Reduced-intensity transplantation for lymphomas using haploidentical related donors vs HLA-matched unrelated donors. Blood. 2016;127:938-947. [PMID: 26670632 DOI: 10.1182/blood-2015-09-671834]

Impact of type of reduced-intensity conditioning regimen on the outcomes of allogeneic haematopoietic cell transplantation in classical Hodgkin lymphoma

Reduced-intensity conditioning (RIC) allogeneic haematopoietic cell transplantation (allo-HCT) is a curative option for select relapsed/refractory Hodgkin lymphoma (HL) patients; however, there are sparse data to support superiority of any particular conditioning regimen. We analyzed 492 adult patients undergoing human leucocyte antigen (HLA)-matched sibling or unrelated donor allo-HCT for HL between 2008 and 2016, utilizing RIC with either fludarabine/busulfan (Flu/Bu), fludarabine/melphalan (Flu/Mel140) or fludarabine/cyclophosphamide (Flu/Cy). Multivariable regression analysis was performed using a significance level of <0·01. There were no significant differences between regimens in risk for non-relapse mortality (NRM) (P = 0·54), relapse/progression (P = 0·02) or progression-free survival (PFS) (P = 0·14). Flu/Cy conditioning was associated with decreased risk of mortality in the first 11 months after allo-HCT (HR = 0·28; 95% CI = 0·10-0·73; P = 0·009), but beyond 11 months post allo-HCT it was associated with a significantly higher risk of mortality, (HR = 2·46; 95% CI = 0·1.32-4·61; P = 0·005). Four-year adjusted overall survival (OS) was similar across regimens at 62% for Flu/Bu, 59% for Flu/Mel140 and 55% for Flu/Cy (P = 0·64), respectively. These data confirm the choice of RIC for allo-HCT in HL does not influence risk of relapse, NRM or PFS. Although no OS benefit was seen between Flu/Bu and Flu/Mel 140; Flu/Cy was associated with a significantly higher risk of mortality beyond 11 months from allo-HCT (possibly due to late NRM events).

Ruxolitinib: a potential treatment for corticosteroid refractory acute graft-versus-host disease

INTRODUCTION

Allogeneic transplantation represents a potentially curative procedure for various lethal conditions; however, it is associated with serious immune mediated complications. The most serious complication is graft-versus-host disease (GVHD). Acute GVHD (aGVHD) is unresponsive to initial corticosteroid therapy in ~40% of cases. Corticosteroid-refractory aGVHD (CR-aGVHD) represents a significant unmet need with nearly 60% mortality in patients developing this state.

AREAS COVERED

We review landmark trials which led to the US FDA approval of Ruxolitinb for the treatment of CR-aGVHD. Ruxolitinib phosphate is a Janus Kinase 1 and 2 inhibitor which inhibits pro-inflammatory signaling, and modulates T-cell subsets to an anti-inflammatory phenotype. Ruxolitinib was recently prospectively studied for the treatment of CR-aGVHD in the REACH1 trial, which added Ruxolitinib to corticosteroid therapy. This trial demonstrated favorable results with 73% of patients ultimately responding. Among responders, over 70% remained alive at 6 months. These results led to the US FDA to approve ruxolitinib as treatment for CR-aGVHD, the first approval of its kind.

EXPERT OPINION

Ruxolitinib represents the standard option for CR-aGVHD. Future studies should identify patients less likely to respond to ruxolitinib and/or focus on a more targeted approaches to reduce infectious complications and cytopenias seen with this drug.

Effects of stem cell transplantation in patients with peripheral T-cell lymphoma not otherwise specified and angioimmunoblastic T-cell lymphoma

The effects of stem cell transplantation (SCT) in patients with peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL) remain controversial. We analyzed the feasibility of SCT and risk factors associated with outcomes of PTCL-NOS and AITL patients to identify the potential clinical efficacy of SCT. We retrospectively analyzed the data of PTCL-NOS (n = 83) and AITL (n = 112) patients who received autologous (n = 10 and 16, respectively) or allogeneic (n = 12 and 4, respectively) SCT, or no SCT (n = 61 and 92, respectively) between 2008 and 2018. All PTCL-NOS and AITL diagnoses were reconfirmed by an experienced hematopathologist. Median age at PTCL-NOS and AITL diagnoses in the SCT group was younger than that in the no SCT group. Significant risk factors for lower overall survival were intermediate-high and high-risk international prognostic indexes in PTCL-NOS patients (P = 0.0052), and a > 2 modified prognostic index for T-cell lymphoma (P = 0.0079) and no SCT (P = 0.028) in AITL patients. Autologous or allogeneic SCT compared with no SCT in AITL patients resulted in 3-year overall survival of 68.6% and 100% vs. 57.2% (P = 0.018). Strategies should be developed to improve selection of PTCL-NOS and AITL patients suitable for SCT and/or additional novel therapies.

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.

Wide availability of HLA-matched or a few loci-mismatched donors in the graft-vs-host direction among nonsibling first-degree relatives

Although outcomes of hematopoietic stem cell transplantation from alternative donors have been improved, it has not yet challenged the precedence of HLA-matched or a few loci-mismatched donors. Because the availabilities of these donors among nonsibling relatives have been scarcely discussed, we analyzed them using a large Japanese dataset of HLA typing. Data set included HLA data from 2838 patients and their relatives, distributed in all parts of Japan. Antigen mismatches at the HLA-A, -B, -DR loci and allele mismatches at the HLA-A, -B, -C, -DRB1 loci were examined. The availabilities of 0 to 1/6 antigen-mismatched donors among one parent-candidate and one sibling-candidate were 24.3% and 33.9%, and those of 0 to 2/8 allele-mismatched donors were 18.6% and 32.1%, respectively. Additional HLA-C antigen mismatches (18.1% vs 0.0%) along with the possession of 1 to 3/8 allele mismatches (31.3% vs 3.0%) were more frequently observed in parent-candidates than in sibling-candidate. Most multiple allele-mismatched pairs had HLA-B allele mismatches. In conclusion, expanding donor searches to include nonsibling relatives could widen the availability of conventional relative donors with 0 to 1/6 antigen mismatches or 0 to 2/8 allele mismatch to 20% to 30%. High-resolution typing including HLA-C locus examination should be performed, because additional mismatches at HLA-C loci along with multiple allele mismatches were often observed, especially among nonsibling pairs.

Indications for Hematopoietic Cell Transplantation and Immune Effector Cell Therapy: Guidelines from the American Society for Transplantation and Cellular Therapy

The American Society for Transplantation and Cellular Therapy (ASTCT) published its first white paper on indications for autologous and allogeneic hematopoietic cell transplantation (HCT) in 2015. It was identified at the time that periodic updates of indications would be required to stay abreast with state of the art and emerging indications and therapy. In recent years the field has not only seen an improvement in transplantation technology, thus widening the therapeutic scope of HCT, but additionally a whole new treatment strategy using modified immune effector cells, including chimeric antigen receptor T cells and engineered T-cell receptors, has emerged. The guidelines review committee of the ASTCT deemed it optimal to update the ASTCT recommendations for indications for HCT to include new data and to incorporate indications for immune effector cell therapy (IECT) where appropriate. The guidelines committee established a multiple stakeholder task force consisting of transplant experts, payer representatives, and a patient advocate to provide guidance on indications for HCT and IECT. This article presents the updated recommendations from the ASTCT on indications for HCT and IECT. Indications for HCT/IECT were categorized as (1) Standard of care, where indication is well defined and supported by evidence; (2) Standard of care, clinical evidence available, where large clinical trials and observational studies are not available but have been shown to be effective therapy; (3) Standard of care, rare indication, for rare diseases where demonstrated effectiveness exists but large clinical trials and observational studies are not feasible; (4) Developmental, for diseases where preclinical and/or early-phase clinical studies show HCT/IECT to be a promising treatment option; and (5) Not generally recommended, where available evidence does not support the routine use of HCT/IECT. The ASTCT will continue to periodically review these guidelines and update them as new evidence becomes available.

Hematopoietic stem cell transplantation for blood cancers in the era of precision medicine and immunotherapy

Hematopoietic stem cell transplantation (HCT) has been an integral component in the treatment of many hematologic malignancies. Since the development of HCT nearly 50 years ago, the role of this modality has evolved as newer treatment approaches have been developed and integrated into the standard of care. In the last decade, novel and highly active targeted therapies and immunotherapies have been approved for many hematologic malignancies, raising the question of whether HCT continues to retain its prominent role in the treatment paradigms of various hematologic malignancies. In this review, the authors have described the current role of autologous and allogeneic HCT in the treatment of patients with acute leukemias, aggressive B-cell lymphomas, and multiple myeloma and discussed how novel targeted therapies and immunotherapies have changed the potential need, timing, and goal of HCT in patients with these diseases.

Matched-Pair Analysis of Transplant from Haploidentical, Unmanipulated Bone Marrow Donor versus HLA Identical Sibling for Patients with Hematologic Malignancies

A matched-pair analysis of transplant-related outcomes was carried out in 116 of 255 consecutive patients who received transplants from an HLA identical sibling (n = 58) or haploidentical related donor (n = 58). The 2 patient series were matched with 9 variables: period of transplant, patient and donor age, sex, diagnosis, disease phase, conditioning regimen, donor-recipient sex, and cytomegalovirus (CMV) status combinations. As graft-versus-host disease (GVHD) prophylaxis, all patients received the standard cyclosporine and methotrexate association with the addition of anti-thymocyte globulins, mycophenolate mofetil, and basiliximab in haploidentical, unmanipulated bone marrow recipients. Anti-infectious management, transfusion policy, and supportive care were identical for all patients. By comparing the 2 patient series, no statistically significant difference was observed for the cumulative incidence of advanced acute and extensive chronic GVHD, transplant-related mortality, and relapse. With a median follow-up of 3.5 years, the 5-year disease-free survival was 37% ± 6% and 36% ± 6% for HLA identical sibling and haploidentical recipients, respectively. The results of transplant from HLA identical siblings and haploidentical donors are comparable. Regardless of the HLA matching, other factors known to affect the transplant outcomes, such as donor-recipient age, sex, and CMV status combinations, might drive the search for the best donor.

Impact and Intricacies of Bone Marrow Microenvironment in B-cell Lymphomas: From Biology to Therapy

Lymphoma, a group of widely prevalent hematological malignancies of lymphocyte origin, has become the focus of significant clinical research due to their high propensity for refractory/relapsed (R/R) disease, leading to poor prognostic outcomes. The complex molecular circuitry in lymphomas, especially in the aggressive phenotypes, has made it difficult to find a therapeutic option that can salvage R/R disease. Furthermore, the association of lymphomas with the Bone Marrow (BM) microenvironment has been found to portend worse outcomes in terms of heightened chances of relapse and acquired resistance to chemotherapy. This review assesses the current therapy options in three distinct types of lymphomas: diffuse large B-cell lymphoma, follicular lymphoma and mantle cell lymphoma. It also explores the role of the BM tumor microenvironment as a secure 'niche' for lymphoma cells to grow, proliferate and survive. It further evaluates potential mechanisms through which the tumor cells can establish molecular connections with the BM cells to provide pro-tumor benefits, and discusses putative therapeutic strategies for disrupting the BM-lymphoma cell communication.

Current Status and Future Directions in Graft-Versus-Host Disease Prevention Following Allogeneic Blood and Marrow Transplantation in Adults

Graft-versus-host disease (GvHD) in its acute and chronic forms continues to represent a significant barrier to the success and wide-applicability of blood and marrow transplantation as a potentially curative treatment modality for a number of benign and malignant blood conditions. Presently, calcineurin inhibitor (CNI)-based regimens remain the most commonly used prevention strategy, although post-transplant cyclophosphamide is emerging as an alternative approach, and is providing a backbone for innovative CNI-free combinations. In this paper, we review the current strategies used for the prevention of GvHD, and highlight some of the developing and promising combinations.

The Predicted Indirectly Recognizable HLA Epitopes (PIRCHE) Score for HLA Class I Graft-versus-Host Disparity Is Associated with Increased Acute Graft-versus-Host Disease in Haploidentical Transplantation with Post-Transplantation Cyclophosphamide

The Predicted Indirectly Recognizable HLA Epitopes (PIRCHE) score quantifies the number of PIRCHEs in patient-donor pairs and represents an in silico measure of indirect alloreactivity. This biologic process is defined as T cell recognition of epitopes derived from mismatched, allogeneic HLA peptides that are subsequently presented by shared HLA molecules. Its association with clinical outcome has not been examined in haploidentical hematopoietic cell transplantation (haplo-HCT) with post-transplantation cyclophosphamide (PTCy). We hypothesized that the PIRCHE score (PS) would correlate with indirect alloreactivity and predict graft-versus-host disease (GVHD) risk and the incidence of relapse after haplo-HCT with PTCy. We retrospectively analyzed 148 patients who underwent peripheral blood stem cell T cell-replete haplo-HCT with PTCy at a single center between 2009 and 2016. For each patient-donor pair, the PS was calculated using the PIRCHE online matching tool. PSs were categorized by class and vector. The median class I graft-versus-host (GVH) PS was 11 (range, 0 to 56), and the median class I host-versus-graft (HVG) PS was 10 (range, 0 to 51). Class I GVH PS was associated with increased risk of grade II-IV acute GVHD (adjusted hazard ratio, 1.03 per PS unit increase; 95% confidence interval, 1.01 to 1.05; P= .008) but not of chronic GVHD or relapse. Our data show that use of the PS is a novel strategy for predicting clinical outcome in haplo-HCT; further studies using registry data and prospective cohorts are warranted to validate these findings.

CD4+FOXP3+ Regulatory T Cell Therapies in HLA Haploidentical Hematopoietic Transplantation

Since their discovery CD4⁺FOXP3⁺ regulatory T cells (Tregs) represented a promising tool to induce tolerance in allogeneic hematopoietic cell transplantation. Preclinical models proved that adoptive transfer of Tregs or the use of compounds that can favor their function in vivo are effective for prevention and treatment of graft-vs.-host disease (GvHD). Following these findings, Treg-based therapies have been employed in clinical trials. Adoptive immunotherapy with Tregs effectively prevents GvHD induced by alloreactive T cells in the setting of one HLA haplotype mismatched hematopoietic transplantation. The absence of post transplant pharmacologic immunosuppression unleashes T-cell mediated graft-vs.-tumor (GvT) effect, which results in an unprecedented, almost complete control of leukemia relapse in this setting. In the present review, we will report preclinical studies and clinical trials that demonstrate Treg ability to promote donor engraftment, protect from GvHD and improve GvT effect. We will also discuss new strategies to further enhance in vivo efficacy of Treg-based therapies.

Where does transplant fit in the age of targeted therapies?

The role of hematopoietic cell transplantation (HCT) for indolent lymphoma has evolved over the last 5 years with the availability of novel low-toxicity therapies and a better understanding of the prognosis of these entities. However, despite numerous treatment options for patients with follicular lymphoma, none are thought to be curative, and many require ongoing therapy with chronic toxicity. Historical trials indicate that autologous HCT as initial consolidation leads to improved progression-free survival, but not overall survival (OS) and, thus, is not typically recommended. However, autologous HCT for chemosensitive relapse can be carried out with ∼1% early mortality risk, affording disease control lasting a median of 3 to 5 years and the potential to improve OS. These results may compare favorably in efficacy, toxicity, and cost vs multiple sequential novel therapies with shorter durations of benefit. Recent data indicate that autologous HCT in follicular lymphoma patients with early initial progression will result in more than one third being alive and without relapse at 5 years, leading to improved OS when used within a year of the first recurrence. Unlike other available therapies, allogeneic HCT has the potential to cure up to one half of those transplanted with indolent B-cell non-Hodgkin lymphoma, although the risks need to be recognized and appropriate patient and donor selection is critical to ensure the best outcomes. HCT continues to remain a viable option in the current era of multiple targeted agents.

Allogeneic transplantation in elderly patients ≥65 years with non-Hodgkin lymphoma: a time-trend analysis

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative therapy for relapsed/refractory and high-risk non-Hodgkin lymphoma (NHL). However, no large studies have evaluated allo-HCT utilization in elderly NHL patients (≥65 years). Using the CIBMTR registry, we report a time-trend analysis of 727 NHL patients (≥65 years) undergoing the first allo-HCT from 2000 to 2015 in the United States (US). Study cohorts were divided by time period: 2000-2005 (N = 76) vs. 2006-2010 (N = 238) vs. 2011-2015 (N = 413). Primary outcome was overall survival (OS). Secondary outcomes included progression-free survival (PFS), relapse/progression (R/P), and non-relapse mortality (NRM). Median age at transplant, use of reduced-intensity conditioning, and graft source remained stable, while use of unrelated donors increased in the most current era. The 1-year probabilities of NRM from 2000 to 2005 vs. 2006-2010 vs. 2011-2015 were 24% vs. 19% vs. 21%, respectively (p = 0.67). Four-year probability of R/P was similar among the three cohorts: 48% (2000-2005), 40% (2006-2010), and 40% (2011-2015) (p = 0.39). The 4-year probabilities of PFS and OS (2000-2005 vs. 2006-2010 vs. 2011-2015) showed significantly improved outcomes in more recent time periods: 17% vs. 31% vs. 30% (p = 0.02) and 21% vs. 42% vs. 44% (p < 0.001), respectively. Utilization of allo-HCT increased in elderly NHL patients in the US since 2000 with improving survival outcomes.

Haploidentical Stem Cell Transplantation With Posttransplant Cyclophosphamide Therapy vs Other Donor Transplantations in Adults With Hematologic Cancers: A Systematic Review and Meta-analysis

Importance

Use of haploidentical (HAPLO) stem cell transplantation with posttransplant cyclophosphamide is rapidly increasing in adults with hematologic cancers. However, its specific role compared with other transplant strategies has yet to be identified.

Objective

To synthesize the existing evidence regarding outcomes of stem cell transplantations comparing HAPLO stem cell transplantation and posttransplant cyclophosphamide therapy with transplantations from matched related donors (MRDs), matched unrelated donors (MUDs), or mismatched unrelated donors (MMUDs).

Data Sources

PubMed, Cochrane Library, ClinicalTrials.gov, and meeting abstracts were searched for the key words haploidentical and cyclophosphamide from inception through March 1, 2019.

Study Selection

Studies comparing HAPLO stem cell transplantation and posttransplant cyclophosphamide therapy with transplantations from other donors in adults with hematologic cancers were eligible for meta-analysis.

Data Extraction and Synthesis

Pooled odds ratios (ORs) and 95% CIs were calculated using a random-effects model.

Main Outcomes and Measures

Main outcomes were all-cause mortality, nonrelapse mortality, and relapse.

Results

A total of 30 studies including 22 974 participants were analyzed. HAPLO stem cell transplantation with posttransplant cyclophosphamide therapy was associated with increased all-cause mortality compared with MRDs (OR, 1.17; 95% CI, 1.05-1.30), similar all-cause mortality compared with MUDs (OR, 1.06; 95% CI, 0.96-1.18), and reduced all-cause mortality compared with MMUDs (OR, 0.75; 95% CI, 0.61-0.92). Regarding nonrelapse mortality, HAPLO stem cell transplantation with posttransplant cyclophosphamide was associated with worse outcomes compared with MRDs (OR, 1.20; 95% CI, 1.04-1.40) but better outcomes compared with MUDs (OR, 0.75; 95% CI, 0.61-0.92) and MMUDs (OR, 0.51; 95% CI, 0.25-1.02). In terms of relapse, HAPLO stem cell transplantation with posttransplant cyclophosphamide was associated with similar outcome compared with MRDs (OR, 1.01; 95% CI, 0.86-1.17) and MMUDs (OR, 1.06; 95% CI, 0.77-1.47) but showed increased relapse compared with MUDs (OR, 1.20; 95% CI, 1.03-1.40).

Conclusions and Relevance

Results of this meta-analysis suggest that MRDs, if available, remain the optimal donors regarding mortality and HAPLO stem cell transplantation with posttransplant cyclophosphamide may be preferred over MMUDs. Prospective comparisons with MUDs are needed.

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.

Pretransplant active disease status and HLA class II mismatching are associated with increased incidence and severity of cytokine release syndrome after haploidentical transplantation with posttransplant cyclophosphamide

Cytokine release syndrome (CRS) represents a life‐threatening side effect after haploidentical stem cell transplantation (Haplo‐SCT) with posttransplant cyclophosphamide (PT‐Cy). Factors predictive of CRS development is still a matter of debate. We retrospectively analyzed 102 consecutive patients receiving a bone marrow (BM) (n = 42) or peripheral blood stem cells (PBSC) (n = 60) Haplo‐SCT with PT‐Cy. The two cohorts were similar in main patients’ characteristics besides disease type (P = .02). Cumulative incidence of grades 1, 2, and ≥3 CRS was 80%, 52%, and 15% at a median of 2, 4, and 7 days, respectively. Moderate/High‐grade fever (39°‐41°), grade 1 and grade ≥3 CRS occurred more frequently after PBSC relative to BM grafts (68% vs 33%, P = .0005; 87% vs 71%, P = .009; 20% vs 7%, P = .07). Only patients experiencing grade ≥3 CRS had a worse outcome in terms of 1‐year overall survival (OS) and nonrelapse mortality (NRM): 39% vs 80% (P = .002) and 40% vs 8% (P = .005), respectively. By univariate analysis the only factors associated with the increased risk of ≥3 CRS were pretransplant disease status (8% for complete remission, 11% for partial remission, and 38% for active disease, P = .002), HLA‐DRB1 mismatching (57% vs 14%, P = .007), and PBSC graft (P = .07). By multivariable analysis, only pretransplant disease status (hazard ratio, HR: 6.84, P = .005) and HLA‐DRB1 mismatching (HR: 17.19, P = .003) remained independent predictors of grade ≥3 CRS. Only grade ≥3 CRS is clinically relevant for the final outcome of patients receiving Haplo‐SCT with PT‐Cy, is more frequent after a PBSC graft and is associated with pretransplant active disease and HLA‐DRB1 mismatching.

Hematopoietic cell transplant nurse coordinators' perceptions of related donor care: a European survey from the EBMT Nurses Group

Allogeneic haematopoietic cell transplantation (HCT) is a curative procedure for patients with haematological malignancies and immune deficiencies. A human leukocyte antigen (HLA) identical sibling is only available for 25-35% of patients in need. The improvement in haplo-identical transplantation has led to a marked increase in cell donation from relatives. Despite international recommendations, discrepancies in related-donors (RD) care exist between centres, particularly regarding medical suitability criteria, consenting procedures and donor follow-up. This European survey aimed to explore hematopoietic cell transplantation coordinators nurses' (HCT-CNs) perceptions of RD care, in particular the association with the presence or not of an independent unit (IU). Ninety-three HCT-CNs from seventy-six EBMT centres responded, representing 19 countries (response rate: 27%). Our results did not show a significant association between IU and HCT-CNs perceptions of related-donors care. The practices for RD care vary among centres regarding presence or not of an IU (48%), person caring for RD (haematologist in 54%, HCT physician in 17%, HCT-CNs in 20%), person to whom the results of HLA typing are communicated, use of a booklet for RD, follow-up or not and periodicity of follow-up. Qualitative data highlight the related-donation ethical issues and the need for improvement in RD care. HCT-CNs' main concerns were: the necessary confidentiality to insure the voluntary status of RD, the perceived conflict of interest felt by professionals when managing both patients and RD, plus the psychosocial aspects of related-donation. Even if there is a variety of a practice among centres, the presence of an IU is not significantly associated with an improvement in RD care.

Optimized Timing of Post-Transplantation Cyclophosphamide in MHC-Haploidentical Murine Hematopoietic Cell Transplantation

Post-transplantation cyclophosphamide (PTCy) reduces the risks of severe acute and chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). Yet, the standard clinical dose and timing of PTCy were partly extrapolated from MHC-matched skin allografting models and were partly empirical. Here we investigated the impact of differential dosing and timing of PTCy on its efficacy in preventing GVHD in a murine MHC-haploidentical HCT model. Administration of PTCy on days +3/+4 was superior to administration on days +1/+2, +5/+6, or +7/+8, whereas low-dose (10 mg/kg/day) PTCy on days +1/+2 actually led to accelerated death. Although the optimal timing of PTCy dosing was day +2 or +3 in the skin allografting models, in our MHC-haploidentical HCT model, PTCy on days +2/+3 was inferior to PTCy on days +3/+4 at lower doses. PTCy administered on days +3/+4, +4/+5, or +3/+5 were similarly efficacious. Single-day versus 2-day dosing schedules demonstrated that PTCy is maximally effective when given on day +4. Flow cytometric analysis showed that optimal PTCy dosing schedules both decreased alloreactive CD4⁺CD25^-Foxp3^- T cell proliferation at day +7 and allowed preferential CD4⁺CD25⁺Foxp3⁺ T cell reconstitution at day +21, suggesting that this combination may be a potential predictive biomarker of successful GVHD prevention by PTCy. These results show that the dose, timing, and cumulative exposure of PTCy all are critical for its efficacy in preventing GVHD. We are currently investigating the clinical relevance of these findings in a protocol seeking to optimize PTCy dose and timing and test these T cell endpoints as candidate biomarkers of successful GVHD prevention by PTCy.

Haploidentical transplantation using posttransplant cyclophosphamide as GVHD prophylaxis in patients over age 70

Hematologic malignancies in older people are unlikely to be cured with chemotherapy alone. Advances in allogeneic blood or marrow transplantation (alloBMT), especially nonmyeloablative (NMA) conditioning and the use of haploidentical donors, now make this therapy available to older people; however, long-term outcomes and predictors of success are unclear. We reviewed the outcomes of 93 consecutive patients aged 70 and older (median, 72; range, 70-78), who underwent haploidentical BMT at Johns Hopkins Hospital between 1 September 2009 and 1 April 2018. All patients received NMA conditioning and posttransplantation cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis. The 2-year overall survival was 53%, and 2-year event-free survival was 43%. The 180-day cumulative incidence (CuI) of nonrelapse mortality (NRM) was 14%, and the 2-year CuI was 27%. The 2-year CuI of relapse was 30%. Of 78 patients who were alive and had their weight recorded on day 180, weight loss predicted subsequent NRM (subdistribution hazard ratio, 1.0; 95% CI, 1-1.13; P = .048). In conclusion, haploidentical BMT with PTCy is feasible and relatively safe in septuagenarians. Although early, 6-month NRM was relatively low at 14%, but overall NRM continued to climb to 27% at 2 years, at least in part because of late deaths that appeared to be somewhat age related. Further studies to elucidate predictors of NRM are warranted.

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.

Is a matched unrelated donor search needed for all allogeneic transplant candidates?

Donor availability for allogeneic transplantation remains an important factor in determining outcomes of a successful transplant. We examined outcomes of 242 patients treated over 3 years who had a matched unrelated donor (MUD) search at our institution. One hundred sixty patients (66%) had a 10 of 10 MUD identified, and 85 (53%) proceeded to MUD transplantation. White patients and those with common haplotypes were more likely to have a MUD identified (odds ratio [OR], 7.4 [P < .0001]; OR, 41.6 [P < .0001]), and were more likely to proceed to transplantation with a MUD (OR, 11.2 [P < .0001]; OR, 85.1 [P = .002]). In addition, patients who were newly diagnosed/in remission at the time of MUD search had a higher probability of receiving a transplant (OR, 2.01 [P = .013]) and better progression-free survival (PFS; P < .0001). In multivariate analysis for patients who received a transplant, donor type did not influence PFS at 3 years, which was 40% for MUD and 57% for haploidentical transplants, respectively (hazard ratio, 1.2 [P = .50]). In conclusion, race, haplotype frequency, and disease status at the time of MUD search influence the probability of identifying a MUD and receiving a transplant. Patients with a low likelihood of receiving a MUD transplant may proceed to a haploidentical transplant as soon as indicated, as this approach does not appear to compromise transplant outcomes.

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.

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.

Haploidentical Transplantation with Post-Transplant Cyclophosphamide versus Unrelated Donor Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis

Hematopoietic stem cell transplantation (HSCT) is the standard treatment for patients with high-risk hematologic malignancies. Only approximately 25% of siblings are HLA-matched, and thus alternative donors-unrelated or haploidentical-are usually the only options available. This meta-analysis aimed to compare haploidentical HSCT with post-transplantation cyclophosphamide and unrelated donor (URD) HSCT. We searched the PubMed and Cochrane databases for pertinent studies indexed between 2008 and 2018. Twenty observational studies (with a total of 1783 haploidentical HSCT recipients and 6077 URD HSCT recipients) were included. Results for overall survival, graft-versus-host disease (GVHD), nonrelapse mortality (NRM), and relapse incidence were pooled. Measures of association used were hazard ratios and risk differences. The median age was 51 years for haploidentical transplant recipients and 52 years for URD transplant recipients. Peripheral blood stem cell (PBSC) grafts were more frequent in the URD transplant recipients (85%) than in the haploidentical transplant recipients (31%). Overall survival was not different between the 2 groups. NRM was lower for haploidentical transplantation. All forms of GVHD (acute grades II-IV and III-IV and moderate, severe, and extensive chronic) were lower with haploidentical donor HSCT. The risk of chronic GVHD was fairly proportional to the differential use of PBSC grafts across studies, however. All included studies were retrospective, representing the major limitation of this meta-analysis. In conclusion, haploidentical HSCT for hematologic malignancies achieved the same overall survival as URD HSCT, with a lower incidence of GVHD and NRM. The increased frequency of PBSC use in the unrelated donor group could partially explain the higher cGVHD rate. Haploidentical transplantation with post-transplantation cyclophosphamide should strongly be considered as the first option for adult patients with hematologic malignancies who do not have matched sibling donors in experienced centers. This systematic review has been registered at PROSPERO (65790).

Discussion on the indication of allogeneic stem cell transplantation for advanced cutaneous T cell lymphomas

Advanced cutaneous T cell lymphoma (CTCL) patients have a dismal prognosis, especially those relapsing or progressing after systemic therapy. No curative therapies are available, but some new agents have prolonged disease-free survival time with a good toxicity profile. Allogeneic stem cell transplantation (allo-SCT) offers the longest disease-free survival, potentially representing the best therapeutic option for eligible patients. In the present article, we discuss current evidence about allo-SCT for CTCL patients, timing, and new therapeutic options before allo-SCT, taking into account some considerations that may impact clinical outcome.

Hematopoietic-cell transplantation for lymphoma in the era of genetically engineered cellular therapy: it's not quite time to scrap the old vehicle for the new car

PURPOSE OF REVIEW

Second-line platinum-based salvage chemotherapy followed by high-dose chemotherapy and autologous hematopoietic-cell transplantation (AHCT) has remained the standard of care (SOC) for relapsed and primary refractory (r/r) diffuse large B-cell lymphoma (DLBCL) for greater than 2 decades. In the postrituximab era, this strategy has yielded disappointing outcomes for r/r patients with curability in less one-quarter of the patients by intention-to-treat.

RECENT FINDINGS

Given the Food and Drug Administration (FDA) approval of chimeric antigen receptor (CAR) modified T cells directed against CD19 (CD19 CAR T) for DLBCL following two lines of therapy and/or failed AHCT, encouragement with this therapy in the second line for r/r patients has naturally prompted randomized phase III studies against the aforementioned SOC. The predominant hurdle to procession to AHCT is chemotherapy sensitivity after platinum-based salvage therapy.

SUMMARY

In this review, we will discuss recent investigations to improve response rates in r/r DLBCL with the intent of proceeding to potentially curative AHCT, as well as investigations to decrease progression post-AHCT. In addition, data regarding currently FDA approved CD19 CAR T cells will be reviewed. Within 2-3 years, we will know if the multicenter/multinational studies of CD19 CAR T will replace SOC salvage therapy and AHCT in the second-line. The role of allogeneic HCT will also be briefly reviewed in the context of these therapies.

Outcomes of haploidentical vs matched sibling transplantation for acute myeloid leukemia in first complete remission

HLA-haploidentical hematopoietic cell transplantation (Haplo-HCT) using posttransplantation cyclophosphamide (PT-Cy) has improved donor availability. However, a matched sibling donor (MSD) is still considered the optimal donor. Using the Center for International Blood and Marrow Transplant Research database, we compared outcomes after Haplo-HCT vs MSD in patients with acute myeloid leukemia (AML) in first complete remission (CR1). Data from 1205 adult CR1 AML patients (2008-2015) were analyzed. A total of 336 patients underwent PT-Cy-based Haplo-HCT and 869 underwent MSD using calcineurin inhibitor-based graft-versus-host disease (GVHD) prophylaxis. The Haplo-HCT group included more reduced-intensity conditioning (65% vs 30%) and bone marrow grafts (62% vs 7%), consistent with current practice. In multivariable analysis, Haplo-HCT and MSD groups were not different with regard to overall survival (P = .15), leukemia-free survival (P = .50), nonrelapse mortality (P = .16), relapse (P = .90), or grade II-IV acute GVHD (P = .98). However, the Haplo-HCT group had a significantly lower rate of chronic GVHD (hazard ratio, 0.38; 95% confidence interval, 0.30-0.48; P < .001). Results of subgroup analyses by conditioning intensity and graft source suggested that the reduced incidence of chronic GVHD in Haplo-HCT is not limited to a specific graft source or conditioning intensity. Center effect and minimal residual disease-donor type interaction were not predictors of outcome. Our results indicate a lower rate of chronic GVHD after PT-Cy-based Haplo-HCT vs MSD using calcineurin inhibitor-based GVHD prophylaxis, but similar other outcomes, in patients with AML in CR1. Haplo-HCT is a viable alternative to MSD in these patients.

Is It Time to Revisit the Role of Allogeneic Transplantation in Lymphoma?

PURPOSE OF REVIEW

A multitude of new drug and cell therapy approvals for lymphoma has prompted questions about the role of allogeneic blood or marrow transplantation (allo-BMT). We sought to review the latest evidence examining the role of allo-BMT for lymphoma in this evolving landscape.

RECENT FINDINGS

Despite several new drug classes, there remains a large unmet need, particularly in hard to treat subtypes of lymphoma and for patients with relapsed/refractory disease. Allo-BMT can provide an opportunity for cure due to a potent graft vs lymphoma effect in high-risk relapse/refractory follicular lymphoma, mantle cell lymphoma, and aggressive T cell lymphomas. Chimeric antigen receptor T cell therapy and checkpoint blockers have improved outcomes for patients with relapsed /aggressive B cell lymphomas and Hodgkin lymphoma respectively; the role of allo-BMT consolidation in the treatment algorithm for responders to these therapies is an evolving topic. Expanded donor availability including haploidentical relatives has improved access to allo-BMT. Non-myeloablative conditioning regimens and post-transplant cyclophosphamide prophylaxis have improved early transplant-related morbidity and rates of graft versus host disease and translated into long-term survival for patients with lymphoid malignancies. Patient selection remains key, but allo-BMT remains the only modality able to deliver durable long-term remissions across different types of lymphoma.

Peripheral Blood Stem Cells versus Bone Marrow for T Cell-Replete Haploidentical Transplantation with Post-Transplant Cyclophosphamide in Hodgkin Lymphoma

Haploidentical stem cell transplantation (haplo-SCT) with post-transplant cyclophosphamide (PT-Cy) represents a potential curative strategy for patients with Hodgkin lymphoma (HL) when a matched related or unrelated donor is not available. The role of graft source, either bone marrow (BM) or peripheral blood stem cells (PBSCs), in this setting has not been fully elucidated. We performed a retrospective study on 91 patients with HL to compare the outcome after BM (n = 53) or PBSC (n = 38) transplant. Eighty-nine patients engrafted with no difference between BM and PBSCs in terms of median time for neutrophil (20 versus 20 days, P = .405) and platelet (26 versus 26.5 days, P = .994) engraftment. With a median follow-up of 40.2 months, 100-day cumulative incidences of grades II to IV acute graft-versus host disease (GVHD) and grades II to IV acute GVHD were 24% and 4%, respectively. Graft source was not associated with a different risk of acute GVHD both by univariate and multivariate analyses. Consistently, 1-year cumulative incidence of chronic GVHD was 7% with no differences between the 2 graft types (P = .761). Two-year rates of overall survival (OS), progression-free survival (PFS), nonrelapse mortality, and GVHD/relapse-free survival (GRFS) were 67%, 58%, 20%, and 52%, respectively. By univariate analysis, pretransplant disease status was the main variable affecting all outcomes. By multivariate analysis, PBSCs resulted in a protective factor for OS (hazard ratio [HR], .29; P = .006), PFS (HR, .38; P = .001), and GRFS (HR, .44; P = .020). The other independent variables affecting the final outcome were pretransplant disease status and hematopoietic cell transplant-specific comorbidity index. In conclusion, when planning a haplo-SCT with PT-Cy for patients with poor-risk HL, graft type is an important variable to take into account when selecting the best available donor.

HLA-haploidentical stem cell transplantation using posttransplant cyclophosphamide

HLA-haploidentical stem cell transplantation using posttransplant cyclophosphamide has spread rapidly worldwide. This strategy was initially developed in the setting of bone marrow transplantation following nonmyeloablative conditioning. Recently, peripheral blood stem cell grafts and/or myeloablative conditioning regimen have been widely used. In Japan, prospective, multicenter, phase II studies have been conducted by the Japan Study Group for Cell Therapy and Transplantation to evaluate the safety and efficacy of HLA-haploidentical peripheral blood stem cell transplantation using posttransplant cyclophosphamide (PTCy-haploPBSCT). In the first such study (JSCT Haplo 13 study), we demonstrated that PTCy-haploPBSCT after busulfan-based reduced-intensity conditioning (RIC) enables stable donor engraftment and low incidences of both acute and chronic graft-versus-host disease (GVHD). In the second (JSCT Haplo 14 study), we showed that both myeloablative conditioning (MAC) and RIC are valid options for PTCy-haploPBSCT. Emerging evidence, including our findings, suggests that donor type (HLA-haploidentical donor versus HLA-matched related or unrelated donor) may no longer be a significant predictor of transplant outcome.

Risk factors predicting graft-versus-host disease and relapse-free survival after allogeneic hematopoietic stem cell transplantation in relapsed or refractory non-Hodgkin's lymphoma

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is still considered a definitive curative modality for refractory or relapsed non-Hodgkin’s lymphoma (NHL). However, transplant-related morbidity and mortality remain a considerable challenge. The graft-versus-host disease (GVHD)–free with relapse-free survival (GRFS) rate and GRFS-related prognostic factors have not been fully examined for NHL alone. We evaluated 104 consecutive patients with refractory or relapsed aggressive NHL receiving allo-HSCT at a single institution. With a median follow-up of 31.5 months, the estimated 3-year overall survival (OS), disease-free survival (DFS), the cumulative incidence rates of relapse, and non-relapse mortality were 45.9%, 45.9%, 36.0%, and 17.0%, respectively. The patients with overall grades III–IV acute GVHD had markedly inferior OS and DFS (p = 0.040 for OS and p = 0.028 for DFS). However, patients with more than mild stage chronic GVHD showed superior OS and DFS (p = 0.004 and p = 0.008, respectively). The 1- and 3-year GRFS rates were 44.5% and 36.9%, respectively. The negative bone marrow involvement at diagnosis, chemosensitive disease status, and fewer exposure lines of chemotherapy before transplantation significantly increased the GRFS incidence. However, no transplant-associated factors were related to GRFS incidence. Furthermore, applying dynamic GRFS method which excepted patients whose chronic GVHD was fully resolved within short-period, survival rate significantly increased over time (36.9% vs. 41.9%, p = 0.045 for conventional GRFS vs. dynamic GRFS at 3 years after transplantation). In conclusion, these results suggest that GRFS is also a useful endpoint to assess transplant outcomes, and the dynamic GRFS calculation, including rapidly manageable chronic GVHD, is a more practical method for patients with refractory or relapsed heterogenous subtypes of NHL.

Mechanism of action of posttransplantation cyclophosphamide: more than meets the eye

For high-risk and refractory hematological malignancies, allogeneic hematopoietic stem cell transplantation (alloHSCT) is the only available curative therapy, with benefits derived from the antigenic disparity between recipient cancer and the incoming immune system. This immunologic mismatch can also lead to lethal graft-versus-host disease (GVHD), and immunosuppression strategies, including high-dose posttransplantation cyclophosphamide (PTCy), have been developed to allow for safe alloHSCT delivery. In this issue of JCI, Wachsmuth et al. present the results of preclinical studies designed to evaluate the mechanisms that underlie efficacy of PTCy after alloHSCT. The results of this study challenge previous reports indicating that alloreactive T cell elimination and thymic clonal deletion are primary mediators of PTCy efficacy and provide strong evidence to support FoxP3+CD4+ Tregs as important effectors of PTCy benefits.

Post-transplantation cyclophosphamide prevents graft-versus-host disease by inducing alloreactive T cell dysfunction and suppression

Post-transplantation cyclophosphamide (PTCy) recently has had a marked impact on human allogeneic hematopoietic cell transplantation (HCT). Yet, our understanding of how PTCy prevents graft-versus-host disease (GVHD) largely has been extrapolated from major histocompatibility complex (MHC)-matched murine skin allografting models that were highly contextual in their efficacy. Herein, we developed a T-cell-replete, MHC-haploidentical, murine HCT model (B6C3F1→B6D2F1) to test the putative underlying mechanisms: alloreactive T-cell elimination, alloreactive T-cell intrathymic clonal deletion, and suppressor T-cell induction. In this model and confirmed in four others, PTCy did not eliminate alloreactive T cells identified using either specific Vβs or the 2C or 4C T-cell receptors. Furthermore, the thymus was not necessary for PTCy's efficacy. Rather, PTCy induced alloreactive T-cell functional impairment which was supported by highly active suppressive mechanisms established within one day after PTCy that were sufficient to prevent new donor T cells from causing GVHD. These suppressive mechanisms included the rapid, preferential recovery of CD4+CD25+Foxp3+ regulatory T cells, including those that were alloantigen-specific, which served an increasingly critical function over time. Our results prompt a paradigm-shift in our mechanistic understanding of PTCy. These results have direct clinical implications for understanding tolerance induction and for rationally developing novel strategies to improve patient outcomes.

Comparison of Graft Acquisition and Early Direct Charges of Haploidentical Related Donor Transplantation versus Umbilical Cord Blood Transplantation

Alternative donor allogeneic hematopoietic cell transplants (HCTs), such as double umbilical cord blood transplants (dUCBT) and haploidentical related donor transplants (haplo-HCT), have been shown to be safe and effective in adult patients who do not have an HLA-identical sibling or unrelated donor available. Most transplant centers have committed to 1 of the 2 alternative donor sources, even with a lack of published randomized data directly comparing outcomes and comparative data on the cost-effectiveness of dUCBT versus haplo-HCT. We conducted a retrospective study to evaluate and compare the early costs and charges of haplo-HCT and dUCBT in the first 100 days at 2 US transplant centers. Forty-nine recipients of haplo-HCT (at 1 center) and 37 with dUCBT (at another center) were included in the analysis. We compared graft acquisition, inpatient/outpatient, and total charges in the first 100 days. The results of the analysis showed a significantly lower cost of graft acquisition and lower total charges (for 100-day HCT survivors) in favor of haplo-HCT. Importantly, to control for the obvious shortcomings of comparing costs at 2 different transplant centers, adjustments were made based on the current (2018) local wage index and inflation rate. In the absence of further guidance from a prospective study, the cost analysis in this study suggests that haplo-HCT may result in early cost savings over dUCBT and may be preferred by transplant centers and for patients with more limited resources.

Outcomes of Medicare-age eligible NHL patients receiving RIC allogeneic transplantation: a CIBMTR analysis

The application of allogeneic hematopoietic cell transplantation (allo-HCT) in non-Hodgkin lymphoma (NHL) patients ≥65 years in the United States is limited by lack of Medicare coverage for this indication. Using the Center for International Blood and Marrow Transplant Research (CIBMTR) database, we report allo-HCT outcomes of NHL patients aged ≥65 years (older cohort; n = 446) compared with a cohort of younger NHL patients aged 55-64 years (n = 1183). We identified 1629 NHL patients undergoing a first reduced-intensity conditioning (RIC) or nonmyeloablative conditioning allo-HCT from 2008 to 2015 in the United States. Cord blood or haploidentical transplants were excluded. The median age was 68 years (range 65-77) for the older cohort vs 60 years (range 55-64) in the younger cohort. The 4-year adjusted probabilities of nonrelapse mortality (NRM), relapse/progression (R/P), progression-free survival (PFS), and overall survival (OS) of the younger and older groups were 24% vs 30% (P = .03), 41% vs 42% (P = .82), 37% vs 31% (P = .03), and 51% vs 46% (P = .07), respectively. Using multivariate analysis, compared with the younger group, the older cohort was associated with increased NRM, but there was no difference between the 2 cohorts in terms of R/P, PFS, or OS. The most common cause of death was disease relapse in both groups. In NHL patients eligible for allo-HCT, there was no difference in OS between the 2 cohorts. Age alone should not determine allo-HCT eligibility in NHL, and Medicare should expand allo-HCT coverage to older adults.

Related donor transplants: has posttransplantation cyclophosphamide nullified the detrimental effect of HLA mismatch?

We sought to identify whether posttransplantation cyclophosphamide (PT-Cy) reduces or eliminates the detrimental impact of HLA mismatching on outcomes of HLA-haploidentical related donor transplantation for acute leukemia. Data from 2143 donor-recipient pairs (n = 218 haploidentical sibling; n = 218 offspring; n = 1707 HLA-matched sibling) with acute myeloid or lymphoblastic leukemia were studied. All received a calcineurin inhibitor for graft-versus-host disease (GVHD) prophylaxis while high-dose PT-Cy was also given to recipients of haploidentical transplant. Patient age correlated with donor-recipient relationship: haploidentical siblings donated to patients aged 18 to 54 years whereas offspring donated to patients aged 55 to 76 years. Therefore, transplant outcomes were examined separately in the 2 patient age groups. In patients aged 18 to 54 years, there were no significant differences in outcomes except chronic GVHD, which was lower after haploidentical sibling compared to HLA-matched sibling transplant (hazard ratio [HR], 0.63; P < .001). In patients aged 55 to 76 years, despite lower chronic GVHD (HR, 0.42; P < .001), graft failure (14% vs 6%; P = .003), nonrelapse mortality (HR, 1.48; P = .02), and overall mortality (HR, 1.32; P = .003) were higher after transplant from offspring compared with an HLA-matched sibling. These data demonstrate a superior outcome in older recipients when using an HLA-matched sibling instead of offspring, although there were differences in transplant platforms (GVHD prophylaxis and graft type) between the 2 groups. Validation of these findings requires a prospective randomized trial wherein the transplant platforms can be closely matched.

Impact of Donor Type and Melphalan Dose on Allogeneic Transplantation Outcomes for Patients with Lymphoma

We analyzed 186 patients with lymphoma who underwent allogeneic stem cell transplantation (ASCT) with fludarabine-melphalan (FM) conditioning and different types of donors (25 haploidentical [HD], 98 matched unrelated [MUD], and 63 matched related [MRD]) at our institution between September 2009 and January 2018. Patients received fludarabine 160 mg/m² (40 mg/m²/day for 4 days) in combination with 1 dose of melphalan 140 mg/m² (FM140) or 100 mg/m² (FM100). Engraftment was similar among the 3 groups (92%, 89%, and 98%, respectively; P = .7). The 6-month cumulative incidence of grade III-IV acute graft-versus-host disease (GVHD) was 4% in the HD group, 14% in the MUD group, and 8% in the MRD group (P not significant), and the respective 3-year cumulative incidence of chronic GVHD was 5%, 16%, and 26% (P not significant). The respective 3-year nonrelapse mortality and relapse rates were 31%, 32%, and 10% (HD versus MUD, P = .9; HD versus MRD, P = .02) and 15%, 21%, and 39% (HD versus MUD, P = .4; HD versus MRD, P = .04). At 3 years, progression-free survival (PFS) was 59%, 44%, and 46% (P not significant); overall survival (OS) was 52%, 54%, and 67% (P not significant); and GVHD-free, relapse-free survival was 39%, 31%, and 24% (P not significant). No differences in the 3-year PFS (57% versus 43%; P = .3) and OS (64% versus 58%; P = .7) were seen between patients receiving FM100 and those receiving FM140. Our data demonstrate that in patients with lymphoma, ASCT with HD transplants have similar outcomes as ASCT with HLA-matched transplants, and the FM100 conditioning regimen appears to be at least as effective as the FM140 regimen.

Haploidentical Stem Cell Transplantation With Post-Transplantation Cyclophosphamide for Aggressive Lymphomas: How Far Have We Come and Where Are We Going?

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplant cyclophosphamide (PTCy) offers universal donor availability and can potentially cure relapsed or primary refractory Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). However, a conditioning regimen intensity that balances the graft-versus-lymphoma (GvL) effect with regimen-related toxicities (RRTs) has not yet been optimized. Limited data exist on the management of relapse, which is common post-transplant. Few prospective or randomized control trials have been conducted on lymphoma patients undergoing haplo-HSCT. Therefore, the current review aims to summarize published retrospective data in the field to help guide clinical decision making for high-risk patients. Retrospective studies in the field are characterized by variability in patient population and sample sizes, eligibility criteria, number of prior treatments (e.g., chemotherapy, radiation therapy, and autologous transplant), graft source (bone marrow or peripheral blood), as well as choice and intensity of the conditioning regimen (non-myeloablative, reduced intensity, or myeloablative). Nonetheless, common themes that emerge from the literature include: 1) Enhanced donor availability and selection with haplo-HSCT with success in heterogeneous patient populations; 2) Outcomes that are comparable if not superior to matched related (MRD) or unrelated (MUD) donor transplants; 3) The benefit of PTCy for reducing incidence of relapse and chronic graft-versus-host disease (GvHD); 4) Presence of co-morbidities leading to poorer transplant-related outcomes; and 5) The need for novel approaches to address disease relapse, particularly for patients with active disease at the time of transplant. Excellent transplant-related outcomes with haplo-HSCT with PTCy have been seen for HL and NHL based on retrospective data. Further studies are needed to determine integration with advanced cellular therapy techniques, such as chimeric antigen receptor (CAR) T-cell, antibody drug conjugates, and checkpoint inhibitors. Graft manipulation may be another avenue for future research.

Effect of donor characteristics on haploidentical transplantation with posttransplantation cyclophosphamide

We studied the association between non-HLA donor characteristics (age, sex, donor-recipient relationship, blood group [ABO] match, and cytomegalovirus [CMV] serostatus) and transplant outcomes after T-cell-replete HLA-haploidentical transplantation using posttransplantation cyclophosphamide (PT-Cy) in 928 adults with hematologic malignancy transplanted between 2008 and 2015. Siblings (n = 358) and offspring (n = 450) were the predominant donors, with only 120 patients having received grafts from parents. Although mortality risks were higher with donors aged 30 years or older (hazard ratio, 1.39; P < .0001), the introduction of patient age to the Cox regression model negated the effect of donor age. Two-year survival adjusted for CMV seropositivity, disease, and disease risk index was lower in patients aged 55 to 78 years after transplantation of grafts from donors younger than 30 years (53%) or aged at least 30 years (46%) compared with younger patients who received grafts from donors younger than 30 years (61%) and at least 30 years (60%; P < .0001). Similarly, 2-year survival in patients aged 55 to 78 years was lower after transplantation of grafts from siblings (45%) or offspring (48%) compared with patients aged 18 to 54 years after transplantation of grafts from siblings (62%), offspring (58%), and parents (61%; P < .0001). Graft failure was higher after transplantation of grafts from parents (14%) compared with siblings (6%) or offspring (7%; P = .02). Other non-HLA donor characteristics were not associated with survival or graft failure. The current analyses suggest patient and disease, rather than non-HLA donor characteristics, predominantly influence survival in adults.