Peripheral Blood Grafts Research Articles

Monitoring Intra-cellular Tacrolimus Concentrations in Solid Organ Transplantation: Use of Peripheral Blood Mononuclear Cells and Graft Biopsy Tissue.

Tacrolimus is an essential immunosuppressant for the prevention of rejection in solid organ transplantation. Its low therapeutic index and high pharmacokinetic variability necessitates therapeutic drug monitoring (TDM) to individualise dose. However, rejection and toxicity still occur in transplant recipients with blood tacrolimus trough concentrations (C0) within the target ranges. Peripheral blood mononuclear cells (PBMC) have been investigated as surrogates for tacrolimus’s site of action (lymphocytes) and measuring allograft tacrolimus concentrations has also been explored for predicting rejection or nephrotoxicity. There are relatively weak correlations between blood and PBMC or graft tacrolimus concentrations. Haematocrit is the only consistent significant (albeit weak) determinant of tacrolimus distribution between blood and PBMC in both liver and renal transplant recipients. In contrast, the role of ABCB1 pharmacogenetics is contradictory. With respect to distribution into allograft tissue, studies report no, or poor, correlations between blood and graft tacrolimus concentrations. Two studies observed no effect of donor ABCB1 or CYP3A5 pharmacogenetics on the relationship between blood and renal graft tacrolimus concentrations and only one group has reported an association between donor ABCB1 polymorphisms and hepatic graft tacrolimus concentrations. Several studies describe significant correlations between in vivo PBMC tacrolimus concentrations and ex vivo T-cell activation or calcineurin activity. Older studies provide evidence of a strong predictive value of PBMC C0 and allograft tacrolimus C0 (but not blood C0) with respect to rejection in liver transplant recipients administered tacrolimus with/without a steroid. However, these results have not been independently replicated in liver or other transplants using current triple maintenance immunosuppression. Only one study has reported a possible association between renal graft tacrolimus concentrations and acute tacrolimus nephrotoxicity. Thus, well-designed and powered prospective clinical studies are still required to determine whether measuring tacrolimus PBMC or graft concentrations offers a significant benefit compared to current TDM.

Allogeneic blood or marrow transplantation with haploidentical donor and post-transplantation cyclophosphamide in patients with myelofibrosis: a multicenter study.

We report the results from a multicenter retrospective study of 69 adult patients who underwent haploidentical blood or marrow transplantation (haplo-BMT) with post-transplantation cyclophosphamide (PTCy) for chronic phase myelofibrosis. The median age at BMT was 63 years (range, 41-74). Conditioning regimens were reduced intensity in 54% and nonmyeloablative in 39%. Peripheral blood grafts were used in 86%. The median follow-up was 23.1 months (range, 1.6-75.7). At 3 years, the overall survival, relapse-free survival (RFS), and graft-versus-host-disease (GVHD)-free-RFS were 72% (95% CI 59-81), 44% (95% CI 29-59), and 30% (95% CI 17-43). Cumulative incidences of non-relapse mortality and relapse were 23% (95% CI 14-34) and 31% (95% CI 17-47) at 3 years. Spleen size ≥22 cm or prior splenectomy (HR 6.37, 95% CI 2.02-20.1, P = 0.002), and bone marrow grafts (HR 4.92, 95% CI 1.68-14.4, P = 0.004) were associated with increased incidence of relapse. Cumulative incidence of acute GVHD grade 3-4 was 10% at 3 months and extensive chronic GVHD was 8%. Neutrophil engraftment was reported in 94% patients, at a median of 20 days (range, 14-70). In conclusion, haplo-BMT with PTCy is feasible in patients with myelofibrosis. Splenomegaly ≥22 cm and bone marrow grafts were associated with a higher incidence of relapse in this study.

Bone Marrow versus Peripheral Blood Grafts for Haploidentical Hematopoietic Cell Transplantation with Post-Transplantation Cyclophosphamide

In the coronavirus disease 19 (COVID-19) pandemic era, the number of haploidentical hematopoietic cell transplantations (HCTs) with peripheral blood (PB) grafts increased significantly compared with HCTs with bone marrow (BM) grafts, which may be associated with adverse outcomes. We compared outcomes of HCT in BM graft and PB graft recipients age ≥18 years with hematologic malignancies who underwent T cell- replete haploidentical HCT and received graft-versus-host disease (GVHD) prophylaxis with post-transplantation cyclophosphamide, tacrolimus, and mycophenolate mofetil. Among the 264 patients, 180 (68%) received a BM graft and 84 (32%) received a PB graft. The median patient age was 50 years in both groups. The majority (n = 199; 75%) received reduced-intensity conditioning. The rate of acute leukemia or myelodysplastic syndrome was higher in the BM graft recipients compared with the PB graft recipients (85% [n = 152] versus 55% [n = 46]; P < .01). The median times to neutrophil and platelet engraftment and the incidence of grade II-IV and grade III-IV acute GVHD (aGVHD) were comparable in the 2 groups. Among the patients with grade II-IV aGVHD, the rate of steroid-refractory aGVHD was 9% (95% confidence interval [CI], 5% to 18%) in the BM group versus 32% (95% CI, 19% to 54%) in the PB group (hazard ratio [HR], 3.7, 95% CI, 1.5 to 9.3; P = .006). At 1 year post-HCT, the rate of chronic GVHD (cGVHD) was 8% (95% CI, 4% to 13%) in the BM group versus 22% (95% CI, 14% to 36%) in the PB group (HR, 3.0; 95% CI, 1.4-6.6; P = .005), and the rate of systemic therapy-requiring cGVHD was 2.5% (95% CI, 1% to 7%) versus 14% (95% CI, 7% to 27%), respectively (HR, 5.6; 95% CI, 1.7 to 18; P = .004). The PB group had a significantly higher risk of bacterial and viral infections, with no appreciable advantage in the duration of hospitalization, immune reconstitution, relapse, nonrelapse mortality, or survival. Our data suggest a benefit of the use of BM grafts over PB grafts for haplo-HCT.

Myeloablative Fractionated Busulfan With Fludarabine in Older Patients: Long Term Disease-Specific Outcomes of a Prospective Phase II Clinical Trial

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

Cytokine release syndrome after haploidentical hematopoietic cell transplantation: an international multicenter analysis.

Haploidentical related donor transplantation (haplo-HCT) is associated with cytokine release syndrome (CRS). We conducted a multicenter retrospective study to analyze risk factors for CRS and outcomes after haplo-HCT. We included 451 patients from four academic centers receiving both peripheral blood and bone marrow grafts. Severe CRS was more common with PB vs. BM grafts (19.5% vs 4.9%, OR 2.9, p = 0.05). Multivariable analysis identified recipient CMV sero-positivity, prior transplant, HCT-CI score and donor-recipient sex mismatch as risk factors for severe CRS. Outcomes were analyzed with no CRS as the comparison group. Overall survival (OS) was superior with mild CRS (HR 0.64, p = 0.05) and worst with severe CRS (HR 2.12, p = 0.0038). Relapse risk was significantly decreased in both mild CRS (HR 0.38, p < 0.0001) and severe CRS (HR 0.17, p < 0.0001) groups. The risk of non-relapse mortality was notably higher in severe CRS group (HR 8.0, p < 0.0001), but not in mild CRS group. Acute GVHD was similar among groups. Chronic GVHD at 1 year was 18.5% for no CRS, 23% for mild CRS, and 4.3% for severe CRS (p = 0.0023), with the competing risk of early mortality and short follow up of surviving patients contributing to the low chronic GVHD rates in the severe CRS group.

Cytotoxic T Lymphocyte Antigen 4 (CTLA4) Single Nucleotide Polymorphisms Do Not Impact Outcomes After Unrelated Donor Transplant: A Center For International Blood and Marrow Transplant Research Analysis

Cytotoxic T Lymphocyte Antigen 4 (CTLA4) is a critical T cell molecule that inhibits T cell activation and plays an essential role in T cell homeostasis and immune responses. Genetic variations in the CTLA4 gene have been hypothesized to be possible biologic markers that are predictive of transplant outcomes. Previous investigators have studied single nucleotide polymorphisms (SNPs) of the CTLA4 gene and its impact on hematopoietic cell transplantation (HCT) outcomes with discordant results. AA and AG genotypes in the donor CTLA4 regulatory region involving SNP rs4553808 in patients after unrelated donor (URD) HCT have recently been shown to be an independent predictor of improved relapse free survival (RFS) and overall survival (OS) compared to the GG genotype. To validate these preliminary findings, a Center for International Blood and Marrow Research (CIBMTR) study was performed in a larger, more homogenous cohort of patients.Adult patients with acute myeloid leukemia (AML) and advanced myelodysplastic syndrome (MDS) undergoing a first 8/8 or 7/8 HLA matched URD HCT after myeloablative, non-myeloablative, or reduced intensity conditioning from 2002 to 2007 in first or second complete remission with available donor research samples from the National Marrow Donor Program research repository were included. The primary goal was to evaluate the impact of SNP rs4553808 on RFS, OS, and NRM and the cumulative incidence of acute graft-versus-host disease (aGVHD), and chronic graft-versus-host disease (cGVHD). Any GVHD prophylaxis could be used except in vitro T-cell depletion or use of in vivo/in vitro alemtuzumab. Patients receiving T cell depletion with anti-thymocyte globulin (ATG) were oversampled to allow analysis of any effects on outcomes. An exploratory analysis of 9 other tagSNPs that encompass the entire CTLA4 gene (rs231775, rs231779, rs11571315, rs231777, rs3087243, rs16840252, rs231725, rs10197010, rs11571316) was performed to evaluate for any additional potential associations with clinical outcomes.Each SNP was analyzed in multivariable models adjusting for clinically significant variables using the Cox proportional hazards model. Due to multiple testing, p-values <0.005 were considered significant. The interaction with CTLA4 SNPs and use of ATG was also specifically analyzed. The final analysis included 780 patients with a median followup of 63 months. Median age of recipients and donors was 50 and 34, respectively. 90% of recipients were identified to be of Caucasian descent (N=709). 80% of patients had AML (N=624) and 20% MDS (N=156). Conditioning was 61% ablative, 28% reduced intensity and 11% non-myeloablative, with 74% receiving peripheral blood grafts. 75% were HLA-matched and 25% single locus mismatched. Tacrolimus with methotrexate or mycophenolate mofetil GVHD prophylaxis was given to 62%, cyclosporine-based prophylaxis to 15% while 23% received other regimens. By design, 50% of patients received ATG. Genotyping showed that 552 (71%) were AA, 208 (27%) were AG and 19 (2%) were GG (AG, and particularly GG, were associated with worse outcomes in the prior study). Multivariable analysis adjusting for significant donor and recipient characteristics showed no significant association between SNP rs4553808 and OS (p=0.07), RFS (p=0.41), NRM (p=0.25), and incidence of acute and chronic GVHD (Figure 1). Multivariable analysis of the other 9 tagSNPs also showed no association with transplant outcomes (p>0.005). No interaction was found between the CTLA4 SNPs and use of ATG on outcomes. These results indicate that CTLA4 SNPS do not have impact on outcomes. Other genomic or cellular biomarkers need to be studied to risk stratify patients at high risk of negative clinical events, especially as therapies targeting CTLA4 and PD-1 evolves. [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Comparison of Mobilized Peripheral Blood Stem Cells Versus Unmanipulated Bone Marrow Haploidentical Transplantation Using Post-Transplant Cyclophosphamide: A Retrospective Study of SFGM-TC in 176 Patients

IntroductionThe administration of high dose cyclophosphamide post-transplant (HD-Cy) has improved the outcome of patients who receive an unmanipulated haploidentical graft. The modalities described by the group of Baltimore originally associated a non myeloablative conditioning regimen and the use of a T cell replete bone marrow (BM) graft. Nevertheless, mobilized peripheral blood (PB) is increasingly used as it is more convenient. A very recent report from the United States showed a lower rate of graft versus host disease (GVHD) with BM but an increased risk of relapse in leukemic patients, as compared to PB, leading to a similar overall survival (OS). We report the French experience of haploidentical transplantation using HD-Cy and unmanipulated BM or PB, with a particular interest on the contents of the grafts.Patients and methodsOne hundred seventy-six patients with hematologic malignancy received a haploidentical transplant in 21 French centers from May 2012 to December 2015. We compared the outcome of patients who received a BM graft (n=89) with those receiving a PB graft (N=87). Median age at transplant was 44 year-old (2.5-72). One hundred thirteen (64%) patients had myeloid disease, 19 (11%) had acute lymphoblastic leukemia and 44 (25%) had lymphoid neoplasm. Prophylaxis of GVHD consisted in anticalcineurin and mycophenolate in 94% of the cases. All patients received HD-CY post-transplant (100 mg per kg total dose).ResultsThe 2 groups were comparable for age, disease status at transplant, type of conditioning regimen (RIC 71% and 80% for BM and PB respectively; p=0.16), recipient cytomegalovirus (CMV) seropositive status, ABO mismatch. PB recipients were more likely to receive antithymocyte globulin (ATG) (N=19 vs 0) and to have a higher disease risk index (DRI). The number of CD34+ and CD3+ infused cells was higher in PB grafts (median 2.64x106 CD34/Kg and 26 x106 CD3/Kg for BM and 6.03x106 CD34/Kg and 191 x106 CD3/Kg for PB. Median follow up was 281 days (6-1851).In univariate analysis, the rate of patients who recovered neutrophils and platelet (>50G/L) were similar in both groups (91% and 75% vs 96% and 75% for BM vs PB respectively). However, median time to neutrophil engraftment was significantly longer in BM than in PB group (20 days (13-59) vs 18 days (13-45) respectively, p=0.004). Median time to platelet recovery was not significantly different (30 days (17-250) vs 24 days (13-52) in BM and PB, p=0.14). Patients who recovered neutrophils received a graft which contained more CD3+ cells than patients who did not (p=0.007).At one year, OS, progression free survival (PFS) and relapse were similar in the 2 groups (OS = 64% vs 53% (p=0.1), PFS= 53% vs 46 % (p=0.17) and relapse rate 28% vs 34% (p=0.19) in BM and PB respectively). Acute GVHD II-IV or III-IV and chronic GVHD were similar in both groups (aGVHD II-IV= 18% vs 28% (p=0.09) and aGVHD III-IV = 7% vs 9% (p=0.48), cGVHD=13% vs 15% (p=0.6) in BM and PB respectively), resulting in a similar GVHD-free relapse-free survival (GRFS) at 1 year (48% vs 37% (p=0.09)). Interestingly, the number of infused CD3+ cells/Kg impacted the incidence of acute GVHD II-IV (p=0.049).High DRI and the lack of complete remission at transplant had a significant pejorative effect on OS, PFS, relapse, GRFS and platelet recovery. CMV seropositive recipients had a worse GRFS (p=0.045).ConclusionIn this retrospective study the use of PB instead of BM does not significantly impact the outcome of patients who received a haploidentical unmanipulated graft for a malignant disease with HD-CY. PB graft contained more CD3+ and CD34+ cells than BM and were associated with a faster neutrophils recovery. A higher number of CD3+ cells increased the risk of acute GVHD II-IV in univariate analysis, without significant effect on GRFS. Prospective randomized studies are needed to evaluate the effect of PB vs BM in haploidentical settings. DisclosuresPeffault De Latour:Pfizer: Consultancy, Honoraria, Research Funding; Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Research Funding.

Reduced GvHD in Recipients of BM Derived Versus G-CSF Mobilized Plasmacytoid Dendritic Cells: Role of Inducible IL-12

Introduction: BMT CTN 0201, a randomized clinical trial, demonstrated that overall survival is equivalent between recipients of allogeneic bone marrow (BM) vs. granulocyte-colony stimulating factor (G-CSF) mobilized peripheral blood grafts. Increased graft failure was observed in recipients of BM grafts, while recipients of G-CSF mobilized peripheral blood (G-PB) grafts had more chronic graft-versus-host disease (GvHD) (Anasetti NEJM 2012). Donor plasmacytoid dendritic cell (pDC) content is associated with increased overall survival and decreased acute GvHD related mortality among recipients of BM grafts from unrelated donors, but not G-PB grafts (Waller JCO 2014). We have previously shown that in murine bone marrow transplant (BMT), donor pDC from the bone marrow reduce GvHD and improve survival while maintaining graft-versus-leukemia effect when added to grafts containing purified hematopoietic stem cells (HSC) and T cells (Lu BLOOD 2012). We hypothesized that the difference in chronic GvHD observed in BMT CTN 0201 is due to donor pDC content and function that vary according to graft source differences: BM vs. G-PB.Methods and Results: To assess the effects of pDC source on overall survival and GvHD, we used an established MHC mismatched model of murine BMT (C57BL/6 to B10.BR). To test whether the graft source of donor pDC was relevant to GvHD, we used flow cytometry to sort populations of HSC and T cells from untreated donor mice and pDC from either untreated BM or G-CSF mobilized splenocytes. We performed a BMT with 5,000 HSC, 1 million T cells, and either 50,000 BM or G-PB pDC from C57BL/6 mice into B10.BR recipients. Overall survival was significantly reduced among recipients of G-PB donor pDC compared with recipients of BM pDC, while late stage GvHD was higher in recipients of G-PB pDC (Fig. 1).To determine possible differences in function of pDC from each graft source: BM vs. G-PB, we assessed cytokine and enzymatic profiles by flow cytometry. Intracellular levels of IL-12 was significantly higher in CpG stimulate purified BM pDC compared to G-PB pDC co-cultured with purified T cells stimulated by anti-CD3/CD28 beads (Fig. 2). Additionally, Th1 polarization was higher in T cells sitmulated with anti-CD3/CD38 and cocultured with BM pDC, resulting in higher TNFa and IFNy production from these T cells. Levels of intracellular cytokines IFNa and IL-10 and levels of IDO showed no significant differences between pDC from Bm vs. G-PB.The transplant detailed above was repeated with BM pDC from wild-type (WT) mice or IL-12 KO mice. Overall survival of recipients of IL-12 KO BM pDC was significantly reduced when compared with recipients of WT BM pDC (Fig. 3).Conclusion: These data confirm that donor BM pDC are protective against lethal GvHD and indicate a loss of GvHD protection in donor pDC from G-PB grafts due to decreased inducible IL-12 synthesis. Because both graft sources are widely used clinically, mechanisms to recapitulate the immune-modulating properties of BM pDC in pDC of G-PB grafts are of great interest to the BMT field. [Display omitted] DisclosuresWaller:National Institutes of Health: Research Funding; Celldex: Consultancy; Cerus: Equity Ownership; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding; Katz Foundation: Research Funding; AMGEN: Consultancy; Chimerix: Equity Ownership; Helocyte: Consultancy; Cambium Medical Technologies: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; PRA: Consultancy; Coulter Foundation: Research Funding.

Allogeneic Transplantation for TP53+ AML: Prognostic Factors for Survival

IntroductionTransplant outcomes for TP53+ AML have been poor and survival is arguably one of the worst in transplantation. Here we hypothesized that outcomes of TP53+AML/MDS patients are not uniformly poor and aimed to identify prognostic factors for survival for patients with TP53+ AML receiving allogeneic hematopoietic stem cell transplantation.MethodsA total of 83 patients with AML, MDS or MDS progressed to AML treated between 02/2011-03/2017 who received their first allogeneic transplant were identified in the departmental database. The median age was 60 years (range 18-75), median hematopoietic stem-cell transplantation - comorbidity index (HCT-CI) was 4 (range 0-9), Karnofsky performance status (KPS) was >80% (56%). 31 patients (37%) were in CR1/2 the rest were beyond CR1/2. Conditioning regimens were busulfan-based (83%) for HLA-matched transplants and melphalan-based (16%) for HLA mismatched transplants. Donors were matched related (33%), matched unrelated (49%), haploidentical (14%), cord blood (CB) (2%). 39% of the patients had a bone marrow graft while 59% had peripheral blood graft, 2% of the patients had a CB graft. 87% of AML patients were de novo and 13% treatment-related, and 13% of AML/MDS were secondary. Cytogenetic risk group was poor-risk in 99% of the patients. Eleven patients (13%) received maintenance azacitidine post-transplant.ResultsThe median follow-up survivors was 12 months (2.2-42 months). Twenty-one patients (25.3%) were alive at last follow-up and 14 patients (16.9%) disease-free. The median overall survival (OS) was 8 months with 1-year OS 35% (range 25-46%), median progression-free survival (PFS) was 5 months with 1-year PFS 25% (range 16-35%). Non-relapse mortality (NRM) and relapse at 1 year were 20% and 53%, respectively. We evaluated predictors for NRM, relapse, PFS and OS considering the following variables: age, HCT-CI>4 vs. ≤4, KPS >80% vs. ≤80%, disease status CR1/2 vs. other, conditioning regimen, cell source, secondary AML/MDS (Y/N), treatment-related AML/MDS (Y/N) and azacitidine maintenance as a time-dependent variable. In univariate analysis (UVA), factors associated with NRM were HCT-CI>4 (HR2.8,CI1.1-7.6,p=0.04), melphalan-based regimen (HR 4.2,CI1.5-12,p=0.01), KPS≤80% (HR2.6,CI0.9-7.5,p=0.08) and treatment-related AML/MDS (HR3.3,CI1.2-9,p=0.02), while in multivariate analysis (MVA) factors associated with NRM were melphalan-regimen (HR6.5,CI2.1-20,p=0.001), KPS≤80% (HR2.8,CI0.96-8,p=0.06) and treatment-related AML/MDS (HR4.2,CI1.5-12,p=0.007).In MVA, factors associated with better PFS were KPS>80% (HR2.1,CI1.1-3.7,p=0.02) and mid-range busulfan-based conditioning with AUC 20,000-25,000 (HR1.7,CI0.96-3.0,p=0.07), while factors associated with worse OS were HCT-CI>4 (HR3.9,CI1.2-13,p=0.03), KPS≤80% (HR3.04,CI1.6-5.9,p=0.001) and disease not in CR1/2 (HR4.1,CI1.5-11,p=0.004). Since the HR were comparable for the 3 factors, we assigned a score of 1 for each factor and evaluated OS based on the number of adverse prognostic factors present. If none of these factors were present the 1-year OS was 67% (N=14; HR0.2,CI0.05-0.5,p=0.001), if 1 factor was present the 1-year OS was 39% (N=36; HR0.4,CI0.2-0.7,p=0.002) if >1 factor was present the 1-year OS 17% (N=27) (reference) (Figure 1). Azacitidine maintenance did not impact OS or PFS in these patients.In conclusion, patients with TP53+AML can be stratified based on performance status, comorbidity index and disease status at transplant with significant impact on survival. Unfortunately two thirds of all patients were transplanted beyond CR1/2, which could be a contributing factor for the overall poor outcomes in these patients. [Display omitted] DisclosuresKhouri:Novartis: Research Funding.

Pro-Tmune, the Next Generation Graft for Allogeneic Hematopoietic Cell Transplantation: Phase 1 Safety and Efficacy Data

ProTmune, an ex vivo modulated mobilized peripheral blood (mPB) graft, has FDA fast track designation for the reduction of incidence and severity of acute graft-versus-host disease (GvHD) in patients undergoing allogeneic hematopoietic cell transplantation (HCT). Despite the use of standard protocols to prevent its occurrence, 50 to 60% of patients receiving an unrelated allogeneic HCT experience acute GvHD within 60 days post-HCT.Here we report early Phase 1 safety and efficacy data from PROTECT, the ongoing Phase 1 open-label / Phase 2 blinded and randomized controlled trial (RCT) of ProTmune in adult subjects with hematologic malignancy undergoing HCT following myeloablative conditioning using a matched unrelated donor and receiving standard GvHD prophylaxis of methotrexate and tacrolimus.As of July 31, 2017, five subjects were administered ProTmune in the Phase 1 portion of PROTECT. Underlying hematologic diseases included ALL, AML and MDS. Subjects were predominantly female (80%), with mean age of 54 (range 34 to 66) and mean weight of 75.2 +/- 14.7 kg. All subjects remain on study as of July 31, 2017 with a median follow-up of 53 days (range 33 to 224 days).ProTmune was manufactured on-site the day of HCT (Day 0) by pharmacologically modulating a mPB graft ex vivo with two small molecules (FT1050 and FT4145) to enhance the biologic properties and therapeutic function of the graft. All manufacturing runs have been successful, maintaining high cell viability (87.9 +/- 10.9%) and CD34+ cell recovery (87.7 +/- 13.5%). Successful pharmacologic modulation was confirmed by the marked increase in the percentage of cells positive for the potency marker CXCR4 (5.0 +/- 0.1% pre-manufacture to 67.3 +/- 7.9% post-manufacture). ProTmune, containing on average 6.8 +/- 3.6 x106 CD34+ cells/kg and 2.5 +/- 0.5 x108 CD3+ cells/kg, was administered on Day 0.ProTmune has been well tolerated in these five subjects. ProTmune-related AEs were limited to two cases of Grade 1 vomiting on the day of administration. No ProTmune-related SAEs have been reported. All subjects engrafted with no reports of secondary graft failure. Median time to neutrophil engraftment was Day 15 (range Day 14 to Day 21). There have been no disease relapse or deaths.The primary efficacy endpoint is incidence of acute GvHD through Day 100. In Phase 1, one subject was reported to have an acute GvHD event by Day 100 (limited to skin with complete recovery on methylprednisolone).The Phase 1 portion of PROTECT is projected to enroll 6-10 subjects. By the 2017 ASH meeting, enrollment will be complete with at least six subjects projected to have reached Day 100+, and the safety and efficacy results will be updated. [Display omitted] DisclosuresMaziarz:Novartis Pharmaceuticals Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Consultancy, Honoraria; Juno Therapeutics: Honoraria; Kite Therapeutics: Honoraria; Athersys, Inc: Patents & Royalties. Saad:Spectrum: Honoraria; Actinium: Consultancy. Diaz:Fate Therapeutics, Inc: Employment. Medcalf:Fate Therapeutics, Inc: Employment, Equity Ownership. Fremgen:Fate Therapeutics, Inc.: Employment. Storgard:Fate Therapeutics, Inc: Employment.

Graft-Versus-Host Disease (GVHD)-Free Relapse-Free Survival (GRFS) and Chronic Gvhd (CRFS) in Alternative Donor Hematopoietic Cell Transplantation (HCT) in Pediatric Patients

BACKGROUNDGRFS is a composite endpoint developed by the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) to reflect the major outcomes post HCT. Events in GRFS include grade 3-4 acute GVHD (aGVHD 3-4), systemic therapy-requiring chronic GVHD (cGVHD), relapse, or death. We reported that bone marrow (BM) grafts from matched sibling donor (MSD) led to best GRFS at 1-and 2-years compared with peripheral blood (PB) grafts from any donor or umbilical cord blood (UCB). (Holtan et. al. Blood 2015 & Mehta et.al. Haematologica. 2016) These studies excluded haploidentical (haplo) and mismatched (MM)-HCT.Here, we analyzed GRFS and chronic GVHD-free relapse-free survival (CRFS) among alternative donor HCT (UCBT and one-antigen MM (7/8)-BM HCT) for pediatric patients who did not have a MSD or matched unrelated donor. However, because too few patients received 7/8-PB or haplo with post HCT cyclophosphamide, these were excluded. METHODSData were obtained from the CIBMTR. Patients <18 years of age with acute myeloid leukemia or acute lymphoblastic leukemia (ALL) in remission who received UCBT or 7/8-BM HCT between 2000 and 2014 after myeloablative conditioning were included. Exclusion criteria were prior autologous or allogeneic HCT, ex-vivo T-cell depletion or CD34 selection and those with UCB unit <4/6 HLA. Multivariable analysis was done using Cox's proportional hazards (PH) modeling with time-dependent adjustments as needed for stepwise modeling, selecting factors using a threshold of 0.05 for both entry and retention in the model. CRFS was defined as absence of cGVHD, relapse and death. RESULTS1613 patients were analyzed, including UCBT (n=1441) and 7/8-BM (n=172). Overall, most patients had ALL (63%), 64% received total body irradiation based conditioning, about 60% received ATG or alemtuzumab and 86% UCBT used a single unit. Methotrexate based GVHD prophylaxis was more commonly in 7/8-BM (79%) than in UCBT (15%). Other characteristics were similar in two groups. Median follow-up was 71 months in UCBT and 96 months in 7/8-BM groups.In multivariate analysis, 7/8-BM had similar GRFS (HR 1.19, p=0.1) and CRFS (HR 1.11, p=0.36) as UCBT [Fig 1a & 1b]. Risks of aGVHD 3-4 (HR 1.68, p=0.007) at any time and cGVHD (HR 7.11, p<0.0001) beyond 14 months, but not before, were significantly higher in 7/8-BM than UCBT. 7/8-BM group had similar risk of relapse (HR 1.26, p=0.11) as UCBT. Disease free survival (DFS; HR 0.87, p=0.4) was similar in both groups up to 14 months beyond which 7/8-BM had inferior DFS (HR 2.33, p=0.0008). Overall survival (OS; HR 1.08, p=0.6) was similar in both groups. CONCLUSIONUCBT and 7/8 BM groups yield similar long term morbidity and mortality as measured by GRFS and CRFS, but 7/8-BM had higher risk of aGVHD 3-4, late cGVHD, and inferior late DFS. No preference of alternative donor source can be made; based upon this analysis, both are acceptable options. Improvements in GVHD control could broaden the applicability of partially matched BM grafts. [Display omitted] DisclosuresHoltan:Incyte: Other: One-time advisory board member. Arora:Takeda Oncology: Consultancy.

Graft-Versus-Host Disease (GVHD)-Free Relapse-Free Survival (GRFS) and Chronic Gvhd (CRFS) in Alternative Donor Hematopoietic Cell Transplantation (HCT) in Adults

BACKGROUNDGRFS is a composite endpoint developed by the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) to reflect the major outcomes post HCT. Events in GRFS include grade 3-4 acute GVHD (aGVHD 3-4), systemic therapy-requiring chronic GVHD (cGVHD), relapse, or death. We reported that bone marrow (BM) grafts from matched sibling donor (MSD) led to best GRFS at 1-and 2-years compared with peripheral blood (PB) grafts from any donor or umbilical cord blood (UCB). (Holtan et. al. Blood 2015 & Mehta et.al. Haematologica. 2016) These studies excluded haploidentical (haplo) and mismatched (MM)-HCT. The outcomes of this composite endpoint in alternative donor HCT is unknown. Here, we analyzed GRFS and chronic GVHD-free relapse-free survival (CRFS) among alternative donor HCT (UCBT, haplo, one-antigen MM (7/8)-BM or 7/8-PB HCT) for patients with no MSD or matched unrelated donor. METHODSPatients with acute myeloid leukemia (AML) or acute lymphoblastic leukemia in remission, chronic myeloid leukemia or myelodysplastic syndrome who received alternative donor HCT from 2000-2014 were included. Only those haplo patients who received post-HCT cyclophosphamide and only those UCBT done using fludarabine, cyclophosphamide and total body irradiation myeloablative (MA) or reduced intensity (RIC) with or without antithymocyte globulin (ATG) were analyzed. Exclusion criteria were prior autologous or allogeneic HCT, ex-vivo T-cell depletion or CD34 selection and those with UCB unit <4/6 HLA match. Multivariable analysis was done using Cox's proportional hazards (PH) modeling with time-dependent adjustments as needed for stepwise modeling, selecting factors using a threshold of 0.05 for both entry and retention in the model. CRFS was defined survival without cGVHD or relapse. RESULTS2198 patients were analyzed, including UCBT (n=838), haplo (n=159), 7/8-BM (n=241) and 7/8-PB (n=960). Groups (except haplo) were further divided by conditioning and ATG use [Table 1]. AML was most common diagnosis (52%). As expected, patients who received MA conditioning were younger (median 35-43 years) than those who got RIC (median 58-61 years). 81% of UCB group received double cord. Most patients in haplo group received BM graft (71%), and a majority (82%) were from 2012-2014; consequently, follow-up of haplo group (median 25 months) was shorter than others (49-96 months).In multivariate analysis of early post-HCT outcomes (within 4.5 months) adjusted for year of HCT and other covariates, as compared to haplo, UCB, 7/8-BM (MA, no ATG) and 7/8-PB had inferior GRFS. However, beyond 4.5 months, haplo, UCB and 7/8-BM (MA +/- ATG) had similar GRFS while 7/8-PB had inferior GRFS. [Fig 1] Likewise, beyond 4.5 months, as compared to haplo, CRFS was similar in UCB and 7/8-BM (MA +/-ATG), while 7/8-PB had inferior CRFS.As compared to Haplo, risk of aGVHD was significantly higher in all groups, except UCB (RIC + ATG) and the risk of cGVHD (beyond 4.5 months) was higher in 7/8-BM (MA, no ATG) and 7/8-PB but similar in UCB and 7/8-BM (MA + ATG). As compared to haplo, risk of relapse was significantly lower after UCB (MA), 7/8-BM (MA +ATG) and 7/8-PB (MA, no ATG), similar in UCB (RIC + ATG), 7/8-BM (MA, no ATG), 7/8-PB (MA + ATG) and 7/8-PB (RIC +/-ATG) and higher in UCB (RIC, no ATG). Haplo had superior disease free survival compared to UCB, 7/8-PB (MA, no ATG) and 7/8-PB (RIC + ATG), but it was similar in 7/8-PB (MA + ATG) and 7/8-BM (MA +/-ATG). Similarly, haplo had superior overall survival compared to any other group. CONCLUSIONLong-term morbidity and mortality as measured by GRFS and CRFS are similar in UCBT, haplo and 7/8 BM groups. The use of 7/8-PB should be avoided given substantially poor GRFS and CRFS. As 7/8-BM group included only younger patients who received MA conditioning, no conclusion can be drawn about its outcome in older patients, for whom either haplo or UCB remain as the preferred donor source. These outcomes may also be a reflection of different GVHD prophylaxis regimens rather than donor type. Ongoing randomized comparison of UCBT versus haplo in the BMT CTN 1101 trial will prospectively evaluate these two groups. [Display omitted] DisclosuresHoltan:Incyte: Other: One-time advisory board member. Arora:Takeda Oncology: Consultancy.

Efficacy of Early Post-Transplant Vaccination Using a Prime and Boost Strategy Is Independent of a Prior History of GvHD: Results from BMT CTN 0201

Introduction: BMT CTN 0201 was a randomized trial of bone marrow (BM) vs G-CSF mobilized peripheral blood (G-PB) grafts in 550 patients with leukemia or MDS undergoing allogeneic hematopoietic stem cell transplantation from unrelated donors. Responses to the 23-valent-pneumococcal vaccine are poor in elderly and immune-compromised patients, including allo-transplant recipients. A secondary objective of BMT CTN 0201 compared responses to post-transplant vaccination using protein-based diphtheria-tetanus (dT) vaccine followed by two doses of a diphtheria-pneumococcal polysaccharide conjugate (PCV7) and the 23-valent pneumococcal polysaccharide vaccine (PPV23).Methods: Vaccination started at 6 months post-transplant with dT followed by PCV7 at 7 and 9 months and PPV23 at 11 months post-transplant. Hepatitis B vaccination occurred at 6, 7 and 11 months. Serological responses in BMT CTN 0201 patients surviving to one year post-transplant were compared among those vaccinated per protocol (N=71), those that received partial vaccination (N=58) or no vaccines (N=39). Primary end-points were the fractions of vaccinated individuals with protective antibody titers to the 14 common pneumococcal bacterial serotypes, Hepatitis B, diphtheria and tetanus. Clinical history of acute or chronic GVHD, blood B-cells and T-cells, and serum immunoglobulin levels were studied as covariates of protective immunological responses.Results: Overall survival at 3 years across the cohorts that received full, partial, or no vaccination was similar (81%, 87%, 84%). Lack of compliance with protocol vaccination did not vary according to whether subjects had a history of acute or chronic GVHD. The frequency of patients with prior history of grade 2-4 acute GVHD or chronic GVHD were similar across the three cohorts (82%, 90%, 82%), with comparable rates of severe grades 3-4 acute (10%, 12%, 13%) and extensive chronic GVHD (63%, 67%, 64%, respectively). Serological responses to vaccines did not differ between recipients of BM vs G-PB grafts, or whether patients had a history of grade 2-4 acute GVHD or chronic GVHD. Serological responses were highly associated with protocol-specified vaccination, with median (range) of titers (ug/mL) for fully vaccinated versus non-vaccinated individuals for HepB: 10.81 (0.05-110) versus 0.49 (0.05-63) p=0.01; tetanus, 2.80 (0.16-20) versus 0.40 (0.05-20) p<0.001; diphtheria: 1.62 (0.05-20) versus 0.08 (0.05-1.2) p<0.001; as well as protective antibody titers to each of the component pneumococcal epitopes shared between PCV7 and PPV23 (Table 1, N=71 fully vaccinated and N=48 with no pneumococcal vaccines). Among the fully-vaccinated cohort, a greater proportion had protective antibodies to individual pneumococcal serotypes present in the PCV7 “prime” vaccine (median 66%) versus those restricted to the PPV23 “boost” vaccine (median 41%). Serum levels of IgA, IgM, and IgG at 12 months post-transplant were correlated with the kinetics of B-cell recovery in the blood at 3, 6, and 12 months. Antibody titers to tetanus, diphtheria and 8/14 of the tested pneumococcal serotypes were correlated with total serum IgG levels at 12 months post-transplant. Titers to diphtheria, a T-cell dependent antigen, were correlated with day +100 blood levels of T-cells, myeloid dendritic cells and B-cells (p<0.05), while antibody levels to serotypes in PCV7 were correlated with day +100 levels of B-cells in the blood.Conclusion: The efficacy of vaccination to specific pneumococcal serotypes among recipients of allogeneic transplants is enhanced by priming with dT and PCV7 prior to vaccination with the PPV23 vaccine. Vaccination is effective in patients with a history of acute or chronic GVHD. Strategies that enhance B-cell recovery post-transplant may improve responses to vaccines, especially those that are T-cell independent. [Display omitted] DisclosuresWaller:National Institutes of Health: Research Funding; Helocyte: Consultancy; Chimerix: Equity Ownership; Cerus: Equity Ownership; Coulter Foundation: Research Funding; PRA: Consultancy; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding; Cambium Medical Technologies: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Katz Foundation: Research Funding; AMGEN: Consultancy; Celldex: Consultancy.

Prediction of Severe Acute Graft-Versus-Host Disease (aGVHD) Based on Whole Transcriptome Sequencing of Donor CD4 T Cells

Background: After decades of intensive research, GVHD remains the unrelenting nemesis of patients and physicians involved in allogeneic hematopoietic cell transplantation (AHCT). While some plasma biomarkers can predict response to GVHD therapy at day 14-post AHCT and at the onset of clinical GVHD, an ideal tool would enable prediction of GVHD prior to transplantation. Recent systems immunology analyses of human cohorts have shown that immune parameters are stable over time within a given person, but display substantial inter-individual variations. We therefore hypothesized that inter-individual variations in T-cell function could explain a fundamental question in GVHD pathogenesis: while all allogeneic donor-recipient pairs are histo-incompatible, only a fraction of recipients present severe aGVHD post-AHCT. In order to address this question, we searched for potential correlation between the whole transcriptome of donor CD4 T cells and the occurrence of aGVHD in their recipient.Methods and Patients: We performed RNA-sequencing on purified CD4 T cells from 330 AHCT donors from three centers (Boston, Calgary, Montreal). Donor and recipient were 8/8 HLA matched siblings. CD4 T lymphocytes were isolated from blood samples collected from donors prior to hematopoietic stem cell mobilisation and collection. Recipients with acute myeloid leukemia (AML), acute lymphoid leukemia (ALL), chronic myeloid leukemia (CML), or myelodysplastic syndromes were included. Both myeloablative and reduced intensity conditioning were included. Peripheral blood and marrow graft were used as source of stem cells. Recipients received standard calcineurin based GVHD prophylaxis. Acute(a) and chronic(c) GVHD were graded according to Glucksberg and IBMTR classification. RNA was poly-A enriched and sequenced on an Ion Proton to an average depth of 40M reads. Expression profiles were computed using TopHat and cuffquant. A nested cross-validation protocol was used to train a logistic regression with either L1 or L2 regularization to predict the onset of acute GVHD of IBMTR grade C and above. An outer 10-fold cross-validation was used for the selection of hyper-parameters (number of genes considered, type and weight of the regularization) and an inner leave-one-out cross-validation was used for the predictor training. Area under the ROC curve (AUC) and relative risks were computed based on out-of-sample predicted risk of GVHD.Results: aGVHD developed in 43%. According to IBMTR classification, severe and potentially lethal aGVHD of grade ≥ C was diagnosed in 13.6% of recipients.Figure 1A presents the cross-validated performance of logistic regression classifier using either all annotated transcripts (solid line, AUC = 0.62) or expression profiles in which miRNA and snoRNA were removed (dashed line, AUC = 0.49). Discrimination between high-risk vs. low-risk donors was absolutely contingent upon the inclusion miRNA and snoRNA expression profile in our algorithm. Depending on the selected threshold applied to our predictive score, we can identify donors whose relative risk to trigger severe aGVHD is increased by 1.8- to 4-fold (Figure 1B depicting bootstrap-based confidence intervals (95%) for relative risks derived for all possible thresholds).Conclusion: Transcriptome sequencing of donor CD4 T cells can segregate donors that carry a high- vs. low-risk of causing severe aGVHD in their recipient. The key variable here was the miRNA and snoRNA expression profile. Considering that i) miRNA and snoRNA detected with our method (poly-A enriched RNA) are mostly located in introns, and ii) that intron retention regulates CD4 T-cell activity (PMID: 27369383), the most parsimonious mechanistic explanation is that the extent of intron retention in donor CD4 T cells determines the risk of severe aGVHD in recipients. Transcriptome sequencing of donor CD4 T cells could become a useful tool to optimize donor selection, personalized GVHD prophylaxis and improve AHCT outcome. [Display omitted] DisclosuresBusque:Novartis Canada Inc.: Honoraria; Pfizer: Honoraria; Bristol Myer Squibb: Honoraria; Paladin: Honoraria.

Ex Vivo T Cell-Depleted and In Vivo T Cell-Depleted Allogeneic Stem Cell Transplantation in Patients with Acute Myeloid Leukemia in First Complete Remission Resulted in Similar Overall Survival Survival: On Behalf of the ALWP of the EBMT and the MSKCC

Background. Myeloablative allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a well-established therapy for adult patients with acute myeloid leukemia (AML) in first complete remission (CR1) with intermediate or high-risk cytogenetics. However regimen-related toxicities, in particular graft-versus-host disease (GVHD) have limited its widespread use. Therefore several strategies have been developed to deplete T cells in order to prevent GVHD. In vivo T-cell depletion (TCD) using antithymocyte globulin (ATG) with an unmanipulated graft is widely used in some centers in Europe, while other centers have develop an effective platform based on ex-vivo TCD CD34 selected (CD34+) graft. The aim of the current study was to compare these two strategies for GVHD prevention.Patients and methods. This retrospective analysis assessed the outcome of all consecutives patients over 18 years at time of transplant with an AML in CR1 with intermediate or high risk cytogenetics who received an in-vivo or ex-vivo T cell depleted myeloablative allo-HSCT using busulfan or total body irradiation based conditioning regimen between 2005 and 2011 and reported to the EBMT ALWP registry centers or at Memorial Sloan Kettering Cancer Center (MSK), respectively. Patients treated in EBMT centers received in vivo TCD with either thymoglobuline or grafalon ATG. In addition, all patients in the ATG group received GVHD prophylaxis consisting of a calcineurin inhibitor in combination with another drug. Patients treated at MSK received an ex-vivo TCD graft (CD34+). TCD was performed by immunomagnetic CD34+ cell selection of peripheral blood grafts. No additional GVHD prophylaxis was administered in those patients. Main transplant outcomes including refined GVHD-free/relapse-free survival (GRFS) were evaluated.Results. A total of 525 patients were included (363 ATG, 162 CD34+) with a median age of 46 (19-77) and 58 (range, 20-73) years, respectively (p<0.001). The ATG cohort had more unrelated donors (67.5% vs. 54.9%, p=0.006). Median follow-up was significantly longer in the CD34+ cohort [58.0 (range, 6-139.0), vs. 24.5, 51.9-131.0) months, p<0.001], therefore all patients were censored at 2 years for comparison between groups. There were no additional differences between cohorts including donor/recipient gender, CMV status and cytogenetic risk. The CD34+ cohort had less relapse (21.6% vs. 30%, p=0.03), grade II-IV aGVHD (11.3% vs. 21.2%, p=0.006), III-IV aGVHD (1.3% vs. 6.2%, p=0.01), cGVHD (2.5% vs. 27.6%, p<0.0001) and extensive cGVHD (0.6% vs. 11.3%, p=0<0.0001) and a higher GRFS (61% vs. 47%, p=0.0007) while there was no difference regarding OS (67.6% vs. 56.4%, p=0.31), LFS (61% vs. 57.9%, p=0.29) and NRM (17.4%, vs 12.1%, p=0.16). In multivariate analysis, the cumulative incidence of grade II-IV aGVHD and chronic GVHD were higher in the ATG cohort [HR 2.0 (95% CI 1.1-3.7), p=0.02 and HR 15.1 (95% CI 5.3-42.2), p<0.0001]. There were no statistical differences between both approach in terms of relapse, NRM, OS, and LFS. Parameters associated with a lower GRFS were ATG group, adverse cytogenetic and use of an unrelated donor [HR 1.7 (95% CI 1.2-2.5) p=0.001; HR 1,7 (95% CI 1.3-2.2) p=0.0002 and HR 1.5 (95% CI 1.1-2.0) p=0.01]. Cytogenetic status (high risk versus intermediate risk) also has a significant impact on relapse incidence [HR 2.1 (95% CI 1.4-3.0), p<0.0001] and LFS [HR 1.7 (95% CI 1.2-2.3) p=0.0006]. Finally there was significantly more death related to infection in the CD34 group (16/52, vs. 19/112, p=0.04).Conclusion. The cumulative incidence of acute (total and severe) and chronic GVHD were higher after allo-HSCT with ATG, leading to a lower GRFS in those patients. In contrast, enhance immunosuppression in the CD34+ group lead to a higher incidence of infectious related death. Overall NRM, OS and LFS are similar after ex-vivo CD34 selected and in-vivo ATG TCD allo-HSCT from related/unrelated donors in patients with AML in CR1 and intermediate/high-risk cytogenetic. Both approaches are associated with a good disease control and a high OS, and should be compared in a prospective randomized trial. DisclosuresMohty:Sanofi: Honoraria, Speakers Bureau.

The Combination of GROβ and AMD3100 Leads to Rapid and Robust Mobilization of Hematopoietic Stem Cells in Nonhuman Primates

▪Introduction: Mobilized peripheral blood grafts are currently the predominant source of hematopoietic stem and progenitor cells (HSPC) for both autologous and allogeneic transplantation. The most common clinical hematopoietic stem cell mobilization protocol is five days of Filgrastim (G-CSF). This regimen requires daily injections, has been associated with bone pain and often results in unpredictably low yields. A rapid mobilization method that ideally only required a single treatment and had robust and predictable kinetics would be a significant improvement over the current standard of care. In mice, a unique CXCR2 agonist, GROβ, induces rapid mobilization of stem and progenitor cells 15 minutes after a single injection. When co-administered with plerixafor (AMD3100), an inhibitor of CXCR4, a synergistic increase in mobilization results, with a graft enriched in highly engraftable hematopoietic stem cells (Hoggatt et al., Blood 2016 128:368). Here, we present data demonstrating that combination treatment with GROβ and AMD3100 synergistically mobilizes CD34+ cells and colony forming units (CFU) in nonhuman primates (NHP).Methods: Cynomolgus macaques were injected with G-CSF (10 µg/kg/day, s.c. for four days), AMD3100 (1 mg/kg, s.c. once) or GROβ (various doses and routes) alone and in combination with AMD3100. Blood was collected at various times post treatment and analyzed by multicolor flow cytometry to quantitate HSPC numbers. Additional aliquots of mobilized blood were plated in methylcellulose and CFU were enumerated seven days later.Results: We tested the effect of GROβ alone or in combination with AMD3100 in Cynomolgus monkeys. As published previously, administration of G-CSF, AMD3100 or G-CSF+AMD3100 induced significant mobilization of hematopoietic stem and progenitor cells. In comparison, a single injection each of GROβ+AMD3100 yielded 4-fold more CD34+ cells compared to four days of G-CSF (p < 0.01). While the combination of G-CSF+AMD3100 mobilized significantly more CD34+ cells compared to GROβ+AMD3100 (p < 0.0001), the numbers of CD34+ CD90+ CD45RA- cells, representing the most primitive of hematopoietic stem and progenitor cells, were equivalent between treatment groups. Similarly, GROβ+AMD3100 treatment elicited 7-fold more CFU compared to animals treated with G-CSF (p < 0.01), 3.5-fold more CFU compared to AMD3100 (p < 0.01) and equivalent CFU compared to G-CSF+AMD3100. Importantly, the frequency of CFU among the CD34+ cells was significantly greater with GROβ+AMD3100 (1 in 4) compared to G-CSF (1 in 10) or G-CSF+AMD3100 (1 in 25). In contrast to the increased CD34+ numbers and CFU, white blood cell (WBC) and neutrophil counts were significantly lower with GROβ+AMD3100 compared to AMD3100 alone or G-CSF+AMD3100.Conclusions: We describe a rapid mobilization method that within four hours of a single treatment results in robust hematopoietic mobilization in nonhuman primates. The GROβ+AMD3100 regimen enriches for primitive CD34+ CD90+ CD45RA- stem and progenitor cells with increased colony forming capacity compared to CD34+ cells mobilized with G-CSF+AMD3100, suggesting a significant graft quality difference with the new regimen. The ability to rapidly mobilize primitive HSC with increased CFU frequency may allow effective single day mobilization of HPSCs for patients requiring a HSCT and be especially useful for HSC based gene therapy and gene editing protocols where HSPC grafts enriched for primitive HSC may reduce manufacturing costs and ensure durability of the gene modified HSC. The ability to achieve increased HSPC numbers without dramatically increasing WBC and neutrophils may be especially advantageous in patient populations where G-CSF mobilization is not well tolerated such as Sickle Cell Disease, or where G-CSF leads to increased disease activity such as in autologous transplant for Multiple Sclerosis. A single treatment that results in robust mobilization that is equivalent to G-CSF may allow for a one-day collection method of donor stem cells, and these findings in nonhuman primates support clinical exploration. DisclosuresFalahee:Magenta Therapeutics: Employment, Equity Ownership. Goncalves:Magenta Therapeutics: Employment, Equity Ownership. Hyzy:Magenta Therapeutics: Employment, Equity Ownership. Proctor:Magenta Therapeutics: Employment, Equity Ownership. Hoggatt:Magenta Therapeutics: Consultancy, Equity Ownership, Patents & Royalties. Morrow:Magenta Therapeutics: Employment, Equity Ownership. Cooke:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties.

The 47th Annual Meeting of the European Society for Blood and Marrow Transplantation: Pharmacist Committee – Poster Session (P183-P186)

Background: CD6 is a co-stimulatory receptor predominantly expressed on T cells. CD6high CD4+ T cells were recently shown to drive Th1/Th17 immune responses in inflammatory bowel disease and may have a similar role in acute graft-versus-host disease (aGHVD). The CD6 ligand, activated leukocyte cell adhesion molecule (ALCAM), is expressed on antigen presenting cells, as well as epithelial and endothelial cells of aGVHDtarget organs (e.g. skin, GI tract). Previous studies in patients receiving allogeneic hematopoietic cell transplants showed that ex vivo depletion of donor CD6+ T cells lowered the incidence of aGVHD, providing a rationale for therapeutically targeting CD6 in aGVHD. Itolizumab is a humanized IgG1 monoclonal antibody that binds CD6 and blocks interaction with ALCAM to inhibit T cell activity and trafficking that is being evaluated as treatment for aGVHD. Methods: Here we present interim study results from EQUATE (as of 2020 Nov 13), an ongoing US-based Phase 1b/2 study of itolizumab in combination with steroids for newly diagnosed severe aGVHD (Grade III-IV). Phase 1b involves an open-label, dose-escalation study evaluating doses from 0.4 to 2.4 mg/kg (IV Q2 weeks through Day 57). Results: Ten subjects have completed treatment through Day 57: 0.4 mg/kg (n=4), 0.8 mg/kg (n=3), and 1.6 mg/kg (n=3). All subjects received corticosteroids at an initial dose of 1-2 mg/kg/day. Baseline characteristics include mean age of 48, 90% male, 90% white, 80% with peripheral blood graft source, 80% with HLA matched donor, mean time to GVHD onset of 43 days, and 100% with GI involvement. Across dosing cohorts, all subjects experienced at least 1 adverse event (AE), with hypomagnesemia (n = 3) and peripheral edema (n = 3) being the most common. Most AEs were mild to moderate in severity. One mild infusion reaction AE was noted. Serious AEs that are not unexpected for severe aGVHD on systemic immune suppression were noted in 5 subjects, including recurrent GVHD (n = 1), sepsis (n = 2;1 was considered a DLT) and fever (n = 1). COVID-19 (n = 1) and disseminated nocardia (n = 1) were also reported. Across cohorts, the overall response rate (ORR;complete response [CR] + partial response [PR] + very good partial response [VGPR]) was 80% at Day 29, with 70% of subjects experiencing CR and 10% experiencing VGPR. ORR was sustained through Day 57. At Day 57, 7 subjects had tapered steroids by ≥80% (Fig 1B). Immunologically, itolizumab dose-dependently decreased CD6 levels on T cells within 24 h of first dose, which was maintained throughout the treatment period, particularly at 0.8 and 1.6 mg/kg (Fig 1C). Conclusions: In summary, the preliminary safety and high response rates of itolizumab with steroid therapy in newly diagnosed severe aGVHD is encouraging. Its early risk-benefit profile supports continued study and evaluation in future randomized controlled trials.

Early results of phase 1 study of JSP191, an anti-CD117 monoclonal antibody, with non-myeloablative conditioning in older adults with MRD-positive MDS/AML undergoing allogeneic hematopoietic cell transplantation.

7035 Background: Myeloablative allogeneic hematopoietic cell transplantation (AHCT) is potentially curative for myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but toxicities of conditioning limit its use in older or frail patients. Non-myeloablative (NMA) conditioning achieves better tolerability, at the expense of higher rates of relapse. We have developed a first-in-class monoclonal antibody (mAb), JSP191, which inhibits stem cell factor binding to CD117 (c-Kit), thereby depleting normal and MDS/AML disease-initiating hematopoietic stem cells (HSC). In pre-clinical models, anti-CD117 mAbs potently synergize with low dose total body radiation (TBI) to deplete HSC and facilitate donor cell engraftment. We reasoned that adding JSP191 to a standard NMA conditioning of 2 Gy TBI and fludarabine (Flu) would be safe and result in depletion of measurable residual disease (MRD) in older adults with high-risk MDS/AML entering AHCT. Methods: We report on the first 6 enrolled subjects in our Phase 1 trial (NCT#04429191) of JSP191/TBI/Flu as AHCT conditioning in MDS/AML patients, ≥ 60 years, with MRD detected by cytogenetics (cyto), difference from normal flow cytometry (flow), and/or next-generation sequencing (NGS). Primary endpoints are safety and tolerability of JSP191/TBI/Flu and JSP191 pharmacokinetics. Secondary endpoints include engraftment, donor chimerism, MRD clearance, GVHD, NRM, EFS, and OS at 1 year. JSP191 at 0.6 mg/kg was administered intravenously; serum concentration of JSP191 was used to confirm timing to begin Flu at 30 mg/m2/day x 3 days [Transplant Day (TD)-4, -3, -2] and TBI 2 Gy on TD0. Peripheral blood grafts from HLA-matched related or unrelated donors were administered on TD0 (10-13 days after JSP191). GVHD prophylaxis was tacrolimus, sirolimus, and mycophenolate mofetil. Results: All subjects are still on trial, and there have been no infusion toxicities and no JSP191-related serious adverse events. All subjects engrafted with neutrophil recovery TD+19 to TD+26, and showed ≥94% donor myeloid chimerism in the blood at TD+28. All 3 evaluable subjects with TD+90 follow up showed complete donor (≥95%) total and myeloid chimerism and MRD elimination (Table). Conclusions: These early results are the first to demonstrate that JSP191/TBI/Flu is safe, well-tolerated, and capable of clearing MDS/AML MRD in older adults undergoing NMA AHCT. Clinical trial information: NCT04429191. [Table: see text]

The results of multicenter phase II, double-blind placebo-controlled trial of maintenance ixazomib after allogeneic hematopoietic cell transplantation (alloHCT) for high-risk multiple myeloma (MM) from the Blood and Marrow Transplant Clinical Trials Network (BMT CTN 1302).

7003 Background: The role of alloHCT and subsequent maintenance for the treatment of high-risk MM has not been fully defined. We evaluated the efficacy of ixazomib maintenance therapy after alloHCT using reduced intensity fludarabine/melphalan/bortezomib (Flu/Mel/Bort)-based conditioning regimen to treat patients with high risk MM. Methods: This phase 2 prospective multicenter trial (NCT#02440464) enrolled adults 70 years or younger, with either high-risk MM defined by cytogenetics or plasma cell leukemia (PCL) or relapse within 24 months after autologous HCT. Conditioning regimen consisted of Flu/Mel/Bort. Patients received HLA-matched donor unmanipulated peripheral blood grafts. Graft-versus-host disease (GVHD) prophylaxis was tacrolimus plus methotrexate. Between days +60 and +120 after allogeneic HCT, patients were randomly assigned (1:1, stratified by number of prior progressions) to receive ixazomib at 3 mg orally on days 1, 8, 15 on a 28-day cycle or matching placebo for 12 cycles. The study aimed to enroll 138 patients with 110 patients achieving randomization for a progression-free survival (PFS) comparison ixazomib maintenance vs. placebo. Results: Fifty-seven patients from 15 centers were enrolled (2015-18), of whom 52 (91.2%) received allogeneic HCT, and 43 (82.7%) proceeded to randomization (21 assigned to ixazomib and 22 to placebo). Enrollment was delayed by a clinical hold after enrollment of 17 patients due to toxicity concerns related to the conditioning regimen. Remaining patients were enrolled after an amendment reduced bort to a single pre-HCT dose. These and other delays in enrollment led to premature study closure. Median age was 56 (range, 35-65) years, and 33 patients (57.9%) had high-risk MM with 9 patients (15.8%) with primary PCL. At 24 mo post alloHCT, PFS and OS among all alloHCT recipients was 52% and 85% respectively with a corresponding transplant-related mortality (TRM) of 11%. At 21 mo post-randomization, ixazomib vs. placebo groups had similar PFS (55.3% vs. 59.1%) and OS (95% vs. 87%, p = 0.17). Cumulative incidences of grade III-IV acute GVHD at 100 days (9.5% vs. 0%) or chronic GVHD at 12 months (69% vs 64%) were similar. Best response, incidence of progression for ixazomib vs. placebo groups were similar while cumulative incidence of transplant-related mortality (TRM) at 21 months was 0.0% and 4.5% (90%CI: 0.5-16.5%), respectively. Conclusions: AlloHCT with reduced intensity fludarabine/melphalan and a single pre-HCT dose of bortezomib is safe and can produce durable disease control in extremely high-risk patients. ixazomib maintenance after alloHCT could not be assessed as intended due to early termination of study, but there was no signal of an impact in outcomes. Clinical trial information: NCT02440464.

A phase 2 trial of GVHD prophylaxis with PTCy, sirolimus, and MMF after peripheral blood haploidentical transplantation

AbstractThe introduction of posttransplant cyclophosphamide (PTCy) made performing allogeneic hematopoietic cell transplantation (HCT) from HLA haplotype–incompatible donors possible. In a setting of PTCy and tacrolimus/mycophenolate mofetil (MMF) as a graft-versus-host disease (GVHD) prophylaxis, a peripheral blood (PB) graft source as compared with bone marrow reduces the relapse rate but increases acute GVHD (aGVHD) and chronic GVHD (cGVHD). This phase 2 trial assessed sirolimus and MMF efficacy following PTCy as a GVHD prophylaxis after PB haploidentical HCT (haplo-HCT). With 32 evaluable patients (≥18 years) enrolled, this study had 90% power to demonstrate a reduction in 100-day grade II-IV aGVHD to 20% from the historical benchmark of 40% after haplo-HCT using PTCy/tacrolimus/MMF. At a median follow-up of 16.1 months, the primary end point of the trial was met with a day-100 grade II-IV aGVHD cumulative incidence of 18.8% (95% confidence interval [CI], 7.5% to 34.0%). There were no graft-failure events and the 1-year probability of National Institutes of Health (NIH) moderate/severe cGVHD was 18.8% (95% CI, 7.4% to 34.0%), nonrelapse mortality was 18.8% (95% CI, 7.4% to 34.0%), relapse was 22.2% (95% CI, 9.6% to 38.2%), disease-free survival was 59.0% (95% CI, 44.1% to 79.0%), GVHD-free relapse-free survival was 49.6% (95% CI, 34.9% to 70.5%), and overall survival was 71.7% (95% CI, 57.7% to 89.2%) for the entire cohort. These data demonstrate that GVHD prophylaxis with sirolimus/MMF following PTCy effectively prevents grade II-IV aGVHD after PB haplo-HCT, warranting prospective comparison of sirolimus vs tacrolimus in combination with MMF following PTCy as GVHD prophylaxis after PB HCT. This trial was registered at www.clinicaltrials.gov as #NCT03018223.