HLA Disparity Research Articles

Engraftment Kinetics and Recipient Chimerism Increase to Predict Leukemia Relapse By Ptcy and Non-Ptcy Transplant

Recipient chimerism increase has been used to predict leukemia relapse in post-hematopoietic cell transplant (HCT) patients with conventional GVHD prophylaxis. However, the value of recipient chimerism increase in patients with post-transplant cyclophosphamide (PTCy) is not clear. We compared PTCy to conventional GVHD prophylaxis (non-PTCy) patients regarding engraftment kinetics and the clinical significance of the 2 chimerism parameters, increasing mixed chimerism (IMC) and degree of recipient chimerism increase at the first event (Δ increase). We studied both total and T-cell-specific chimerism. While leukemia relapse is manifested by an increase in total cell recipient chimerism, an increase in T-cell-specific recipient chimerism may be more impactful in predicting relapse because of the effect of increased T-cell-specific chimerism on the graft-versus-leukemia effect.A total of 220 patients (PTCy: 44, non-PTCy: 176) with AML, MDS, and ALL underwent HCT at our institution from January 2014 to September 2020 and were included in this study (Table). Chimerism was tested at least monthly for the first 3 months, followed by every 3 months up until 1-year post-HCT, and then every 6-12 months thereafter. Short tandem repeat or quantitative PCR were used when percent recipient chimerism was ≥5% and <5%, respectively. Cumulative incidence of competing events and Gray's test were applied for engraftment analysis. Relapse and non-relapse mortality were considered as competing risks for engraftment. Mantel-Byar test and Simon-Makuch plot with landmark analysis were used to visualize disease-free survival (DFS) curves. The Cox proportional hazards model with time-dependent covariates was performed to identify the factors affecting relapse.PTCy patients achieved complete donor chimerism (CC) in total cells earlier at a deeper level (>99%) as compared to non-PTCy patients. Deeper total cell CC (>99%) was achieved in 79.5% of PTCy vs. 51% of non-PTCy patients at day 250, while CC (>95%) was achieved in almost 90% of patients in both groups within 100 days (Figure 1A and B). In comparison, the percentage of PTCy patients achieving T-cell-specific CC was significantly higher at day 250 post-HCT: CC (>95%/>99%) was 79.7%/68.4% in PTCy patients vs. 56.1%/37.5% in non-PTCy patients (Figure 1C and D).To evaluate their impact in predicting relapse, IMC was stratified into no IMC, 1 IMC (≥1 nonconsecutive IMC), and 2 IMC (≥2 consecutive IMC), and degree of recipient chimerism increase at the first event (Δ increase) was stratified into <0.1% (no Δ increase), 0.1-1%, and ≥1%.Two IMC (total), 1 IMC (T-cell), and 2 IMC (T-cell) groups were associated with shorter DFS in non-PTCy patients but not in PTCy patients (Figure 2). One and 2 IMC groups (both total and T-cell) were associated with relapse risk in non-PTCy patients. Furthermore, 1 IMC (T-cell) in non-PTCy patients showed a strong association in relapse risk (HR 7.0 (95%CI 2.83-17.8) p<0.0001).Δ increase ≥1% (total and T-cell) and Δ increase ≥0.1% (T-cell) were associated with shorter DFS in non-PTCy patients, while only Δ increase ≥1% (T-cell) only showed a trend towards shorter DFS in PTCy patients (Figure 3). The Cox regression model showed Δ increase ≥1% in both total, and T-cell chimerism was associated with relapse risk in non-PTCy patients (HR 6.4 (95%CI 2.9-14.2) p<0.0001 and HR 7.2 (95%CI 2.9-18.1) p<0.0001, respectively). Δ increase ≥0.1% (T-cell) in non-PTCy patients was also associated with relapse risk (HR 7.2: 95%CI 2.5-20.4, p<0.0001). In comparison, no association was found between Δ increase and relapse risk in PTCy patients.This is one of the most extensive studies investigating engraftment kinetics and the association of total and T-cell recipient chimerism increase to predict leukemia relapse in PTCy and non-PTCy HCT recipients. We found that PTCy HCT recipients achieved deeper engraftment earlier as compared to non-PTCy recipients. In addition, the two chimerism parameters (IMC and Δ increase) are less reliable in predicting relapse in PTCy than non-PTCy recipients. However, other factors, such as disease type, conditioning regimen, and donor HLA disparity, may have affected engraftment kinetics and the significance of chimerism parameters. Further investigations are warranted to elucidate the impact of the engraftment kinetics and recipient chimerism increase to predict relapse, especially in the PTCy setting. [Display omitted] DisclosuresRakszawski: SeaGen: Speakers Bureau. Naik: Takeda: Other: Virtual Advisory Board Member ; Sanofi: Other: Virtual Advisory Board Member ; Kite: Other: Virtual Advisory Board Member. Rybka: Spark Therapeutics: Consultancy; Merck: Consultancy. Claxton: Astellas: Other: Clinical Trial; Novartis: Research Funding; Astex: Research Funding; Cyclacel: Research Funding; Daiichi Sankyo: Research Funding; Incyte: Research Funding.

Significance of Degree of HLA Disparity When Using Haploidentical Donors with T-Replete PBSC and Post-Transplantation Cyclophosphamide (PTCy) in Acute Myeloid Leukemia (AML) in First Complete Hematologic Remission (CR1)

Background: Haploidentical allogeneic hematopoietic cell transplantation (haplo) has expanded applicability of the procedure to patients for whom a suitable HLA compatible donor was not available in the past. A small multicenter retrospective study of 185 patients with hematologic malignancies who received a nonmyeloablative preparative regimen followed by infusion of bone marrow (BM) hematopoietic cells from haploidentical donors showed no significant association between the number of HLA mismatches (HLA-A, -B, -C, and -DRB1 combined) and risk of acute grade 2-4 graft-versus-host disease (GVHD) (hazard ratio [HR]=0.89; P=0.68 for 3-4 mismatches vs fewer antigen mismatches). This haploidentical transplant platform has certainly evolved. Nowadays, G-CSF mobilized peripheral blood stem cells (PBSC) are commonly used owing to its increased convenience vis-à-vis performing a BM harvest.Study population: Here, we evaluate post transplant outcomes when using haploidentical donors with T-replete PBSC and PTCy in AML in CR1. A total of 494 patients (4/8 HLA mismatch (group 1)=360, 2-3/8 HLA mismatch (group 2)=134) underwent the procedure at an EBMT participating center. The primary endpoints were cumulative incidences of grade 2-4 acute GVHD and chronic (all grades) GVHD. Secondary endpoints included cumulative incidence of relapse (RI), non-relapse mortality (NRM), leukemia-free (LFS) and overall survival (OS) and GVHD-free relapse-free survival (GRFS).Results: Group 1 and group 2 were not statistically different in regards to median age at allografting (54.1 vs. 56.1 years, p=0.51), median year of haplo transplantation (2018 vs. 2018, p=0.36), incidence of de novo AML (86.4% vs. 88.1%, p=0.63), Karnofsky equal or more than 90 (77.5% vs. 79.1%, p=0.70), and use of myeloablative conditioning (MAC) (44.7% vs. 48.5%, p=0.45). Patients in group 1 had a longer time from diagnosis to haplo-transplantation (5.3 vs. 4.9 months, p=0.03). In multivariate analysis, group 1 and group 2 did not differ in cumulative incidence of grade 2-4 acute GVHD (Hazard ratio (HR)=0.89 (95%CI=0.62-1.26), p=0.51) but group 1 had a significantly higher incidence of chronic (all grades) GVHD (HR=1.49 (95%CI=1.02-2.16), p=0.04). There was no difference in RI (HR=0.73 (95%CI=0.47-1.14), p=0.17), NRM (HR=1.25 (95%CI=0.78-2.02), p=0.36), LFS (HR=0.95 (95%CI=0.69-1.31), p=0.76), OS (HR=1.09 (95%CI=0.76-1.55), p=0.64) and GRFS (HR=1.07 (95%CI=0.81-1.42), p=0.64) between the groups. Presence of adverse cytogenetics was independently associated with higher RI (HR=1.90 (95%CI=1.20-2.99), p=0.006), inferior LFS (HR=1.59 (95%CI=1.15-2.19), p=0.005), inferior OS (HR=1.48 (95%CI=1.05-2.08), p=0.03), and worse GRFS (HR=1.54 (95%CI=1.17-2.04), p=0.002).Conclusion: Results show that patients undergoing haplo-transplantation with 4/8 (vs. 2-3/8) HLA mismatches have a higher incidence of chronic GVHD (all grades) without adversely affecting acute grade 2-4 GVHD, RI, LFS, OS and GRFS. DisclosuresLabopin: Jazz Pharmaceuticals: Honoraria. Bazarbachi: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Hikma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees. Blaise: Jazz Pharmaceuticals: Honoraria. McDonald: BioCryst Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Forcade: Novartis: Other: travel grant. Ciceri: IRCCS Ospedale San Raffaele: Current Employment. Mohty: Takeda: Honoraria; Astellas: Honoraria; Adaptive Biotechnologies: Honoraria; Novartis: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Sanofi: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Gilead: Honoraria; Jazz: Honoraria, Research Funding; Pfizer: Honoraria; Amgen: Honoraria.

Effectiveness of T-Cell Replete Haploidentical Hematopoietic Stem Cell Transplantation for Refractory/Relapsed B Cell Acute Lymphoblastic Leukemia in Children and Adolescents.

Background: The prognosis of refractory/relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL) remains dismal owing to acquired resistance to chemotherapeutic agents. This study aimed to evaluate the efficacy of T-cell replete HLA haploidentical hematopoietic stem cell transplantation (TCR-haplo-HSCT) for pediatric refractory/relapsed BCP-ALL (RR-BCP-ALL).Methods: Nineteen pediatric patients with RR-BCP-ALL underwent TCR-haplo-HSCT between 2010 and 2019 at the Fukushima Medical University Hospital. The disease status at TCR-haplo-HSCT included complete remission (CR) in eight patients and non-CR with active disease in 11 patients. Total body irradiation-based, busulfan-based, and reduced-intensity conditioning regimens were employed in 11, 6, and 2 patients, respectively. Low-dose anti-thymocyte globulin (thymoglobulin, 2.5 mg/kg) was used in all patients. Graft-vs.-host disease (GVHD) prophylaxis was administered with tacrolimus, methotrexate, and prednisolone.Results: All patients received peripheral blood stem cells as the stem cell source. The HLA disparities in graft vs. host directions were 2/8 in one, 3/8 in five, and 4/8 in 13 patients. Among 18 patients who achieved primary engraftment, acute GVHD occurred in all 18 evaluable patients (grade II, 9; grade III, 8; grade IV, 1), and chronic GVHD was observed in 10 out of 15 evaluable patients. Three patients died because of transplant-related mortality. The 3-year overall survival (OS) and leukemia-free survival rates were 57.4 and 42.1%, respectively. Compared to patients older than 10 years in age (N = 10), those younger than 10 years in age (N = 9) showed an excellent OS rate (3-year OS rate: patients < 10 years old, 100%; patients > 10 years old, 20% [95% confidence interval, 3.1–47.5]; p = 0.002).Conclusions: We suggest that TCR haplo-HSCT with low-dose ATG conditioning has the potential to improve the transplantation outcomes in patients with RR-BCP.

Impact of HLA disparity on the risk of overall mortality in patients with grade II-IV acute GVHD on behalf of the HLA Working Group of Japan Society for Hematopoietic Cell Transplantation.

Acute graft-versus-host disease (aGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Stem cell source or HLA disparity may exert a significant impact on the overall survival (OS) after the development of aGVHD. In order to clarify this point, we performed a retrospective analysis using a database of the Japan Society for HCT. We analyzed the clinical outcomes of 10,035 patients who developed grade II-IV aGVHD. The median age of the patients was 48 years. The probability of 2-year OS after the onset of grade II-IV aGVHD in the study cohort was 54.1%. The multivariate analysis showed that the HLA ≥2-loci mismatched related donor and HLA 1-locus mismatched unrelated donor were significantly associated with an inferior OS after grade II-IV aGVHD. In a subgroup analysis, peripheral blood stem cells and HLA disparity were associated with an inferior OS in patients who received related or unrelated HCT. Thus, the clinical outcome after grade II-IV aGVHD significantly varied as per the combination of the presence of HLA disparity and stem cell source. Further research using other databases is necessary to confirm our findings.

Haploidentical Hematopoietic Stem Cell Transplantation: A New Transplantation Modality Implemented In a Recent Accredited FACT Institution In Latin America

IntroductionThe Foundation for the Accreditation of Cellular Therapy (FACT) has developed and implemented programs of voluntary inspection and accreditation for hematopoietic cellular therapy, and for cord blood banking. These programs are based on the standards of the clinical and laboratory professionals of the American Society of Blood and Marrow Transplantation (ASBMT), the International Society for Cellular Therapy (ISCT), and NETCORD. Our transplantation service was the first Hospital in Latin America to be accreditated by FACT in 2012. FACT accreditated hospitals might have a positive impact in Implementing new procedures and treatment protocols. Haploidentical SCT program was developed in our institution during FACT accreditation process. Since high complexity procedures challange transplantation units, we believe that conducting protocols after FACT accreditation helped the achievment of better standard of care that might be translated in results comparable with international transplantation centres. SCT from Haploidentical donor can be one therapeutic option specially for patients with no available MRD or MUD. In order to overcome HLA disparity, more intensive immunossupresion is usually used that can be associated to higher TRM. These difficulties demand a well stablished transplantation unit. Here we show the first 25 patients who recieved haploidentical SCT during FACT accreditation in a single institution in Brazil. Patients and methods: From april 2008 to july 2013, 25 patients were treated with haploidentical SCT. The median follow-up time was 3,3 months (range ). 8 (32%) patients had AML, 1 (4%) ALL, 1 (4%) JMML, 1(4%) LH, 1 (4%) MDS. 7 (28%) had adrenoleukodystrophy x-linked, 3(23%) had SAA and 2(28%) SCID. 8 (33%) patinets had refreactory disease. Median age at transplantation was 3.3 (range 1-72) years. 12 (48%) patients were in pediatric age range (1 to 18) years. 13 (54%) had donor/receptor ABO incompatibility. 10 (40%) patients were transplanted after myeloablative conditioning regimen (Bussulfan/Fludarabine or Busulfan/fludarabine/thiotepa) and 15(60%) after non-myeloablative conditioning regimen (Fludarabine/cyclophosphamide/TBI200cGy). 22 (88%) patients have received bone marrow as stem cell source and 3 (12%) peripheral blood stem cells. Median total nucleated cell x 108/Kg was 5.5 (range 3.0 to 10.34). Median CD34+x106/Kg 3.61 (range 1.48 to 7.06). Post transplant immunosuppression consisted of tacrolimus/MMF plus post transplant Cyclophosphamide in 22 (88%) patients, steroids plus CsA or tacrolimus in 2 (8%) and T cell depleted graf with no immunosupression in one SCID patient. All patients engrafted by day 28 after transplantation and 4 patients had secondary graft rejection. Only one (4%) patient developed synusoidal obstruction syndrome. 7 (28%) patients developed Acute graft-verus-host disease (3 grade I/II and 4 grade III/IV). 16 patients (64%) developed CMV reactivation. At the end of the follow-up 21 (84%) were alive. Four patients died from relapse at day 100 post transplant, 2 from infection and 1 from coronary heart disease. Sencondary graft failure had a negative impact in overal survival (HR: 14 (IC: 1,2-157), p= 0,033). Conclusion: The FACT accretidation process can promote improvement and progress in stem cell transplantation process, by controlling every aspect that impacts the quality of products and therapeutic care. In our center, there was a process developed in order to meet FACT standards that brought better patient care. We have shown the first 25 haploidentical patients who was treted after this accreditation, showing similar results when comparing to international centres and previous publications. We believe that these results could only be achieved in a transplant unit that meets specific quality control guided by FACT. Disclosures:No relevant conflicts of interest to declare.

Genetic susceptibility to acute graft versus host disease in pediatric patients undergoing HSCT.

The most frequent complication of allogeneic hematopoietic stem cell transplantation is acute Graft versus Host Disease (aGVHD). Proliferation and differentiation of donor T cells initiate inflammatory response affecting the skin, liver, and gastrointestinal tract. Besides recipient-donor HLA disparities, disease type, and the conditioning regimen, variability in the non-HLA genotype have an impact on aGVHD onset, and genetic variability of key cytokines and chemokines was associated with increased risk of aGVHD. To get further insight into the recipient genetic component of aGVHD grades 2-4 in pediatric patients, we performed an exome-wide association study in a discovery cohort (n = 87). Nine loci sustained correction for multiple testing and were analyzed in a validation group (n = 168). Significant associations were replicated for ERC1 rs1046473, PLEK rs3816281, NOP9 rs2332320 and SPRED1 rs11634702 variants through the interaction with non-genetic factors. The ERC1 variant was significant among patients that received the transplant from HLA-matched related individuals (p = 0.03), bone marrow stem cells recipients (p = 0.007), and serotherapy-negative patients (p = 0.004). NOP9, PLEK, and SPRED1 effects were modulated by stem cell source, and serotherapy (p < 0.05). Furthermore, ERC1 and PLEK SNPs correlated with aGVHD 3-4 independently of non-genetic covariates (p = 0.02 and p = 0.003). This study provides additional insight into the genetic component of moderate to severe aGVHD.

The Relationship between HLA Disparity and Clinical Outcomes in Peripheral Blood T Cell Replete Haploidentical Hematopoietic Cell Transplantation

Introduction: For patients undergoing mismatched unrelated donor hematopoietic cell transplant (HCT), increased HLA mismatch has been associated with inferior survival.Whilehaploidentical HCT (haplo-HCT) with high dose post-transplantation cyclophosphamide (PTCy) offers a viable alternative for patients who do not have a matched sibling donor or matched unrelated donor, limited data are available regarding the impact of HLA disparity on outcomes. Specifically, no analysis to date has examined the role of mismatch degree in the graft-versus-host (GvH) and host-versus-graft (HvG) directions in a large, heterogenous cohort of patients undergoing peripheral blood T cell replete haplo-HCT. Thus, the purpose of our study was to examine the relationship between HLA disparity and clinical outcomes in patients receiving a peripheral blood T cell replete haplo-HCT.Methods: We performed a single center retrospective study on 148 patients receiving PTCy-based peripheral blood T cell replete haplo-HCT from January 2010 to September 2016 (see table of patient characteristics). All patients age ≥ 18 were included regardless of diagnosis. Data on the match status at the following HLA loci were collected: A, B, C, DRB1, and DQB1. Patients were excluded from analyses for incomplete HLA loci data. Total mismatches (MM), class I, and class II mismatches were studied individually and mismatches were further classified as bidirectional, host-versus-graft (HvG), or graft-versus-host (GvH). The primary outcome was overall survival, and secondary outcomes included relapse-free survival, relapse, treatment-related mortality, acute graft-versus-host disease (GVHD), chronic GVHD, neutrophil engraftment, and platelet engraftment.Results: HLA disparity was not associated with overall survival, relapse-free survival, relapse, treatment-related mortality, acute GVHD, or chronic GVHD. Greater HvG MM was associated with slower platelet and neutrophil engraftment. Specifically, patients with2 class II HvG MM's had significantly longer platelet engraftment time (median 35 vs. 28 days, p=0.025) when compared with 0-1 mismatches. Similarly, 4-5 total HvG MM had a trend towards longer platelet engraftment (median 35 vs. 31 days, p=0.056) when compared with 1-3 total HvG MM. 3 Class I HvG MM had a trend towards longer neutrophil engraftment (median 20 vs. 17 days, p=0.083) when compared with 0-2 class I HvG MM. Additionally, 2 class II HvG MM had a trend towards longer neutrophil engraftment (median 19 vs. 17 days, p=0.062) when compared with 0-1 class II HvG MM.Conclusions: A higher number of class II HvG mismatches was associated with longer platelet engraftment but a greater level of HLA disparity was not associated with other clinical outcomes. Consequently, our data does not support selecting haploidentical donors based on HLA mismatch. Limitations of this study include its small sample size, treatment at a single center, and retrospective nature. Future prospective studies are needed to validate these findings. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Haploidentical Hematopoietic Stem Cell Allogeneic Transplantation with High Dose Post Transplantation Cyclophosphamide for Patients over 60 Years of Age

Recent advances in the field of haploidentical hematopoietic stem cell transplantation (Haplo-SCT) allowed larger access to allogeneic treatment in absence of HLA-matched donor. Indeed, former limitations associated with HLA disparity could be overcome by the use of post-transplant cyclophosphamide (PT-Cy) as part of GVHD prophylaxis. Low toxicity observed after PT-Cy Haplo-SCT enabled its diffusion to older patients who are disproportionally affected with hematological malignancies. The aim of our study was to assess the outcome after Haplo-SCT in this specific setting of elderly patients.Inclusion criteria were: age >= 60 years; first Haplo-SCT for hematological malignancy at 2 institutions from 2011 to 2016; PT-Cy as part of GVHD prophylaxis. All types of graft source and conditioning regimens were allowed except sequential conditioning regimen.Geriatric assessment was performed previous Haplo-SCT by geriatric oncologist for patients aged of 65 years or more.One hundred and twenty-one consecutive patients who met inclusion criteria were included.Median age was 66 years (range: 60-75) whereas 23 patients (19%) were 70 years or more. Eighty-two patients were transplanted for myeloid malignancies (68%). Forty-eight patients (39%) had active disease at time of transplantation.Hematopoietic cell transplantation comorbidity index (HCT-CI) was >= 3 in 70 patients (58%) and disease risk index (DRI) was high or very high in 36 patients (30%). Conditioning regimens were based on reduced doses of busulfan (RIC; N=70; 58%) or on low dose TBI (NMAC; N=51; 42%).Peripheral blood stem cells were the most frequently used graft source (N=108; 89%). Ninety-four patients (78%) were transplanted using a child as donor. Fifteen patients received prophylactic donor lymphocyte infusion (DLI) in a median time of 109 days after transplant, as defined by full donor chimerism and no evidence of relapse. Median follow-up was 20 months (range: 6-58).Cumulative incidences of grade II-IV, grade III-IV acute GVHD and moderate to severe chronic GVHD were 23%, 10% and 10 % respectively. 3 patients developed GVHD after DLI. At 2 years, the cumulative incidence of non-relapse mortality (NRM) and relapse were 26% and 23 %, respectively.The 2-year overall survival, progression free survival, and survival with no relapse and no steroid-requiring chronic GVHD were 57%, 52%, and 43 %, respectively. Interestingly, HCT-CI was not able to predict differential outcome in this very specific setting of Haplo-SCT for elderly patients (2-year NRM: 0-2 vs. >=3: 21% vs. 29%, p=0.32).We did not found higher transplantation-related morbidity and mortality in patients aged of 70 years or more. Indeed, day-100 grade II-IV acute GVHD (<70 vs. >=70: 26% vs. 13%, p=0.12), 2-year moderate + severe chronic GVHD (<70 vs. >=70: 8% vs. 20%, p=0.15) and 2-year NRM (<70 vs. >=70: 27% vs. 18%, p=0.36Figure 1A) were not significantly increased in older patients. The very promising outcome in patients >= 70 years of age (PFS: 73%; OS 78%, Figure 1B) supports that a cautious selection of oldest patients allows achieving low toxicity using adequate preparation, mostly NMAC regimens.We can conclude that Haplo-SCT is a valid approach for elderly patients. While HLA disparity was initially considered as a limitation to transplant elderly patients, Haplo-SCT has finally appeared as a particularly well-adapted alternative in this population. The low incidences of GVHD (less than 10% of severe forms) using a PT-Cy platform could explain in part this specific observation and may challenge the use of unrelated donor which is associated with high incidences of GVHD, especially in older patients. Our study underlines that Haplo-SCT using PT-Cy can provide a low-toxicity allogeneic platform for elderly patients, based on which early active post-transplantation strategies should be developed for better disease control. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation from HLA-Identical Siblings Versus Unmanipulated Haploidentical Donors in Relapsing or Refractory Acute Myeloid Leukemia: A Retrospective Study from the ALWP of the EBMT

▪Introduction: Primary refractory or relapsing acute myeloid leukemia (R/R-AML) has very poor prognosis. Allogeneic hematopoietic stem cell transplantation (HSCT) may be the only chance of cure. Therefore a suitable donor should be rapidly searched for, in this setting. In those patients (pts) lacking an HLA-matched sibling donor (MSD), mismatched family donor (haploidentical, Haplo) may represent a valid and rapidly available option.Methods: Herein, we compared the outcomes of pts with R/R-AML undergoing first HSCT from either a MSD (n=1654) or Haplo (n=389) in the period 2007-2015. The Haplo group included pts receiving a T-repleted graft with post-transplant cyclophosphamide (PTCY, n=278), in vivo T-cell depletion (TCD, n=95), or both (n=16).Results: Median age at HSCT was 52 (range 18-74) years. Median follow-up was 16 and 22 months for MSD and Haplo recipients, respectively (p=0.11). At time of HSCT, 41% and 56% presented a primary refractory AML in Haplo and MSD groups, respectively (p<0.01). Compared to MSD, Haplo HSCT were performed more recently (median year 2013 versus 2011, p<0.01) with a higher number of pts having a poor Karnofsky performance status (22% versus 16%, p<0.01) and a positive serology for CMV (83% versus 71%, p<0.001) at time of HSCT, respectively. The latter also had more frequently undergone a previous autologous HSCT (8% vs 3%, p<0.01), had a longer interval from diagnosis to HSCT (7 versus 5 months, p<0.01), received more frequently bone marrow as stem cell source (47% vs 8%, p<0.01), a reduced intensity conditioning regimen (50% vs 43%, p<0.03), and a graft from a male donor (59% versus 53%, p<0.03) as compared to MSD recipients. Compared to Haplo, cumulative incidence (CI) of neutrophil engraftment was higher (93% versus 83%, p<0.01) and associated to a shorter median time to engraftment (15 versus 18 days, p<0.01) in MSD recipients. According to donor type, no differences were found in univariate analysis for the CI of grade II-IV acute graft-versus host disease (aGVHD)(28% versus 27%, p=0.37), while a lower CI of chronic GVHD (cGVHD) (27% versus 42%, p<0.01) and extensive cGVHD (12% and 19%, p<0.01) was observed in HSCT from Haplo compared to MSD, respectively. At two years, overall survival (OS) was 25% and 32% (p<0.01), leukemia-free survival (LFS) 19% and 27% (p<0.01) and GVHD/relapse-free survival (GRFS) 18% and 26% (p<0.01) in HSCT from Haplo and MSD, respectively. Relapse incidence (RI) was similar following HSCT from Haplo and MSD (50% vs 51%, p=0.60), while non-relapse mortality (NRM) was higher for Haplo transplants (31% vs 22% in HSCT from MSD, p<0.001), respectively. In a multivariate analysis adjusted for the differences between the two groups, Haplo HSCT was associated with lower OS (HR 1.19, p<0.04), LFS (HR 1.17, p<0.05) and GRFS (HR 1.22, p<0.02). Higher grade II-IV aGVHD was observed in Haplo recipients. Neither cGVHD (any grade) nor RI differed according to donor type (p=ns). Compared to MSD, Haplo recipients experienced a higher NRM (HR 1.4, p<0.02) mainly related to a higher incidence of infections (41% versus 25%, p<0.01). Regardless of donor type, age as a continuous variable was associated with lower RI (HR 0.99, p<0.01), lower OS (HR 1.01, p<0.01) and higher NRM (HR 1.02, p<0.01). The use of peripheral blood as stem cell source was independently associated with a higher risk of cGVHD (HR 1.64, p<0.01).Conclusions: Our results indicate that for pts with R/R-AML outcome is better with HSCT from a MSD compared to unmanipulated Haplo donor, mainly due to the higher NRM associated with transplants from Haplo and most probably related to a higher incidence of infections and grade II-IV aGVHD. Chronic GVHD as well as RI are similar, indicating once again that despite the broader HLA disparities with Haplo HSCT the graft versus leukemia effect is probably not stronger than after HSCT from MSD (Ringden O, on behalf of the ALWP; Leukemia 2016). In the absence of a MSD, Haplo HSCT may represent a valid alternative, with nearly one quarter of the R/R-AML pts surviving at 2 years from transplant. Future goals in the Haplo setting should be to reduce NRM and rate of infections in order to further improve outcomes. DisclosuresCiceri:GSK: Other: B-thalassemia gene therapy was developed by Fondazione Telethon and Ospedale San Raffaele and has been inlicenced by GSK that provides funding for the clinical trial, Research Funding. Mohty:Sanofi: Honoraria, Speakers Bureau.

Outcomes of Patients with Baseline Marrow Fibrosis at Allogeneic Hematopoietic Cell Transplantation

Introduction:Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative option for several relapsed and refractory hematologic malignancies, including acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Success of allo-HCT lies in complete engraftment of donor hematopoietic cells and reconstitution of donor hematopoiesis. Among the well-defined factors of poor engraftment include HLA disparity between recipient and donor, T-cell-depleted grafts, reduced-intensity conditioning, and low stem cell dose. However, bone marrow reticulin fibrosis (MF) was not clearly defined as a risk factor.Marrow fibrosis has not been observed to be associated with impaired engraftment in primary myelofibrosis patients undergoing allo-HCT. However, in patients with MDS a pre-existent MF showed a poor engraftment and secondary graft failure; Particularly, in patients with higher WHO grade fibrosis tend to have poor donor chimerism and transfusion dependency. But, this was not associated with any adverse effect on survival. Further studies have showed the time to neutrophil engraftment is prolonged in those with higher degree of MF but not in the lower grades. Studies evaluating these findings in AML with marrow fibrosis are lacking.The current study is aimed at estimating the incidence of poor engraftment in AML/MDS patients with MF who underwent allo-HCT at our institution and to compare the incidence between those with and without MF.Methods:We retrospectively reviewed all AML/MDS patients that underwent allo-HCT between 2006 and 2015 at Washington University, St Louis. We included patients aged >18, and that underwent first allo-HCT. Patients that underwent second or later allo-HCT were excluded. Pre-transplantation bone marrows biopsies were evaluated for evidence of reticulin fibrosis and WHO grade (low grade/0-1, high grade/2-3) prior to allo-HCT. Primary end point was complete donor engraftment status measured using PCR based single-tandem repeats at day 30 post-allo-HCT. Secondary end point was to evaluate neutrophil engraftment, absolute platelet engraftment, day 100 engraftment status and survival outcomes. Neutrophil and platelet engraftment were defined per standard CIBMTR criteria.The association between primary outcome and clinical risk factors was examine via univariate and multivariate logistic regression. The associations between neutrophil/platelet engraftment and clinical risk factors were examined via univariate and multivariate general linear modeling. The relationship between marrow fibrosis grade and overall survival, as well as competing risk survival of relapse and non-relapse mortality, was investigated by Cox proportional hazard regression.Results:Seven hundred and twenty-nine patients were included in the final analysis (grade 0/1 n=662; grade2/3 n=67) (Table 1). Patients in higher-grade fibrosis are relatively older (61 vs 56 years) are more likely to have MDS, likely to have active disease at transplantation (55% vs. 31%), and have had reduced intensity conditioning. Compared to patients with completed engraftment, patients in no-engraftment group are older (61.3 vs. 55.5; p= <0.0001) and a greater number of patients in that group have a higher grade of fibrosis (16% vs. 8%; p= 0.0064). Univariate analysis shows higher grade of MF is associated with engraftment failure at day 30 (odds ratio 2.247 95%CI 1.24-4.07; p= 0.008). However, in multivariate analysis, this significance was lost (odds ratio 1.77; CI 0.90-3.50; p= 0.10). MF grade was not associated with neutrophil and platelet engraftment, engraftment status at 100 days, overall survival, relapse free survival and non-relapse mortality. Factors associated with completed engraftment at day 30 post-allo-HCT are summarized in Table 2.Conclusions:Marrow fibrosis preceding allo-HCT was not associated with engraftment failure at day 30 or after transplantation with the adjustment for other risk factors.MF was not associated with other engraftment parameters or survival. Further analyses evaluating the effect of resolution of MF on survival outcomes is underway. It is imperative that several disease and transplantation characteristics play significant role than MF itself in engraftment failure supporting the theory that engraftment is an immunologic function. [Display omitted] DisclosuresVij:Amgen: Honoraria, Research Funding; Abbvie: Honoraria; Takeda: Honoraria, Research Funding; Konypharma: Honoraria; Janssen: Honoraria; Bristol-Meyers-Squibb: Honoraria; Jazz: Honoraria; Celgene: Honoraria.

Characterisation of Naive Immunological Profile of Umbilical Cord Blood: The Role of Mucosal-Associated Invariant T Cells and Functional Defects of T Cells and Natural Killer Cells

Patients undergoing allogeneic haematopoietic stem cell (HSC) transplantation are susceptible to infection and reactivation of viruses, such as cytomegalovirus, due to impairment of the T cell compartment following intensive immunosuppressive therapy. There is a growing interest in evaluating cell-mediated immunity to improve the management of these infections. Over the last two decades, umbilical cord blood (UCB) has emerged as an alternative source of cellular products for the treatment of a range of haematological disorders. UCB HSCs have a number of distinguishing characteristics which differentiate them from adult HSCs, including increased proliferation and increased in vitro colony forming capacity. The use of UCB as HSC grafts for allogeneic stem cell transplant has a number of advantages, including immediate availability and reduced risk of graft-versus-host disease despite donor-recipient HLA disparity. However, the limited number of HSCs present in a single UCB collection and incomplete immune reconstitution because of delayed HSC engraftment has restricted the use of cord blood in stem cell transplantation. In addition, UCB transplantation is associated with lack of transferred adoptive immunity, resulting in transplant related morbidity and mortality due to infectious complications. While the human neonatal immune system is considered to be immature compared with its adult counterpart, the role of the innate immune cells in the immunological naïvety is not fully understood.Here, we describe the collection and characterisation of UCB units collected from a series of Irish mothers who delivered term infants by elective caesarean at a major Irish maternity hospital. Pre analytical variables included maternal factors such as gestation at delivery, blood group, age, medical history and BMI, and neonatal factors such as birth weight and gender. Mononuclear cells (MNC) were isolated and the immunological profile was analyzed by flow cytometry for the surface markers CD3, CD4, CD5, CD8, CD19, CD34, CD45, CD56, CD161 and the Vα24Jα17, Vα7.2, Vδ1, Vδ2 and Vδ3 T cell receptors. Progenitor cell colony forming ability was assessed by CFU-GM and BFU-E assays. Stimulation of T cells, by cross-linking of CD3 and CD28 using tetrameric antibodies, and Natural Killer (NK) cells, with IL12/IL18 and target cells, was assessed by measurement of surface expression of CD107a and intracellular production of IFNγ, IL4 and IL17a.We showed no difference in the overall numbers of B cells, T cells (CD4+ and CD8+) and γδ T cells between UCB (n=23) and adult blood (n=4); however, NK cells (p<0.001) and mucosal-associated invariant T (MAIT) cells (p<0.0001) were significantly depleted in UCB. Stimulated UCB T cells and NK cells (n=17) showed significantly reduced IFNγ production compared to adult blood counterparts (n=4) (p<0.01) Following thaw of cryopreserved UCB MNC, we observed no significant change in CFU-GM, CD34+ cell concentration or immunological profile/function compared to fresh MNC (n=7).Our study suggests that reduced numbers of circulating innate immune cell populations, as well as reduced cytokine responses following stimulation, may contribute to the naïve immunological phenotype and hyporesponsiveness of UCB. Further investigation and manipulation of these innate immune cell populations could improve UCB transferred adoptive immunity potential and assist in the management of post allogeneic stem cell transplant viral infections. DisclosuresNo relevant conflicts of interest to declare.

Gvhd after PBSC-Haploidentical Stem Cell Transplantation (Haplo-SCT) with Post Transplantation-Cyclophosphamide (PT-Cy)

T-cell replete Haplo-SCT using PT-Cy as GVHD part of prophylaxis has become a valid option to perform allogeneic transplantation in patients without an available HLA-matched donor. The absence of additional ex vivo procedure has participated to its increasing use in the field of transplantation. Because of HLA disparity, bone marrow (BM) was initially chosen as stem cell source, based on previous observations of lower incidences of GVHD after HLA-matched donor transplantation, when using BM graft as compared with G-CSF mobilized peripheral blood stem cells (PBSC). In contrast, use of PBSC may improve engraftment and disease control favoring larger adoption of the procedure. However, the use of PBSC graft for Haplo-SCT remains controversial. We here report our experience of PBSC Haplo-SCT using PT-Cy for hematological malignancies.We selected patients (pts) with hematological malignancies who underwent Haplo-SCT using PT-Cy at 2 transplant centers from March 2012 to June 2016, using the following criteria: PBSC as graft source; first allogeneic transplantation; PT-Cy as part of GVHD prophylaxis. Patients with refractory acute leukemia who received sequential conditioning regimens were excluded. GVHD prophylaxis included PT-Cy (D+3 and D+4) in association with calcineurin inhibitors and MMF started from D+5.The aim of this retrospective study was to provide a comprehensive description of GVHD following PBSC Haplo-SCT with PT-Cy. Beyond calculation of the cumulative incidence of both acute and chronic GVHD, we precisely describe GVHD features by grading organ involvement and severity. In addition, we assess the prevalence of GVHD and immunosuppressive treatment (IST) at 3, 6, 9, 12, 15, 18, 21 and 24 months after Haplo-SCT in disease free patients, as well as quality of life.We retrospectively analyzed 181 consecutive pts with a median age of 60 years (19-73). Ninety-seven (54%) pts were affected by myeloid diseases, mostly (29%) AML. Disease risk index was high or very high in 47 pts (26%). Non-myeloablative conditioning regimen (low dose TBI + cyclophosphamide and fludarabine) was used in 92 pts (51%), while the remaining patiens received busulfan-based conditioning regimen, with reduced and myeloablative doses in 67 pts (38%) and 21 (12%) pts, respectively.The median CD34+ and CD3+ cells infused were 5.3 x 10^6/kg (range, 1.5-18.1) and 280 (range, 38-704), respectively.Median time to neutrophil recovery (ANC >500 x106/L) was 21 days (range, 17-112) and 30 days (range, 10-394) to platelet recovery (PLT > 20 G x 109/L).Between 24-48 hours after donor stem cells infusion, 88% of recipients experienced fever with chills (median temperature = 40,1°C). No microbiological proof of infection was found in most pts, while bacterial infection was identified in bloodstream culture in 9 % of pts.Fever completely disappeared the day after the last PT-Cy infused dose in 79% of patients.The incidence of grade II-IV and III-IV aGVHD was 23% and 8% at 100 days, respectively. Among patiens who developed aGVHD, 58 (82%) presented with isolated skin involvement, while gut GVHD was responsible for most grade III-IV GVHD (16/20, 80%).The cumulative incidence of cGVHD was 18% at 2 years. According to NIH classification, half of the patients who developed cGVHD presented with mild forms, without needing systemic treatment (mostly skin and mucosa involvement), while severe forms occurred in 3% of GVHD cases.As shown in Figure 1, at 6 months post Haplo-SCT, IST was discontinued in 40% of disease-free patients. In addition, most patients who were disease-free at 2 years were living with no immunosuppressive treatment (98%) and no GVHD (94%).At 2 years, NRM, relapse, PFS, OS and GRFS were 21%, 17%, 62%, 66% and 50%, respectivelyWe conclude that PBSC Haplo-SCT using PT-Cy is a feasible procedure, with low incidences of severe forms of both acute and chronic GVHD. In addition, we pointed out that almost all surviving patients were living without GVHD and IST at 2 years, suggesting a preserved quality of life. Thus, as previously shown using BM as graft source, PT-Cy allows performing T-replete Haplo-SCT with low incidence of GVHD also using PBSC, with very low long term GVHD-related morbidity. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Adoptive Immunotherapy with Rapidly-Generated Multivirus-Specific T Cells Against AdV, EBV, CMV, HHV6 and BK after Allogeneic Hematopoietic Stem Cell Transplant

Viral infections remain a significant cause of morbidity and mortality after allogeneic stem cell transplantation (HSCT). We now report on the outcomes of 67 patients infused with either donor-derived (n=21) or third party “off the shelf” (n=46) virus-specific T cells (VSTs) with activity against 5 common post-transplant viruses (EBV, CMV, Adv, BK, HHV6).We generated 84 clinical-grade VST lines by stimulating 30x106 PBMCs with overlapping peptide libraries spanning Adv (Hexon, Penton), CMV (pp65, IE1), EBV (LMP2, EBNA1, BZLF1), BKV (Large T, VP1) and HHV6 (U11, U14, U90) antigens. After a 9-11 day expansion phase in a G-Rex device in the presence of activating cytokines, a mean of 399x106 T cells (range 89-1006x106) were harvested. The lines were polyclonal, comprising both CD4+ (60±2%) and CD8+ (31±2%) cells and expressed central CD45RO+/CD62L+/CCR7+ (38±3%) and effector memory markers CD45RO+/CD62L-/CCR7- (10±1%). VST specificity was dependent on the donor's prior exposure to viruses; thus, 81/84 lines had activity against Adv (Hexon: 384±44; Penton: 293±50 SFC/2x105), 50/84 against CMV (IE1: 294±52; pp65 1009±194), 66/84 against EBV (LMP2: 153±26; EBNA1: 132±17; BZLF1: 91±25), 53/84 against BK (Large T: 134±22; VP1: 158±29) and 57/84 against HHV-6 (U90: 111±25; U14: 94±13; U11: 46±8).Twenty one allogeneic HSCT recipients were infused with donor-derived VSTs in a dose escalation study with informed consent; 4 on DL1 (5x106/m2), 4 on DL2 (1x107/m2) and 13 on DL3 (2x107/m2). Four patients received the cells prophylactically and remained free of viral infections up to 3 months post-infusion. The remaining patients were infused for one or more active infections. There were 4 cases of Grade I-II GvHD, of which only one required treatment with steroids. Based on viral load measurements and symptom assessment a single VST infusion successfully controlled active infections associated with all our targeted viruses (ORR 95%): CMV (7 CR, 1PR); EBV (7 CR, 1PR); Adv (6 CR); HHV6 (5 CR, 1PR, 1NR) and BKV (8 CR, 2 PR, 1 NR). Overall, we used VSTs to treat 7 cases of viral disease- EBV-PTLD (n=1), HHV-6 encephalitis (n=1), BKV hemorrhagic cystitis (HC) (n=5). The infused cells successfully cleared the EBV-PTLD (without rituximab) and HHV6 encephalitis, while all patients with BKV HC had marked improvement or resolution of symptoms post-VSTs.Based on the safety and efficacy profile of VSTs we extended our approach to third party recipients. To date we have treated 46 patients, all of whom had drug-refractory infections. Patients received 1-3 doses (fixed dose - 2x107 cells/m2) with 3rd party VSTs matching at one to six of eight HLA alleles. Despite the HLA disparity the cells have proven safe with three cases of de novo grade I-II GvHD documented. Third party VSTs successfully controlled active infections in 42 of 45 evaluable patients (ORR 94%): CMV (13 CR, 5 PR, 1 NR); EBV (2 CR); AdV (7 CR, 2 NR); BKV (5 CR, 14 PR); and HHV-6 (4 PR). Of note, 30 of 46 patients were treated for viral disease - CMV colitis (n=3), CMV encephalitis (n=1), EBV-PTLD (n=1), AdV respiratory tract infection (RTI) (n=2), AdV RTI and enteritis (n=1), AdV HC (n=1), HHV-6 encephalitis (n=2), BKV HC (n=17), BKV nephritis (n=2). All patients with BK-HC, 2 of 3 patients with CMV colitis, and the patients with CMV encephalitis, AdV RTI, enteritis and HC, and HHV-6 encephalitis had marked improvement or resolution of symptoms within 6 weeks following VST treatment. In more than 50% of responders (n=24) we detected an increase in the circulating frequency of VSTs post-infusion, which were confirmed to be 3rd party VST origin in 14 and remained detectable for up to 12 weeks post-infusion.Overall our experience with adoptively-transferred VSTs demonstrates not only the safety profile of the cells, even when administered as a 3rd party product, but also the efficacy of the infused cells in patients with up to 4 simultaneous/sequential infections, and HSCT recipients with virus associated disease. DisclosuresTzannou:ViraCyte LLC: Consultancy. Lulla:ASBMT Young Investigator Award: Research Funding; ASH Scholar Award: Research Funding; Leukemia Texas Research grant: Research Funding; Junior Faculty sees funding-Baylor College of Medicine: Research Funding; Lymphoma SPORE: Research Funding; Leukemia Texas: Membership on an entity's Board of Directors or advisory committees. Vera:Marker Therapeutics: Equity Ownership; ViraCyte LLC: Equity Ownership; Wilson Wolf Manufacturing: Consultancy. Rooney:ViraCyte LLC: Membership on an entity's Board of Directors or advisory committees. Heslop:Cell Medica: Patents & Royalties: EBV specific T cells, Research Funding; Viracyte: Equity Ownership; Marker Therapeutics: Equity Ownership; Celgene: Research Funding. Leen:ViraCyte LLC: Equity Ownership.

Incidence and risk factors of late-onset hemorrhagic cystitis after single umbilical cord blood transplantation with myeloablative conditioning regimen.

To explore the incidence and risk factors of late-onset hemorrhagic cystitis (LOHC) in patients undergoing single umbilical cord blood transplantation for hematological malignancies. Clinical data from 234 patients who consecutively underwent single UCBT using a myeloablative conditioning regimen without antithymocyte globulin in our center were retrospectively analyzed. In total, 64 (27.4%) patients developed LOHC with a median onset time of 40.5 (range 8-154) days, and 15 (6.4%) patients gradually developed grade III-IV LOHC. The incidence of LOHC was marginally higher in adults (31.0%) than in children (23.7%) (p = 0.248). HLA matching ≤ 6/8 (HR = 2.624, 95% CI 1.112-6.191, p = 0.028) was an independent risk factor for LOHC. The overall survival of LOHC patients (59.8%, 95% CI 61.7-85.5%) was significantly lower than that of patients without LOHC (86.8%, 95% CI 79.6-91.6%) at 130days post transplantation (p = 0.036). Patients with less well-matched grafts have a higher incidence of LOHC. Inherent deficiencies in immunity in the context of HLA disparity and more intense pharmacologic immunosuppression after severe acute graft-versus-host disease may contribute to viral activation. Prevention and treatment of LOHC have the potential to prolong long-term survival.

Impact of the combination of donor age and HLA disparity on the outcomes of unrelated bone marrow transplantation.

Impact of donor age considering HLA disparity on hematopoietic cell transplantation (HCT) outcomes has not been fully evaluated. We evaluated 8486 patients who received unrelated bone marrow transplantation (UR-BMT) from 8/8 or 7/8 HLA-matched donors. Compared to 8/8 HLA-matched younger donors (<40 years), 8/8 HLA-matched older donors (subdistribution hazard ratio [SHR], 1.16; 95% CI, 0.97-1.38) and 7/8 HLA-matched younger donors (SHR, 1.33; 95% CI, 1.11-1.58) were associated with increased risk of grade III-IV acute graft-versus-host disease (aGVHD). 7/8 HLA-matched older donors had further increased risk (SHR, 2.00; 95% CI, 1.68-2.38) due to interaction between donor age and HLA disparity (p for interaction = 0.038). Progression-free survival (PFS) after UR-BMT with 8/8 HLA-matched younger donors was comparable to that after UR-BMT with 8/8 HLA-matched older donors, whereas UR-BMT with 7/8 HLA-matched younger or older donors was significantly associated with lower PFS than UR-BMT with 8/8 HLA-matched younger donors (younger donor; HR, 1.12; 95% CI, 1.04-1.21, older donor; HR, 1.28; 95% CI, 1.17-1.40; p for interaction = 0.079). In conclusion, adverse effect of increased donor age requires attention, especially in HLA-mismatched UR-BMT due to interaction between donor age and HLA disparity. Intensive aGVHD prophylaxis may be required to improve outcomes after HCT with mismatched older donors.

High-Dose Cyclophosphamide and Tacrolimus as Graft-versus-Host Disease Prophylaxis for Matched and Mismatched Unrelated Donor Transplantation

The optimal prophylaxis regimen for graft-versus-host disease (GVHD) in the setting of single-locus mismatched unrelated donor (MMUD) allogeneic hematopoietic stem cell transplantation (alloHSCT) is unclear. The use of high-dose post-transplant cyclophosphamide (PTCy) after haploidentical transplantation is effective at overcoming the negative impact of HLA disparity on survival. Limited information is available regarding the efficacy of this strategy in alloHSCT from MMUDs. Most of the published studies have used the triple immunosuppressant model of haploidentical transplant combining PTCy with calcineurin inhibitors and mycophenolate mofetil or methotrexate. In our study, we propose the use of a simpler GVHD prophylaxis protocol comprising PTCy in combination with tacrolimus for MMUD and matched unrelated donor (MUD) alloHSCT. We performed a retrospective analysis of 109 consecutive recipients of alloHSCT from unrelated donors (MMUD, n=55; MUD, n=54) in a single center. Graft source was primarily peripheral blood (98%). No differences were observed between the MMUD and MUD groups with respect to 100-day cumulative incidence of grade II to IV acute GVHD (aGVHD; 31% versus 32%, respectively, P=.9), grade III to IV aGVHD (9% versus 7%, P=.7), and moderate/severe chronic GVHD (cGVHD) at 2 years (18% versus 14%, P=.6). Both groups showed similar cumulative incidence of 1 year nonrelapse mortality (13% versus 9%; P=.5) and 3-year relapse rates (24% versus 25%, P=.7). Progression-free survival and overall survival at 3 years for MMUD and MUD were 56% and 57% (P=.9) and 64% and 65% (P=.6), respectively. The 3-year probability of survival free of moderate/severe cGVHD and relapse was 56% and 55%, respectively. GVHD prophylaxis with PTCy and tacrolimus achieves low rates of severe aGVHD and cGVHD, as well as good survival outcomes, in recipients of both MMUD and MUD peripheral blood alloHSCT. This strategy overcomes the negative impact of single-locus HLA disparity.

HLA Eplet Mismatch Analysis of a Large Multi-Center Pediatric Heart Transplant Cohort: Not All Transplants are Immunologically Equal

<h3>Purpose</h3> Allograft rejection is driven by HLA disparity between donor and recipient despite of the use of various immunosuppression protocols. To better define the risk of allograft failure or complications from overt immunosuppression we applied the epitope-based mismatch approach to quantify the degree of HLA disparity in a in a large multi-center pediatric heart transplant (pHTX) cohort that has been followed for 3-5 years. <h3>Methods</h3> 274 pHTX recipient/donor pairs were retrospectively HLA genotyped by Next-Generation Sequencing and evaluated for HLA allele (alMM) and eplet mismatch (epMM) loads. HLAMatchmaker version 2.2 was used to determine epMM load at HLA-A/B/C, -DRB1/3/4/5, -DQA1/DQB1 and -DPA1/DPB1. <h3>Results</h3> Overall, the average total alMM was 13(±2). 76% were ≥5 HLA-A/B/C allele mismatches, 67% were ≥3 HLA-DRB and ≥3 HLA-DQ allele mismatch. The average epMM load was 60 (±17), range 16-112 (Table). 94% of cases had >11 HLA-DR or DQ epMM, a threshold previously shown to be associated with development of HLA donor-specific antibody in renal transplantation. While 159 cases (61.6%) had both DR and DQ epMM >11, only DR epMM or only DQ epMM >11 occurred in 31 (12.0%) and 50 (19.4%) cases, respectively (Figure). Therefore, this cohort can be divided into 3 groups for Class II epMM load: 6% (16) of cases with low, 36% (99) with intermediate and 58% (159) with high load. <h3>Conclusion</h3> Although this pHTx cohort is highly mismatched, for HLA alleles, there is a large range based on epMM, especially for HLA-DR and -DQ indicating that allele level typing is insufficient for determination of the true degree of mismatching. By correlating these data with clinical parameters, we aim to determine risk stratification based on epMM load in pediatric heart transplantation.

Single cord blood transplantation for acute myeloid leukemia patients aged 60 years or older: a retrospective study in Japan

The availability of alternative donor sources could allow elderly patients to receive allogeneic hematopoietic cell transplantation (HCT). We retrospectively evaluated the outcomes of single-unit cord blood transplantation (CBT) in 1577 patients aged ≥60 years with acute myeloid leukemia (AML) in Japan between 2002 and 2017. In total, 990 (63%) patients were not in complete remission (CR) at the time of CBT. A myeloablative conditioning regimen (52%) and calcineurin inhibitor (CI) + mycophenolate mofetil (MMF)-based graft-versus-host disease (GVHD) prophylaxis (45%) were more commonly used. With a median follow-up for survivors of 31 months, the probability of overall survival and the cumulative incidence of leukemia-related mortality at 3 years was 31% and 29%, respectively. The cumulative incidence of non-relapse mortality (NRM) at 100 days and 3 years were 24% and 41%, respectively. The cumulative incidences of grade II-IV and grade III-IV acute GVHD at 100 days and extensive chronic GVHD at 2 years were 44%, 16%, and 14%, respectively. The cumulative incidence of neutrophil engraftment was 80% at 42 days. Results of multivariate analysis indicated that the following factors were significantly associated with higher overall mortality: performance status ≥1, hematopoietic cell transplantation-specific comorbidity index ≥3, adverse cytogenetics, extramedullary disease at diagnosis, and non-CR status at CBT. By contrast, female sex, HLA disparities ≥2, mycophenolate mofetil-based GVHD prophylaxis, and recent CBT were significantly associated with lower overall mortality. In conclusion, single CBT offers a curative option for AML patients aged ≥60 years with careful patient selection.

302 - Impact of HLA Disparity on the Risk of Overall Mortality in Patients Who Developed Grade II-IV Acute GVHD

302 - Impact of HLA Disparity on the Risk of Overall Mortality in Patients Who Developed Grade II-IV Acute GVHD

CD8+ T-Cell Repertoire in Human Leukocyte Antigen Class I-Mismatched Alloreactive Immune Response.

In transplantation, direct allorecognition is a complex interplay between T-cell receptors (TCR) and HLA molecules and their bound peptides expressed on antigen-presenting cells. In analogy to HLA mismatched hematopoietic stem cell transplantation (HSCT), the TCR CDR3β repertoires of alloreactive cytotoxic CD8+ responder T cells, defined by the cell surface expression of CD137 and triggered in vitro by HLA mismatched stimulating cells, were analyzed in different HLA class I mismatched combinations. The same HLA mismatched stimulatory cells induced very different repertoires in distinct but HLA identical responders. Likewise, stimulator cells derived from HLA identical donors activated CD8+ cells expressing very different repertoires in the same mismatched responder. To mimic in vivo inflammation, expression of HLA class l antigens was upregulated in vitro on stimulating cells by the inflammatory cytokines TNFα and IFNβ. The repertoires differed whether the same responder cells were stimulated with cells treated or not with both cytokines. In conclusion, the selection and expansion of alloreactive cytotoxic T-cell clonotypes expressing a very diverse repertoire is observed repeatedly despite controlling for HLA disparities and is significantly influenced by the inflammatory status. This makes prediction of alloreactive T-cell repertoires a major challenge in HLA mismatched HSCT.