Prospective study of nonmyeloablative, HLA-mismatched unrelated BMT with high-dose posttransplantation cyclophosphamide

The outcome of two or more HLA loci mismatched unrelated donor hematopoietic cell transplantation for acute leukemia: an ALWP of the EBMT study

A mismatched unrelated (MMUD) donor represents an alternative therapeutic option for patients who need allogeneic hematopoietic cell transplantation (allo-HCT) and do not have a human leukocyte antigen (HLA) matched donor. We studied outcomes of patients with acute leukemia transplanted from ≥2 HLA allele MMUD. The study population consisted of 465 patients. The median follow-up period was 63 and 75 months in the AML and ALL groups, respectively. The incidence of grade II-IV and grade III-IV acute (a) graft-versus-host disease (GVHD) during the first 100 days was 37% and 16%, respectively. Total and extensive chronic (c) GVHD rates at 2 years were 38% and 17%, respectively. In the entire population, the 5-year relapse incidence (RI), non-relapse mortality (NRM), leukemia-free survival (LFS), overall survival and refined GVHD-free, relapse-free survival (GRFS) was 33%, 31%, 37%, 41%, and 27%, respectively. In the multivariate analysis, HLA-DR mismatch was a poor prognostic factor, giving a significantly higher NRM [hazard ratio (HR), 1.67, p = 0.02]; poorer LFS (HR, 1.42, p = 0.03); OS (HR, 1.46, p = 0.03) and higher aGVHD grade II-IV (HR, 1.46, p = 0.05). In this study, allo-HCT from ≤6/8 HLA allele MMUD in acute leukemia patients resulted in acceptable LFS and refined GRFS. HLA-DR mismatch was a poor prognostic factor.

Post-transplantation cyclophosphamide GvHD prophylaxis after hematopoietic stem cell transplantation from 9/10 or 10/10 HLA-matched unrelated donors for acute leukemia

HLA-matching largely contributes to unrelated donor hematopoietic cell transplantation (UD-HCT) success but, due to the selective deletion of alloreactive T-cells, post-transplantation cyclophosphamide (PTCy) could modulate its negative impact on outcomes. We retrospectively compared acute leukemia patients receiving 10/10 or 9/10 HLA allele-matched UD-HCT with PTCy-GvHD prophylaxis between 2010 and 2017, reported to EBMT registry. The 100-day incidence of grade ≥2 and grade ≥3 aGvHD were comparable for 10/10 and 9/10 UD (28% versus 28%, p = 0.8 and 10% versus 8%, p = 0.5, respectively). The 2-year cGvHD and extensive cGvHD were similar between 10/10 and 9/10 UD (35% versus 44%, p = 0.2 and 21% versus 20%, p = 0.6, respectively). The 2-year nonrelapse mortality was 20% after 10/10 and 16% after 9/10 UD-HCT (p = 0.1). Relapse incidence at 2-year was 24% for 10/10 and 28% for 9/10 UD-HCT (p = 0.4). Leukemia-free survival at 2-year was the same for 10/10 and 9/10 UD (56 and 56%, p = 0.6, respectively), with comparable overall survival (62 and 59%, p = 0.9, respectively). Multivariate analysis showed no effect of HLA-matching on outcomes. An advanced disease status and patient disability remained the most important factors portending a worse survival. PTCy could alleviate the detrimental effect of HLA-allele mismatching in UD-HCT, potentially expanding the donor pool for acute leukemia patients.

Post-transplantation Cyclophosphamide: From HLA-Haploidentical to Matched-Related and Matched-Unrelated Donor Blood and Marrow Transplantation

Following allogeneic blood and marrow transplantation (BMT), graft-versus-host disease (GvHD) continues to represent a significant cause of treatment failure, despite the routine use of conventional, mainly calcineurin inhibitor-based prophylaxis. Recently, post-transplant cyclophosphamide (PTCy) has emerged as a safe and efficacious alternative. First, omitting the need for ex vivo T-cell depletion in the setting of haploidentical transplantation, growing evidence supports PTCy role in GvHD prevention in matched-related and matched-unrelated transplants. Through improved understanding of GvHD pathophysiology and advancements in drug development, PTCy emerges as a unique opportunity to design calcineurin inhibitor-free strategies by integrating agents that target different stages of GvHD development.

PTCy-based haploidentical vs matched related or unrelated donor reduced-intensity conditioning transplant for DLBCL

This study retrospectively compared long-term outcomes of nonmyeloablative/reduced intensity conditioning (NMC/RIC) allogeneic hematopoietic cell transplantation (allo-HCT) from a haploidentical family donor (haplo-HCT) using posttransplant cyclophosphamide (PTCy) with those of matched sibling donor (MSD) and matched unrelated donor (MUD) with or without T-cell depletion (TCD+/TCD-) in patients with relapsed diffuse large B-cell lymphoma (DLBCL). Adult patients with DLBCL who had undergone their first NMC/RIC allo-HCT between 2008 and 2015 were included. Recipients of haplo-HCT were limited to those receiving graft-versus-host disease (GVHD) prophylaxis with PTCy. GVHD prophylaxis in MSD was limited to calcineurin inhibitor (CNI)-based approaches without in vivo TCD, while MUD recipients received CNI-based prophylaxis with or without TCD. Outcome analyses for overall survival (OS) and progression-free survival (PFS), nonrelapse mortality (NRM), and disease relapse/progression were calculated. A total of 1438 patients (haplo, 132; MSD, 525; MUD TCD+, 403; and MUD TCD-, 378) were included. Patients with haplo donors were significantly older, had a better performance status and had more frequently received total body irradiation-based conditioning regimens and bone marrow grafts than MSD and MUD TCD+ or TCD-. 3-year OS, PFS, NRM and relapse/progression incidence after haplo-HCT was 46%, 38%, 22%, and 41%, respectively, and not significantly different from outcomes of matched donor transplants on multivariate analyses. Haplo-HCT was associated with a lower cumulative incidence of chronic GVHD compared with MSD, MUD TCD+/TCD-. NMC/RIC haplo-HCT with PTCy seems to be a valuable alternative for patients with DLBCL considered for allo-HCT but lacking a matched donor.

Incorporating posttransplant cyclophosphamide-based prophylaxis as standard-of-care outside the haploidentical setting: challenges and review of the literature

Posttransplant high-dose cyclophosphamide (PTCy) effectively prevents GvHD after haploidentical SCT. However, its use in HLA-matched SCT has been less explored. Fifty-six consecutive patients who underwent allo-SCT for hematological malignancies have been included in this prospective single-center protocol. Donors have been HLA-identical siblings, fully-matched unrelated or 1-allele-mismatched unrelated donors in 30%, 32%, and 37% of cases, respectively. Nine patients have received a TBI-containing MAC regimen, while the remaining (84%) received RIC platforms based on Fludarabine plus Busulfan/Melphalan. Due to the high graft failure (GF) rate (21%) in a preliminary analysis in the allo-RIC cohort (n = 29), protocol amendments have been implemented, with no further cases of GF after the introduction of mini-thiotepa (0/18). The overall incidence of grade II-IV acute GvHD is 24% (95% CI: 17-31%) with four steroid-refractory cases. Severe chronic GvHD has occurred in only 1 of 43 evaluable cases. The 1-year NRM and relapse are 18% (95% CI: 12-26%) and 30% (18-42%) and the OS and DFS are 78% and 64%, respectively. These outcomes support the feasibility of using PTCy as a SOC outside the haplo-setting, albeit mini-thiotepa (3 mg/kg) was incorporated in the standard allo-RIC platforms to prevent GF. Despite the limitations of a single-center experience and the short follow-up, these protocols show promising results with particular benefit in reducing the occurrence of moderate-to-severe GvHD.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

Is post-transplant cyclophosphamide a true game-changer in allogeneic transplantation: The struggle to unlearn

Close HLA matching of donors and recipients has been the dogma for successful allogeneic blood or marrow transplantation (BMT), to limit the complications of graft rejection and graft-versus-host disease (GVHD). However, many patients in need, especially those in certain racial and ethnic groups such as African-Americans and Hispanics, are unable to find matches despite increased availability of unrelated donors. Unfortunately, despite many early attempts to develop safe, related haploidentical allogenic BMT, mortality rates exceeding 50% from severe GVHD led most centers to steer away from such transplants by the mid-1990s. However, recent advances based largely on the development of high-dose post-transplant cyclophosphamide GVHD prophylaxis, now yield results with haploidentical related donors that approach those with matched donors. With emerging data that younger donor age may be the most important donor selection criterion, HLA-mismatched donors may even have advantages over matched donors in certain situations. Although the exact role that haploidentical donors should play in donor selection strategies is still being defined, the lack of an HLA-matched donor should no longer ever be an exclusion for allogeneic BMT. Unfortunately, this progress in donor availability has not yet been fully recognized by the medical community. Such a discordance between new advances and their clinical translation highlights that changing standard practice is difficult and takes longer than it should, at least in part because it requires "unlearning" long-standing behaviors.

Mechanisms of Graft-versus-Host Disease Prevention by Post-transplantation Cyclophosphamide: An Evolving Understanding

Post-transplantation cyclophosphamide (PTCy) has been highly successful at preventing severe acute and chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). The clinical application of this approach was based on extensive studies in major histocompatibility complex (MHC)-matched murine skin allografting models, in which cyclophosphamide was believed to act via three main mechanisms: (1) selective elimination of alloreactive T cells; (2) intrathymic clonal deletion of alloreactive T-cell precursors; and (3) induction of suppressor T cells. In these models, cyclophosphamide was only effective in very specific contexts, requiring particular cell dose, cell source, PTCy dose, and recipient age. Achievement of transient mixed chimerism also was required. Furthermore, these studies showed differences in the impact of cyclophosphamide on transplanted cells (tumor) versus tissue (skin grafts), including the ability of cyclophosphamide to prevent rejection of the former but not the latter after MHC-mismatched transplants. Yet, clinically PTCy has demonstrated efficacy in MHC-matched or partially-MHC-mismatched HCT across a wide array of patients and HCT platforms. Importantly, clinically significant acute GVHD occurs frequently after PTCy, inconsistent with alloreactive T-cell elimination, whereas PTCy is most active against severe acute GVHD and chronic GVHD. These differences between murine skin allografting and clinical HCT suggest that the above-mentioned mechanisms may not be responsible for GVHD prevention by PTCy. Indeed, recent work by our group in murine HCT has shown that PTCy does not eliminate alloreactive T cells nor is the thymus necessary for PTCy's efficacy. Instead, other mechanisms appear to be playing important roles, including: (1) reduction of alloreactive CD4⁺ effector T-cell proliferation; (2) induced functional impairment of surviving alloreactive CD4⁺ and CD8⁺ effector T cells; and (3) preferential recovery of CD4⁺ regulatory T cells. Herein, we review the history of cyclophosphamide's use in preventing murine skin allograft rejection and our evolving new understanding of the mechanisms underlying its efficacy in preventing GVHD after HCT. Efforts are ongoing to more fully refine and elaborate this proposed new working model. The completion of this effort will provide critical insight relevant for the rational design of novel approaches to improve outcomes for PTCy-treated patients and for the induction of tolerance in other clinical contexts.

How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.

Prospective Randomized Study Comparing Myeloablative Unrelated Umbilical Cord Blood Transplantation versus HLA-Haploidentical Related Stem Cell Transplantation for Adults with Hematologic Malignancies

In this prospective randomized study, we compared the outcomes of single-unit umbilical cord blood transplantation (UCBT) and unmanipulated haploidentical stem cell transplantation (haplo-SCT) with post-transplantation cyclophosphamide (PTCy) in adults with hematologic malignancies. All patients received a myeloablative conditioning (MAC) regimen consisting of thiotepa, busulfan, and fludarabine, with antithymocyte globulin (ATG) added for UCBT recipients. Nineteen patients were randomized to UCBT and the other 26 to haplo-HSCT. Four patients (15%) allocated to the haplo-HSCT arm lacked a suitable donor and were crossed over to the UCBT arm. Finally, 23 underwent UCBT and 22 underwent haplo-HSCT. The cumulative incidence of neutrophil recovery was 87% at a median of 19 days (range, 13 to 24 days) in the UCBT arm versus 100% at a median of 17 days (range, 13 to 25 days) in the haplo-SCT arm (P = .04). Platelet recovery was 70% at a median of 40 days (range, 18 to 129 days) in the UCBT arm versus 86% at a median of 24 days (range, 12 to 127 days) in the haplo-HCT arm (P = .02). Rates of acute graft-versus-host disease (GVHD) grade II-IV or grade III-IV, overall chronic GVHD, and extensive chronic GVHD in the UCBT and Haplo-SCT arms were 43% versus 36% (P = .8), 9% versus 9% (P = 1), 66% versus 43% (P = .04), and 41% versus 23% (P = .2), respectively. Two-year nonrelapse mortality and relapse in the 2 arms were 52% versus 23% (P = .06) and 17% versus 23% (P = .5), respectively. Two-year disease-free survival, overall survival, and GVHD/relapse-free survival in the 2 arms were 30% versus 54% (P = .2), 35% versus 59% (P = .1), and 17% versus 40% (P = .04), respectively. Our data show that in the context of an MAC regimen, haplo-SCT with PTCy provides improved outcomes compared with ATG-containing single-unit UCBT.

Phase I study of graft-versus-host disease prophylaxis including bortezomib for allogeneic hematopoietic cell transplantation from unrelated donors with one or two HLA loci mismatches in Japanese patients

This phase I study was designed for graft-versus-host disease (GVHD) prophylaxis including bortezomib in allogeneic hematopoietic cell transplantation (allo-HCT) from human leukocyte antigen (HLA)-mismatched unrelated donors in Japanese patients. Patients were administered bortezomib on days 1, 4, and 7, with short-term methotrexate and tacrolimus. Three bortezomib dose levels were prepared (1.0, 1.3, and 1.5 mg/m²). A dose of 1.3 mg/m² was planned for administration to the initial six patients, and was adjusted if dose-limiting toxicity developed. Five of six patients enrolled for the initial dose had bone marrow donors. Two cases had single-antigen and single-allele mismatches; four had single-antigen mismatch at the A, B, C, and/or DRB1 loci in the GVH direction. All patients achieved neutrophil engraftment and complete donor chimerism. Three patients developed grade II acute GVHD, and none developed grade III-IV GVHD or any dose-limiting toxicity attributable to bortezomib by day 100. Two patients developed late-onset acute GVHD, and two developed chronic GVHD, but all cases were manageable. All patients were alive without relapse after a median follow-up period of 52 months. The optimal dose of bortezomib was determined to be 1.3 mg/m². Prophylaxis against GVHD using a regimen including bortezomib thus seems feasible for HLA-mismatched unrelated allo-HCT.

Posttransplant cyclophosphamide vs antithymocyte globulin in HLA-mismatched unrelated donor transplantation

The use of anti-thymocyte globulin (ATG) has represented the standard of care in graft-versus-host disease (GVHD) prophylaxis in patients undergoing a mismatched unrelated donor (MMUD) transplant. The safety and feasibility of posttransplant cyclophosphamide (PTCY) in this setting have been reported recently, but no study has compared the outcomes of PTCY vs ATG in 9/10 MMUD transplants. Using the registry data of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we performed a matched-pair analysis comparing those 2 strategies in a 9/10 MMUD setting. Ninety-three patients receiving PTCY were matched with 179 patients receiving ATG. A significantly lower incidence of severe acute GVHD was observed with PTCY compared with ATG. Recipients of the former also showed higher leukemia-free survival and GVHD/relapse-free survival (GRFS). When performing a subgroup analysis including patients receiving peripheral blood stem cells, being in complete remission, or receiving the same associated immunosuppressive agents, superiority of PTCY over ATG was confirmed. Similar to the haploidentical setting, use of PTCY is an effective anti-GVHD prophylaxis in the 9/10 MMUD transplant. Use of PTCY may also provide better outcomes in long-term disease control. These results need confirmation in large prospective randomized trials.

Immune checkpoint inhibitors as a bridge to allogeneic transplantation with posttransplant cyclophosphamide

Published reports suggest that immune checkpoint inhibitors (ICIs) before allogeneic blood or marrow transplantation (alloBMT) may increase the incidence of graft-versus-host disease (GvHD), immune-related adverse events, and nonrelapse mortality (NRM); this led to the US Food and Drug Administration issuing a "Warning and Precaution" regarding the potential for life-threatening immune-mediated complications associated with alloBMT after nivolumab and pembrolizumab. We retrospectively reviewed the outcomes of 14 consecutive patients who received ICIs as their final salvage therapy before T-cell-replete alloBMT using reduced-intensity conditioning. All patients received posttransplant cyclophosphamide (PTCy), which significantly limits severe GvHD, even in the mismatched-donor setting. There was no grade 3-4 acute GvHD (aGvHD), and all 6 cases of grade 2 aGvHD readily resolved with immunosuppression. No patient experienced veno-occlusive disease of the liver, other immune-related adverse events, chronic GvHD, or NRM. There have been 2 relapses (15-month median follow-up), with 12 of 14 patients remaining alive, well, and progression-free. The only death was a result of disease relapse. Although more experience is needed, our data suggest that concerns over immunologic complications associated with ICIs should not preclude allogeneic bone marrow transplantation with PTCy as GvHD prophylaxis.

Addition of sirolimus to standard cyclosporine plus mycophenolate mofetil-based graft-versus-host disease prophylaxis for patients after unrelated non-myeloablative haemopoietic stem cell transplantation: a multicentre, randomised, phase 3 trial

BACKGROUND

Acute graft-versus-host-disease (GVHD) after non-myeloablative human leucocyte antigen (HLA)-matched, unrelated donor, allogeneic haemopoietic stem cell transplantation (HSCT) is associated with considerable morbidity and mortality. This trial aimed to evaluate the efficacy of adding sirolimus to the standard cyclosporine and mycophenolate mofetil prophylaxis therapy for preventing acute GVHD in this setting.

METHODS

This multicentre, randomised, phase 3 trial took place at nine HSCT centres based in the USA, Denmark, and Germany. Eligible patients were diagnosed with advanced haematological malignancies treatable by allogeneic HSCT, had a Karnofsky score greater than or equal to 60, were aged older than 50 years, or if they were aged 50 years or younger, were considered at high risk of regimen-related toxicity associated with a high-dose pre-transplantation conditioning regimen. Patients were randomly allocated by an adaptive randomisation scheme stratified by transplantation centre to receive either the standard GVHD prophylaxis regimen (cyclosporine and mycophenolate mofetil) or the triple-drug combination regimen (cyclosporine, mycophenolate mofetil, and sirolimus). Patients and physicians were not masked to treatment. All patients were prepared for HSCT with fludarabine (30 mg/m² per day) 4, 3, and 2 days before receiving 2 or 3 Gy total body irradiation on the day of HSCT (day 0). In both study groups, 5·0 mg/kg of cyclosporine was administered orally twice daily starting 3 days before HSCT, and (in the absence of GVHD) tapered from day 96 through to day 150. In the standard GVHD prophylaxis group, 15 mg/kg of mycophenolate mofetil was given orally three times daily from day 0 until day 30, then twice daily until day 150, and (in the absence of GVHD) tapered off by day 180. In the triple-drug group, mycophenolate mofetil doses were the same as in the standard group, but the drug was discontinued on day 40. Sirolimus was started 3 days before HSCT, taken orally at 2 mg once daily and adjusted to maintain trough concentrations between 3-12 ng/mL through to day 150, and (in the absence of GVHD) tapered off by day 180. The primary endpoint was the cumulative incidence of grade 2-4 acute GVHD at day 100 post-transplantation. Secondary endpoints were non-relapse mortality, overall survival, progression-free survival, cumulative incidence of grade 3-4 acute GVHD, and cumulative incidence of chronic GVHD. Efficacy and safety analyses were per protocol, including all patients who received conditioning treatment and underwent transplantation. Toxic effects were measured according to the Common Terminology Criteria for Adverse Events (CTCAE). The current study was closed prematurely by recommendation of the Data and Safety Monitoring Board on July 27, 2016, after 168 patients received the allocated intervention, based on the results of a prespecified interim analysis for futility. This study is registered with ClinicalTrials.gov, number NCT01231412.

FINDINGS

Participants were recruited between Nov 1, 2010, and July 27, 2016. Of 180 patients enrolled in the study, 167 received the complete study intervention and were included in safety and efficacy analyses: 77 patients in the standard GVHD prophylaxis group and 90 in the triple-drug group. At the time of analysis, median follow-up was 48 months (IQR 31-60). The cumulative incidence of grade 2-4 acute GVHD at day 100 was lower in the triple-drug group compared with the standard GVHD prophylaxis group (26% [95% CI 17-35] in the triple-drug group vs 52% [41-63] in the standard group; HR 0·45 [95% CI 0·28-0·73]; p=0·0013). After 1 and 4 years, non-relapse mortality increased to 4% (95% CI 0-9) and 16% (8-24) in the triple-drug group and 16% (8-24) and 32% (21-43) in the standard group (HR 0·48 [0·26-0·90]; p=0·021). Overall survival at 1 year was 86% (95% CI 78-93) in the triple-drug group and 70% in the standard group (60-80) and at 4 years it was 64% in the triple-drug group (54-75) and 46% in the standard group (34-57%; HR 0·62 [0·40-0·97]; p=0·035). Progression-free survival at 1 year was 77% (95% CI 68-85) in the triple-drug group and 64% (53-74) in the standard drug group, and at 4 years it was 59% in the triple-drug group (49-70) and 41% in the standard group (30-53%; HR 0·64 [0·42-0·99]; p=0·045). We observed no difference in the cumulative incidence of grade 3-4 acute GVHD (2% [0-5] in the triple-drug group vs 8% [2-14] in the standard group; HR 0·55 [0·16-1·96]; p=0·36) and chronic GVHD (49% [39-59] in triple-drug group vs 50% [39-61] in the standard group; HR 0·94 [0·62-1·40]; p=0·74). In both groups the most common CTCAE grade 4 or higher toxic effects were pulmonary.

INTERPRETATION

Adding sirolimus to cyclosporine and mycophenolate mofetil resulted in a significantly lower proportion of patients developing acute GVHD compared with patients treated with cyclosporine and mycophenolate mofetil alone. Based on these results, the combination of cyclosporine, mycophenolate mofetil, and sirolimus has become the new standard GVHD prophylaxis regimen for patients treated with non-myeloablative conditioning and HLA-matched unrelated HSCT at the Fred Hutchinson Cancer Research Center.

FUNDING

National Institutes of Health.

Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide for Primary Immunodeficiencies and Inherited Disorders in Children

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for some inherited disorders, including selected primary immunodeficiencies (PIDs). In the absence of a well-matched donor, HSCT from a haploidentical family donor (HIFD) may be considered. In adult recipients high-dose post-transplant cyclophosphamide (PTCY) is increasingly used to mitigate the risks of graft failure and graft-versus-host disease (GVHD). However, data on the use of PTCY in children (and especially those with inherited disorders) are scarce. We reviewed the outcomes of 27 children transplanted with an HIFD and PTCY for a PID (n = 22) or osteopetrosis (n = 5) in a single center. The median age was 1.5 years (range, .2 to 17). HSCT with PTCY was a primary procedure (n = 21) or a rescue procedure after graft failure (n = 6). The conditioning regimen was myeloablative in most primary HSCTs and nonmyeloablative in rescue procedures. After a median follow-up of 25.6 months, 24 of 27 patients had engrafted. Twenty-one patients are alive and have been cured of the underlying disease. The 2-year overall survival rate was 77.7%. The cumulative incidences of acute GVHD grade ≥ II, chronic GVHD, and autoimmune disease were 45.8%, 24.2%, and 29.6%, respectively. There were 2 cases of grade III acute GVHD and no extensive cGVHD. The cumulative incidences of blood viral replication and life-threatening viral events were 58% and 15.6%, respectively. There was evidence of early T cell immune reconstitution. In the absence of an HLA-identical donor, HIFD HSCT with PTCY is a viable option for patients with life-threatening inherited disorders.

Three prophylaxis regimens (tacrolimus, mycophenolate mofetil, and cyclophosphamide; tacrolimus, methotrexate, and bortezomib; or tacrolimus, methotrexate, and maraviroc) versus tacrolimus and methotrexate for prevention of graft-versus-host disease with haemopoietic cell transplantation with reduced-intensity conditioning: a randomised phase 2 trial with a non-randomised contemporaneous control group (BMT CTN 1203)

BACKGROUND

Prevention of graft-versus-host disease (GvHD) without malignant relapse is the overall goal of allogeneic haemopoietic cell transplantation (HCT). We aimed to evaluate regimens using either maraviroc, bortezomib, or post-transplantation cyclophosphamide for GvHD prophylaxis compared with controls receiving the combination of tacrolimus and methotrexate using a novel composite primary endpoint to identify the most promising intervention to be further tested in a phase 3 trial.

METHODS

In this prospective multicentre phase 2 trial, adult patients aged 18-75 years who received reduced-intensity conditioning HCT were randomly assigned (1:1:1) by random block sizes to tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide (cyclophosphamide 50 mg/kg on days 3 and 4, followed by tacrolimus starting on day 5 and mycophenolate mofetil starting on day 5 at 15 mg/kg three times daily not to exceed 1 g from day 5 to day 35); tacrolimus, methotrexate, and bortezomib (bortezomib 1·3 mg/m2 intravenously on days 1, 4, and 7 after HCT); or tacrolimus, methotrexate, and maraviroc (maraviroc 300 mg orally twice daily from day -3 to day 30 after HCT). Methotrexate was administered as a 15 mg/m2 intravenous bolus on day 1 and 10 mg/m2 intravenous bolus on days 3, 6, and 11 after HCT; tacrolimus was given intravenously at a dose of 0·05 mg/kg twice daily (or oral equivalent) starting on day -3 (except the post-transplantation cyclophosphamide, as indicated), with a target level of 5-15 ng/mL. Tacrolimus was continued at least until day 90 and was tapered off by day 180. Each study group was compared separately to a contemporary non-randomised prospective cohort of patients (control group) who fulfilled the same eligibility criteria as the trial, but who were treated with tacrolimus and methotrexate at centres not participating in the trial. The primary endpoint (GvHD-free, relapse-free survival [GRFS]) was defined as the time from HCT to onset of grade 3-4 acute GvHD, chronic GvHD requiring systemic immunosuppression, disease relapse, or death. The study was analysed by modified intention to treat. The study is closed to accrual and this is the planned analysis. This trial is registered with ClinicalTrials.gov, number NCT02208037.

FINDINGS

Between Nov 17, 2014, and May 18, 2016, 273 patients from 31 US centres were randomly assigned to the three study arms: 89 to tacrolimus, methotrexate, and bortezomib; 92 to tacrolimus, methotrexate, and maraviroc; 92 to tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide; and six were excluded. Between Aug 1, 2014, and Sept 14, 2016, 224 controls received tacrolimus and methotrexate. Controls were generally well matched except for more frequent comorbidities than the intervention groups and a different distribution of types of conditioning regimens used. Compared with controls, the hazard ratio for GRFS was 0·72 (90% CI 0·54-0·94; p=0·044) for tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide, 0·98 (0·76-1·27; p=0·92) for tacrolimus, methotrexate, and bortezomib, and 1·10 (0·86-1·41; p=0·49) for tacrolimus, methotrexate, and maraviroc. 238 patients experienced grade 3 or 4 toxicities: 12 (13%) had grade 3 and 67 (73%) grade 4 events with tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide; ten (11%) had grade 3 and 68 (76%) had grade 4 events with tacrolimus, methotrexate, and bortezomib; and 18 (20%) had grade 3 and 63 (68%) had grade 4 events with tacrolimus, methotrexate, and maraviroc. The most common toxicities were haematological (77 [84%] for tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide; 73 [82%] for tacrolimus, methotrexate, and bortezomib; and 78 [85%] for tacrolimus, methotrexate, and maraviroc) and cardiac (43 [47%], 44 [49%], and 43 [47%], respectively).

INTERPRETATION

Tacrolimus, mycophenolate mofetil, and post-transplantation cyclophosphamide was the most promising intervention, yielding the best GRFS; this regimen is thus being prospectively compared with tacrolimus and methotrexate in a phase 3 randomised trial.

FUNDING

US National Health, Lung, and Blood Institute; National Cancer Institute; National Institute of Allergy and Infectious Disease; and Millennium Pharmaceuticals.

Hematopoietic stem cell transplant with HLA-mismatched grafts: impact of donor, source, conditioning, and graft versus host disease prophylaxis

INTRODUCTION

Allogeneic hematopoietic cell transplantation is frequently used to treat malignant and non-malignant conditions, and many patients lack a human leukocyte antigen (HLA) matched related or unrelated donor. For those patients, available alternative graft sources include HLA mismatched unrelated donors, cord blood, or haplo-identical donors. These graft sources have unique characteristics and associated outcomes requiring graft-specific variations to conditioning regimens, graft-versus-host disease prophylaxis, and post-transplant care. Areas covered: This manuscript will cover approaches in selecting donors, conditioning regimens, graft versus host disease prophylaxis, post-transplant care, and ongoing clinical trials related to mismatched grafts. Expert commentary: In the setting, haplo-identical grafts are increasingly popular due to low graft versus host disease (GVHD) risk and control of cellular dose. We recommend young male donors, utilizing bone marrow with post-transplant cyclophosphamide for GVHD prophylaxis. Cord blood transplant is appropriate for young healthy patients, and we recommend 6/8 HLA matched grafts with at least 2.0 × 10⁷/kg total nucleated cell dose. For mismatched unrelated donors we recommend young male donors, utilizing bone marrow with in vivo T-cell conditioning with post-transplant cyclophosphamide, alemtuzumab, or ATG. With these transplants, significant post-transplant surveillance and infectious prophylaxis is key to reducing treatment-related mortality.

Sequential HLA-haploidentical transplantation utilizing post-transplantation cyclophosphamide for GvHD prophylaxis in high-risk and relapsed/refractory AML/MDS

This study evaluates the role of sequential therapy in HLA-haploidentical transplantation (haplo-HSCT) of high-risk, relapsed/refractory AML/MDS. We analyzed the course of 33 adults with active disease at time of transplantation (AML n = 30; MDS n = 3; median age 58 years, range: 32-71). Sequential therapy consisted of cytoreductive chemotherapy (FLAMSA n = 21; clofarabine n = 12) applied shortly prior to reduced intensity conditioning for T-cell-replete haplo-HSCT using post-transplantation cyclophosphamide as GvHD prophylaxis. No graft rejection was observed. Complete remission at day +30 was achieved in 97% of patients. CI of acute GvHD grade II-IV and chronic GvHD was 24% (no grade IV) and 23%, respectively. NRM at 1 and 3 years was 15%, each. Severe regimen-related toxicities (grade III-IV) were observed in 58%, predominantly involving the gastrointestinal tract (diarrhea 48%, mucositis 15%, transient elevation of transaminases 18%). Probability of relapse at 1 and 3 years was 28% and 35%. At a median follow-up of 36 months, the estimated 1- and 3-year overall survival was 56% and 48%. Disease-free survival was 49% and 40%, respectively. At 3 years, GvHD and relapse-free survival (GRFS) was 24% while chronic GvHD and relapse-free survival (CRFS) was 29%. Thus, our results indicate that sequential haplo-HSCT is an effective salvage treatment providing high anti-leukemic activity, favorable tolerance, and acceptable toxicity in patients suffering from advanced AML/MDS.

Allogeneic hematopoietic cell transplantation; the current renaissance

Allogeneic hematopoietic cell transplantation (HCT) provides the best chance for cure for many patients with malignant and nonmalignant hematologic disorders. Recent advances in selecting candidates and determining risk, procedure safety, utilization in older patients, use of alternative donors, and new or novel application of anti-cancer, immunosuppressive and antimicrobial agents have improved outcomes and expanded the role of HCT in hematologic disorders. Relapse remains the predominant cause of failure but enlightened use of new targeted and immunotherapeutic agents in combination with HCT promises to reduce relapse and further improve HCT outcomes.

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.

Single Antigen-Mismatched Unrelated Hematopoietic Stem Cell Transplantation Using High-Dose Post-Transplantation Cyclophosphamide Is a Suitable Alternative for Patients Lacking HLA-Matched Donors

The optimal prophylaxis regimen for graft-versus-host disease (GVHD) in the setting of mismatched unrelated donor (MMUD) allogeneic hematopoietic stem cell transplantation (alloHSCT) is not defined. The use of high-dose post-transplant cyclophosphamide (PTCy) in haploidentical transplantation has proven feasible and effective in overcoming the negative impact of HLA disparity on survival. We hypothesized that PTCy could also be effective in the setting of MMUD transplantation. We retrospectively analyzed 86 consecutive adult recipients of alloHSCT in our institution, comparing 2 contemporaneous groups: PTCy MMUD (n = 26) versus matched unrelated donor (MUD) (n = 60). Graft source was primarily peripheral blood (92%). All PTCy MMUD were HLA 7/8 (differences in HLA class I loci in 92% of patients) and received PTCy plus tacrolimus ± mofetil mycophenolate as GVHD prophylaxis. No differences were observed between PTCy MMUD and MUD in the 100-day cumulative incidence of acute GVHD grades II to IV (31% versus 22%, respectively; P = .59) and III to IV (8% versus 10%, P = .67). There was a trend for a lower incidence of moderate to severe chronic GVHD at 1 year after PTCy MMUD in comparison with MUD (22% versus 41%, P = .098). No differences between PTCy MMUD and MUD were found regarding nonrelapse mortality (25% versus 18%, P = .52) or relapse rate (11% versus 19%, P = .18). Progression-free survival and overall survival at 2 years were similar in both cohorts (67% versus 54% [HR, .84; 95% CI, .38 to 1.88; P = .68] and 72% versus 57% [HR, .71; 95% CI, .31 to 1.67; P = .44], respectively). The 2-year cumulative incidence of survival free of moderate to severe chronic GVHD and relapse tended to be higher in the PTCy MMUD group (47% versus 24%; HR, .60; 95% CI, .31 to 1.14; P = .12). We conclude that HLA 7/8 MMUD transplantation using PTCy plus tacrolimus is a suitable alternative for those patients who lack a MUD.

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.

Reduced-Intensity Haploidentical Bone Marrow Transplantation with Post-Transplant Cyclophosphamide for Solid Tumors in Pediatric and Young Adult Patients

High-risk, recurrent, or refractory solid tumors in pediatric, adolescent, and young adult (AYA) patients have an extremely poor prognosis despite current intensive treatment regimens. We piloted an allogeneic bone marrow transplant platform using reduced-intensity conditioning (RIC) and partially HLA-mismatched (haploidentical) related donors for this population of pediatric and AYA solid tumor patients. Sixteen patients received fludarabine, cyclophosphamide, melphalan, and low-dose total body irradiation RIC haploidentical BMT (haploBMT) followed by post-transplantation cyclophosphamide (PTCy), mycophenolate mofetil, and sirolimus. All assessable patients were full donor chimeras on day 30 with a median neutrophil recovery of 19 days and platelet recovery of 21 days. One patient (7%) exhibited secondary graft failure associated with concomitant infection. The median follow-up time was 15 months. Overall survival was 88%, 56%, and 21% at 6, 12, and 24 months, respectively. Median survival from transplant date was 14 months with a median progression-free survival 7 months. We observed limited graft-versus-host disease in 3 patients and nonrelapse mortality in 1 patient. We demonstrated that RIC haploBMT with PTCy is feasible and has acceptable toxicities in patients with incurable pediatric and AYA solid tumors; thus, this approach serves as a platform for post-transplant strategies to prevent relapse and optimize progression-free survival.