Graft versus Host Disease (GvHD)

Graft versus host disease (GvHD) is the clinical condition in which bone marrow-derived mesenchymal stromal cells (MSCs) have been most frequently studied. In this review, we summarize the experience from clinical trials that have paved the way to translation. While MSC-based therapy has shown an exceptional safety profile, identifying potency assays and disease biomarkers that reliably predict the capacity of a specific MSC batch to alleviate GvHD has been difficult. As GvHD diagnosis and staging are based solely on clinical criteria, individual patients recruited in the same clinical trial may have vastly different underlying biology, obscuring trial outcomes and making it difficult to determine the benefit of MSCs in subgroups of patients. An accumulating body of evidence indicates the importance of considering not only the cell product but also patient-specific biomarkers and/or immune characteristics in determining MSC responsiveness. A mode of action where intravascular MSC destruction is followed by monocyte-efferocytosis-mediated skewing of the immune repertoire in a permissive inflammatory environment would both explain why cell engraftment is irrelevant for MSC efficacy and stress the importance of biologic differences between responding and nonresponding patients. We recommend a combined analysis of clinical outcomes and both biomarkers of disease activity and MSC potency assays to identify patients with GvHD who are likely to benefit from MSC therapy.

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Severe graft-versus-host disease (GVHD) is a life-threatening complication after allogeneic transplantation with haemopoietic stem cells. Mesenchymal stem cells modulate immune responses in vitro and in vivo. We aimed to assess whether mesenchymal stem cells could ameliorate GVHD after haemopoietic-stem-cell transplantation.

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Steroid-refractory chronic graft-vs-host disease (cGvHD) contributes to morbidity after allogeneic hematopoietic stem cell transplantation. Here, we report on 11 patients with severe, refractory cGvHD treated with repeated infusions of allogeneic bone marrow-derived mesenchymal stromal cells (MSC) over a 6- to 12-month period. Six patients responded to MSC treatment following National Institutes of Health response criteria, accompanied by improvement in GvHD-related symptoms and quality of life. This response was durable, with systemic immunosuppressive therapy withdrawn from two responders, and a further two free from steroids and tapering calcineurin inhibitors. All responders displayed a distinct immune phenotype characterized by higher levels of naïve T cells and B cells before treatment compared with the nonresponders, and a significantly higher fraction of CD31+ naïve CD4+ T cells. MSC treatment was associated with significant increases in naïve T cells, B cells, and Tregs 7 days after each infusion. Skin biopsies showed resolution of epidermal pathology. CXCL9 and CXCL10 showed differential responses in responder and nonresponder patients. Our data support the use of MSC infusions as treatment for steroid-refractory cGvHD with durable responses. We propose CXCL9 and CXCL10 as early biomarkers for responsiveness to MSC treatment. Our results highlight the importance of the MSC recipient immune phenotype in promoting treatment response..

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Steroid-refractory acute graft-versus-host disease (SR-aGVHD) following hematopoietic cell transplantation (HSCT) is associated with poor clinical outcomes. Currently, there are no safe and effective therapies approved for use in the pediatric population under the age of 12 years. Accordingly, there is an urgent need for new treatments that are safe, well tolerated, and effective in managing this debilitating and potentially fatal complication of HSCT. In early phase clinical trials, mesenchymal stromal cells (MSCs) have demonstrated efficacy in the treatment of acute GVHD (aGVHD) in pediatric patients. We now report the results of a phase 3, prospective, single-arm, multicenter study (NCT02336230) in 54 children with primary SR-aGVHD who were naive to other immunosuppressant therapies for aGVHD treated with MSC product (remestemcel-L) dosed at 2 × 106 cells/kg twice weekly for 4 weeks. Remestemcel-L therapy significantly improved day 28 overall response rate (OR) compared with the prespecified control OR value of 45% (70.4% versus 45%, P = .0003). The statistically significant OR (70.4%) was sustained through day 100, including an increase in complete response from 29.6% at day 28 to 44.4% at day 100. Overall survival was 74.1% at day 100 and 68.5% at day 180. Overall response in all participants at day 28 was highly predictive of improved survival through 180 days, and survival was significantly greater in day 28 responders compared with nonresponders through day 100 (86.8% versus 47.1% for responders and nonresponders, respectively, P = .0001) and through day 180 (78.9% versus 43.8%, P = .003). Remestemcel-L was well tolerated with no identified infusion-related toxicities or other safety concerns. This study provides robust, prospective evidence of the safety, tolerability, and efficacy of remestemcel-L as first-line therapy after initial steroid failure in pediatric SR-aGVHD.

Uncontrolled studies have suggested that bone marrow-derived mesenchymal stem cells (MSCs) may be effective against acute graft-versus-host disease (aGVHD). We conducted a multicenter, randomized study to assess the efficacy of using ex vivo cultured adult human MSC (remestemcel-L) in addition to second-line therapy to treat steroid-refractory aGVHD (NCT00366145). In total, 260 patients, 6 months to 70 years of age, were enrolled from August 2006 to May 2009 and were randomized 2:1 to receive 8 intravenous infusions of remestemcel-L or placebo, given over 4 weeks, in addition to second-line therapy according to institutional standards. Four additional infusions over 4 weeks were indicated for patients with incomplete response at day 28. Randomization was stratified by aGVHD grade. Efficacy and safety were assessed through 180 days of follow-up, with the primary endpoint being durable complete response (DCR), defined as complete resolution of aGVHD symptoms for any period of at least 28 days after beginning treatment. Remestemcel-L did not meet the primary endpoint of greater DCR in the intent-to-treat population (35% versus 30%; P = 0.42). In post hoc analyses, patients with liver involvement who received at least 1 infusion of remestemcel-L had a higher DCR, and higher overall complete or partial response rate (OR) than those who received placebo (29% versus 5%; P = .047). Among high-risk patients (aGVHD grades C and D), remestemcel-L demonstrated significantly higher OR at day 28 than placebo (58% versus 37%; P = 0.03). Furthermore, pediatric patients had a higher OR with MSCs compared with placebo (64% versus 23%; P = .05). Similar rates of adverse events were observed between treatment groups. Remestemcel-L was safe and well tolerated. Results of this study did not demonstrate superior DCR compared with placebo when added to standard of care. The favorable clinical responses seen in some patient subsets may warrant further investigation.

Because of their well-described immunosuppressive properties, allogeneic adult human mesenchymal stromal cells (MSC) derived from bone marrow have demonstrated safety and efficacy in steroid refractory acute graft versus host disease (SR aGVHD). Clinical trials have resulted in variable success and an optimal source of MSC has yet to be defined. Based on the importance of maternal-fetal interface immune tolerance, extraembryonic fetal tissues, such as the umbilical cord, may provide an superior tissue source of MSC to mediate immunomodulation in aGVHD.

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Survival at 12 months post randomisation was 53% (n=8) in the MSC and 77% (n=10) in the control arm. Deaths in the MSC-treated patients (within 12 months) occurred due to relapse (n=1), and aGVHD (n=6). Deaths in the control arm (within 12 months) were due to relapse (n=1), aGVHD (n=1) and cGVHD (n=1). Time to death was similar in both arms (post randomisation; median 93 days (range: 28–210) in MSC arm and 86 days (range: 46–295) in control arm). The use of 12-month overall survival as a primary endpoint is vulnerable to variations in treatment factors outside GVHD therapy.

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Mesenchymal stem cells (MSCs) may be used to treat steroid-refractory graft versus host disease (GVHD). However, the effects of MSCs in haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) have not been confirmed in randomized studies.

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Despite the curative potential of hematopoietic cell transplantation (HCT) for hematologic malignancies, graft-versus-host disease (GVHD) remains a substantial cause of morbidity and mortality, particularly if treatment is refractory. Treatment with additional immunosuppression including steroids often leads to opportunistic infections and organ dysfunction. Novel therapies are greatly needed, specifically ones that lead to responses in treatment-refractory patients and are better tolerated. Mesenchymal stromal cells (MSCs) are non-hematopoietic tolerogenic cells present in normal bone marrow (BM), which can be expanded ex vivo to therapeutic doses. Their safety and efficacy have been assessed in inflammatory disorders including GVHD, but heterogeneity in clinical responses has led some to examine MSC manufacturing and administration procedures, which may impact in vivo efficacy. We hypothesized that autologous, early-passage, and culture-recovered (after freeze and thaw) MSCs would be safe and may have superior efficacy. In this phase I single-center trial, we assessed MSC safety and early efficacy of an escalating number of doses (2 × 106/kg doses; dose level 1, single dose; dose level 2, two weekly doses; dose level 3, four weekly doses) in patients aged ≥12 years with treatment-refractory acute or chronic GVHD. Eleven enrolled patients received some or all planned MSC infusions, with a median age at enrollment of 37 years. The most common primary HCT indication was leukemia, and the median time from HCT to first MSC infusion was 2.6 years. MSC infusion was well tolerated, with all severe adverse events expected and determined to be unlikely or definitely not related to the study. Thus, no dose-limiting toxicities occurred in the three dose levels. Three of four patients with acute GVHD (or overlap with acute features) had responses seen at any timepoint, ranging from partial to complete. In those with a chronic GVHD indication (n = 7), an overall response at 3 months was partial in five, stable in one, and progressive in one. No appreciable differences were seen between dose levels in peripheral blood lymphocyte subsets. In conclusion, autologous and culture-recovered MSCs were safe in the setting of refractory GVHD following HCT for hematologic malignancy, and clinical responses were most notable in patients with acute GVHD.

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Cell therapy is a promising approach for the treatment of refractory ocular disease. This study investigated the efficacy of mesenchymal stromal cells (MSCs) for the treatment of dry eye associated with chronic graft-versus-host disease (cGVHD) and assessed the immunomodulatory effects of MSCs on regulatory CD8(+)CD28(-) T lymphocytes. A total of 22 patients with refractory dry eye secondary to cGVHD were enrolled. The symptoms of 12 out of 22 patients abated after MSCs transplantation by intravenous injection, improving in the dry eye scores, ocular surface disease index scores and the Schirmer test results. The clinical improvements were accompanied by increasing level of CD8(+)CD28(-) T cells, but not CD4(+)CD25(+) T cells, in the 12 patients who were treated effectively. They had significantly higher levels of Th1 cytokines (interleukin (IL)-2 and interferon-γ) and lower levels of Th2 cytokines (IL-10 and IL-4). In addition, CD8(+) T cells were prone to differentiation into CD8(+)CD28(-) T cells after co-culture with MSCs in vitro. In conclusion, transfusion of MSCs improved the clinical symptoms in patients (54.55%) with refractory dry eye secondary to cGVHD. MSCs appear to exert their effects by triggering the generation of CD8(+)CD28(-) T cells, which may regulate the balance between Th1 and Th2.

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Refractory acute graft-versus-host disease (aGVHD) is a major cause of death after allogeneic hematopoietic stem cell transplantation. This study evaluated the immunomodulation effects of mesenchymal stromal cells (MSCs) from bone marrow of a third-party donor for refractory aGVHD. Forty-seven patients with refractory aGVHD were enrolled: 28 patients receiving MSC and 19 patients without MSC treatment. MSCs were given at a median dose of 1 × 10(6) cells/kg weekly until patients got complete response or received 8 doses of MSCs. After 125 doses of MSCs were administered, with a median of 4 doses (range, 2 to 8) per patient, overall response rate was 75% in the MSC group compared with 42.1% in the non-MSC group (P = .023). The incidence of cytomegalovirus, Epstein-Barr virus infections, and tumor relapse was not different between the 2 groups during aGVHD treatment and follow-up. The incidence and severity of chronic GVHD in the MSC group were lower than those in the non-MSC group (P = .045 and P = .005). The ratio of CD3(+)CD4(+)/CD3(+)CD8(+) T cells, the frequencies of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs), and the levels of signal joint T cell-receptor excision DNA circles (sjTRECs) after MSCs treatment were higher than those pretreatment. MSC-treated patients exhibited higher Tregs frequencies and sjTRECs levels than those in the non-MSC group at 8 and 12 weeks after treatment. MSCs derived from bone marrow of a third-party donor are effective to refractory aGVHD. It might reduce the incidence and severity of chronic GVHD in aGVHD patients by improving thymic function and induction of Tregs but not increase the risks of infections and tumor relapse.

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Despite the efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT), the procedure is still associated with high toxicity in patients with refractory graft-versus-host disease (GvHD). Mesenchymal stromal cells (MSCs) are a new mode of therapy in the context of allo-HSCT. The objective of this study was to evaluate the safety and feasibility of the use of adipose tissue-derived MSCs (AT-MSCs) in patients with chronic GvHD.

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