in cohort 2, but these differences were not significant. In the multivariable model adjusted for age, sex, race, ethnicity, MDS risk, and geographic location, cohort 2 was associated with a significantly lower hazard of overall death compared to cohort 1, HR for OS of 0.97 (95%CI, 0.95 - 0.99, p<0.001). Similarly, the modern era of treatment was associated with lower cancer-specific death compared to cohort 1, HR for CCS 0.93 (95%CI, 0.89 - 0.93, p=0.038). MDS histologic risk was the strongest factor associated with higher risk of overall and cancer-specific death. Other factors significantly associated with worse OS and CSS were advancing age, male sex, Hispanic ethnicity and unmarried status (Table 2). When analysis was restricted to patients with high risk MDS, cohort 2 was associated with a lower hazard of cancer-specific death, HR for CSS 0.90 (95%CI, 0.84 - 0.94, p=0.006), but no significant difference in overall death, HR for OS 0.96 (95%CI, 0.91 - 1.02, p=0.17).Discussion:In a SEER analysis, we found that the modern paradigm of MDS treatment, including access to lenalidomide, HMA, ESA and RIC-SCT, is associated with only modest survival gains at the population level. Across all MDS risk groups, improvements in cancer-specific death were larger than those seen for overall death and, in high risk MDS, a significant gain in CSS did not translate into longer OS. These data suggest there is a need for targeting non-cancer excess mortality in patients with MDS, who usually present with a high comorbidity burden. Strategies to optimize medical conditions coexisting with MDS and better supportive care may help consolidate the gains associated with currently available MDS-directed therapies. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Role of Allogeneic Reduced Intensity Conditioning Stem Cell Transplantation (RIC-SCT) in Older Patients with Acute Myeloid Leukemia (AML): Analysis of the ALFA-1200 Study

Background - According to recommendations, AML patients with intermediate- or adverse-risk genetics are candidates for allogeneic SCT in first complete remission (CR1). In practice, only a minority of them undergoes SCT because of older age, comorbidities, poor tolerance of prior therapy, inability to achieve CR, or early relapse. The benefit associated with RIC-SCT is particularly difficult to assess in older patients, due to lower SCT numbers and strong selection biases.Patients & Methods - Between 2012 and 2016, 509 patients aged ≥60 years (median, 68 years [60-85]) were enrolled in the prospective older AML ALFA-1200 trial. Eighty-eight patients (17%) had secondary or therapy-related AML. ECOG performance status was 0/1/2/3/NA in 219/219/57/9/5 patients and comorbidity index (HCT-CI) was 0/1/2/3/4+/NA in 226/92/66/61/54/10 patients, respectively. Risk subgroup distribution was 76 favorable (15%), 347 intermediate (68%), and 86 adverse (17%), according to the ELN-2010 classification retaining double mutations only as favorable CEBPA mutations. Chemotherapy consisted of cytarabine (200 mg/m2/d CIV on day 1-7) and idarubicin (12 mg/m2/d on day 1-3) followed by 2 courses with intermediate-dose cytarabine at 1500 mg/m2/12h on days 1/3/5, reduced to 1000 mg/m2/dose in patients aged ≥70 years. Patients with intermediate- or adverse-risk AML and/or those who needed two courses to reach CR were eligible for allogeneic SCT in CR1 if a suitable donor (HLA-identical [id] sibling or 9-10/10 matched unrelated donor) and no acquired contra-indication.Overall Results - During first induction, 43 patients died before response evaluation, while 335 patients reached CR. Among the 131 patients with resistant AML, 71 received a second intensive course and 34 achieved CR (overall CR rate, 72.5%). The 60- and 100-day mortality rates were 9.4 and 13.0%, respectively. With a median follow-up of 26 months, 201/369 CR patients relapsed and 164 died, including 30 deaths in CR1. Median overall survival (OS) was 20.7 months (95% CI, 17.5-24.8) and OS was 46.8% (95% CI, 41.9-51.4) at 2 years. Median OS was 49.7, 22.5 and 9.4 months in the favorable, intermediate and adverse ELN-risk subgroup, respectively.Role of SCT - Among the 305 CR patients eligible for SCT, 93 proceeded to SCT in CR1. In addition, 22 patients with primary refractory AML and 25 patients relapsing prior to SCT eventually received SCT. Patients transplanted in CR1 were younger (median age, 64 [60-73] vs 70 [60-81] years; p<0.001) and had lower comorbidity index (HCT-CI≥3, 14 vs 26%; p=0.025) than the remaining eligible patients. We thus analyzed the role of SCT in CR1 in the 214 eligible patients aged 70 years old or less (ELN-risk: 2 favorable, 176 intermediate, 38 adverse). Ninety of them were actually transplanted in CR1 (ELN risk: 75 intermediate, 15 adverse; median time from CR to SCT, 113 days; stem cell source: 28 geno-id, 50 pheno-id, 8 haplo-id, 4 cord blood; conditioning regimen: 12 NMA, 66 RIC, 12 sequential-RIC). These 90 transplanted patients were still younger than the 124 non-transplanted patients (p=0.005) but their ELN-risk and HCT-CI distribution were similar. Among them, 22 patients relapsed and 29 died, including 18 deaths in CR1. At 2 years post-SCT, transplant related mortality (TRM) was 20.4% (95% CI, 13.2-30.9), cumulative incidence of relapse was 22.7% (95% CI, 15.0-33.4), and OS was 65.1% (95% CI, 52.9-75.0). Age, secondary AML, ELN-risk, type of stem cell source, or conditioning regimen did not significantly influence post-transplant survival. In a time-dependent SCT analysis, OS was not significantly prolonged in the SCT cohort (HR, 0.77 [95% CI, 0.49-1.21]; p=0.26). As illustrated on Figure 1, an OS benefit associated with SCT was only observed in the adverse ELN-risk subset (HR, 0.20 [95% CI, 0.07-0.63]: p=0.006), while not in the intermediate ELN-risk subset (HR, 1.08 [95% CI, 0.65-1.80]; p=0.76), with a significant interaction (p=0.005). Finally, SCT did not significantly prolonged OS in the 47 out of 319 patients with refractory/relapsed AML who eventually received SCT (HR, 0.69 [95% CI, 0.39-1.22]: p=0.21).Conclusion - In older AML patients, due to persistent high TRM and relapse incidence, RIC-SCT significantly prolongs survival in the adverse ELN-risk AML subset only. Even if a longer follow-up is needed, patients with intermediate ELN-risk AML do no seem to benefit from SCT in CR1 as compared to standard chemotherapy. [Display omitted] DisclosuresDe Botton:Servier: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Agios: Honoraria, Research Funding. Socié:Alexion Pharmaceuticals, Inc.: Consultancy.

Abatacept is effective as GVHD prophylaxis in unrelated donor stem cell transplantation for children with severe sickle cell disease

AbstractWe report results of a phase 1 multicenter stem cell transplantation (SCT) trial from HLA-matched (n = 7) or one-antigen–mismatched (n = 7) unrelated donors (URD) using bone marrow or cord blood as stem cell source, following reduced-intensity conditioning (RIC) in severe sickle cell disease (SCD). Conditioning included distal alemtuzumab, fludarabine, and melphalan (matched donors), with thiotepa (mismatched donors). Abatacept, a selective inhibitor of T cell costimulation, was added to tacrolimus and methotrexate as graft-versus-host disease (GVHD) prophylaxis to offset GVHD risks, and was administered for longer duration in bone marrow recipients than in cord blood recipients because of increased incidence of chronic GVHD with bone marrow. Median age at transplant was 13 years (range, 7-21 years). The incidence of grades II to IV and grades III to IV acute GVHD at day +100 was 28.6% and 7%, respectively. One-year incidence of chronic GVHD was 57% and mild/limited in all but 1 patient who received abatacept for a longer duration. Only 1 patient developed reversible posterior encephalopathy syndrome and recovered. With a median follow-up of 1.6 years (range, 1-5.5 years), the 2-year overall and disease-free survival was 100% and 92.9%, respectively. The encouraging results from the phase 1 portion of this RIC SCT trial, despite risk factors such as older age, URD, and HLA-mismatch, support further evaluation of URD SCT in clinical trial settings. The phase 2 portion of the trial is in progress. This trial was registered atwww.clinicaltrials.govas NCT03128996.

Distinct Evolutionary Patterns in Chronic Lymphocytic Leukemia (CLL) during Resistance to Graft-Versus-Leukemia (GvL)

Distinct Evolutionary Patterns in Chronic Lymphocytic Leukemia (CLL) during Resistance to Graft-Versus-Leukemia (GvL)

Abatacept Is Effective for Gvhd Prophylaxis after Unrelated Donor Stem Cell Transplantation (URD SCT) for Severe Sickle Cell Disease (SCD)

Background In 2016, results from the first URD SCT for SCD (the SCURT Trial) revealed a 2-year overall survival (OS) and event-free survival (EFS) of 79% (95% CI 59-90) and 69% (95% CI, 48-82) respectively following reduced intensity conditioning (RIC).1 Though the RIC approach provided successful engraftment in the majority, the transplant approach was not considered safe for widespread adoption due to high rates of graft-versus-host disease (GVHD) especially in children &amp;gt;13 years, a predominant cause of mortality. Strategies to minimize GVHD were essential if URD SCT was to be considered with curative intent in SCD. Aim/Method Multicenter trial (NCT03128996) with the primary objective of determining EFS in non-malignant disorders at one-year was amended as follows. The phase I SCD cohort included conditioning with hydroxyurea, proximal alemtuzumab, fludarabine, and melphalan in patients with 8/8 HLA-matched URD (-A, -B, - C and -DRB1).1 Thiotepa (8 mg/kg) was added in 7/8 HLA-mismatched SCT. GVHD prophylaxis included a calcineurin inhibitor and methotrexate as previously described. Abatacept (10 mg/kg) was administered on days -1, +5, +14, +28, +60, +100, +180, +270 and +365 based on efficacy described against acute GVHD with early dosing after SCT for malignant disorders.2,3 The latter 3 doses were omitted in cord transplant recipients. Result Thirteen children (7-21 years) underwent SCT (8/8 URD marrow- 7; 7/8 URD marrow or cord-6) primarily for stroke (N=6), ≥3 severe vaso-occlusive pain crises (N=4) or ≥2 acute chest syndrome episodes per year (N=3). The conditioning regimen was well tolerated. One patient had primary graft rejection after CMV infection (7%) and had autologous recovery. All other patients engrafted; neutrophils at median of 18 days (10-24), platelets at median of 28 days (16-39) and are surviving free of SCD with median follow-up of 12 months (range 4-59). Myeloid lineage donor chimerism was &amp;gt;95% and lymphoid was 39%- 100% at day+100. Two-year OS and EFS was 100% and 92.3% (95% CI, 6.57-35.7), respectively. The day+100 incidence of grade II-IV and III-IV acute GVHD incidence was 23% and 15% respectively. One-year incidence of chronic GVHD was 38%. However, only one patient (7%) developed extensive cGVHD. One patient (7%) developed posterior reversible encephalopathy syndrome and recovered. Viral replication in blood was detected in 7 of 13 patients (7 CMV, 1 EBV reactivation). No patient developed EBV PTLD or required EBV-related intervention. Conclusion In comparison to previous experience1 with RIC and URD SCT, our early observations are (1) a lower incidence of PRES (7 vs 34%) (2) low incidence of severe acute GVHD (15% vs 17% grade III -IV) despite mismatched donors, (3) low incidence of extensive chronic GVHD (7% vs 38%) and (4) no mortality despite patient age (10/13 were &amp;gt;13 years old). We attribute this gain to avoiding steroid use, and the benefit of including abatacept into the treatment regimen. The engraftment, safety, and immune reconstitution profile continue to be monitored in this ongoing trial now accruing in a Phase II cohort. As we and others work toward expanding donor options for SCD transplants, we submit that all alternate donor transplants for severe SCD are experimental and should be performed on clinical trials that track success and pitfalls. Reference: 1. Shenoy S et al. A trial of unrelated donor marrow transplantation for children with severe sickle cell disease. Blood. 2016 Nov 24; 128(21): 2561-2567. 2. Koura et al. In vivo T cell costimulation blockade with abataceptfor acute graft-versus-host disease prevention: a first-in-disease trial. Biol Blood Marrow Transplant. 2013 Nov; 19(11): 1638-49. 3. Watkins BK et al. T cell co-stimulation blockade with CTLA-4 Ig (Abatacept) for acute GVHD prevention in HLA-matched and mismatched unrelated donor transplantation: Results of a Phase 2 trial. Abstract 65. ASTCT Meetings, Houston 2019. Figure Disclosures Shah: Jazz pharmaceuticals: Speakers Bureau. OffLabel Disclosure: Abatacept, FDA approved for rheumatoid arthritis is a fusion protein that inhibits T-cell activation by binding to CD80/CD86 on antigen-presenting cells (APCs).It is used for acute graft-versus-host disease (aGVHD) prevention during unrelated-donor hematopoietic cell transplantation in this study

Clinical significance of low-dose total body irradiation in HLA-mismatched reduced-intensity stem cell transplantation

The significance of low-dose total body irradiation (TBI) in HLA-mismatched reduced-intensity conditioning stem cell transplantation (RICT) remains unknown. We, retrospectively, evaluated the impact of low-dose TBI in patients with hematological malignancies who received first RICT from ≥1 antigen-mismatched donors between 2004 and 2014. Of the 575 patients, 361 patients received low-dose TBI (2 or 4 Gy). There were no significant differences in neutrophil engraftment or platelet recovery between TBI and non-TBI groups. The benefit of low-dose TBI on neutrophil engraftment was not observed in any subgroups. Low-dose TBI was not associated with decreased secondary graft failure. Suppressed mixed chimerism and autologous hematopoiesis by low-dose TBI was observed. There were no significant differences in cumulative incidences of acute GVHD or nonrelapse mortality rates in either group; however, low-dose TBI improved overall survival (OS), especially in patients with high-risk disease, multi-HLA mismatch, and fludarabine/busulfan conditioning. Multivariate analysis demonstrated that low-dose TBI was an independent prognostic factor for OS. Compared with the non-TBI group, 4 Gy TBI, but not 2 Gy TBI, was associated with increased acute GVHD and reduced relapse. These findings suggest that low-dose TBI may be beneficial for patients at high risk for relapse in HLA-mismatched RICT.

A Time-to-Event Model for Acute Kidney Injury after Reduced-Intensity Conditioning Stem Cell Transplantation Using a Tacrolimus- and Sirolimus-based Graft-versus-Host Disease Prophylaxis

There is a paucity of data evaluating acute kidney injury (AKI) incidence and its relationship with the tacrolimus–sirolimus (Tac-Sir) concentrations in the setting of reduced-intensity conditioning (RIC) after allogeneic stem cell transplantation (allo-HSCT). This multicenter retrospective study evaluated risk factors of AKI defined by 2 classification systems, Kidney Disease Improving Global Outcome (KDIGO) score and “Grade 0-3 staging,” in 186 consecutive RIC allo-HSCT recipients with Tac-Sir as graft-versus-host disease prophylaxis. Conditioning regimens consisted of fludarabine and busulfan (n = 53); melphalan (n = 83); or a combination of thiotepa, fludarabine, and busulfan (n = 50). A parametric model, with detailed Tac-Sir consecutive blood levels, describing time to AKI was developed using the NONMEM software version 7.4. Overall, 81 of 186 (44%) RIC allo-HSCT recipients developed AKI with a cumulative incidence of 42% at a median follow-up of 25 months. Time to AKI was best described using a piecewise function. AKI-predicting factors were melphalan-based conditioning regimen (HR, 1.96; P < .01), unrelated donor (HR, 1.79; P = .04), and tacrolimus concentration: The risk of AKI increased 2.3% per each 1-ng/mL increase in tacrolimus whole blood concentration (P < .01). In multivariate analysis, AKI grades 2 and 3 according to KDIGO staging were independent risk factors for 2-year nonrelapse mortality (HR, 2.8; P = .05; and HR, 6.6; P < .0001, respectively). According to the KDIGO score, overall survival decreased with the increase in severity of AKI: 78% for patients without AKI versus 68%, 50%, and 30% for grades 1, 2, and 3, respectively (P < .0001). In conclusion, AKI is frequent after Tac-Sir–based RIC allo-HSCT and has a negative impact on outcome. This study presents the first predictive model describing time to AKI as a function of tacrolimus drug concentration.

Fludarabine/Busulfan versus Fludarabine/Melphalan Conditioning in Patients Undergoing Reduced-Intensity Conditioning Hematopoietic Stem Cell Transplantation for Lymphoma

There is at present little data to guide the choice of conditioning for patients with lymphoma undergoing reduced-intensity conditioning (RIC) allogeneic stem cell transplantation (SCT). In this study, we compared the outcomes of patients undergoing RIC SCT who received fludarabine and melphalan (FluMel), the standard RIC regimen used by the Spanish Group of Transplantation, and fludarabine and busulfan (FluBu), the standard RIC regimen used by the Dana-Farber Cancer Institute/Brigham and Women's Hospital. We analyzed 136 patients undergoing RIC SCT for lymphoma with either FluBu (n = 61) or FluMel (n = 75) conditioning between 2007 and 2014. Median follow-up was 36 months. The cumulative incidence of grades II to IV acute graft-versus-host disease (GVHD) was 13% with FluBu and 36% with FluMel (P = .002). The cumulative incidence of nonrelapse mortality (NRM) at 1 year was 3.3% with FluBu and 31% with FluMel (P < .0001). The cumulative incidence of relapse at 1 year was 29% with FluBu and 10% with FluMel (P = .08). The 3-year disease-free survival rate was 47% with FluBu and 36% with FluMel (P = .24), and the 3-year overall survival rate was 62% with FluBu and 48% with FluMel (P = .01). In multivariable analysis, FluMel was associated with a higher risk of acute grades II to IV GVHD (HR, 7.45; 95% CI, 2.30 to 24.17; P = .001) and higher risk of NRM (HR, 4.87; 95% CI, 1.36 to 17.44; P = .015). The type of conditioning was not significantly associated with relapse or disease-free survival in multivariable models. However, conditioning regimen was the only factor significantly associated with overall survival: FluMel conditioning was associated with a hazard ratio for death of 2.78 (95% CI, 1.23 to 6.27; P = .014) compared with FluBu. In conclusion, the use of FluBu as conditioning for patients undergoing SCT for lymphoma was associated with a lower risk of acute GVHD and NRM and improved overall survival when compared with FluMel in our retrospective study. These results confirm the differences between these RIC regimens in terms of toxicity and efficacy and support the need for comparative prospective studies.

High Rates of Early Donor Chimerism in Intermediate and Poor Risk Patients Undergoing Stem Cell Transplantation Using Reduced Toxicity Ablative Conditioning Regimen Incorporating Busulfan Pharmacokinetics

Abstract Reduced toxicity ablative conditioning regimens are increasingly used for allogeneic stem cell transplantation (allo-SCT). The impact of early donor cell chimerism on outcomes of T cell–replete reduced-intensity conditioning SCT in myeloid disorders is ill defined. To explore the impact of measuring busulfan pharmacokinetics in conditioning regimens on early donor chimerism, we undertook a retrospective analysis of patients with myeloid disorders who received four days of fludarabine and busulfan with or without measuring busulfan pharmacokinetics at our center in the last 10 years. Methods: Chimerism assay was performed using a quantitative fluorescence-based short tandem repeat– polymerase chain reaction (STR-PCR) with capillary electrophoresis for PCR product resolution. Results: Thirty patients were identified and included in the analysis. All patients were conditioned with fludarabine (40 mg/m2/day x 4 doses), busulfan (3.2mg/kg/dose IV x 4 doses). Of these thirty patients, 7 had busulfan pharmacokinetics measured. There were 21 male and 9 female patients with a median age of 62 years (range 48–72yrs). Median time to follow up was 13.3 months. Diagnoses included AML (N=17), MDS (N=10), MPN (N=1), CMML (N=2). Disease risk was considered advanced in 17 patients, intermediate in 3 and early in 10. All patients in the busulfan pharmacokinetic group had advanced disease except one had early disease. Regarding cytogenetics, all patients in the busulfan pharmacokinetics group had high or intermediate risk cytogenetics. Median blast number at time of SCT was 5%. Stem cell source included peripheral blood in all patients. Eleven patients received matched related donor (MRD) SCT, 15 had matched unrelated donor (MUD) SCT and 4 had mismatched unrelated donor (MMUD) SCT. Prophylaxis of GVHD consisted of tacrolimus and methotrexate in MRD, and tacrolimus, methotrexate and anti-thymocyte globulin in MUD and MMUD. All patients engrafted neutrophils and platelets promptly (median 13 and 14 days, respectively). There were no primary graft failures. Total Donor cell Chimerism analysis in the Busulfan pharmacokinetics group showed 100% donor at both time points (days 30, 100) in all patients except in one who relapsed at day 30 (85.7%). While in the non-pharmacokinetics group only 7 out of 23 (30%) patients had complete chimerism at day 30 and day 100. Complete donor chimerism at day 100 in the non-pharmacokinetics group was 47.8% compared to 85.7% in the pharmacokinetic group (p=0.18). Ten out of 23 patients (43.5%) in the non-pharmacokinetics group had decreasing donor chimerism by day 100, while in the pharmacokinetic group only one patient (14%) who relapsed had decreasing donor chimerism by day 100 with an odds ratio of 0.241 (95% Confidence Interval =0.025-2.357; p-value=0.22). None developed sinusoidal obstructive syndrome. Conclusion: In this small cohort of consecutive patients from a single center, we found that patients with myeloid disorders who received fludarabine busulfan for 4 days incorporating busulfan pharmacokinetics had a trend for higher rates of early complete donor chimerism and less decreasing donor chimerism by day100, although not statistically significant, despite having intermediate or high risk disease at time of SCT. Longer follow up is needed for our patients to see if there is effect on relapse or survival but previous studies have showed that low or decreasing donor chimerism early after SCT is an independent risk factor for relapse and impaired survival. This is especially important in myeloid disorders. Busulfan pharmacokinetics may help target better level for inducing early total donor chimerism and donor chimerism may identify high-risk patient cohorts who may benefit from additional therapeutic interventions. These results should be interpreted with caution given the retrospective design of the study and the small number of patients. Disclosures No relevant conflicts of interest to declare.

Expansion of the Endosteal Hematopoietic Stem Cell Niche Following Myeloablative and Reduced Intensity Conditioning Is Triggered By Hematopoietic Cell Loss

The efficiency and durability of donor hematopoietic stem cell (HSC) engraftment at specialized niches within recipient bone marrow (BM) are critical determinants of successful clinical stem cell transplant (SCT). Osteolineage elements of BM niches play active, critical roles in regulating HSC engraftment, differentiation, and self-renewal both during homeostasis and post-SCT. We have previously shown that SCT preparative regimens consisting of myeloablative total body irradiation (MB-TBI) result in expansion of osteolineage niche cells at the endosteal surface of metaphyseal bone. This expansion is facilitated by IGF-1 and megakaryocyte-derived PDGF-BB signaling, and is required for optimal HSC engraftment. However, the pathway that integrates these signals to induce expansion remains undefined, and whether expansion is unique to conditioning with MB-TBI due to direct effects on osteolineage cells is also not known. We now present data using chemotherapy-based and reduced intensity conditioning (RIC) models, demonstrating that niche expansion is triggered by hematopoietic cell loss, and not by direct effects of conditioning agents on the niche.In vitro, MB-TBI (1125 cGy) inhibited primary murine osteoblast (OB) growth and increased apoptosis (Annexin V+ OB at 72 hours: TBI 17% versus control 4%, p < 0.001). In contrast, busulfan treatment caused significantly less OB growth inhibition versus MB-TBI, with no increased apoptosis compared to sham-treated controls. We therefore conditioned wildtype (WT) C57BL/6 mice with myeloablative busulfan (Day -7 to -4) and cyclophosphamide (Day -3 to -2) (BuCy) in a schedule similar to clinical SCT regimens. Endosteal niche expansion increased over this time course, correlating with the extent of hematopoietic ablation, with most expansion occurring prior to cyclophosphamide administration. Maximal expansion occurred by the end of the treatment course, and based on a quantitative scoring index, was not significantly different than maximal MB-TBI-induced niche expansion, demonstrating that niche expansion is not specific to radiation-based conditioning. As with MB-TBI treatment, BuCy-treated recipients of GFP+donor BM consistently exhibited >95% donor chimerism.We next investigated whether RIC regimens can mediate niche expansion, using an anti-cKit antibody (clone ACK2) known to enable donor engraftment when administered alone in immunodeficient mice or in combination with low dose irradiation (LD-TBI, 300 cGy) in WT mice. ACK2 treatment alone resulted in modest endosteal cell expansion (33% of MB-TBI induced expansion), correlating with transient reductions in host BM cellularity, but absence of definitive donor engraftment in ACK2-treated WT mice. In contrast, LD-TBI alone or in combination with ACK2 produced 58% and 74%, respectively, of the endosteal expansion seen following MB-TBI. Interestingly, while these regimens reduced total BM cellularity by 85% (LD-TBI) and 93% (LD-TBI + ACK2), and led to clearance of BM Lin-Sca1+cKit+(LSK) progenitors, this lack of full niche expansion correlated with incomplete and inconsistent donor chimerism in SCT recipients.Finally, to prove that endosteal niche expansion results from signals triggered specifically by hematopoietic cell loss, we crossed mice expressing Cre-recombinase under control of the CD45 promoter (CD45Cre) with mice expressing inducible diphtheria toxin receptor (iDTRlox). When treated with diphtheria toxin (DT), BM cellularity in these mice was reduced by 90%, and this targeted ablation of hematopoietic cells was sufficient to induce similar expansion of endosteal mesenchymal cells as seen with radiation or chemotherapy-based conditioning regimens.Taken together, our results demonstrate that endosteal niche expansion occurs in response to both radiation- and chemotherapy-based SCT conditioning, and that the degree of expansion correlates with both conditioning intensity and with the subsequent degree of donor cell engraftment/chimerism in SCT recipients. Importantly, expansion is triggered not by direct effects of the preparative regimen on mesenchymal niche cells, but rather by loss of hematopoietic cells. These findings provide important insights into how SCT conditioning modulates niche function, and suggests that therapeutic strategies to enhance niche function may be effective in improving engraftment outcomes following RIC SCT. DisclosuresNo relevant conflicts of interest to declare.

Graft Versus HIV-1 Reservoir Effect after Allogeneic Stem Cell Transplantation

Background: The use of a stem cell source homozygous for the CCR5 delta32 mutation is of particular interest in HIV+ patients in need of an allogeneic hematopoietic stem cell transplantation (SCT) given the high natural resistance against HIV-1 acquisition. In the absence of such cell source, the impact of allogeneic SCT on human immunodeficiency virus type 1 (HIV-1) reservoirs in patients receiving combination antiretroviral therapy (cART) is unknown.Methods: Size of HIV-1 reservoirs was investigated in 3 patients with hematological malignancies receiving cART, who underwent allogeneic SCT (Table 1). Patient 1 received a myeloablative single cord blood (wild type (WT) CCR5), supported with third party HLA-mismatched CD34+ cells (haplo-cord SCT). Patients 2 and 3 underwent reduced intensity conditioning SCT of an HLA-matched sibling (heterozygous CCR5 delta32 donor and WT CCR5 donor, respectively). In-depth analysis of the HIV-1 reservoir was performed in the post-transplant period using droplet digital PCR and hemi-nested qPCR (proviral DNA copies/million PBMC). Chimerism analysis was performed by short tandem repeat PCR (STR-PCR).Results: Proviral DNA showed a decreasing dynamics after allogeneic SCT and became undetectable in all 3 patients at 9, 18 and 1 months, respectively (Table 1). In patient 1, negativity of proviral HIV-1 DNA coincided with achievement of complete chimerism while being free of immunosuppression. Patient 2 showed undetectable proviral DNA together with the development of skin chronic GvHD. Finally, undetectable proviral DNA and complete chimerism was achieved in patient 3 early after transplantation. All patients remained in complete hematological remission.Conclusion: All our patients showed a small HIV-1 reservoir after allogeneic SCT. The coincidence of achievement of negative proviral HIV-1 DNA and complete chimerism and/or development of GvHD suggests a role of Ògraft versus HIV-1 reservoir effectÓ in the control of HIV infection. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

High Rates of Early Donor Chimerism in Intermediate and Poor Risk Patients Undergoing Stem Cell Transplantation Using Reduced Toxicity Ablative Conditioning Regimen Incorporating Busulfan Pharmacokinetics

▪Reduced toxicity ablative conditioning regimens are increasingly used for allogeneic stem cell transplantation (allo-SCT). The impact of early donor cell chimerism on outcomes of T cell–replete reduced-intensity conditioning SCT in myeloid disorders is ill defined. To explore the impact of measuring busulfan pharmacokinetics in conditioning regimens on early donor chimerism, we undertook a retrospective analysis of patients with myeloid disorders who received four days of fludarabine and busulfan with or without measuring busulfan pharmacokinetics at our center in the last 10 years.Methods: Chimerism assay was performed using a quantitative fluorescence-based short tandem repeat– polymerase chain reaction (STR-PCR) with capillary electrophoresis for PCR product resolution.Results: Thirty patients were identified and included in the analysis. All patients were conditioned with fludarabine (40 mg/m2/day x 4 doses), busulfan (3.2mg/kg/dose IV x 4 doses). Of these thirty patients, 7 had busulfan pharmacokinetics measured. There were 21 male and 9 female patients with a median age of 62 years (range 48–72yrs). Median time to follow up was 13.3 months. Diagnoses included AML (N=17), MDS (N=10), MPN (N=1), CMML (N=2). Disease risk was considered advanced in 17 patients, intermediate in 3 and early in 10. All patients in the busulfan pharmacokinetic group had advanced disease except one had early disease. Regarding cytogenetics, all patients in the busulfan pharmacokinetics group had high or intermediate risk cytogenetics. Median blast number at time of SCT was 5%. Stem cell source included peripheral blood in all patients. Eleven patients received matched related donor (MRD) SCT, 15 had matched unrelated donor (MUD) SCT and 4 had mismatched unrelated donor (MMUD) SCT. Prophylaxis of GVHD consisted of tacrolimus and methotrexate in MRD, and tacrolimus, methotrexate and anti-thymocyte globulin in MUD and MMUD.All patients engrafted neutrophils and platelets promptly (median 13 and 14 days, respectively). There were no primary graft failures. Total Donor cell Chimerism analysis in the Busulfan pharmacokinetics group showed 100% donor at both time points (days 30, 100) in all patients except in one who relapsed at day 30 (85.7%). While in the non-pharmacokinetics group only 7 out of 23 (30%) patients had complete chimerism at day 30 and day 100. Complete donor chimerism at day 100 in the non-pharmacokinetics group was 47.8% compared to 85.7% in the pharmacokinetic group (p=0.18). Ten out of 23 patients (43.5%) in the non-pharmacokinetics group had decreasing donor chimerism by day 100, while in the pharmacokinetic group only one patient (14%) who relapsed had decreasing donor chimerism by day 100 with an odds ratio of 0.241 (95% Confidence Interval =0.025-2.357; p-value=0.22). None developed sinusoidal obstructive syndrome.Conclusion: In this small cohort of consecutive patients from a single center, we found that patients with myeloid disorders who received fludarabine busulfan for 4 days incorporating busulfan pharmacokinetics had a trend for higher rates of early complete donor chimerism and less decreasing donor chimerism by day100, although not statistically significant, despite having intermediate or high risk disease at time of SCT. Longer follow up is needed for our patients to see if there is effect on relapse or survival but previous studies have showed that low or decreasing donor chimerism early after SCT is an independent risk factor for relapse and impaired survival. This is especially important in myeloid disorders. Busulfan pharmacokinetics may help target better level for inducing early total donor chimerism and donor chimerism may identify high-risk patient cohorts who may benefit from additional therapeutic interventions. These results should be interpreted with caution given the retrospective design of the study and the small number of patients. DisclosuresNo relevant conflicts of interest to declare.

Stem cell transplantation for primary immune deficiency

In this article, we summarize the recent advances in treating primary immune deficiency (PID) disorders by stem cell transplantation (SCT); we have focused on articles published in the past 2 years since the last major review of SCT for PID. Analyses of the outcomes of SCT for PID by specific molecular defect have clarified which conditions are receptive to unconditioned transplants and which require more myeloablative conditioning. Improved outcomes for 'difficult' conditions [adenosine deaminase-severe combined immunodeficiency (ADA-SCID), major histocompatibility complex class II deficiency] and potential advantages of using cord blood as a stem cell source have also been described. Newborn screening for SCID identifies well babies with SCID: the optimal SCT protocol for such young infants remains to be determined. Reduced toxicity conditioning has been successfully used to treat conditions such as Wiskott-Aldrich syndrome and chronic granulomatous disease, offering curative engraftment with reduced transplant-related mortality. Similarly, treating children with familial hemophagocytic lymphohistiocytosis using reduced intensity conditioning SCT results in much improved outcomes. Advances in next generation sequencing have identified new diseases amenable to SCT, such as DOCK8 deficiency, resulting in improved quality of life and protection from malignancy. Recent studies suggest that further improvements in treating PID with SCT are possible with a greater understanding of the genetics and immunobiology of these diseases, facilitating the matching of donor type and conditioning regimens, or indeed alternative therapies (such as gene therapy) to specific PID disorders.

Transplant in Chronic Lymphocytic Leukemia: To Do It or Not and If So, When and How?

Most patients with chronic lymphocytic leukemia (CLL) have an indolent clinical course, but the disease remains incurable with standard therapy and the prognosis is dismal for those patients with disease refractory to available treatment options. The only potentially curative treatment is allogeneic hematopoietic stem cell transplantation (SCT), but since CLL is a disease of elderly patients, few patients are candidates for myeloablative allogeneic SCT. Although autologous SCT is feasible and has low treatment-related mortality, it is not curative. The widespread adoption of reduced-intensity conditioning (RIC) allogeneic SCT has made this approach applicable to the elderly patient population with CLL. This approach relies on the documented graft-versus-leukemia (GVL) effect and is strong in CLL. Steps to further decrease the morbidity and mortality of the RIC SCT and in particular to reduce the incidence of chronic extensive graft-versus-host disease (GVHD) remain a major focus. Many potential treatments are available for CLL, and appropriate patient selection and SCT timing remain controversial and the focus of ongoing clinical trials. The use of SCT must always be weighed against the risk of the underlying disease, particularly in a setting where improvements in treatment are leading to improved outcome. The major challenge remains how to identify which patients with CLL merit this approach and where in the treatment course this treatment can be applied optimally.

The Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI) and Survival Following Extracorporeal Photopheresis, Pentostatin, and Reduced Dose Total Body Irradiation Conditioning

The Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI) and Survival Following Extracorporeal Photopheresis, Pentostatin, and Reduced Dose Total Body Irradiation Conditioning

Pulmonary Veno-occlusive Disease Following Reduced-intensity Allogeneic Bone Marrow Transplantation for Acute Myeloid Leukemia

We report a case of pulmonary veno-occlusive disease (PVOD) following allogeneic bone marrow transplantation (BMT) for the treatment of acute myeloid leukemia (AML) from an HLA mismatched mother using a reduced-intensity conditioning (RIC) regimen including gemtuzumab ozogamicin. The patient was a 21-year-old male who complained of dyspnea with hypoxemia followed by loss of consciousness. The abnormalities in chest CT and echocardiography were compatible with a diagnosis of PVOD. Treatment with 1 mg/kg of oral prednisolone resolved dyspnea and hypoxemia within a few days, and chest CT abnormalities disappeared in a week. This report is the first to describe PVOD following RIC stem cell transplantation.

Inhibition of Lymphocyte Trafficking Using a CCR5 Antagonist – Final Results of a Phase I/II Study

Abstract 1011Inhibition of lymphocyte trafficking early after allogeneic stem cell transplantation (SCT) may prevent GvHD without interfering with GvL activity. Animal models and genomic data in humans indicate that the interaction between CCR5 and its ligands CCL3, CCL4 and RANTES is pivotal in the pathogenesis of GvHD. Maraviroc (MVC; Selzentry®, Pfizer) is the first oral CCR5 antagonist in clinical use. The antiviral properties of MVC in HIV infection are known, but its effects on chemotaxis and immune function in patients without HIV infection have not been explored. We hypothesized that CCR5 inhibition early after allogeneic SCT would reduce lymphocyte chemotaxis and result in low rates of acute GvHD without impairing engraftment or antitumor activity.In vitro, MVC effectively and specifically inhibited CCR5 internalization and reduced RANTES-induced chemotaxis in concentrations achievable in humans, recapitulating a defect observed in homozygotes for the del32-CCR5 polymorphism. MVC had no effect on hematopoietic colony formation, T-cell mediated cytotoxicity and T-cell proliferation.Between May 2009 and March 2011, we enrolled 38 pts in a phase I/II study of reduced intensity conditioned (RIC) allogeneic SCT. Patients had high-risk features by age (median=62, range 21–74), donor source (matched related 34%, matched unrelated 50%, single-antigen mismatch 16%) and comorbidities (comorbidity index: low 55%, intermediate 34%, high 11%). Underlying diseases were AML (15), MDS (6), NHL (8), myelofibrosis (4), aplastic anemia, myeloma, CLL, Hodgkin, CML (1 each). Pts received fludarabine 120mg/m2 and IV busulfan 6.4 mg/kg followed by peripheral blood stem cells. In addition to standard GvHD prophylaxis with tacrolimus and methotrexate, MVC was given from day −2 to +30. Pharmacokinetic analysis on the first 13 pts identified 300 mg bid as the appropriate dose (Reshef, ASH 2010). MVC was well tolerated, and adverse events were similar to the expected toxicity observed in patients undergoing RIC SCT. The median time to ANC>500/μL was 15 d (range 10–27) and to platelets>20k/μL was 19 d (range 9–84). The median whole blood and T-cell donor chimerism at day 100 was 96.5% (range 0–100%) and 85% (range 0–100%) respectively.Median follow-up was 200 days (range 12–760). Among 35 evaluable patients, the cumulative incidences of any acute GvHD and grade III–IV acute GvHD at day 100 were 14.7 ± 6.2% and 2.9 ± 2.9%, respectively. Importantly, in the first 100 days, there were no cases of acute GvHD involving the liver or gut. At day 180, the rate of acute GvHD was 20.7 ± 7.1%, largely confined to the skin with low rates of GvHD in the liver (3 ± 3%) and gut (7.4 ± 5.3%). In evaluable pts who received a graft from their HLA-matched sibling (11), there was no GvHD before day 100 and only two cases of acute GvHD before day 180.We compared these results to a cohort of 38 well-matched consecutive patients treated at our institution with RIC SCT using an identical regimen but without MVC between 2009 and 2011. We observed a similar incidence of acute GvHD (all grades) at day 100 (14.7 ± 6.2 vs. 16 ± 6.1%; P=0.88), but a 64% decrease in the MVC group at day 180 (20.7 ± 7.1 vs. 45.4 ± 9%; P=0.03). The incidence rates of severe GvHD (grade III–IV) were 2.9 ± 2.9% in the MVC group vs. 5.5 ± 3.8% in the comparator group at day 100 (P=0.59) and 6.5 ± 4.5% vs. 18.1 ± 6.8% at day 180 (P=0.15).Treatment-related mortality in pts receiving MVC was low. At 1 year, non-relapse mortality rate was 7.6 ± 5.5% (control group: 15.7 ± 6.6%; P=0.35). Infectious complications were seen at a rate that is expected with RIC SCT. Recovery of lymphocyte counts and lymphocyte subsets was not impaired by MVC.We evaluated whether a protective effect against GvHD was associated with an increase in relapse. In the MVC group, the incidence of relapse was 34.2 ± 8.8% at day 180; this was not significantly different from the comparator group (43.9 ± 8.8%, P=0.44), implying preservation of the graft-versus-tumor effect with MVC. Rates of overall survival and relapse-free survival were similar in both groups.Pharmacodynamic testing revealed that sera from patients taking MVC prevented CCR5 internalization by RANTES and blocked T-cell chemotaxis in vitro, providing evidence for in vivo biological activity and supporting the hypothesized mechanism of action.In summary, inhibition of lymphocyte trafficking is a novel, specific and potentially effective strategy to reduce the incidence of acute GvHD. Disclosures:Off Label Use: Use of maraviroc in GvHD prophylaxis will be discussed. Frey:Pfizer: Speakers Bureau. Vonderheide:Pfizer: Research Funding. Porter:Pfizer: Research Funding.

Reduced-Intensity Conditioning Stem Cell Transplantation: Comparison of Double Umbilical Cord Blood and Unrelated Donor Grafts

There are little data comparing umbilical cord blood (UBC) and conventional stem cell sources for reduced-intensity conditioning (RIC) hematopoietic stem cell transplantation (HSCT). We performed a retrospective analysis of RIC HCST using double UCB (dUCB) grafts and RIC HSCT using unrelated donor (URD) grafts. The study included 64 dUCB transplantations and 221 URD transplantations performed at Dana-Farber Cancer Institute and Massachusetts General Hospital between 2004 and 2008. The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 14.1% for dUCB and 20.3% for URD (P = .32). The 2-year cumulative incidence of chronic GVHD was significantly lower in dUCB compared with URD (21.9% versus 53.9%; P < .0001). The 2-year cumulative incidence of nonrelapse mortality was significantly higher in dUCB (26.9% versus 10.4%; P = .0009). In our analysis, dUCB HSCT and URD HSCT had comparable 3-year overall survival (46% in dUCB and 50% in URD; P = .49) and progression-free survival (30% in dUCB and 40% in URD; P = .47). dUCBT was associated with greater nonrelapse mortality despite less chronic GVHD. Our findings suggest that the use of 2 partially matched UCB units appears to be a suitable alternative for patients undergoing RIC HSCT without an HLA-matched donor.

A Polymorphism in the Splice Donor Site of ZNF419 Results in the Novel Renal Cell Carcinoma-Associated Minor Histocompatibility Antigen ZAPHIR

Nonmyeloablative allogeneic stem cell transplantation (SCT) can induce remission in patients with renal cell carcinoma (RCC), but this graft-versus-tumor (GVT) effect is often accompanied by graft-versus-host disease (GVHD). Here, we evaluated minor histocompatibility antigen (MiHA)-specific T cell responses in two patients with metastatic RCC who were treated with reduced-intensity conditioning SCT followed by donor lymphocyte infusion (DLI). One patient had stable disease and emergence of SMCY.A2-specific CD8+ T cells was observed after DLI with the potential of targeting SMCY-expressing RCC tumor cells. The second patient experienced partial regression of lung metastases from whom we isolated a MiHA-specific CTL clone with the capability of targeting RCC cell lines. Whole genome association scanning revealed that this CTL recognizes a novel HLA-B7-restricted MiHA, designated ZAPHIR, resulting from a polymorphism in the splice donor site of the ZNF419 gene. Tetramer analysis showed that emergence of ZAPHIR-specific CD8+ T cells in peripheral blood occurred in the absence of GVHD. Furthermore, the expression of ZAPHIR in solid tumor cell lines indicates the involvement of ZAPHIR-specific CD8+ T cell responses in selective GVT immunity. These findings illustrate that the ZNF419-encoded MiHA ZAPHIR is an attractive target for specific immunotherapy after allogeneic SCT.

Relapse incidence and leukemia-free survival (LFS) in patients (pts) older than age 60 with AM undergoing stem cell transplantation: A report of the East German Study Group Hematology and Oncology (OSHO).

6523 Background: Complete remission rates similar to those of younger pts are obtained in elderly AML pts (OSHO AML 1997). However, OS and LFS remain dismal because of extremely high relapse rates. In the AML 2004 study, reduced intensity conditioning SCT was introduced to reduce relapse in patients with a compatible related/unrelated donor. In this analysis we compared outcome of patients with a donor to patients without a donor. Methods: Of the 663 pts, 597 were entered into the study specific arm and 66 in the common arm of the German Intergroup Study. Of those 447 and 52 pts were evaluable, respectively. The majority of pts were male (56.9%), the median age 68 years and the median Karnofsky score 80%. Karyotype was normal in 46.9% and unfavorable in 21.2%, while 55.9% had de novo AML. Induction therapy consisted of AraC 100 mg/m2 c. i. over 7 days / Daunorubicin 60 mg/m2 i.v. on days 3 - 5 in the standard arm and of AraC 2g/m2 on days 1, 3, 5 and 7 / mitoxantrone 10 mg/m2 i.v. day 1 - 3 in the study arm. SCT were performed following reduced intensity conditioning. Results: CR was observed in 62% of pts after induction in the study arm and in 62% in the standard arm. A total of 76 pts had a stem cell donor and 129 no donor. There was no significant difference between the populations except for median age 68 in the chemotherapy vs. 65 a in the SCT arm (p<0.001). OS at 3 a was 35 ± 6% in the chemotherapy compared to 49 ± 6% in the SCT arm. Accordingly, LFS at 3 a was 27 ± 5% for chemotherapy as compared to 39 ± 7% in the SCT arm (p=0.04) and due to reduced relapse incidence (73±5% vs. 45±7%, respectively; p 0.001). Only SCT and favorable risk cytogenetics were independent factors for increased LFS. Both variables were independent risk factors for lower relapse rate, as was de novo AML. In contrast, high WBC at diagnosis and SCT were significantly associated in a multivariate analysis with increased treatment related mortality. Conclusions: SCT in comparison to chemotherapy is associated with increased LFS and lower relapse independently of cytogenetic risk. The biggest differences in LFS and relapse between SCT and chemotherapy were noted among pts with high risk cytogenetic disease.