Alternative donor BMT with posttransplant cyclophosphamide as initial therapy for acquired severe aplastic anemia.

Severe aplastic anemia (SAA) is a marrow failure disorder with high morbidity and mortality. It is treated with bone marrow transplantation (BMT) for those with fully matched donors, or immunosuppressive therapy (IST) for those who lack such a donor, which is often the case for underrepresented minorities. We conducted a prospective phase 2 trial of reduced-intensity conditioning HLA-haploidentical BMT and posttransplantation cyclophosphamide (PTCy)-based graft-versus-host (GVHD) prophylaxis as initial therapy for patients with SAA. The median patient age was 25 years (range, 3-63 years), and the median follow-up time was 40.9 months (95% confidence interval [CI], 29.4-55.7). More than 35% of enrollment was from underrepresented racial/ethnic groups. The cumulative incidence of grade 2 or 4 acute GVHD on day 100 was 7% (95% CI, not applicable [NA]-17), and chronic GVHD at 2 years was 4% (95% CI, NA-11). The overall survival of 27 patients was 92% (95% CI, 83-100) at 1, 2, and 3 years. The first 7 patients received lower dose total body irradiation (200 vs 400 cGy), but these patients were more likely to have graft failure (3 of 7) compared with 0 of 20 patients in the higher dose group (P = .01; Fisher exact test). HLA-haploidentical BMT with PTCy using 400 cGy total body irradiation resulted in 100% overall survival with minimal GVHD in 20 consecutive patients. Not only does this approach avoid any adverse ramifications of IST and its low failure-free survival, but the use of haploidentical donors also expands access to BMT across all populations. This trial was registered at www.clinicaltrials.gov as NCT02833805.

HLA informs risk predictions after haploidentical stem cell transplantation with posttransplantation cyclophosphamide.

Hematopoietic cell transplantation from HLA-haploidentical related donors is increasingly used to treat hematologic cancers; however, characteristics of the optimal haploidentical donor have not been established. We studied the role of donor HLA mismatching in graft-versus-host disease (GVHD), disease recurrence, and survival after haploidentical donor transplantation with posttransplantation cyclophosphamide (PTCy) for 1434 acute leukemia or myelodysplastic syndrome patients reported to the Center for International Blood and Marrow Transplant Research. The impact of mismatching in the graft-versus-host vector for HLA-A, -B, -C, -DRB1, and -DQB1 alleles, the HLA-B leader, and HLA-DPB1 T-cell epitope (TCE) were studied using multivariable regression methods. Outcome was associated with HLA (mis)matches at individual loci rather than the total number of HLA mismatches. HLA-DRB1 mismatches were associated with lower risk of disease recurrence. HLA-DRB1 mismatching with HLA-DQB1 matching correlated with improved disease-free survival. HLA-B leader matching and HLA-DPB1 TCE-nonpermissive mismatching were each associated with improved overall survival. HLA-C matching lowered chronic GVHD risk, and the level of HLA-C expression correlated with transplant-related mortality. Matching status at the HLA-B leader and HLA-DRB1, -DQB1, and -DPB1 predicted disease-free survival, as did patient and donor cytomegalovirus serostatus, patient age, and comorbidity index. A web-based tool was developed to facilitate selection of the best haploidentical-related donor by calculating disease-free survival based on these characteristics. In conclusion, HLA factors influence the success of haploidentical transplantation with PTCy. HLA-DRB1 and -DPB1 mismatching and HLA-C, -B leader, and -DQB1 matching are favorable. Consideration of HLA factors may help to optimize the selection of haploidentical related donors.

Double unrelated umbilical cord blood vs HLA-haploidentical bone marrow transplantation: the BMT CTN 1101 trial.

Results of 2 parallel phase 2 trials of transplantation of unrelated umbilical cord blood (UCB) or bone marrow (BM) from HLA-haploidentical relatives provided equipoise for direct comparison of these donor sources. Between June 2012 and June 2018, 368 patients aged 18 to 70 years with chemotherapy-sensitive lymphoma or acute leukemia in remission were randomly assigned to undergo UCB (n = 186) or haploidentical (n = 182) transplant. Reduced-intensity conditioning comprised total-body irradiation with cyclophosphamide and fludarabine for both donor types. Graft-versus-host disease prophylaxis for UCB transplantation was cyclosporine and mycophenolate mofetil (MMF) and for haploidentical transplantation, posttransplant cyclophosphamide, tacrolimus, and MMF. The primary end point was 2-year progression-free survival (PFS). Treatment groups had similar age, sex, self-reported ethnic origin, performance status, disease, and disease status at randomization. Two-year PFS was 35% (95% confidence interval [CI], 28% to 42%) compared with 41% (95% CI, 34% to 48%) after UCB and haploidentical transplants, respectively (P = .41). Prespecified analysis of secondary end points recorded higher 2-year nonrelapse mortality after UCB, 18% (95% CI, 13% to 24%), compared with haploidentical transplantation, 11% (95% CI, 6% to 16%), P = .04. This led to lower 2-year overall survival (OS) after UCB compared with haploidentical transplantation, 46% (95% CI, 38-53) and 57% (95% CI 49% to 64%), respectively (P = .04). The trial did not demonstrate a statistically significant difference in the primary end point, 2-year PFS, between the donor sources. Although both donor sources extend access to reduced-intensity transplantation, analyses of secondary end points, including OS, favor haploidentical BM donors. This trial was registered at www.clinicaltrials.gov as #NCT01597778.

HLA-haploidentical vs matched unrelated donor transplants with posttransplant cyclophosphamide-based prophylaxis.

Posttransplant cyclophosphamide (PTCy) graft-versus-host disease (GVHD) prophylaxis has enabled haploidentical (Haplo) transplantation to be performed with results similar to those after matched unrelated donor (MUD) transplantation with traditional prophylaxis. The relative value of transplantation with MUD vs Haplo donors when both groups receive PTCy/calcineurin inhibitor/mycophenolate GVHD prophylaxis is not known. We compared outcomes after 2036 Haplo and 284 MUD transplantations with PTCy GVHD prophylaxis for acute leukemia or myelodysplastic syndrome in adults from 2011 through 2018. Cox regression models were built to compare outcomes between donor types. Recipients of myeloablative and reduced-intensity regimens were analyzed separately. Among recipients of reduced-intensity regimens, 2-year graft failure (3% vs 11%), acute grades 2 to 4 GVHD (hazards ratio [HR], 0.70; P = .022), acute grades 3 and 4 GVHD (HR, 0.41; P = .016), and nonrelapse mortality (HR, 0.43; P = .0008) were lower after MUD than with Haplo donor transplantation. Consequently, disease-free (HR, 0.74; P = .008; 55% vs 41%) and overall (HR, 0.65; P = .001; 67% vs 54%) survival were higher with MUD than with Haplo transplants. Among recipients of myeloablative regimens, day-100 platelet recovery (95% vs 88%) was higher and grades 3 and 4 acute (HR, 0.39; P = .07) and chronic GVHD (HR, 0.66; P = .05) were lower after MUD than with Haplo donor transplantation. There were no differences in graft failure, relapse, nonrelapse mortality, and disease-free and overall survival between donor types with myeloablative conditioning regimens. These data extend and confirm the importance of donor-recipient HLA matching for allogeneic transplantation. A MUD is the preferred donor, especially for transplantations with reduced-intensity conditioning regimens.

Non-Myeloablative Allogeneic Transplantation with Post-Transplant Cyclophosphamide after Immune Checkpoint Inhibition for Classic Hodgkin Lymphoma: A Retrospective Cohort Study.

: Immune checkpoint inhibitors (ICIs) are approved in relapsed classic Hodgkin lymphoma (cHL). The safety and effectiveness of allogeneic blood or marrow transplantation (alloBMT) in ICI-pretreated patients with cHL remain unclear. The aim of this study is to assess outcomes of patients with cHL receiving ICIs before alloBMT using post-transplantation cyclophosphamide (PTCy) graft-versus-host-disease (GVHD) prophylaxis.  : We performed a retrospective study of relapsed/refractory patients with cHL undergoing alloBMT with PTCy at Johns Hopkins between November 2004 and September 2019. Engraftment, GVHD incidence, nonrelapse mortality, progression-free survival (PFS), and overall survival (OS) were compared between patients receiving pre-alloBMT ICI or standard salvage chemotherapy.  : We identified 105 consecutive relapsed/refractory patients with cHL, of whom 37 (35.2%) received ICIs and 68 (64.7%) received chemotherapy without ICIs (no-ICI) before alloBMT. ICI and no-ICI patients experienced a 3-year estimated OS of 94% versus 78% (hazard ratio [HR], 0.35; 95% confidence interval [CI], 0.08 to 1.56; P = .17) and a 3-year estimated PFS of 90% and 65% (HR, 0.3; 95% CI, 0.09 to 1; P = .05), respectively. We observed no statically significant difference in the 12-month cumulative incidence of acute grade II to IV GVHD or in the 24-month incidence of chronic GVHD.  : ICIs do not increase acute or chronic GVHD incidence compared with salvage chemotherapy. Patients with cHL receiving ICIs prior to alloBMT experienced outstanding PFS and OS. Thus, ICI therapy is safe in patients with cHL when undergoing alloBMT with PTCy and may improve post-alloBMT disease progression and survival.

Allogeneic Haploidentical Blood or Marrow Transplantation with Post-Transplantation Cyclophosphamide in Chronic Lymphocytic Leukemia.

Allogeneic blood or marrow transplantation (allo-BMT) remains the only treatment for chronic lymphocytic leukemia (CLL) with curative potential. Although post-transplantation cyclophosphamide (PTCy) reduces allo-BMT toxicity by decreasing the risk of graft-versus-host disease (GVHD), its effect on CLL allo-BMT outcomes is unknown. We studied 64 consecutive patients with CLL who underwent nonmyeloablative (NMA) haploidentical allo-BMT at Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. In this cohort, the 4-year overall survival was 52% (95% confidence interval [CI], 40% to 68%), and progression-free survival was 37% (95% CI, 26% to 54%). Six patients experienced engraftment failure. PTCy prophylaxis was associated with a modest cumulative incidence of 1-year grade II-IV acute GVHD (27%; %95% CI, 15% to 38%) and %%%2-year chronic GVHD (17%; 95% CI, 7% to 26%). We demonstrate that NMA haploidentical allo-BMT with PTCy is a safe and effective treatment option.

Thrombotic Microangiopathy after Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis.

Transplant-associated thrombotic microangiopathy (taTMA) is a systemic vascular illness associated with significant morbidity and mortality, resulting from a convergence of risk factors after allogeneic blood or marrow transplantation (alloBMT). The diagnosis of taTMA has been a challenge, but most criteria include an elevated lactate dehydrogenase (LDH), low haptoglobin, and schistocytes on peripheral blood smear. We performed a retrospective review of the 678 consecutive adults who received high-dose post-transplantation cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis between January 1, 2015, and August 31, 2018. In April 2016, we initiated a monitoring program of weekly LDH and haptoglobin measurements and blood smears when those 2 parameters were both abnormal on all of our adult patients undergoing alloBMT for hematologic malignancies. During the entire period, the 1-year cumulative incidence of taTMA was 1.4% (95% confidence interval, 0.5% to 2.3%). Eight patients were taking tacrolimus at the time of diagnosis, and 1 was not on any immunosuppression. Eight of 9 patients (89%) were hypertensive. Four patients had invasive infections at the time of diagnosis, 4 patients required renal replacement therapy, and 5 of 9 patients were neurologically impaired. Eculizumab was given to 6 patients (0.9%), of whom 2 died and 4 recovered with resolution of end-organ dysfunction. The paucity of events made the determination of risk factors difficult; however, the low incidence of taTMA in this cohort may be related to the limited use of myeloablative conditioning regimens, low incidence of severe GVHD, and use of PTCy. PTCy-based GVHD prophylaxis appears to be associated with a low incidence of severe taTMA.

Shortened-Duration Immunosuppressive Therapy after Nonmyeloablative, Related HLA-Haploidentical or Unrelated Peripheral Blood Grafts and Post-Transplantation Cyclophosphamide.

With post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis, nonmyeloablative (NMA) HLA-haploidentical (haplo) and HLA-matched blood or marrow transplantation (BMT) have comparable outcomes. Previous reports have shown that discontinuation of immunosuppression (IS) as early as day 60 after infusion of a bone marrow (BM) haplo allograft with PTCy is feasible. There are certain diseases in which peripheral blood (PB) may be favored over BM, but given the higher rates of GVHD with PB, excessive GVHD is of increased concern. We report a completed, prospective single-center trial of stopping IS at days 90 and 60 after NMA PB stem cell transplantation (PBSCT). Between 12/2015-7/2018, 117 consecutive patients with hematologic malignancies associated with higher rates of graft failure after NMA conditioned BMT and PTCy, received NMA PB allografts on trial. The primary objective of this study was to evaluate the safety and feasibility of reduced-duration IS (from day 5 through day 90 in the D90 cohort and through day 60 in the D60 cohort). Of the 117 patients (median age, 64 years; range, 22 to 78 years), the most common diagnoses were myelodysplastic syndrome (33%), acute myelogenous leukemia (with minimal residual disease or arising from an antecedent disorder) (32%), myeloproliferative neoplasms (19%), myeloma (9%), and chronic lymphoblastic leukemia (7%). Shortened IS was feasible in 75 patients (64%) overall. Ineligibility for shortened IS resulted most commonly from GVHD (17 patients), followed by early relapse (11 patients), nonrelapse mortality (NRM) (7 patients), patient/ physician preference (4 patients) or graft failure (3 patients). Of the 57 patients in the D90 cohort, 33 (58%) stopped IS early as planned, and among the 60 patients in the D60 cohort, 42 (70%) stopped IS early as planned. The graft failure rate was 2.6%. After IS cessation, the median time to diagnosis of grade II-IV acute GVHD was 21 days in the D90 cohort and 32 days in the D60 cohort, with almost all cases developing within 40 days. Approximately one-third of these patients resumed IS. All outcome measures were similar in the 2 cohorts and our historical outcomes with 180 days of IS. The cumulative incidence of grade III-IV acute GVHD was low, 2% in the D90 cohort and 7% in the D60 cohort. The incidence of severe chronic GVHD at 2 years was 9% in the D90 cohort and 5% in the D60 cohort. The 2-year overall survival was 67% for both the D90 and D60 cohorts. The 2-year progression-free survival was 47% for the D90 cohort and 52% for the D60 cohort, and the GVHD-free, relapse-free survival was <35% for both cohorts. These data suggest that reduced-duration IS in patients undergoing NMA PBSCT with PTCy is feasible and has an acceptable safety profile. © 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Optimal Donor for African Americans with Hematologic Malignancy: HLA-Haploidentical Relative or Umbilical Cord Blood Transplant.

Although hematopoietic cell transplantation from an HLA-matched unrelated donor is potentially curative for hematologic malignancies, survival is lower for African Americans compared with Caucasians. Because only approximately 20% of African Americans will have an HLA-matched unrelated donor, many of these patients undergo HLA-haploidentical relative or umbilical cord blood transplantation. In this study, we analyzed outcomes after HLA-haploidentical related donor (n = 249) and umbilical cord blood (n = 118) transplantations in African American patients with hematologic malignancy between 2008 and 2016. The predominant disease was acute myelogenous leukemia for recipients of both types of donor grafts. The incidences of grade II-IV and III-IV acute graft-versus-host disease were higher after umbilical cord blood transplantation compared with HLA-haploidentical relative transplantation (56% and 29%, respectively, versus 33% and 11%, respectively; P < .0001). The 2-year incidence of transplantation-related mortality adjusted for age and conditioning regimen intensity was higher after umbilical cord blood transplantation compared with HLA-haploidentical related donor transplantation (31% versus 18%; P = .008); however, there were no between-group differences in the 2-year adjusted incidence of relapse (30% versus 34%; P = .51), overall survival (54% versus 57%; P = .66), or disease-free survival (43% versus 47%; P = .46). Our findings show that the use of HLA-haploidentical and umbilical cord blood transplants expands the access to transplantation with comparable leukemia-free and overall survival for African Americans with hematologic malignancies.

Development of Grade II Acute Graft-versus-Host Disease Is Associated with Improved Survival after Myeloablative HLA-Matched Bone Marrow Transplantation using Single-Agent Post-Transplant Cyclophosphamide.

Post-transplant cyclophosphamide (PTCy) can be used as the sole immunosuppression after myeloablative conditioning (MAC) for HLA-matched bone marrow transplantation (BMT). However, the effects of graft-versus-host disease (GVHD) with this platform are undefined. We retrospectively analyzed 298 consecutive adult patients with hematologic malignancies who engrafted after MAC HLA-matched sibling donor (MSD; n = 187) or HLA-matched unrelated donor (MUD; n = 111) T-cell-replete BMT with PTCy 50 mg/kg on days +3 and +4. After MSD and MUD BMT, 35% and 57% of patients, respectively, developed grade II acute GVHD (aGVHD) by 100 days, 11% and 14% grade III to IV aGVHD by 100 days, and 9% and 16% chronic GVHD (cGVHD) by 1 year. In landmark analyses at 100 days after HLA-matched BMT, 4-year overall survival (OS) and progression-free survival (PFS) were 57% (95% confidence interval [CI], .49 to .67) and 40% (95% CI, .31 to .51) in patients without grades II to IV aGVHD, and 68% (95% CI, .59 to .78) and 54% (95% CI, .44 to .65) in patients with grade II aGVHD. In adjusted time-dependent multivariable analyses, grade II aGVHD was associated with improved OS (hazard ratio, .58; 95% CI, .37 to .89; P = .01) and PFS (hazard ratio, .50; 95% CI, .34 to .74; P < .001) after HLA-matched BMT with PTCy. The ability of PTCy to limit grades III to IV aGVHD and cGVHD while maintaining grade II aGVHD may contribute to its effectiveness, and further attempts to reduce aGVHD may be detrimental.

Severe Cytokine Release Syndrome after Haploidentical Peripheral Blood Stem Cell Transplantation.

Inflammatory cytokines released by activated lymphocytes and innate cells in the context of cellular therapy can cause fever, vasodilatation, and end-organ damage, collectively known as cytokine release syndrome (CRS). CRS can occur after allogeneic blood or marrow transplantation, but is especially prevalent after HLA-haploidentical (haplo) peripheral blood transplantation (PBT). We reviewed charts of all patients who underwent haplo-PBT between October 1, 2013, and September 1, 2017 and graded CRS in these patients. A total of 146 consecutive patients who underwent related haplo-PBT were analyzed. CRS occurred in 130 patients (89%), with most cases of mild severity (grade 0 to 2). Severe CRS (grade 3 to 5) occurred in 25 patients (17%). In this group with severe CRS, 13 patients had encephalopathy, 12 required hemodialysis, and 11 were intubated. Death from the immediate complications of CRS occurred in 6 patients (24% of the severe CRS group and 4% of the entire haplo-PBT cohort). The cumulative probability of nonrelapse mortality (NRM) was 38% at 6 months for the patients with severe CRS and 8% (121 of 146) in patients without severe CRS. In conclusion, CRS occurs in nearly 90% of haplo-PBTs. Older haplo-PBT recipients (odds ratio [OR], 2.4; 95% confidence interval [CI], .83 to 6.75; P = .11) and those with a history of radiation therapy (OR, 3.85; 95% CI, 1.32 to 11.24; P = .01) are at increased risk of developing severe CRS. Although most recipients of haplo-PBT develop CRS, <20% experience severe complications. The development of severe CRS is associated with a significantly increased risk of NRM.

Lower Graft-versus-Host Disease and Relapse Risk in Post-Transplant Cyclophosphamide-Based Haploidentical versus Matched Sibling Donor Reduced-Intensity Conditioning Transplant for Hodgkin Lymphoma.

Classic Hodgkin lymphoma (cHL) patients with relapsed or refractory disease may benefit from allogeneic hematopoietic cell transplantation (allo-HCT), but many lack a matched sibling donor (MSD). Herein, we compare outcomes of 2 reduced-intensity conditioning (RIC) HCT platforms in cHL: T cell-replete related donor haploidentical (haplo) HCT with a post-transplant cyclophosphamide (PTCy)-based approach versus an MSD/calcineurin inhibitor (CNI)-based approach. The study included 596 adult patients who underwent a first RIC allo-HCT for cHL between 2008 and 2016 using either a haplo-PTCy (n = 139) or MSD/CNI-based (n = 457) approach. Overall survival (OS) was the primary endpoint. Secondary endpoints included acute graft-versus-host disease (aGVHD) and chronic GVHD (cGVHD), nonrelapse mortality (NRM), relapse/progression, and progression-free survival (PFS). On multivariate analysis, there was no significant difference between haplo/PTCy and MDS/CNI-based approaches in terms of OS (hazard ratio [HR], 1.07; 95% confidence interval [CI], .79 to 1.45; P = .66) or PFS (HR, .86; 95% CI, .68 to 1.10; P = .22). Haplo/PTCy was associated with a significantly higher risk of grades II to IV aGVHD (odds ratio [OR], 1.73, 95% CI, 1.16 to 2.59; P = .007), but the risk of grades III to IV aGVHD was not significantly different between the 2 cohorts (OR, .61; 95% CI, .29 to 1.27; P = .19). The haplo/PTCy platform provided a significant reduction in cGVHD risk (HR, .45; 95% CI, .32 to .64; P < .001), and a significant reduction in relapse risk (HR, .74; 95% CI, .56 to .97; P = .03). There was a statistically nonsignificant trend toward higher NRM with a haplo/PTCy approach (HR, 1.65; 95% CI, .99 to 2.77; P = .06). Haplo/PTCy-based approaches are associated with lower incidences of cGVHD and relapse, with PFS and OS outcomes comparable with MSD/CNI-based approaches. There was a leaning toward higher NRM with a haplo/PTCy-based platform. These data show that haplo/PTCy allo-HCT in cHL results in survival comparable with MSD/CNI-based allo-HCT.

Low immunosuppressive burden after HLA-matched related or unrelated BMT using posttransplantation cyclophosphamide.

The intensive and prolonged immunosuppressive therapy required to prevent or treat graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (alloBMT) puts patients at substantial risk for life-threatening infections, organ toxicity, and disease relapse. Posttransplantation cyclophosphamide (PTCy) can function as single-agent GVHD prophylaxis after myeloablative, HLA-matched related (MRD), or HLA-matched unrelated (MUD) donor T-cell-replete bone marrow allografting, obviating the need for additional prophylactic immunosuppression. However, patients who develop GVHD require supplemental treatment. We assessed the longitudinal requirement for immunosuppressive therapy in 339 patients treated with this transplantation platform: 247 receiving busulfan/cyclophosphamide (BuCy) conditioning (data collected retrospectively) and 92 receiving busulfan/fludarabine (BuFlu) conditioning (data collected prospectively). Approximately 50% of MRD patients and 30% of MUD patients never required immunosuppression beyond PTCy. In patients requiring further immunosuppression, typically only 1 to 2 agents were required, and the median durations of systemic pharmacologic immunosuppression for the BuCy MRD, BuFlu MRD, BuCy MUD, and BuFlu MUD groups all were 4.5 to 5 months. For these 4 groups, 1-year probabilities of being alive and off all systemic immunosuppression were 61%, 53%, 53%, and 51% and 3-year probabilities were 53%, 48%, 49%, and 56%, respectively. These data suggest that PTCy minimizes the global immunosuppressive burden experienced by patients undergoing HLA-matched alloBMT.

Grade II Acute Graft-versus-Host Disease and Higher Nucleated Cell Graft Dose Improve Progression-Free Survival after HLA-Haploidentical Transplant with Post-Transplant Cyclophosphamide.

Compared with standard graft-versus-host disease (GVHD) prophylaxis platforms, post-transplantation cyclophosphamide (PTCy) after T cell-replete HLA-haploidentical (haplo) bone marrow transplantation (BMT) reduces the risk of grades III to IV acute (a) and chronic (c) GVHD, but maintains similar rates of grade II aGVHD. Given that mild GVHD has been associated with reduced treatment failure in HLA-matched BMT, we evaluated the risk factors for and effects of GVHD on survival in 340 adults with hematologic malignancies who engrafted after nonmyeloablative haplo-BMT with PTCy, mycophenolate mofetil, and tacrolimus. The cumulative incidence at 100 days of grade II and grades III to IV aGVHD were 30% (95% confidence interval [CI], 25% to 35%) and 2% (95% CI, 1% to 4%), respectively. The 1-year cumulative incidence of cGVHD was 10% (95% CI, 7% to 13%). In landmark analyses at 100 days, the 4-year probabilities of overall survival (OS) and progression-free survival (PFS) were, 48% (95% CI, 41% to 56%) and 39% (95% CI, 32% to 47%) for patients without grades II to IV aGVHD, compared with 63% (95% CI, 53% to 73%) and 59% (95% CI, 50% to 71%) for patients with grade II aGVHD (P = .05 and P = .009). In multivariable modeling, when compared with patients who never experienced GVHD, the hazard ratio (HR) for OS and PFS in patients with grade II aGVHD was .78 (95% CI, .54 to 1.13; P = .19) and .69 (95% CI, .48 to .98; P = .04). Higher nucleated cell graft dose was also associated with improved OS (HR, .88; 95% CI, .78 to 1.00; P = .05) and PFS (HR, .89; 95% CI, .79 to 1.0; P = .05) and decreased risk of grades III to IV aGVHD (subdistribution HR, .66; 95% CI, .46 to .96; P = .03). PTCy reduces grades III to IV aGVHD and cGVHD, but retains similar incidence of grade II aGVHD, the development of which improves PFS. Higher nucleated cell graft dose goals may also improve survival after nonmyeloablative haplo-BMT with PTCy.

Proceedings From the Fourth Haploidentical Stem Cell Transplantation Symposium (HAPLO2016), San Diego, California, December 1, 2016.

The resurgence of haploidentical stem cell transplantation (HaploSCT) over the last decade is one of the most important advances in the field of hematopoietic stem cell transplantation (HSCT). The modified platforms of T cell depletion either ex vivo (CD34+ cell selection, "megadoses" of purified CD34+ cells, or selective depletion of T cells) or newer platforms of in vivo depletion of T cells, with either post-transplantation high-dose cyclophosphamide or intensified immune suppression, have contributed to better outcomes, with survival similar to that in HLA-matched donor transplantation. Further efforts are underway to control viral reactivation using modified T cells, improve immunologic reconstitution, and decrease the relapse rate post-transplantation using donor-derived cellular therapy products, such as genetically modified donor lymphocytes and natural killer cells. Improvements in treatment-related mortality have allowed the extension of haploidentical donor transplants to patients with hemoglobinopathies, such as thalassemia and sickle cell disease, and the possible development of platforms for immunotherapy in solid tumors. Moreover, combining HSCT from a related donor with solid organ transplantation could allow early tapering of immunosuppression in recipients of solid organ transplants and hopefully prevent organ rejection in this setting. This symposium summarizes some of the most important recent advances in HaploSCT and provides a glimpse in the future of fast growing field.

Early Fever after Haploidentical Bone Marrow Transplantation Correlates with Class II HLA-Mismatching and Myeloablation but Not Outcomes.

Noninfectious fevers are common early after T cell-replete HLA haploidentical (haplo) peripheral blood transplants and have been associated with cytokine release syndrome and overall mortality. However, less is known regarding the incidence and associations of early fever after bone marrow transplantation (BMT) with post-transplant cyclophosphamide (PTCy). We hypothesized that early fever would be associated with myeloablative conditioning (MAC), because of its relative increase in tissue damage augmenting antigen presentation and class II HLA-mismatching because of recognition of antigen-presenting cells by CD4+ T cells. In 672 recipients of MAC HLA-matched related donor (MRD) (n = 183), MAC HLA-matched unrelated donor (MUD) (n = 115), MAC haplo (n = 79), or nonmyeloablative (NMA) haplo (n = 295) T cell-replete BMT with PTCy, we retrospectively analyzed early noninfectious fever defined as temperature of ≥38.3°C once or ≥38.0°C twice or more on days 1 to 6. Fever occurred in 13% after MAC MRD, 23% after MAC MUD, 44% after NMA haplo, and 84% after MAC haplo BMT (P < .0001). Survival outcomes did not differ between patients with and without early fever. In NMA haplo BMT, mismatch in the graft-versus-host direction at HLA-DRB1 or -DPB1 (but not HLA-A, -B, -Cw, or -DQB1) was associated with early fever compared with no mismatches at these loci (P < .0001 and P = .02, respectively). In multivariable modeling, -DRB1 or -DPB1 mismatch and higher CD3+ graft cell dose were significantly associated with early fever. Early fever is more common after haplo compared with HLA-matched BMT. Fever is associated with myeloablation, -DRB1 or -DPB1 mismatching, and higher CD3+ graft cell dose but not survival.

Shortened-Duration Tacrolimus after Nonmyeloablative, HLA-Haploidentical Bone Marrow Transplantation.

With post-transplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis, nonmyeloablative HLA-haploidentical (NMA haplo) and HLA-matched blood or marrow transplantation (BMT) have comparable outcomes. Early discontinuation of immunosuppression may reduce the risk of relapse and improve immune reconstitution, but may increase the risk of GVHD. We conducted a prospective trial of NMA haplo BMT for patients with hematologic malignancies (median age, 61 years), evaluating the safety of early discontinuation of tacrolimus. All patients received T cell-replete bone marrow followed by high-dose PTCy, mycophenolate mofetil, and tacrolimus. Tacrolimus was prespecified to stop without taper at day +90, +60, or +120, contingent on having ≥5% donor T cells, no relapse, and no grade II-IV acute or significant chronic GVHD. Safety stopping rules were based on ≥5% graft failure, ≥10% nonrelapse mortality (NRM), or a ≥20% combined incidence of severe acute and chronic GVHD from the tacrolimus stop date through day +180. Of the 47 patients in the day +90 arm, 23 (49%) stopped tacrolimus as planned. Of the 55 patients in the day +60 arm, 38 (69%) stopped as planned. Safety stopping criteria were not met. In both arms, at day +180, the probability of grade II-IV acute GVHD was <40%, that of grade III-IV acute GVHD was <8%, and that of NRM was <5%. The 1-year probabilities of chronic GVHD and NRM were <15% and <10%, respectively, in both arms. The 1-year GVHD-free relapse-free survival was higher in the day 60 arm. Thus, stopping tacrolimus as early as day +60 is feasible and carries acceptable risks after NMA haplo BMT with PTCy. This approach may facilitate post-transplantation strategies for relapse reduction.

Haploidentical Bone Marrow Transplantation with Post-Transplant Cyclophosphamide Using Non-First-Degree Related Donors.

Outcomes of nonmyeloablative (NMA) haploidentical (haplo) blood or marrow transplant (BMT) with post-transplantation cyclophosphamide (PTCy) using non-first-degree relatives are unknown. We evaluated 33 consecutive adult patients (median age, 56 years) with hematologic malignancies who underwent NMA haplo T cell-replete BMT with PTCy at Johns Hopkins using second- or third-degree related donors. Donors consisted of 10 nieces (30%), 9 nephews (27%), 7 first cousins (21%), 5 grandchildren (15%), and 2 uncles (6%). Thirty-one patients (94%) reached full donor chimerism by day 60. The estimated cumulative incidence (CuI) of grades II to IV acute graft-versus-host disease (aGVHD) at day 180 was 24% (90% confidence interval [CI], 9% to 38%). Only 1 patient experienced grades III to IV aGVHD. At 1 year the CuI of chronic GVHD was 10% (90% CI, 0% to 21%). The CuI of nonrelapse mortality at 1 year was 5% (90% CI, 0% to 14%). At 1 year the probability of relapse was 31% (90% CI, 12% to 49%), progression-free survival 64% (90% CI, 48% to 86%), and overall survival 95% (90% CI, 87% to 100%). The 1-year probability of GVHD-free, relapse-free survival was 57% (90% CI, 41% to 79%). NMA haplo BMT with PTCy from non-first-degree relatives is an acceptably safe and effective alternative donor platform, with results similar to those seen with first-degree relatives.

Anti-CD45 radioimmunotherapy without TBI before transplantation facilitates persistent haploidentical donor engraftment.

Many patients with hematologic malignancies cannot tolerate hematopoietic cell transplantation (HCT), whereas others may not have a compatible human leukocyte antigen-matched donor. To overcome these limitations, we optimized a conditioning regimen employing anti-CD45 radioimmunotherapy (RIT) replacing total body irradiation (TBI) before haploidentical HCT in a murine model. Mice received 200 to 400 µCi (90)Y-anti-CD45 antibody (30F11), with or without fludarabine (5 days starting day -8), with cyclophosphamide (CY; days -2 and +2) for graft-versus-host disease prophylaxis, and 1.5 × 10(7) haploidentical donor bone marrow cells (day 0). Haploidentical bone marrow transplantation (BMT) with 300 µCi (90)Y-anti-CD45 RIT and CY, without TBI or fludarabine, led to mixed chimeras with 81.3 ± 10.6% mean donor origin CD8(+) cells detected 1 month after BMT, and remained stable (85.5 ± 11% mean donor origin CD8(+) cells) 6 months after haploidentical BMT. High chimerism levels were induced across multiple hematopoietic lineages 28 days after haploidentical BMT with 69.3 ± 14.1%, 75.6 ± 20.2%, and 88.5 ± 11.8% CD3(+) T cells, B220(+) B cells, and CD11b(+) myeloid cells, respectively. Fifty percent of SJL leukemia-bearing mice treated with 400 µCi (90)Y-DOTA-30F11, CY, and haploidentical BMT were cured and lived >200 days. Mice treated with 200 µCi (90)Y-DOTA-30F11 had a median overall survival of 73 days, while untreated leukemic mice had a median overall survival of 34 days (P < .001, Mantel-Cox test). RIT-mediated haploidentical BMT without TBI may increase treatment options for aggressive hematologic malignancies.

Transplantation tolerance: from theory to clinic.

Tolerance induction and alloreactivity can be applied to the clinic for the transplantation of solid organs and in the treatment of human cancers respectively. Hematopoietic chimerism, the stable coexistence of host and donor blood cells, guarantees that a solid organ from the same donor will be tolerated without a requirement for maintenance immunosuppression, and it also serves as a platform for the adoptive immunotherapy of hematologic malignancies using donor lymphocyte infusions. This review focuses on clinically relevant methods for inducing hematopoietic chimerism and transplantation tolerance, with a special emphasis on reduced intensity transplantation conditioning and high dose, post-transplantation cyclophosphamide to prevent graft rejection and graft-versus-host disease (GVHD). Reduced intensity transplantation regimens permit a transient cooperation between donor and host immune systems to eradicate malignancy without producing GVHD. Their favorable toxicity profile also enables the application of allogeneic stem cell transplantation to treat non-malignant disorders of hematopoiesis and to induce tolerance for solid organ transplantation.