Active infection at the time of CD34+ selected stem cell boost is associated with treatment failure and poor survival.

BACKGROUND: The use of CD34+ selected stem cell boost (SCB) post allogeneic hematopoietic cell transplant (alloHCT) has been increasing. Predictors of treatment failure following SCB, both in the context of poor graft function (PGF) or other settings, are not well-characterized. We report among the largest single center retrospective experiences of the use of SCB and evaluate potential predictors of response and outcomes. METHODS: 58 patients who underwent HCT between 2015 and 2022 and who received SCB were identified. The indication for SCB was predominantly PGF, defined as the presence of 2 or more cytopenias for at least two consecutive weeks beyond day +14 after alloHCT in the presence of ≤ 30% bone marrow cellularity and ≥ 90% donor myeloid chimerism in the absence of morphological disease. RESULTS: The median dose of infused CD34+ selected SCB products was 3.88 x 106 CD34+ cells/kg (range: 0.99-9.92). The median 2-year OS and NRM following SCB was 47% and 38%, respectively. The cumulative incidences of 6-month grade III-IV acute and 2-year moderate-severe chronic GVHD following SCB were 3.4% and 12%, respectively. Overall response (CR + PR) was attained in 36/58 (62%) patients, and in 69% with PGF. On multivariable analysis, an active infection at the time of SCB was the greatest predictor of poor response and survival (p=0.013) following SCB. CONCLUSION: SCB can restore hematopoiesis in the majority of patients, particularly for those with poor graft function in whom there is no active infection at infusion.

Comparison of Older Related versus Younger Unrelated Donors for Older Recipients of Allogeneic Hematopoietic Cell Transplantation with Acute Myeloid Leukemia or Myelodysplastic Syndrome: A Large Single-Center Analysis.

For patients undergoing allogeneic hematopoietic cell transplantation (alloHCT), HLA-matched related donors (MRDs) have traditionally been the preferred donor source. However, as the age of recipients increases, their sibling donors are aging as well. In this study, we investigated whether younger matched unrelated donors (MUDs) might be a better donor source than similarly aged sibling donors for patients age >60 years with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). A total of 499 patients age 60 to 70 years with AML or MDS who underwent alloHCT from an older MRD (donor age ≥50 years) or a younger MUD (donor age ≤35 years) between 2010 and 2022 were evaluated. Of these, 360 patients (72%) received an MUD graft and 139 (28%) received an MRD graft. The median recipient age was 64 years in the MRD group and 66 years in the MUD group. With a median follow-up among survivors of 53 months (range, 9 to 147 months ), the 4-year progression-free survival was 40% in the MRD group and 41% in the MUD group (P = .79) and the 4-year overall survival was 50% and 44%, respectively (P = .15), with no between-group differences in nonrelapse mortality, relapse, and acute or chronic graft-versus-host disease. In the MUD group, we also compared the effect of donor age 18 to 24 years and donor age 25 to 35 years and found no differences in outcomes between the groups. We conclude that outcomes are comparable between the use of older MRDs and use of younger MUDs for elderly patients with AML or MDS, that there is no donor age effect among younger MUDs, and that the use of either donor type is reasonable.

AKI treated with kidney replacement therapy in critically Ill allogeneic hematopoietic stem cell transplant recipients.

Acute kidney injury (AKI) is a frequent complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT), but few studies have focused on AKI treated with kidney replacement therapy (AKI-KRT), particularly among critically ill patients. We investigated the incidence, risk factors, and 90-day mortality associated with AKI-KRT in 529 critically ill adult allo-HSCT recipients admitted to the ICU within 1-year post-transplant at two academic medical centers between 2011 and 2021. AKI-KRT occurred in 111 of the 529 patients (21.0%). Lower baseline eGFR, veno-occlusive disease, thrombotic microangiopathy, admission to an ICU within 90 days post-transplant, and receipt of invasive mechanical ventilation (IMV), total bilirubin ≥5.0 mg/dl, and arterial pH <7.40 on ICU admission were each associated with a higher risk of AKI-KRT. Of the 111 patients with AKI-KRT, 97 (87.4%) died within 90 days. Ninety-day mortality was 100% in each of the following subgroups: serum albumin ≤2.0 g/dl, total bilirubin ≥7.0 mg/dl, arterial pH ≤7.20, IMV with moderate-to-severe hypoxemia, and ≥3 vasopressors/inotropes at KRT initiation. AKI-KRT was associated with a 6.59-fold higher adjusted 90-day mortality in critically ill allo-HSCT vs. non-transplanted patients. Short-term mortality remains exceptionally high among critically ill allo-HSCT patients with AKI-KRT, highlighting the importance of multidisciplinary discussions prior to KRT initiation.

Opportunistic Infections in Patients Receiving Post-Transplantation Cyclophosphamide: Impact of Haploidentical versus Unrelated Donor Allograft.

Post-transplantation cyclophosphamide (PTCy) is an effective strategy for graft-versus-host disease (GVHD) prophylaxis and is the standard of care for haploidentical hematopoietic cell transplantation (HCT). It is increasingly used for matched and mismatched unrelated donor (MUD/MMUD) HCT, but infections remain a concern. The objective of this study was to evaluate the characteristics and risk factors for infections in haploidentical and unrelated donor HCT recipients treated with PTCy-based GVHD prophylaxis. This single-center retrospective study examined 354 consecutive adults undergoing HCT with PTCy-based GVHD prophylaxis (161 MUD/MMUD; 193 haploidentical) between 2015 and 2022. Opportunistic infections (OIs), including cytomegalovirus (CMV), adenovirus (AdV), Epstein-Barr virus (EBV), and invasive fungal disease (IFD), were assessed from day 0 through day +365. The 1-year cumulative incidence functions of OIs and nonrelapse mortality (NRM) were calculated using dates of relapse and repeat HCT as competing risks. Secondary analysis evaluated risk factors for OIs and NRM using univariate and multivariable Cox regression models. Haploidentical HCT recipients had an increased risk of OIs compared to unrelated donor allograft recipients (39% for haploidentical versus 25% for MUD/MMUD; hazard ratio [HR], 1.70; 95% confidence interval [CI], 1.16 to 2.49; P = .006). On multivariable analysis, haploidentical donor (HR, 1.50; 95% CI, 1.01 to 2.23; P = .046), prior HCT (HR, 1.99; 95% CI, 1.29 to 3.09; P = .002), and diagnosis of aGVHD (HR, 1.47; 95% CI, 1.02 to 2.14; P = .041) were associated with increased risk of OIs. NRM within the first year was not significantly different between the 2 cohorts (HR, 1.11; 95% CI, .64 to 1.93; P = .70). Overall, haploidentical donor was a significant risk factor for OIs in patients receiving PTCy, although 1-year NRM was not different between haploidentical HCT and MUD/MMUD HCT recipients. CMV and AdV infections were significantly increased among haploidentical HCT recipients, whereas the incidences of EBV infection and IFD were similar in the 2 cohorts. Our findings may have implications for infection monitoring and prophylaxis in the setting of PTCy, particularly in haploidentical HCT recipients.

Long-term health outcomes of allogeneic hematopoietic stem cell transplantation.

Background: Fifty years of hematopoietic cell transplantation (HCT) has ushered in an exciting era of cellular therapy and has led to enormous progress in improving the outcomes of patients with both malignant and non-malignant hematologic disease. As the survival of transplanted patients has increased, so has the recognition of long-term complications related to this therapy. Purpose: The goal of this review is to highlight some of the most common long-term complications of HCT. Data sources: To this end, we have conducted a review of the published literature on the long-term complications of HCT encompassing the past 50 years. Study selection: We have endeavored to include long-term complications reported in research articles, case series and case reports, reviews, and abstracts. We have focused primarily on adult allogeneic HCT, but have included some data from studies of pediatric allogeneic HCT as well. We have also prioritized the literature published in the last 15 years. Data extraction: Key data supporting the onset and prevalence of the most common long-term complications was extracted. Limitations: While the list of long-term complications extracted and reported was comprehensive, it was not exhaustive. Conclusions: We have endeavored to highlight some of the most common long-term complications of HCT, the recognition and management of which constitutes an important part of HCT survivorship care.

Posttransplant cyclophosphamide vs tacrolimus-based GVHD prophylaxis: lower incidence of relapse and chronic GVHD.

The ability of posttransplant cyclophosphamide (PTCY) to facilitate haploidentical transplantation has spurred interest in whether PTCY can improve clinical outcomes in patients with HLA-matched unrelated donors undergoing peripheral blood stem cell transplantation (PBSCT). We investigated our institutional experience using PTCY-based graft-versus-host disease (GVHD) prophylaxis compared with conventional tacrolimus-based regimens. We compared overall survival, progression-free survival (PFS), relapse, nonrelapse mortality, and acute and chronic GVHD in 107 adult patients receiving a PTCY-based regimen vs 463 patients receiving tacrolimus-based regimens for GVHD prophylaxis. The 2 cohorts were well balanced for baseline characteristics except that more patients in the PTCY cohort having received 7-of-8-matched PBSCT. There was no difference in acute GVHD. All-grade chronic GVHD and moderate-to-severe chronic GVHD were substantially reduced in patients receiving PTCY compared with in those receiving tacrolimus-based regimens (2-year moderate-to-severe chronic GVHD: 12% vs 36%; P < .0001). Recipients of PTCY-based regimens also had a lower incidence of relapse compared with recipients of tacrolimus-based regimens (25% vs 34% at 2-years; P = .027), primarily in patients who received reduced intensity conditioning. This led to improved PFS in the PTCY cohort (64% vs 54% at 2 years; P = .02). In multivariable analysis, the hazard ratio was 0.59 (P = .015) for PFS and the subdistribution hazard ratio was 0.27 (P < .0001) for moderate-to-severe chronic GVHD and 0.59 (P = .015) for relapse. Our results suggest that PTCY prophylaxis is associated with lower rates of relapse and chronic GVHD in patients who receive HLA-matched unrelated donor PBSCT.

Cytokine release syndrome in haploidentical stem cell transplant may impact T-cell recovery and relapse.

Cytokine release syndrome (CRS) following haploidentical hematopoietic cell transplantation (HCT) resembles CRS after chimeric antigen receptor-T therapy. We conducted this single-center retrospective study to evaluate the association of posthaploidentical HCT CRS with clinical outcomes and immune reconstitution. One hundred sixty-nine patients who underwent haploidentical HCT between 2011 and 2020 were identified. Of these, 98 patients (58%) developed CRS after HCT. CRS was diagnosed based on the presence of fever within the first 5 days after HCT without evidence of infection or infusion reaction and was graded according to established criteria. The development of posthaploidentical HCT CRS was associated with a lower incidence of disease relapse (P = .024) but with an increased risk of chronic graft-versus-host disease GVHD (P = .01). The association of CRS with a lower incidence of relapse was not confounded by graft source or disease diagnosis. Neither CD34 nor total nucleated cell dose was associated with CRS independently of graft type. In patients developing CRS, CD4+ Treg (P < .0005), CD4+ Tcon (P < .005), and CD8+ T cells (P < .005) increased 1 month after HCT compared with those who did not develop CRS, but not at later time points. The increase in CD4+ regulatory T cells 1 month after HCT was most notable among patients with CRS who received a bone marrow graft (P < .005). The development of posthaploidentical HCT CRS is associated with a reduced incidence of disease relapse and a transient effect on post-HCT immune reconstitution of T cells and their subsets. Therefore, the validation of these observations in a multicenter cohort is required.

Clinical Features of Acute Kidney Injury in the Early Post-Transplantation Period Following Reduced-Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation.

Allogeneic hematopoietic stem cell transplantation (HCT) is a potentially curative therapy for patients with hematologic malignancies but is associated with acute kidney injury (AKI). To date, few studies have examined risk factors for AKI at engraftment, or the relationship between AKI and clinical outcomes. This study examined the incidence and risk factors for periengraftment AKI, as well as the association between AKI and overall survival (OS) and nonrelapse mortality (NRM). We conducted a retrospective analysis of adult patients undergoing reduced-intensity conditioning (RIC) allogeneic HCT at the Dana-Farber Cancer Institute between 2012 and 2019. Periengraftment (day 0 to day 30) AKI incidence and severity were defined using modified KDIGO (Kidney Disease: Improving Global Outcomes) criteria. Factors associated with periengraftment AKI risk were examined using Cox regression analysis. The impact of periengraftment AKI on OS and NRM (defined as death without recurrent disease after HCT), was evaluated using Cox regression and the Fine and Gray competing risks model, respectively. Kidney recovery, defined as a return of serum creatinine (SCr) to within 25% of baseline or liberation from kidney replacement therapy (KRT), was examined at day 90 post-HCT. Periengraftment AKI occurred in 330 of 987 patients (33.4%) at a median of 13 days (interquartile range, 4 to 30 days) post-transplantation. Factors associated with a higher multivariable-adjusted risk of AKI were supratherapeutic rapamycin (hazard ratio [HR], 1.56; 95% confidence interval [CI], 1.20 to 2.03; P < .001), fludarabine/melphalan conditioning (HR, 1.35, 95% CI, 1.01 to 1.81; P = .05, compared to fludarabine/busulfan and fludarabine, cyclophosphamide, and total body irradiation), HCT Comorbidity Index ≥4 (HR, 1.43; 95% CI, 1.14 to 1.79; P = .002), albumin <3.4 g/dL (HR, 2.04; 95% CI, 1.33 to 3.12; P = .001), hemoglobin ≤12 (HR, 1.96; 95% CI, 1.38 to 2.78; P < .001), supratherapeutic tacrolimus (HR, 1.45; 95% CI, 1.07 to 1.95; P = .02), and baseline SCr >1.1 mg/dL (HR, 1.87; 95% CI, 1.48 to 2.35; P < .001). Periengraftment AKI was associated with worse OS (HR, 1.40; 95% CI, 1.16 to 1.71; P < .001) and NRM (subdistribution HR, 2.10; 95% CI, 1.52 to 2.89; P < .001). Kidney recovery occurred in 18%, 15%, and 30% of patients with stage 1, stage 2, and stage 3 AKI without KRT, respectively, and 4 of 16 patients (25%) were liberated from KRT. Periengraftment AKI is common among RIC allogeneic HCT recipients. We identified several important risk factors for periengraftment AKI. Its association with worse OS and NRM underscores the importance of timely recognition and management.

Health-Related Quality of Life in Double Umbilical Cord Blood versus Haploidentical Marrow Transplantation: A Quality of Life Analysis Report of BMT CTN 1101.

The Blood and Marrow Transplant Clinical Trials Network study 1101 (BMT CTN 1101; ClinicaTrials.gov identifier NCT01597778) was a multicenter phase III randomized trial comparing the clinical outcomes and quality of life (QoL) of patients with hematologic malignancies undergoing double umbilical cord blood transplantation (dUCBT) or HLA-haploidentical bone marrow transplantation (haplo-BMT) after reduced-intensity conditioning. At a 5-year follow-up, there were no significant differences in progression- free survival (PFS) or overall survival (OS) between the 2 cohorts. The impact of alternative donor source on QoL is unknown, however. English- and Spanish-speaking patients completed the Functional Assessment of Cancer Therapy-General (FACT-G), Short Form 36 (SF-36), EuroQoL-5 Dimensions EQ-5D, and Global QoL patient-reported outcome (PRO) assessments pretransplantation and at 12 and 24 months post-transplantation. We compared longitudinal QoL measures between the dUCBT and haplo-BMT cohorts and investigated the association of QoL and clinical outcomes using an inverse probability weighted-independent estimating equations method, accounting for missingness and baseline variables. We found no significant differences between the 2 cohorts in any of the QoL scores pretransplantation and at 12 and 24 months post-transplantation. Pretransplantation scores were the only significant predictors of post-transplantation QoL scores. Relapse and grade III-IV acute graft-versus-host disease (GVHD) were associated with significant declines in mean FACT-BMT and SF-36 Physical Component scores, and chronic GVHD was associated with a decline in mean EQ-5D utility scores. There were no significant associations between pretransplantation QoL scores and OS or PFS. Donor type did not impact post-transplantation QoL. Pretransplantation QoL scores and clinical events of GVHD and relapse were the only predictors of post-transplantation QoL. QoL was not associated with survival in either treatment arm. PROs may be valuable tools in pretransplantation risk assessment strategies to improve QoL outcomes.

The natural killer cell immunotherapy platform: An overview of the landscape of clinical trials in liquid and solid tumors.

The translation of natural killer (NK) cells to the treatment of malignant disease has made significant progress in the last few decades. With a variety of available sources and improvements in both in vitro and in vivo NK cell expansion, the NK cell immunotherapy platform has come into its own. The enormous effort continues to further optimize this platform, including ways to enhance NK cell persistence, trafficking to the tumor microenvironment, and cytotoxicity. As this effort bears fruit, it is translated into a plethora of clinical trials in patients with advanced malignancies. The adoptive transfer of NK cells, either as a standalone therapy or in combination with other immunotherapies, has been applied for the treatment of both liquid and solid tumors, with numerous early-phase trials showing promising results. This review aims to summarize the key advantages of NK cell immunotherapy, highlight several of the current approaches being taken for its optimization, and give an overview of the landscape of clinical trials translating this platform into clinic.

Invasive Yeast Infection after Haploidentical Donor Hematopoietic Cell Transplantation Associated with Cytokine Release Syndrome.

The use of haploidentical donor hematopoietic cell transplantation (haploHCT) has expanded, but recent reports raise concern for increased rates of infectious complications. The incidence and risk factors for invasive fungal disease (IFD) after haploHCT have not been well elucidated. This study aimed to evaluate the incidence and risk factors for IFD after haploHCT. The identification of key risk factors will permit targeted prevention measures and may explain elevated risk for other infectious complications after haploHCT. This single-center retrospective study included all adults undergoing haploHCT between May 2011 and May 2021 (n = 205). The 30-day and 1-year cumulative incidences of proven or probable IFD and 1-year nonrelapse mortality (NRM) were assessed. Secondary analyses evaluated risk factors for invasive yeast infection (IYI) using univariate and multivariable Cox regression models. Twenty-nine patients (14%) developed IFD following haploHCT. Nineteen (9.3%) developed IYI in the first year, 13 of which occurred early, with a 30-day cumulative incidence of 6.3% (95% confidence interval [CI], 2.9% to 9.6%) and increased NRM in patients with IYI (53.9% versus 10.9%). The majority of yeast isolates (17 of 20; 85%) were fluconazole- susceptible. The incidence of IYI in the first 30 days after haploHCT was 10% in the 110 patients (54%) who developed cytokine release syndrome (CRS) and 21% in the 29 patients (14%) who received tocilizumab. On multivariable analysis, acute myelogenous leukemia (hazard ratio [HR], 6.24; 95% CI, 1.66 to 23.37; P = .007) and CRS (HR, 4.65; 95% CI, 1.00 to 21.58; P = .049) were associated with an increased risk of early IYI after haploHCT. CRS after haploHCT is common and is associated with increased risk of early IYI. The identification of CRS as a risk factor for IYI raises questions about its potential association with other infections after haploHCT. Recognition of key risk factors for infection may permit the development of individualized strategies for prevention and intervention and minimize potential side effects.

Innovative Strategies to Improve the Clinical Application of NK Cell-Based Immunotherapy.

Natural killer cells constitute a part of the innate immune system that mediates an effective immune response towards virus-infected and malignant cells. In recent years, research has focused on exploring and advancing NK cells as an active immunotherapy platform. Despite major advances, there are several key challenges that need to be addressed for the effective translation of NK cell research to clinical applications. This review highlights some of these challenges and the innovative strategies being developed to overcome them, including in vitro expansion, in vivo persistence, infiltration to the tumor site, and prevention of exhaustion.

Autologous cellular therapy for myeloma: Giving ex vivo expanded NK cells their due.

Ex vivo feeder-free autologous NK cell expansion is an efficient modality for clinical translation. In this issue of Cell Reports Medicine, Nahi et al. describe the use of this approach as consolidation therapy for multiple myeloma,1 thereby reviving an alternate avenue for NK cell therapy.

Expansion, persistence, and efficacy of donor memory-like NK cells infused for posttransplant relapse.

BackgroundResponses to conventional donor lymphocyte infusion for postallogeneic hematopoietic cell transplantation (HCT) relapse are typically poor. Natural killer (NK) cell-based therapy is a promising modality to treat post-HCT relapse.MethodsWe initiated this ongoing phase I trial of adoptively transferred cytokine-induced memory-like (CIML) NK cells in patients with myeloid malignancies who relapsed after haploidentical HCT. All patients received a donor-derived NK cell dose of 5 to 10 million cells/kg after lymphodepleting chemotherapy, followed by systemic IL-2 for 7 doses. High-resolution profiling with mass cytometry and single-cell RNA sequencing characterized the expanding and persistent NK cell subpopulations in a longitudinal manner after infusion.ResultsIn the first 6 enrolled patients on the trial, infusion of CIML NK cells led to a rapid 10- to 50-fold in vivo expansion that was sustained over months. The infusion was well tolerated, with fever and pancytopenia as the most common adverse events. Expansion of NK cells was distinct from IL-2 effects on endogenous post-HCT NK cells, and not dependent on CMV viremia. Immunophenotypic and transcriptional profiling revealed a dynamic evolution of the activated CIML NK cell phenotype, superimposed on the natural variation in donor NK cell repertoires.ConclusionGiven their rapid expansion and long-term persistence in an immune-compatible environment, CIML NK cells serve as a promising platform for the treatment of posttransplant relapse of myeloid disease. Further characterization of their unique in vivo biology and interaction with both T cells and tumor targets will lead to improvements in cell-based immunotherapies.Trial RegistrationClinicalTrials.gov NCT04024761.FundingDunkin' Donuts, NIH/National Cancer Institute, and the Leukemia and Lymphoma Society.

Impact of cryopreservation and transit times of allogeneic grafts on hematopoietic and immune reconstitution.

We sought to evaluate the impact of cryopreservation of unrelated donor (URD) peripheral blood stem cell (PBSC) grafts on engraftment, chimerism, and immune reconstitution in the context of the COVID-19 pandemic. We reviewed stem cell product characteristics and clinical outcomes in 101 patients receiving cryopreserved PBSCs from URDs between January 1, 2019 and 31 December, 2020, compared with 203 patients receiving fresh URD PBSCs. We observed no differences in 6-month overall survival, progression-free survival, or nonrelapse mortality. Patients receiving cryopreserved PBSCs had delayed platelet engraftment and impaired reconstitution of white blood cells and T-cell subsets at day 30. Thirty-four percent of patients receiving cryopreserved grafts had CD3 chimerism <50% at day 30 after transplantation, compared with 14% of patients receiving fresh PBSCs (P = .0002). At day 100, this difference persisted (CD3+ chimerism <50%: 17% of cryopreserved cohort vs 6% of fresh cohort; P = .016). Greater product age at infusion was associated with increased graft failure, independent of cryopreservation. Receipt of grafts >48 hours old at time of cryopreservation or infusion significantly increased the risk of graft failure (subdistribution hazard ratio = 4.57; 95% confidence interval, 1.71-12.3; P = .0025). Our data indicate that cryopreservation is associated with similar overall short-term clinical outcomes compared with fresh PBSC. However, patients must be monitored closely for increased risk of other potentially adverse outcomes, including graft failure and poor immune recovery, particularly for grafts with older overall age at infusion. Longer-term follow-up is needed to determine impact on relapse and survival.

Therapeutic options for steroid-refractory acute and chronic GVHD: an evolving landscape.

Introduction: The traditional therapeutic modalities to manage SR-acute GVHD have focused on the inhibition of the alloreactive T-cell response, while in the setting of SR-chronic GVHD the focus has been on a combination of T-cell and B-cell targeting strategies. However, new therapeutic modalities have shown promise. The purpose of this review is to summarize the current treatment landscape of SR-acute and chronic GVHD.Areas covered: A systematic search of MEDLINE, EMBASE, and clinicaltrials.gov databases for published articles, abstracts, and clinical trials pertaining to available therapeutic modalities for SR-acute and SR-chronic GVHD was conducted. Also highlighted is a number of ongoing clinical trials in both SR-acute and SR-chronic GVHD with strategies targeting the JAK-1/2 pathway, the Treg:Tcon ratio, the immunomodulation mediated by mesenchymal stem cells, and the gut microbiome, among others. Expert opinion: Ruxolitinib has emerged as the preferred therapeutic modality for SR-acute GVHD, with alpha-1-antitrypsin and extracorporeal photophoresis (ECP) being reasonable alternatives. Ruxolitinib and Ibrutinib are among the preferred options for SR-chronic GVHD, with ECP being a viable alternative particularly if the skin is involved. A number of novel therapeutic modalities, including those enhancing the activity of regulatory T-cells have shown great promise in early phase trials of SR-chronic GVHD.

Key Aspects of the Immunobiology of Haploidentical Hematopoietic Cell Transplantation.

Hematopoietic stem cell transplantation from a haploidentical donor is increasingly used and has become a standard donor option for patients lacking an appropriately matched sibling or unrelated donor. Historically, prohibitive immunological barriers resulting from the high degree of HLA-mismatch included graft-vs.-host disease (GVHD) and graft failure. These were overcome with increasingly sophisticated strategies to manipulate the sensitive balance between donor and recipient immune cells. Three different approaches are currently in clinical use: (a) ex vivo T-cell depletion resulting in grafts with defined immune cell content (b) extensive immunosuppression with a T-cell replete graft consisting of G-CSF primed bone marrow and PBSC (GIAC) (c) T-cell replete grafts with post-transplant cyclophosphamide (PTCy). Intriguing studies have recently elucidated the immunologic mechanisms by which PTCy prevents GVHD. Each approach uniquely affects post-transplant immune reconstitution which is critical for the control of post-transplant infections and relapse. NK-cells play a key role in haplo-HCT since they do not mediate GVHD but can successfully mediate a graft-vs.-leukemia effect. This effect is in part regulated by KIR receptors that inhibit NK cell cytotoxic function when binding to the appropriate HLA-class I ligands. In the context of an HLA-class I mismatch in haplo-HCT, lack of inhibition can contribute to NK-cell alloreactivity leading to enhanced anti-leukemic effect. Emerging work reveals immune evasion phenomena such as copy-neutral loss of heterozygosity of the incompatible HLA alleles as one of the major mechanisms of relapse. Relapse and infectious complications remain the leading causes impacting overall survival and are central to scientific advances seeking to improve haplo-HCT. Given that haploidentical donors can typically be readily approached to collect additional stem- or immune cells for the recipient, haplo-HCT represents a unique platform for cell- and immune-based therapies aimed at further reducing relapse and infections. The rapid advancements in our understanding of the immunobiology of haplo-HCT are therefore poised to lead to iterative innovations resulting in further improvement of outcomes with this compelling transplant modality.

Combination of the Centre for International Blood and Marrow Transplant Registry Risk Score and the Global Severity Score Enhances Prognostic Risk Stratification in Patients Receiving Frontline Therapy for Chronic Graft-versus-Host Disease.

The Centre for International Blood and Marrow Transplant Registry (CIBMTR) score has been shown to be prognostic for overall survival (OS) and nonrelapse mortality (NRM) but has been shown in several single-center studies to classify a large proportion of patients with chronic graft-versus-host disease (cGVHD) in the lower risk groups (RG1 to RG2), thereby limiting its prognostic utility for those patients. We evaluate the CIBMTR score, the Global Severity Score (GSS), and a novel risk score developed to improve on the limitations of the CIBMTR with respect to clinically relevant outcomes, including failure-free survival (FFS), in patients receiving frontline systemic treatment for cGVHD. We identified 277 patients between 2002 and 2012 at the Princess Margaret Cancer Centre in Toronto, Canada, who developed cGVHD and were treated with at least 1 line of systemic therapy. cGVHD was graded by GSS, and patients were stratified by CIBMTR. We evaluated OS, NRM, relapse, and FFS within GSS grade groups, as well as CIBMTR RGs, and used a novel prognostic risk score. The median FFS duration was 164 days in the severe GSS group versus 238 days in the moderate-grade group and 304 days in mild-grade group (P= .001). The median FFS duration was 501 days in CIBMTR RG1 versus 291 days in RG2 and 166 days in RG3 to RG6 (P = .003). A novel risk score combining the GSS and CIBMTR scores was prognostic of OS, NRM, and FFS and was able to subdivide patients with cGVHD in CIBMTR RG1 to RG2 into distinct prognostic risk categories. The CIBMTR risk score and the GSS are well correlated with FFS, OS, and NRM following frontline systemic treatment for cGVHD. A new risk score model combining the CIBMTR risk score and the GSS could enhance risk stratification in the lower CIBMTR risk groups.