Monocytes in leukapheresis products affect the outcome of CD19-targeted CAR T-cell therapy in patients with lymphoma.

ABSTRACT: CD19-directed chimeric antigen receptor (CAR) T cells can induce durable remissions in relapsed/refractory large B-cell lymphomas (R/R LBCLs), but 60% of patients do not respond or relapse. Biological mechanisms explaining lack of response are emerging, but they are largely unsuccessful in predicting disease response at the patient level. Additionally, to maximize the cost-effectiveness of CAR T-cell therapy, biomarkers able to predict response and survival before CAR T-cell manufacturing would be desirable. We performed transcriptomic and functional evaluations of leukapheresis products in 95 patients with R/R LBCL enrolled in a prospective observational study, to identify correlates of response and survival to tisagenlecleucel and axicabtagene ciloleucel. A signature composed of 4 myeloid genes expressed by T cells isolated from leukapheresis products is able to identify patients with a very short progression-free survival (PFS), highlighting the impact of monocytes in CAR T-cell therapy response. Accordingly, response and PFS were also negatively influenced by high circulating absolute monocyte counts at the time of leukapheresis. The combined evaluation of peripheral blood monocytes at the time of leukapheresis and the 4-gene signature represents a novel tool to identify patients with R/R LBCL at very high risk of progression after CAR T-cell therapy and could be used to plan trials evaluating CAR T cells vs other novel treatments or allogeneic CAR T cells. However, it also highlights the need to incorporate monocyte depletion strategies for better CAR T production.

Romidepsin-CHOEP followed by high-dose chemotherapy and stem-cell transplantation in untreated Peripheral T-Cell Lymphoma: results of the PTCL13 phase Ib/II study.

The standard treatment for young patients with untreated PTCLs is based on anthracycline containing-regimens followed by high-dose-chemotherapy and stem-cell-transplantation (HDT + SCT), but only 40% of them can be cured. Romidepsin, a histone-deacetylase inhibitor, showed promising activity in relapsed PTCLs; in first line, Romidepsin was added with CHOP. We designed a study combining romidepsin and CHOEP as induction before HDT + auto-SCT in untreated PTCLs (PTCL-NOS, AITL/THF, ALK-ALCL), aged 18-65 years. A phase Ib/II trial was conducted to define the maximum tolerated dose (MTD) of Ro-CHOEP, and to assess efficacy and safety of 6 Ro-CHOEP as induction before HDT. The study hypothesis was to achieve a 18-month PFS of 70%. Twenty-one patients were enrolled into phase Ib; 7 dose-limiting toxicities were observed, that led to define the MTD at 14 mg/ms. Eighty-six patients were included in the phase II. At a median follow-up of 28 months, the 18-month PFS was 46.2% (95%CI:35.0-56.7), and the 18-month overall survival was 73.1% (95%CI:61.6-81.7). The overall response after induction was 71%, with 62% CRs. No unexpected toxicities were reported. The primary endpoint was not met; therefore, the enrollment was stopped at a planned interim analysis. The addition of romidepsin to CHOEP did not improve the PFS of untreated PTCL patients.

Combination of Deauville score and quantitative positron emission tomography parameters as a predictive tool of anti-CD19 chimeric antigen receptor T-cell efficacy.

BACKGROUND: Autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy is an effective treatment for approximately 40% of relapsed/refractory large B cell lymphomas (LBCL), and early identification of patients at risk for relapse or progression after CAR T-cell therapy represents a clinical need. METHODS: The authors conducted a single-center prospective study on 47 relapsed/refractory LBCL receiving CAR T-cell therapy to evaluate the prognostic value of baseline and after infusion 18 F-fluorodeoxyglucose positron emission tomography (PET)-computed tomography. Qualitative and quantitative metabolic parameters were evaluated before lymphodepletion, at day 30 and 90 post-infusion. RESULTS: Deep variation of standardized uptake value (SUV)mean between baseline and day 30 correlated with response at day 90 (hazard ratio [HR], 1.49; 95% confidence interval [CI], 1.01-2.2); p = .04) and better progression-free survival (PFS) (HR, 0.63; 95% CI, 0.41-0.97); p = .04). In the overall population, 1-year PFS was 63% for Deauville score (DS)1-3 and 39% for DS4-5 patients, respectively (p = .02), however, the prognostic role of DS was lost when survivals are analyzed by considering 38 patients not progressing at 30 days. In these patients, in partial response or stable disease, the combination of DS and variation of SUVmean allowed identification of three groups with different prognosis: patients with DS1-3 and those with DS4-5 and decreased SUVmean had similar 1-year PFS of 62% and 61%, whereas patients with DS4-5 and increased SUVmean had a poorer 1-year PFS of 33% (p = .04). CONCLUSIONS: PET parameters and association of DS and variation of SUVmean at 30 days could help in identify patients at high risk of CAR T-cell failure. LAY SUMMARY: This is a single-center prospective study on 47 lymphoma patients receiving commercial chimeric antigen receptor T-cell therapy aimed to evaluate the prognostic value of baseline and after infusion 18 F-fluorodeoxyglucose positron emission tomography. Among patients in partial remission or stable disease at day 30, the authors observed two subgroups with significantly different prognosis; patients with Deauville score (DS)4-5 and a concomitant reduction of standardized uptake value (SUV)mean had higher probability of long-lasting response than those with DS4-5 and an increase of SUVmean .

Phenotypic Composition of Commercial Anti-CD19 CAR T Cells Affects In Vivo Expansion and Disease Response in Patients with Large B-cell Lymphoma.

PURPOSE: In clinical trials, the expansion and persistence of chimeric antigen receptor (CAR) T cells correlate with therapeutic efficacy. However, properties of CAR T cells that enable their in vivo proliferation have still to be consistently defined and the role of CAR T bag content has never been investigated in a real-life setting. EXPERIMENTAL DESIGN: Residual cells obtained after washing 61 anti-CD19 CAR T product bags were analyzed to identify tisagenlecleucel/Tisa-cel and axicabtagene ciloleucel/Axi-cel phenotypic features associated with postinfusion CAR T-cell in vivo expansion and with response and survival. RESULTS: While Tisa-cel was characterized by a significant enrichment in CAR+CD4+ T cells with central memory (P < 0.005) and effector (P < 0.005) phenotypes and lower rates of CAR+CD8+ with effector memory (P < 0.005) and naïve-like (P < 0.05) phenotypes as compared with Axi-cel, the two products displayed similar expansion kinetics. In vivo CAR T-cell expansion was influenced by the presence of CAR T with a CD8+ T central memory signature (P < 0.005) in both Tisa-cel and Axi-cel infusion products and was positively associated with response and progression-free survival (P < 0.05). CONCLUSIONS: Our data indicate that despite the great heterogeneity of Tisa-cel and Axi-cel products, the differentiation status of the infused cells mediates CAR T-cell in vivo proliferation that is necessary for antitumor response.

Targeting the DNA Damage Response to Increase Anthracycline-Based Chemotherapy Cytotoxicity in T-Cell Lymphoma.

Mature T-cell lymphomas (MTCLs) represent a heterogeneous group of aggressive non-Hodgkin lymphomas comprising different entities. Anthracycline-based regimens are considered the standard of care in the front-line treatment. However, responses to these approaches have been neither adequate nor durable, and new treatment strategies are urgently needed to improve survival. Genomic instability is a common feature of cancer cells and can be caused by aberrations in the DNA damage response (DDR) and DNA repair mechanisms. Consistently, molecules involved in DDR are being targeted to successfully sensitize cancer cells to chemotherapy. Recent studies showed that some hematological malignancies display constitutive DNA damage and intrinsic DDR activation, but these features have not been investigated yet in MTCLs. In this study, we employed a panel of malignant T cell lines, and we report for the first time the characterization of intrinsic DNA damage and basal DDR activation in preclinical models in T-cell lymphoma. Moreover, we report the efficacy of targeting the apical kinase ATM using the inhibitor AZD0156, in combination with standard chemotherapy to promote apoptotic cell death. These findings suggest that DDR is an attractive pathway to be pharmacologically targeted when developing novel therapies and improving MTCL patients' outcomes.

T-cell immune response after mRNA SARS-CoV-2 vaccines is frequently detected also in the absence of seroconversion in patients with lymphoid malignancies.

Patients affected by lymphoid malignancies (LM) are frequently immune-compromised, suffering increased mortality from COVID-19. This prospective study evaluated serological and T-cell responses after complete mRNA vaccination in 263 patients affected by chronic lymphocytic leukaemia, B- and T-cell lymphomas and multiple myeloma. Results were compared with those of 167 healthy subjects matched for age and sex. Overall, patient seroconversion rate was 64·6%: serological response was lower in those receiving anti-cancer treatments in the 12 months before vaccination: 55% vs 81·9% (P < 0·001). Anti-CD20 antibody plus chemotherapy treatment was associated with the lowest seroconversion rate: 17·6% vs. 71·2% (P < 0·001). In the multivariate analysis conducted in the subgroup of patients on active treatment, independent predictors for seroconversion were: anti-CD20 treatment (P < 0·001), aggressive B-cell lymphoma diagnosis (P = 0·002), and immunoglobulin M levels <40 mg/dl (P = 0·030). The T-cell response was evaluated in 99 patients and detected in 85 of them (86%). Of note, 74% of seronegative patients had a T-cell response, but both cellular and humoral responses were absent in 13·1% of cases. Our findings raise some concerns about the protection that patients with LM, particularly those receiving anti-CD20 antibodies, may gain from vaccination. These patients should strictly maintain all the protective measures.

Dose-adjusted EPOCH and rituximab for the treatment of double expressor and double-hit diffuse large B-cell lymphoma: impact of TP53 mutations on clinical outcome.

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease, including one-third of cases overexpressing MYC and BCL2 proteins (double expressor lymphoma, DEL) and 5-10% of patients with chromosomal rearrangements of MYC, BCL2 and/or BCL-6 (double/triple-hit lymphomas, DH/TH). TP53 mutations are detected in 20- 25% of DEL. We report the efficacy of dose-adjusted EPOCH and rituximab (DA-EPOCH-R) in a series of 122 consecutive patients, including DEL (n=81, 66%), DEL-MYC (n=9, 7%), DEL-BCL2 (n=13, 11%), or high-grade lymphomas (DH/TH) (n=19, 16%). Central nervous system (CNS) prophylaxis included intravenous methotrexate (n=66), intrathecal chemotherapy (IT) (n=40) or no prophylaxis (n=16). Sixty-seven patients (55%) had highintermediate or high International Prognostic Index (IPI) and 30 (25%) had high CNS-IPI. The 2-year progression-free survival (PFS) and overall survival (OS) for the entire study population were 74% and 84%, respectively. There was a trend for inferior OS for DH/TH (2-year OS: 66%, P=0.058) as compared to all the others. The outcome was significantly better for the IPI 0-2 versus IPI 3-5 (OS: 98% vs. 72%, P=0.002). DA-EPOCH-R did not overcome the negative prognostic value of TP53 mutations: 2-year OS of 62% versus 88% (P=0.036) were observed for mutated as compared to wild-type cases, respectively. Systemic CNS prophylaxis conferred a better 2-year OS (94%) as compared to IT or no prophylaxis (76% and 65%, respectively; P=0.008). DA-EPOCH-R treatment resulted in a favorable outcome in patients with DEL and DEL with single rearrangement, whereas those with multiple genetic alterations such as DEL-DH/TH and TP53 mutated cases still have an inferior outcome.

CDKN2A deletion is a frequent event associated with poor outcome in patients with peripheral T-cell lymphoma not otherwise specified (PTCL-NOS).

Nodal peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) remains a diagnosis encompassing a heterogenous group of PTCL cases not fitting criteria for more homogeneous subtypes. They are characterized by a poor clinical outcome when treated with anthracycline-containing regimens. A better understanding of their biology could improve prognostic stratification and foster the development of novel therapeutic approaches. Recent targeted and whole exome sequencing studies have shown recurrent copy number abnormalities (CNAs) with prognostic significance. Here, investigating 5 formalin-fixed, paraffin embedded cases of PTCL-NOS by whole genome sequencing (WGS), we found a high prevalence of structural variants and complex events, such as chromothripsis likely responsible for the observed CNAs. Among them, CDKN2A and PTEN deletions emerged as the most frequent aberration, as confirmed in a final cohort of 143 patients with nodal PTCL. The incidence of CDKN2A and PTEN deletions among PTCL-NOS was 46% and 26%, respectively. Furthermore, we found that co-occurrence of CDKN2A and PTEN deletions is an event associated with PTCL-NOS with absolute specificity. In contrast, these deletions were rare and never co-occurred in angioimmunoblastic and anaplastic lymphomas. CDKN2A deletion was associated with shorter overall survival in multivariate analysis corrected by age, IPI, transplant eligibility and GATA3 expression (adjusted HR =2.53; 95% CI 1.006-6.3; p=0.048). These data suggest that CDKN2A deletions may be relevant for refining the prognosis of PTCL-NOS and their significance should be evaluated in prospective trials.

Timing the initiation of multiple myeloma.

The evolution and progression of multiple myeloma and its precursors over time is poorly understood. Here, we investigate the landscape and timing of mutational processes shaping multiple myeloma evolution in a large cohort of 89 whole genomes and 973 exomes. We identify eight processes, including a mutational signature caused by exposure to melphalan. Reconstructing the chronological activity of each mutational signature, we estimate that the initial transformation of a germinal center B-cell usually occurred during the first 2nd-3rd decades of life. We define four main patterns of activation-induced deaminase (AID) and apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC) mutagenesis over time, including a subset of patients with evidence of prolonged AID activity during the pre-malignant phase, indicating antigen-responsiveness and germinal center reentry. Our findings provide a framework to study the etiology of multiple myeloma and explore strategies for prevention and early detection.

Integrative analysis of the genomic and transcriptomic landscape of double-refractory multiple myeloma.

In multiple myeloma, novel treatments with proteasome inhibitors (PIs) and immunomodulatory agents (IMiDs) have prolonged survival but the disease remains incurable. At relapse, next-generation sequencing has shown occasional mutations of drug targets but has failed to identify unifying features that underlie chemotherapy resistance. We studied 42 patients refractory to both PIs and IMiDs. Whole-exome sequencing was performed in 40 patients, and RNA sequencing (RNA-seq) was performed in 27. We found more mutations than were reported at diagnosis and more subclonal mutations, which implies ongoing evolution of the genome of myeloma cells during treatment. The mutational landscape was different from that described in published studies on samples taken at diagnosis. The TP53 pathway was the most frequently inactivated (in 45% of patients). Conversely, point mutations of genes associated with resistance to IMiDs were rare and were always subclonal. Refractory patients were uniquely characterized by having a mutational signature linked to exposure to alkylating agents, whose role in chemotherapy resistance and disease progression remains to be elucidated. RNA-seq analysis showed that treatment or mutations had no influence on clustering, which was instead influenced by karyotypic events. We describe a cluster with both amp(1q) and del(13) characterized by CCND2 upregulation and also overexpression of MCL1, which represents a novel target for experimental treatments. Overall, high-risk features were found in 65% of patients. However, only amp(1q) predicted survival. Gene mutations of IMiD and PI targets are not a preferred mode of drug resistance in myeloma. Chemotherapy resistance of the bulk tumor population is likely attained through differential, yet converging evolution of subclones that are overall variable from patient to patient and within the same patient.

Tyrosine kinase inhibition to improve anthracycline-based chemotherapy efficacy in T-cell lymphoma.

BACKGROUND: Anthracycline-containing regimens, namely cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) or CHOEP (CHOP + etoposide), represent the current standard of care for patients with newly diagnosed peripheral T-cell lymphomas (PTCLs), although responses are unsatisfactory. In this study, we investigated the pathways able to mitigate the sensitivity to CHOP-based regimens in preclinical models of T-cell lymphoma (TCL) to select agents for the development of CHOP-based drug combinations. METHODS: We performed gene expression profiling of malignant T-cell lines exposed to CHOEP; flow cytometry was employed to study the effects of drug combinations on cell viability, cell cycle distribution, apoptosis and mitochondrial membrane depolarisation. Western blot analyses were performed to study cell signalling downstream of the T-cell receptor and apoptosis. The in vivo effect of the drug combination was tested in xenograft models. RESULTS: We highlighted a modulation of tyrosine kinases belonging to the T-cell receptor pathway upon chemotherapy that provided the rationale for combining the tyrosine kinase inhibitor dasatinib with CHOEP. Dasatinib improves CHOEP activity and reduces viability in vitro. Furthermore, combination treatment results in tumour growth inhibition in in vivo xenograft mouse models. CONCLUSIONS: Our data provide the rationale for clinical testing of the dasatinib-CHOEP combination in patients with T-cell lymphoma.

Integration of transcriptional and mutational data simplifies the stratification of peripheral T-cell lymphoma.

The histological diagnosis of peripheral T-cell lymphoma (PTCL) can represent a challenge, particularly in the case of closely related entities such as angioimmunoblastic T-lymphoma (AITL), PTCL-not otherwise specified (PTCL-NOS), and ALK-negative anaplastic large-cell lymphoma (ALCL). Although gene expression profiling and next generations sequencing have been proven to define specific features recurrently associated with distinct entities, genomic-based stratifications have not yet led to definitive diagnostic criteria and/or entered into the routine clinical practice. Herein, to improve the current molecular classification between AITL and PTCL-NOS, we analyzed the transcriptional profiles from 503 PTCLs stratified according to their molecular configuration and integrated them with genomic data of recurrently mutated genes (RHOA G17V , TET2, IDH2 R172 , and DNMT3A) in 53 cases (39 AITLs and 14 PTCL-NOSs) included in the series. Our analysis unraveled that the mutational status of RHOA G17V , TET2, and DNMT3A poorly correlated, individually, with peculiar transcriptional fingerprints. Conversely, in IDH2 R172 samples a strong transcriptional signature was identified that could act as a surrogate for mutational status. The integrated analysis of clinical, mutational, and molecular data led to a simplified 19-gene signature that retains high accuracy in differentiating the main nodal PTCL entities. The expression levels of those genes were confirmed in an independent cohort profiled by RNA-sequencing.

Noninvasive Molecular Monitoring in Multiple Myeloma Patients Using Cell-Free Tumor DNA: A Pilot Study.

Novel treatments for multiple myeloma (MM) have increased rates of complete response, raising interest in more accurate methods to evaluate residual disease. Cell-free tumor DNA (cfDNA) analysis may represent a minimally invasive approach complementary to multiparameter flow cytometry (MFC) and molecular methods on bone marrow aspirates. A sequencing approach using the Ion Torrent Personal Genome Machine was applied to identify clonal IGH gene rearrangements in tumor plasma cells (PCs) and in serial plasma samples of 25 patients with MM receiving second-line therapy. The same clonal IGH rearrangement identified in tumor PCs was detected in paired plasma samples, and levels of IGH cfDNA correlated with outcome and mirrored tumor dynamics evaluated using conventional laboratory parameters. In addition, IGH cfDNA levels reflected the number of PCs enumerated by MFC immunophenotyping even in the complete response context. Patients determined by MFC to be free of minimal residual disease were characterized by low frequencies of tumor clonotypes in cfDNA and longer survival. This pilot study supports the clinical applicability of the noninvasive monitoring of tumor levels in plasma samples of patients with MM by IGH sequencing.

Analysis of the genomic landscape of multiple myeloma highlights novel prognostic markers and disease subgroups.

In multiple myeloma, next-generation sequencing (NGS) has expanded our knowledge of genomic lesions, and highlighted a dynamic and heterogeneous composition of the tumor. Here we used NGS to characterize the genomic landscape of 418 multiple myeloma cases at diagnosis and correlate this with prognosis and classification. Translocations and copy number abnormalities (CNAs) had a preponderant contribution over gene mutations in defining the genotype and prognosis of each case. Known and novel independent prognostic markers were identified in our cohort of proteasome inhibitor and immunomodulatory drug-treated patients with long follow-up, including events with context-specific prognostic value, such as deletions of the PRDM1 gene. Taking advantage of the comprehensive genomic annotation of each case, we used innovative statistical approaches to identify potential novel myeloma subgroups. We observed clusters of patients stratified based on the overall number of mutations and number/type of CNAs, with distinct effects on survival, suggesting that extended genotype of multiple myeloma at diagnosis may lead to improved disease classification and prognostication.

Next-generation sequencing of a family with a high penetrance of monoclonal gammopathies for the identification of candidate risk alleles.

BACKGROUND: The authors describe a family with a high penetrance of plasma cell dyscrasias, suggesting inheritance of an autosomal dominant risk allele. METHODS: The authors performed whole-exome sequencing and reported on a combined approach aimed at the identification of causative variants and risk loci, using the wealth of data provided by this approach. RESULTS: The authors identified gene mutations and single-nucleotide polymorphisms of potential significance, and pinpointed a known risk locus for myeloma as a potential area of transmissible risk in the family. CONCLUSIONS: To the authors' knowledge, the current study is the first to provide a whole-exome sequencing approach to such cases, and a framework analysis that could be applied to further understanding of the inherited risk of developing plasma cell dyscrasias. Cancer 2017;123:3701-3708. © 2017 American Cancer Society.

Circulating miRNA panel for prediction of acute graft-versus-host disease in lymphoma patients undergoing matched unrelated hematopoietic stem cell transplantation.

Acute graft-versus-host disease (aGVHD) results in significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Noninvasive diagnostic and prognostic tests for aGVHD are currently lacking, but would be beneficial in predicting aGVHD and improving the safety of allo-HSCT. Circulating microRNAs exhibit marked stability and may serve as biomarkers in several clinical settings. Here, we evaluated the use of circulating microRNAs as predictive biomarkers of aGVHD in lymphoma patients after allo-HSCT from matched unrelated donors (MUDs). After receiving informed consent, we prospectively collected plasma samples from 24 lymphoma patients before and after unmanipulated MUD allo-HSCT; microRNAs were then isolated. Fourteen patients developed aGVHD symptoms at a median of 48 days (range: 32-90) post-transplantation. Two patients developed intestinal GVHD, eight cutaneous GVHD, and four multiorgan GVHD. The microRNA expression profile was examined using quantitative real-time polymerase chain reaction (qRT-PCR). MicroRNAs 194 and 518f were significantly upregulated in aGVHD samples compared with samples taken from non-aGVHD patients. Remarkably, these upregulated microRNAs could be detected before the onset of aGVHD. Pathway prediction analysis indicated that these microRNAs may regulate critical pathways involved in aGVHD pathogenesis. Considering the noninvasive characteristics of plasma sampling and the feasibility of detecting miRNAs after allo-HSCT using real-time polymerase chain reaction, our results indicate that circulating microRNAs have the potential to enable an earlier aGVHD diagnosis and might assist in individualizing therapeutic strategies after MUD allo-HSCT. Nevertheless, standardization of blood sampling and analysis protocols is mandatory for the introduction of miRNA profiling into routine clinical use.

Pharmacologic Inhibition of JAK1/JAK2 Signaling Reduces Experimental Murine Acute GVHD While Preserving GVT Effects.

PURPOSE: Immune-mediated graft-versus-tumor (GVT) effects can occur after allogeneic hematopoietic stem cell transplantation (HSCT), but GVT is tightly linked to its main complication, graft-versus-host disease (GVHD). Strategies aimed at modulating GVHD, while maintaining the GVT effect, are needed to improve the cure rate of transplant. Given the emerging role of Janus-activated kinase (JAK) signaling in lymphoproliferative and myeloproliferative diseases and its established function at dictating T-cell differentiation, we postulated that JAKs might be potential therapeutic targets through a pharmacologic approach. EXPERIMENTAL DESIGN: We examined the effect of JAK1/JAK2 modulation by ruxolitinib in a mouse model of fully MHC mismatched bone marrow transplant comprising in vivo tumor inoculation. RESULTS: JAK1/JAK2 inhibition by ruxolitinib improved both overall survival (P = 0.03) and acute GVHD pathologic score at target organs (P ≤ 0.001) of treated mice. In addition, treatment with ruxolitinib was associated with a preserved GVT effect, as evidenced by reduction of tumor burden (P = 0.001) and increase of survival time (P = 0.01). JAK1/JAK2 inhibition did not impair the in vivo acquisition of donor T-cell alloreactivity; this observation may account, at least in part, to the preserved GVT effect. Rather, JAK1/JAK2 inhibition of GVHD was associated with the modulation of chemokine receptor expression, which may have been one factor in the reduced infiltration of donor T cells in GVHD target organs. CONCLUSIONS: These data provide further evidence that JAK inhibition represents a new and potentially clinically relevant approach to GVHD prevention.