Amphiregulin, ST2,and REG3α Biomarker Risk Algorithms as Predictors of Non-Relapse Mortality in Patients with Acute GVHD.

Graft-vs-host disease (GVHD) is a major cause of non-relapse mortality (NRM) following allogeneic hematopoietic cell transplant (HCT). Algorithms containing either the GI GVHD biomarker amphiregulin (AREG) or a combination of two GI GVHD biomarkers, (ST2+REG3α) when measured at GVHD diagnosis are validated predictors of NRM risk, but have never been assessed in the same patients using identical statistical methods. We measured serum concentrations of ST2, REG3, and AREG by ELISA at the time of GVHD diagnosis in 715 patients divided by date of transplant into training (2004-2015) and validation (2015-2017) cohorts. The training cohort (n=341) was used to develop algorithms for predicting probability of 12 month NRM that contained all possible combinations of 1-3 biomarkers and a threshold corresponding to the concordance probability was used to stratify patients for risk of NRM. Algorithms were compared to each other based on several metrics including the area under the receiver operating characteristics curve (AUC), proportion of patients correctly classified, sensitivity, and specificity using only the validation cohort (n=374). All algorithms were strong discriminators of 12 month NRM, whether or not patients were systemically treated (n=321). An algorithm containing only ST2+REG3α had the highest AUC (0.757), correctly classified the most patients (75%), and more accurately risk stratified those who developed Minnesota standard risk GVHD and for patients who received post-transplant cyclophosphamide-based prophylaxis. An algorithm containing only AREG more accurately risk stratified patients with Minnesota high risk GVHD. Combining ST2, REG3α, and AREG into a single algorithm did not improve performance.

The MAGIC algorithm probability predicts treatment response and long-term outcomes to second-line therapy for acute GVHD.

The significance of biomarkers at second-line treatment for acute graft-versus-host disease (GVHD) is not well characterized. We analyzed clinical data and serum samples at initiation of second-line systemic treatment of acute GVHD from 167 patients from 17 centers of the Mount Sinai Acute GVHD International Consortium (MAGIC) between 2016 and 2021. Sixty-two patients received ruxolitinib-based therapy while 102 received other systemic agents. In agreement with prospective trials, ruxolitinib resulted in higher day 28 (D28) ORR compared to non-ruxolitinib therapies (55% vs 31%, P=0.003) and patients who received ruxolitinib had significantly lower non-relapse mortality (NRM) than those who received non-ruxolitinib therapies (point estimates at 2-year: 35% vs 61%, p=0.002). Biomarker analyses demonstrated that the benefit from ruxolitinib was observed only in patients with low MAGIC algorithm probabilities (MAPs) at the start of second-line treatment. Among patients with a low MAP, those who received ruxolitinib experienced significantly lower NRM than those who received non-ruxolitinib therapies (point estimates at 2-year: 12% vs 41%, p=0.016). However, patients with a high MAP experienced high NRM regardless of treatment with ruxolitinib or non-ruxolitinib therapies (point estimates at 2-year: 67% vs 80%, p=0.65). A landmark analysis demonstrated that the relationship between D28 response and NRM largely depends on the MAP level at initiation of second-line therapy. In conclusion, the MAP measured at second-line systemic treatment for acute GVHD predicts treatment response and NRM. Outcomes of patients with high MAP are poor, regardless of treatment choice, and ruxolitinib appears to primarily benefit patients with low MAP.

Strain specific differences in vitamin D3 response: impact on gut homeostasis.

Vitamin D3 regulates a variety of biological processes irrespective of its well-known importance for calcium metabolism. Epidemiological and animal studies indicate a role in immune regulation, intestinal barrier function and microbiome diversity. Here, we analyzed the impact of different vitamin D3- containing diets on C57BL/6 and BALB/c mice, with a particular focus on gut homeostasis and also investigated effects on immune cells in vitro. Weak regulatory effects were detected on murine T cells. By trend, the active vitamin D3 metabolite 1,25-dihydroxyvitamin D3 suppressed IFN, GM-CSF and IL-10 cytokine secretion in T cells of C57BL/6 but not BALB/c mice, respectively. Using different vitamin D3-fortified diets, we found a tissue-specific enrichment of mainly CD11b+ myeloid cells but not T cells in both mouse strains e.g. in spleen and Peyer's Patches. Mucin Reg3γ and Batf expression, as well as important proteins for gut homeostasis, were significantly suppressed in the small intestine of C57BL76 but not BALB/c mice fed with a high-vitamin D3 containing diet. Differences between both mouse stains were not completely explained by differences in vitamin D3 receptor expression which was strongly expressed in epithelial cells of both strains. Finally, we analyzed gut microbiome and again an impact of vitamin D3 was detected in C57BL76 but not BALB/c. Our data suggest strain-specific differences in vitamin D3 responsiveness under steady state conditions which may have important implications when choosing a murine disease model to study vitamin D3 effects.

A Validated Risk Stratification That Incorporates MAGIC Biomarkers Predicts Long-Term Outcomes in Pediatric Patients with Acute GVHD.

Acute graft versus host disease (GVHD) is a common and serious complication of allogeneic hematopoietic cell transplantation (HCT) in children but overall clinical grade at onset only modestly predicts response to treatment and survival outcomes. Two tools to assess risk at initiation of treatment were recently developed. The Minnesota risk system stratifies children for risk of nonrelapse mortality (NRM) according to the pattern of GVHD target organ severity. The Mount Sinai Acute GVHD International Consortium (MAGIC) algorithm of 2 serum biomarkers (ST2 and REG3α) predicts NRM in adult patients but has not been validated in a pediatric population. We aimed to develop and validate a system that stratifies children at the onset of GVHD for risk of 6-month NRM. We determined the MAGIC algorithm probabilities (MAPs) and Minnesota risk for a multicenter cohort of 315 pediatric patients who developed GVHD requiring treatment with systemic corticosteroids. MAPs created 3 risk groups with distinct outcomes at the start of treatment and were more accurate than Minnesota risk stratification for prediction of NRM (area under the receiver operating curve (AUC), .79 versus .62, P = .001). A novel model that combined Minnesota risk and biomarker scores created from a training cohort was more accurate than either biomarkers or clinical systems in a validation cohort (AUC .87) and stratified patients into 2 groups with highly different 6-month NRM (5% versus 38%, P < .001). In summary, we validated the MAP as a prognostic biomarker in pediatric patients with GVHD, and a novel risk stratification that combines Minnesota risk and biomarker risk performed best. Biomarker-based risk stratification can be used in clinical trials to develop more tailored approaches for children who require treatment for GVHD.

A Day 14 Endpoint for Acute GVHD Clinical Trials.

The overall response rate (ORR) 28 days after treatment has been adopted as the primary endpoint for clinical trials of acute graft versus host disease (GVHD). However, physicians often need to modify immunosuppression earlier than day (D) 28, and non-relapse mortality (NRM) does not always correlate with ORR at D28. We studied 1144 patients that received systemic treatment for GVHD in the Mount Sinai Acute GVHD International Consortium (MAGIC) and divided them into a training set (n=764) and a validation set (n=380). We used a recursive partitioning algorithm to create a Mount Sinai model that classifies patients into favorable or unfavorable groups that predicted 12 month NRM according to overall GVHD grade at both onset and D14. In the Mount Sinai model grade II GVHD at D14 was unfavorable for grade III/IV GVHD at onset and predicted NRM as well as the D28 standard response model. The MAGIC algorithm probability (MAP) is a validated score that combines the serum concentrations of suppression of tumorigenicity 2 (ST2) and regenerating islet-derived 3-alpha (REG3α) to predict NRM. Inclusion of the D14 MAP biomarker score with the D14 Mount Sinai model created three distinct groups (good, intermediate, poor) with strikingly different NRM (8%, 35%, 76% respectively). This D14 MAGIC model displayed better AUC, sensitivity, positive and negative predictive value, and net benefit in decision curve analysis compared to the D28 standard response model. We conclude that this D14 MAGIC model could be useful in therapeutic decisions and may offer an improved endpoint for clinical trials of acute GVHD treatment.

A genome-wide association study on hematopoietic stem cell transplantation reveals novel genomic loci associated with transplant outcomes.

Introduction: Data on genomic susceptibility for adverse outcomes after hematopoietic stem cell transplantation (HSCT) for recipients are scarce. Methods: We performed a genome wide association study (GWAS) to identify genes associated with survival/mortality, relapse, and severe graft-versus-host disease (sGvHD), fitting proportional hazard and subdistributional models to data of n=1,392 recipients of European ancestry from three centres. Results: The single nucleotide polymorphism (SNP) rs17154454, intronic to the neuronal growth guidant semaphorin 3C gene (SEMA3C), was genome-wide significantly associated with event-free survival (p=7.0x10-8) and sGvHD (p=7.5x10-8). Further associations were detected for SNPs in the Paxillin gene (PXN) with death without prior relapse or sGvHD, as well as for SNPs of the Plasmacytoma Variant Translocation 1 gene (PVT1, a long non-coding RNA gene), the Melanocortin 5 Receptor (MC5R) gene and the WW Domain Containing Oxidoreductase gene (WWOX), all associated with the occurrence of sGvHD. Functional considerations support the observed associations. Discussion: Thus, new genes were identified, potentially influencing the outcome of HSCT.

Lipocalin-2 expression identifies an intestinal regulatory neutrophil population during acute graft-versus-host disease.

Acute graft-versus-host disease (aGVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT), for which therapeutic options are limited. Strategies to promote intestinal tissue tolerance during aGVHD may improve patient outcomes. Using single-cell RNA sequencing, we identified a lipocalin-2 (LCN2)-expressing neutrophil population in mice with intestinal aGVHD. Transfer of LCN2-overexpressing neutrophils or treatment with recombinant LCN2 reduced aGVHD severity, whereas the lack of epithelial or hematopoietic LCN2 enhanced aGVHD severity and caused microbiome alterations. Mechanistically, LCN2 induced insulin-like growth factor 1 receptor (IGF-1R) signaling in macrophages through the LCN2 receptor SLC22A17, which increased interleukin-10 (IL-10) production and reduced major histocompatibility complex class II (MHCII) expression. Transfer of LCN2-pretreated macrophages reduced aGVHD severity but did not reduce graft-versus-leukemia effects. Furthermore, LCN2 expression correlated with IL-10 expression in intestinal biopsies in multiple cohorts of patients with aGVHD, and LCN2 induced IGF-1R signaling in human macrophages. Collectively, we identified a LCN2-expressing intestinal neutrophil population that reduced aGVHD severity by decreasing MHCII expression and increasing IL-10 production in macrophages. This work provides the foundation for administration of LCN2 as a therapeutic approach for aGVHD.

Interferon regulatory factor 4 plays a pivotal role in the development of aGVHD-associated colitis.

Interferon regulatory factor 4 (IRF4) is a master transcription factor that regulates T helper cell (Th) differentiation. It interacts with the Basic leucine zipper transcription factor, ATF-like (BATF), depletion of which in CD4+ T cells abrogates acute graft-versus-host disease (aGVHD)-induced colitis. Here, we investigated the immune-regulatory role of Irf4 in a mouse model of MHC-mismatched bone marrow transplantation. We found that recipients of allogenic Irf4-/- CD4+ T cells developed less GVHD-related symptoms. Transcriptome analysis of re-isolated donor Irf4-/- CD4+ T helper (Th) cells, revealed gene expression profiles consistent with loss of effector T helper cell signatures and enrichment of a regulatory T cell (Treg) gene expression signature. In line with these findings, we observed a high expression of the transcription factor BTB and CNC homolog 2; (BACH2) in Irf4-/- T cells, which is associated with the formation of Treg cells and suppression of Th subset differentiation. We also found an association between BACH2 expression and Treg differentiation in patients with intestinal GVHD. Finally, our results indicate that IRF4 and BACH2 act as counterparts in Th cell polarization and immune homeostasis during GVHD. In conclusion, targeting the BACH2/IRF4-axis could help to develop novel therapeutic approaches against GVHD.

Bacteria and bacteriophage consortia are associated with protective intestinal metabolites in patients receiving stem cell transplantation.

The microbiome is a predictor of clinical outcome in patients receiving allogeneic hematopoietic stem cell transplantation (allo-SCT). Microbiota-derived metabolites can modulate these outcomes. How bacteria, fungi and viruses contribute to the production of intestinal metabolites is still unclear. We combined amplicon sequencing, viral metagenomics and targeted metabolomics from stool samples of patients receiving allo-SCT (n = 78) and uncovered a microbiome signature of Lachnospiraceae and Oscillospiraceae and their associated bacteriophages, correlating with the production of immunomodulatory metabolites (IMMs). Moreover, we established the IMM risk index (IMM-RI), which was associated with improved survival and reduced relapse. A high abundance of short-chain fatty acid-biosynthesis pathways, specifically butyric acid via butyryl-coenzyme A (CoA):acetate CoA-transferase (BCoAT, which catalyzes EC 2.8.3.8) was detected in IMM-RI low-risk patients, and virome genome assembly identified two bacteriophages encoding BCoAT as an auxiliary metabolic gene. In conclusion, our study identifies a microbiome signature associated with protective IMMs and provides a rationale for considering metabolite-producing consortia and metabolite formulations as microbiome-based therapies.

Inhibition of RIP1 improves immune reconstitution and reduces GVHD mortality while preserving graft-versus-leukemia effects.

Graft-versus-host disease (GVHD) remains the major cause of morbidity and nonrelapse mortality (NRM) after hematopoietic cell transplantation (HCT). Inflammatory cytokines mediate damage to key GVHD targets such as intestinal stem cells (ISCs) and also activate receptor interacting protein kinase 1 (RIP1; RIPK1), a critical regulator of apoptosis and necroptosis. We therefore investigated the role of RIP1 in acute GVHD using samples from HCT patients, modeling GVHD damage in vitro with both human and mouse gastrointestinal (GI) organoids, and blocking RIP1 activation in vivo using several well-characterized mouse HCT models. Increased phospho-RIP1 expression in GI biopsies from patients with acute GVHD correlated with tissue damage and predicted NRM. Both the genetic inactivation of RIP1 and the RIP1 inhibitor GNE684 prevented GVHD-induced apoptosis of ISCs in vivo and in vitro. Daily administration of GNE684 for 14 days reduced inflammatory infiltrates in three GVHD target organs (intestine, liver, and spleen) in mice. Unexpectedly, GNE684 administration also reversed the marked loss of regulatory T cells in the intestines and liver during GVHD and reduced splenic T cell exhaustion, thus improving immune reconstitution. Pharmacological and genetic inhibition of RIP1 improved long-term survival without compromising the graft-versus-leukemia (GVL) effect in lymphocytic and myeloid leukemia mouse models. Thus, RIP1inhibition may represent a nonimmunosuppressive treatment for GVHD.

Pooled allogeneic faecal microbiota MaaT013 for steroid-resistant gastrointestinal acute graft-versus-host disease: a single-arm, multicentre phase 2 trial.

Background: Failure of gastrointestinal acute graft-versus-host disease (GI-aGvHD) to respond to steroid therapy is associated with limited further therapeutic options. We aimed to assess the safety and efficacy of the first-in-human use of the pooled allogeneic faecal microbiota, MaaT013, for the treatment of steroid-refractory GI-aGvHD. Methods: This prospective, international, single-arm, phase 2a study reports clinical outcomes from a 24-patient cohort with grade III-IV, steroid refractory GI-aGvHD treated with the pooled allogeneic faecal microbiota MaaT013. MaaT013 involved pooling faecal matter from 3 to 8 screened donors then transplanting the pooled batches into patients to treat GI-aGVHD. The 24 patients were treated in the HERACLES study (Aug 2018 to Nov 2020) at 26 sites in Europe and an additional 52 patients were treated in a compassionate use/expanded access program (EAP) in France (July 2018 to April 2021). The primary endpoint was GI response at day 28, defined as the proportion of patients with GI-aGvHD who had a complete response (CR) or very good partial response (VGPR). GvHD grading and staging were assessed according to the revised Glucksberg criteria. Adverse events and severe adverse events were monitored for 6 months and 12 months, respectively. The HERACLES study was registered with ClinicalTrials.gov (NCT03359980). Findings: Compared with single donors, MaaT013 is characterised by higher microbial richness and reduced variability across batches. At day 28 (D28), the GI-overall response rate (ORR) was 38% in the prospective population, including 5 complete responses (CR), 2 very good partial responses (VGPR) and 2 partial responses (PR). In the EAP, the GI-ORR was 58% (17 CR, 9 VGPR and 4 PR). The 12-month overall survival (OS) was 25% in the prospective study and 38% in the EAP. Regarding safety, five infectious complications, including 3 sepsis, could not be excluded from being related to the study procedure in HERACLES. Shotgun sequencing analyses of the identified strains suggest that none were found in MaaT013. In the EAP, 18 pharmacovigilance cases were reported among 52 treated patients, including 11 bacteraemia/sepsis. In HERACLES, we observed in stools from responding patients at D28 a higher microbiota richness and increased levels of beneficial bacteria, in particular butyrate producers, along with increased levels of short-chain fatty acid and bile acids. In contrast, stools from non-responding (NR) patients displayed increased levels of pathogenic pro-inflammatory bacteria along with increased systemic inflammatory parameters. Interpretation: Overall, MaaT013 was safe in this population of highly immunocompromised patients and was associated with responses in some patients with GI-aGvHD and deserves further investigation. Funding: MaaT Pharma.

Incidence and Outcome of Atypical Manifestations of Chronic Graft-versus-Host Disease: Results From a Retrospective Single-Center Analysis.

Chronic graft-versus-host disease (cGVHD) is the leading cause of late nonrelapse mortality (NRM) after allogeneic hematopoietic stem cell transplantation (alloHSCT) and defined by 8 diagnostic target organs. Recently, provisional criteria for atypical manifestations of cGVHD that include manifestations in nonclassic organs as well as atypical manifestations in National Institutes of Health (NIH)-defined organs, were proposed by a NIH task force. Little is known about the incidence, risk factors, and impact on survival of atypical cGVHD, however. The aim of the present study was to analyze these parameters in a sequential patient population. We retrospectively screened 623 patients who underwent alloHSCT at the University Medical Center Regensburg between January 2008 and December 2020 for atypical cGVHD manifestations, applying the provisional NIH taskforce criteria. A total of 102 patients (16.4%) met the criteria, representing 25% of all cGVHD cases, and 14 patients (2.2%) had only atypical cGVHD. The most frequent manifestations were immune-mediated cytopenias (24.5%), renal cGVHD (13.7%) and (poly)serositis (13.7%). Multivariate analysis identified prior acute GVHD (odds ratio [OR], 2.28 and 2.93) and infusion of donor lymphocytes (OR, 1.77 for both) as risk factors for classic cGVHD and atypical cGVHD, whereas total body irradiation was an independent risk factor for atypical cGVHD manifestations only (OR, 1.76). Compared to patients without cGVHD, those with atypical and NIH-defined cGVHD showed similarly better overall survival (P = .034 and < .001) and low relapse-related mortality (P < .001 for both). NRM was significantly increased by atypical GVHD, but not by NIH-defined cGVHD (P = .019 and .10), which was driven only by a few atypical organ manifestations (eg, renal, restrictive lung disease, peripheral neuropathy), whereas others did not contribute to NRM (eg, thyroid gland, musculoskeletal, pancreas). In summary, atypical cGVHD is more common than previously estimated and has both similarities with and differences from NIH-defined cGVHD. In particular, the increased NRM and a subset of patients with only atypical cGVHD point to the urgent need to capture these manifestations in cGVHD cohorts, including analysis of treatment outcomes.

Multimodal immune cell phenotyping in GI biopsies reveals microbiome-related T cell modulations in human GvHD.

Acute graft-versus-host disease (aGvHD) is a significant complication after allogeneic hematopoietic stem cell transplantation (aHSCT), but major factors determining disease severity are not well defined yet. By combining multiplexed tissue imaging and single-cell RNA sequencing on gastrointestinal biopsies from aHSCT-treated individuals with fecal microbiome analysis, we link high microbiome diversity and the abundance of short-chain fatty acid-producing bacteria to the sustenance of suppressive regulatory T cells (Tregs). Furthermore, aGvHD severity strongly associates with the clonal expansion of mainly CD8 T cells, which we find distributed over anatomically distant regions of the gut, persistent over time, and inversely correlated with the presence of suppressive Tregs. Overall, our study highlights the pathophysiological importance of expanded CD8 T cell clones in the progression of aGvHD toward more severe clinical manifestations and strongly supports the further development of microbiome interventions as GvHD treatment via repopulation of the gut Treg niche to suppress inflammation.

Intestinal IgA-positive plasma cells are highly sensitive indicators of alloreaction early after allogeneic transplantation and associate with both graft-versus-host disease and relapse-related mortality.

Intestinal immunoglobulin A (IgA) is strongly involved in microbiota homeostasis. Since microbiota disruption is a major risk factor of acute graft-versus-host disease (GvHD), we addressed the kinetics of intestinal IgA-positive (IgA+) plasma cells by immunohistology in a series of 430 intestinal biopsies obtained at a median of 1,5 months after allogeneic stem cell transplantation (allo-SCT) from 115 patients (pts) at our center. IgA+ plasma cells were located in the subepithelial lamina propria and suppressed in the presence of histological aGvHD (GvHD Lerner stage 0: 131+/-8 IgA+ plasma cells/mm2; stage 1-2: 108+/-8 IgA+ plasma cells/mm2; stage 3-4: 89+/-16 IgA+ plasma cells/mm2; P=0.004). Overall, pts with IgA+ plasma cells below median had an increased treatment related mortality (P=0.04). Time courses suggested a gradual recovery of IgA+ plasma cells after day 100 in the absence but not in the presence of GvHD. Vice versa IgA+ plasma cells above median early after allo-SCT were predictive of relapse and relapse-related mortality (RRM): pts with low IgA+ cells had a 15% RRM at 2 and at 5 years, while pts with high IgA+ cells had a 31% RRM at 2 years and more than 46% at 5 years; multivariate analysis indicated high IgA+ plasma cells in biopsies (hazard ratio =2.7; 95% confidence interval: 1.04-7.00) as independent predictors of RRM, whereas Lerner stage and disease stage themselves did not affect RRM. In contrast, IgA serum levels at the time of biopsy were not predictive for RRM. In summary, our data indicate that IgA+ cells are highly sensitive indicators of alloreaction early after allo-SCT showing association with TRM but also allowing prediction of relapse independently from the presence of overt GvHD.

Analysis of long-term mortality after total body irradiation-based and melphalan-based chemotherapy conditioning for acute myeloid leukemia.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment option for selected patients with acute myeloid leukemia. Yet, the influence of total body irradiation (TBI)-based conditioning as compared to non-TBI-based conditioning on long-term mortality is unclear. We retrospectively evaluated outcomes after TBI-based (n = 91) and non-TBI-based conditioning (melphalan-based, n = 248) for 1st allo-HSCT patients transplanted at the University Hospital Regensburg between 1999 and 2020. TBI was performed with an average dose rate of 4 cGy/min. Median follow-up was 8.3 years (interquartile range, 4.8-12.9 years). Cumulative incidence rates of 5-year non-relapse mortality (NRM) were 17% (95% confidence interval, CI, 10-25) and 33% (95% CI, 27-40) after TBI- and non-TBI-based conditioning (P < 0.001). Five-year cumulative incidences of relapse (CIR) were 42% (95% CI, 32-52) and 29% (95% CI, 23-35) after TBI- and non-TBI-based conditioning (P = 0.030). The 5-year OS was 54% (95% CI, 43-64) and 55% (95% CI, 48-62) after TBI- and non-TBI-based conditioning. Both groups had similar 100-day acute graft-versus-host disease (aGVHD, 43% vs. 40%) and 5-year chronic GVHD (34% vs. 36%). The multivariable regression models found no associations of TBI with the outcomes NRM, CIR, PFS, OS, aGVHD, and cGVHD. TBI was no risk factor for NRM, even including mortality caused by secondary malignancies. NRM was influenced by patient age, advanced disease status, and the use of female donors for male recipients. TBI- and non-TBI-based conditioning appear to be equally effective and tolerable for AML patients eligible for 1st allo-HSCT.

Restrictive Versus Permissive Use of Broad-spectrum Antibiotics in Patients Receiving Allogeneic Stem Cell Transplantation and With Early Fever Due to Cytokine Release Syndrome: Evidence for Beneficial Microbiota Protection Without Increase in Infectious Complications.

BACKGROUND: Intestinal microbiome contributes to the pathophysiology of acute gastrointestinal (GI) graft-versus-host disease (GvHD) and loss of microbiome diversity influences the outcome of patients after allogeneic stem cell transplantation (SCT). Systemic broad-spectrum antibiotics have been identified as a major cause of early intestinal dysbiosis. METHODS: In 2017, our transplant unit at the university hospital in Regensburg changed the antibiotic strategy from a permissive way with initiation of antibiotics in all patients with neutropenic fever independent of the underlying cause and risk to a restrictive use in cases with high likelihood of cytokine release syndrome (eg, after anti-thymocyte globulin [ATG] therapy). We analyzed clinical data and microbiome parameters obtained 7 days after allogeneic SCT from 188 patients with ATG therapy transplanted in 2015/2016 (permissive cohort, n = 101) and 2918/2019 (restrictive cohort, n = 87). RESULTS: Restrictive antibiotic treatment postponed the beginning of antibiotic administration from 1.4 ± 7.6 days prior to 1.7 ± 5.5 days after SCT (P = .01) and significantly reduced the duration of antibiotic administration by 5.8 days (P < .001) without increase in infectious complications. Furthermore, we observed beneficial effects of the restrictive strategy compared with the permissive way on microbiome diversity (urinary 3-indoxylsulfate, P = .01; Shannon and Simpson indices, P < .001) and species abundance 7 days post-transplant as well as a positive trend toward a reduced incidence of severe GI GvHD (P = .1). CONCLUSIONS: Our data indicate that microbiota protection can be achieved by a more careful selection of neutropenic patients qualifying for antibiotic treatment during allogeneic SCT without increased risk of infectious complications.

Acute graft-versus-host disease.

Acute graft-versus-host disease (GVHD) is a common immune complication that can occur after allogeneic haematopoietic cell transplantation (alloHCT). Acute GVHD is a major health problem in these patients, and is associated with high morbidity and mortality. Acute GVHD is caused by the recognition and the destruction of the recipient tissues and organs by the donor immune effector cells. This condition usually occurs within the first 3 months after alloHCT, but later onset is possible. Targeted organs include the skin, the lower and upper gastrointestinal tract and the liver. Diagnosis is mainly based on clinical examination, and complementary examinations are performed to exclude differential diagnoses. Preventive treatment for acute GVHD is administered to all patients who receive alloHCT, although it is not always effective. Steroids are used for first-line treatment, and the Janus kinase 2 (JAK2) inhibitor ruxolitinib is second-line treatment. No validated treatments are available for acute GVHD that is refractory to steroids and ruxolitinib, and therefore it remains an unmet medical need.