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The therapeutic potential of donor-derived mesenchymal stromal cells (MSCs) has been investigated in diverse diseases 1 , including steroid-resistant acute graft versus host disease (SR-aGvHD) 2 . However, conventional manufacturing approaches are hampered by challenges with scalability and interdonor variability, and clinical trials have shown inconsistent outcomes 3 , 4 . Induced pluripotent stem cells (iPSCs) have the potential to overcome these challenges, due to their capacity for multilineage differentiation and indefinite proliferation 5 , 6 . Nonetheless, human clinical trials of iPSC-derived cells have not previously been completed. CYP-001 (iPSC-derived MSCs) is produced using an optimized, good manufacturing practice (GMP)-compliant manufacturing process. We conducted a phase 1, open-label clinical trial (no. NCT02923375) in subjects with SR-aGvHD. Sixteen subjects were screened and sequentially assigned to cohort A or cohort B ( n  = 8 per group). One subject in cohort B withdrew before receiving CYP-001 and was excluded from analysis. All other subjects received intravenous infusions of CYP-001 on days 0 and 7, at a dose level of either 1 × 10 6 cells per kg body weight, to a maximum of 1 × 10 8 cells per infusion (cohort A), or 2 × 10 6 cells per kg body weight, to a maximum dose of 2 × 10 8 cells per infusion (cohort B). The primary objective was to assess the safety and tolerability of CYP-001, while the secondary objectives were to evaluate efficacy based on the proportion of participants who showed a complete response (CR), overall response (OR) and overall survival (OS) by days 28/100. CYP-001 was safe and well tolerated. No serious adverse events were assessed as related to CYP-001. OR, CR and OS rates by day 100 were 86.7, 53.3 and 86.7%, respectively. The therapeutic application of iPSC-derived MSCs may now be explored in diverse inflammatory and immune-mediated diseases. A GMP-compliant process for generating human iPSC-derived mesenchymal stromal cells tested in a phase 1 trial is safe and well tolerated in subjects with acute steroid-resistant graft versus host disease.

Relapse after allogeneic hematopoietic cell transplantation (HCT) is the leading cause of death in patients with acute myeloid leukemia (AML) entering HCT with poor-risk features1–3. When HCT does produce prolonged relapse-free survival, it commonly reflects graft-versus-leukemia effects mediated by donor T cells reactive with antigens on leukemic cells4. As graft T cells have not been selected for leukemia specificity and frequently recognize proteins expressed by many normal host tissues, graft-versus-leukemia effects are often accompanied by morbidity and mortality from graft-versus-host disease5. Thus, AML relapse risk might be more effectively reduced with T cells expressing receptors (TCRs) that target selected AML antigens6. We therefore isolated a high-affinity Wilms’ Tumor Antigen 1-specific TCR (TCRC4) from HLA-A2+ normal donor repertoires, inserted TCRC4 into Epstein–Bar virus-specific donor CD8+ T cells (TTCR-C4) to minimize graft-versus-host disease risk and enhance transferred T cell survival7,8, and infused these cells prophylactically post-HCT into 12 patients (NCT01640301). Relapse-free survival was 100% at a median of 44 months following infusion, while a concurrent comparative group of 88 patients with similar risk AML had 54% relapse-free survival (P = 0.002). TTCR-C4 maintained TCRC4 expression, persisted long-term and were polyfunctional. This strategy appears promising for preventing AML recurrence in individuals at increased risk of post-HCT relapse.

Irradiation to condition hosts for bone marrow transplantation leads to alterations in intestinal microbiota. Reddy and colleagues demonstrate that these changes result in reduced butyrate production and breakdown of intestinal barrier function. The effect of alterations in intestinal microbiota on microbial metabolites and on disease processes such as graft-versus-host disease (GVHD) is not known. Here we carried out an unbiased analysis to identify previously unidentified alterations in gastrointestinal microbiota–derived short-chain fatty acids (SCFAs) after allogeneic bone marrow transplant (allo-BMT). Alterations in the amount of only one SCFA, butyrate, were observed only in the intestinal tissue. The reduced butyrate in CD326 + intestinal epithelial cells (IECs) after allo-BMT resulted in decreased histone acetylation, which was restored after local administration of exogenous butyrate. Butyrate restoration improved IEC junctional integrity, decreased apoptosis and mitigated GVHD. Furthermore, alteration of the indigenous microbiota with 17 rationally selected strains of high butyrate–producing Clostridia also decreased GVHD. These data demonstrate a heretofore unrecognized role of microbial metabolites and suggest that local and specific alteration of microbial metabolites has direct salutary effects on GVHD target tissues and can mitigate disease severity.

Human FOXP3 + regulatory T (T reg ) cells are central to immune tolerance. However, their heterogeneity and differentiation remain incompletely understood. Here we use single-cell RNA and T cell receptor sequencing to resolve T reg cells from healthy individuals and patients with or without acute graft-versus-host disease (aGVHD) who undergo stem cell transplantation. These analyses, combined with functional assays, separate T reg cells into naïve, activated, and effector stages, and resolve the HLA-DR hi , LIMS1 hi , highly suppressive FOXP3 hi , and highly proliferative MKI67 hi effector subsets. Trajectory analysis assembles T reg subsets into two differentiation paths (I/II) with distinctive phenotypic and functional programs, ending with the FOXP3 hi and MKI67 hi subsets, respectively. Transcription factors FOXP3 and SUB1 contribute to some Path I and Path II phenotypes, respectively. These FOXP3 hi and MKI67 hi subsets and two differentiation pathways are conserved in transplanted patients, despite having functional and migratory impairments under aGVHD. These findings expand the understanding of T reg cell heterogeneity and differentiation and provide a single-cell atlas for the dissection of T reg complexity in health and disease. Human Treg cells are central to immune tolerance, yet their heterogeneity and differentiation remain incompletely understood. Here the authors perform single-cell RNA and T cell receptor sequencing to resolve Treg cells from healthy individuals and patients with or without acute graft-versus-host disease revealing Treg complexity in health and disease.

Fecal microbiota transplant (FMT) has emerged as a potential treatment for severe colitis associated with graft-versus-host disease (GvHD) following hematopoietic stem cell transplant. Bacterial engraftment from FMT donor to recipient has been reported, however the fate of fungi and viruses after FMT remains unclear. Here we report longitudinal dynamics of the gut bacteriome, mycobiome and virome in a teenager with GvHD after receiving four doses of FMT at weekly interval. After serial FMTs, the gut bacteriome, mycobiome and virome of the patient differ from compositions before FMT with variable temporal dynamics. Diversity of the gut bacterial community increases after each FMT. Gut fungal community initially shows expansion of several species followed by a decrease in diversity after multiple FMTs. In contrast, gut virome community varies substantially over time with a stable rise in diversity. The bacterium, Corynebacterium jeikeium , and Torque teno viruses, decrease after FMTs in parallel with an increase in the relative abundance of Caudovirales bacteriophages. Collectively, FMT may simultaneously impact on the various components of the gut microbiome with distinct effects. Fecal microbiota transplant (FMT) is emerging as a potential treatment for graft-versus-host disease (GvHD). Here, the authors examine temporal dynamics of the bacteriome, mycobiome, and virome of a patient with GvHD who received multiple FMTs.

Acute graft-versus-host disease (GVHD) remains a barrier to successful allogeneic hematopoietic cell transplantation (HCT) outcomes. This multicenter, retrospective chart review describes disease progression, treatment patterns, hospitalizations, and clinical outcomes among 475 patients (≥12 years old) who developed grades II–IV acute GVHD after their first HCT (January 2014–June 2016). Median (interquartile range) age at HCT was 55 (44–63) years. From the date of acute GVHD diagnosis, 190 patients (40.0%) experienced progression to more severe disease and/or developed new organ involvement. Among 431 patients with grades II–IV acute GVHD at diagnosis, 73.1% received first-line systemic corticosteroids. During follow-up (median 524 days since acute GVHD diagnosis), 23.4% of patients had an increase in steroid dose and 44.4% were unable to taper below 10 mg/day. Over half of patients (54.9%) required ≥1 hospital readmission within 100 days post-HCT (≥2 readmissions in 22.3%); mean inpatient length of stay upon readmission was 27.5 days. Approximately half of patients (52.8%) died during follow-up; 1-year overall mortality from date of acute GVHD diagnosis and nonrelapse mortality rates were 35.2% and 25.5%, respectively. Overall, patients who developed acute GVHD following HCT had poor clinical outcomes, highlighting the unmet need for early and effective treatment strategies.

Acute graft-versus-host disease (aGVHD) of the lower gastrointestinal (GI) tract is a major cause of morbidity and mortality in patients receiving allogeneic hematopoietic stem cell transplantation (allo-HSCT). Vedolizumab is a gut-selective anti-α 4 β 7 integrin monoclonal antibody that reduces gut inflammation by inhibiting migration of GI-homing T lymphocytes. The efficacy and safety of vedolizumab added to standard GVHD prophylaxis (calcineurin inhibitor plus methotrexate/mycophenolate mofetil) was evaluated for prevention of lower-GI aGVHD after unrelated donor allo-HSCT in a randomized, double-blind, placebo-controlled phase 3 trial. Enrollment closed early during the COVID-19 pandemic with 343 patients randomized ( n  = 174 vedolizumab, n  = 169 placebo), and 333 received ≥1 intravenous dose of 300 mg vedolizumab ( n  = 168) or placebo ( n  = 165) and underwent allo-HSCT. The primary end point was met; Kaplan–Meier (95% confidence interval) estimated rates of lower-GI aGVHD-free survival by day +180 after allo-HSCT were 85.5% (79.2–90.1) with vedolizumab versus 70.9% (63.2–77.2) with placebo (hazard ratio, 0.45; 95% confidence interval, 0.27–0.73; P  < 0.001). For the 5 key secondary efficacy end points analyzed by day +180 after allo-HSCT, rates of lower-GI aGVHD-free and relapse-free survival and grade C–D aGVHD-free survival were significantly higher with vedolizumab versus placebo. No significant treatment differences were found for the other key secondary end points of non-relapse mortality, overall survival and grade B–D aGVHD-free survival, respectively. Incidence of treatment-related serious adverse events analyzed in patients receiving ≥1 dose of study treatment ( n  = 334) was 6.5% ( n  = 11 of 169) vedolizumab versus 8.5% ( n  = 14 of 165) placebo. When added to standard calcineurin inhibitor-based GVHD prevention, lower-GI aGVHD-free survival was significantly higher with vedolizumab versus placebo. ClinicalTrials.gov identifier: NCT03657160 . In a randomized, double-blind phase 3 trial, the anti-α 4 β 7 integrin monoclonal antibody vedolizumab plus standard prophylaxis was superior to placebo plus prophylaxis for prevention of lower gastrointestinal acute graft-versus-host disease in patients following allogeneic hematopoietic stem cell transplantation.

Key Points Acute graft-versus-host disease (GVHD) of the gastrointestinal tract is a common complication in patients after haematopoietic stem cell transplantation (HSCT) that results in considerable morbidity and mortality As the clinical, serological and radiographical findings in gastrointestinal acute GVHD are nonspecific, a broad differential diagnosis should be considered, particularly potential infectious causes and chemotherapeutic or immunosuppressant toxicity Expedient endoscopy and histopathology are helpful in excluding possible conditions that mimic gastrointestinal acute GVHD; nevertheless, the diagnosis is ultimately based on clinical criteria Several novel diagnostic, prognostic, risk and predictive biomarkers have been identified for gastrointestinal acute GVHD; however, none have yet been integrated into routine clinical practice Upon diagnosis of gastrointestinal acute GVHD, timely first-line therapy with systemic corticosteroids (such as prednisone or methylprednisolone) and/or oral non-absorbable corticosteroids (such as beclomethasone or budesonide) is crucial Acute GVHD leads to substantial gastrointestinal symptom burden, including profuse diarrhoea, abdominal pain, severe malnutrition and gastrointestinal bleeding; providing supportive and palliative care is a critical role of the gastroenterologist Following haematopoietic stem cell transplantation for the treatment of haematopoietic diseases, acute graft-versus-host disease (GVHD) of the gastrointestinal tract is a common complication that presents distinct diagnostic and therapeutic challenges. In this Review, the authors tailor their discussion of the diagnosis, staging and clinical management of gastrointestinal acute GVHD for practising gastroenterologists. Haematopoietic stem cell transplantation (HSCT) is central to the management of many haematological disorders. A frequent complication of HSCT is acute graft-versus-host disease (GVHD), a condition in which immune cells from the donor attack healthy recipient tissues. The gastrointestinal system is among the most common sites affected by acute GVHD, and severe manifestations of acute GVHD of the gut portends a poor prognosis in patients after HSCT. Acute GVHD of the gastrointestinal tract presents both diagnostic and therapeutic challenges. Although the clinical manifestations are nonspecific and overlap with those of infection and drug toxicity, diagnosis is ultimately based on clinical criteria. As reliable serum biomarkers have not yet been validated outside of clinical trials, endoscopic and histopathological evaluation continue to be utilized in diagnosis. Once a diagnosis of gastrointestinal acute GVHD is established, therapy with systemic corticosteroids is typically initiated, and non-responders can be treated with a wide range of second-line therapies. In addition to treating the underlying disease, the management of complications including profuse diarrhoea, severe malnutrition and gastrointestinal bleeding is paramount. In this Review, we discuss strategies for the diagnosis and management of acute GVHD of the gastrointestinal tract as they pertain to the practising gastroenterologist.

Chronic graft-versus-host disease (cGVHD) is one of the major causes of late mortality after allogenic hematopoietic stem cell transplantation. Moderate-to-severe cGVHD is associated with poor health-related quality of life and substantial disease burden. While corticosteroids with or without calcineurin inhibitors comprise the first-line treatment option, the prognosis for patients with steroid-refractory cGVHD (SR-cGVHD) remains poor. The mechanisms underlying steroid resistance are unclear, and there are no standard second-line treatment guidelines for patients with SR-cGVHD. In this review, we provide an overview on current treatment options of cGVHD and use a series of theoretical case studies to elucidate the rationale of choices of second- and third-line treatment options for patients with SR-cGVHD based on individual patient profiles.