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.

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 £ 10 6 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.

Clinical outcomes in children with steroid-refractory acute graft-versus-host disease (SR-aGVHD) are generally poor, with a high mortality rate and limited therapeutic options. Here we report our updated investigational experience with mesenchymal stromal cell (MSC) therapy with remestemcel-L in a multicenter expanded access protocol (ClinicalTrials.gov identifier NCT00759018) in 241 children with aGVHD who failed to respond to steroids with or without other secondary and tertiary immunosuppressive therapies. A total of 241 children with grade B-D SR-aGVHD were enrolled at 50 sites in 8 countries and received 8 biweekly i.v. infusions of human MSCs, 2 £ 10 6 per kg for 4 weeks, with an option for an additional 4 weekly infusions after day +28 for subjects who achieved either a partial response (PR) or mixed response. The mean age of the subjects was 9.6 years; 39% were female, and 60% were white. Most of the subjects had grade C (30%) or grade D (50%) disease, and in most cases, the subjects had failed to respond to other immunosuppressive agents after failing steroids. The primary endpoint was overall response (OR; the sum of complete response [CR] and PR) at day +28. Across all subjects, a 28-day OR was observed in 157 patients (65.1%), with 34 (14.1%) achieving CR and 123 (51.3%) achieving PR. Stratified by aGVHD grade at baseline, the OR rate at day +28 was 72.9% for patients with aGVHD grade B, 67.1% for those with aGVHD grade C, and 60.8% for those with aGVHD grade D. Survival through day +100, a secondary endpoint of the study, was 66.9% (n = 160 of 239). Importantly, survival through day +100 was significantly greater in subjects who achieved a day +28 OR compared with nonresponders (82.1% versus 38.6%; P < .001, log-rank test). Remestemcel-L safety was generally well tolerated, with no infusional toxicity and no identified safety concerns. In summary, this update to the remestemcel-L expanded access program confirms the reported clinical and survival benefits of remestemcel-L therapy in children with aGVHD who have exhausted all conventional therapeutic options.

Rationale There are limited therapeutic options for patients with coronavirus disease (COVID-19)-related acute respiratory distress syndrome with inflammation-mediated lung injury. Mesenchymal stromal cells offer promise as immunomodulatory agents. Objectives Evaluation of efficacy and safety of allogeneic mesenchymal cells in mechanically-ventilated patients with moderate or severe COVID-19–induced respiratory failure. Methods Patients were randomized to two infusions of 2 million cells/kg or sham infusions, in addition to the standard of care. We hypothesized that cell therapy would be superior to sham control for the primary endpoint of 30-day mortality. The key secondary endpoint was ventilator-free survival within 60 days, accounting for deaths and withdrawals in a ranked analysis. Measurements and Main Results At the third interim analysis, the data and safety monitoring board recommended that the trial halt enrollment as the prespecified mortality reduction from 40% to 23% was unlikely to be achieved ( n = 222 out of planned 300). Thirty-day mortality was 37.5% (42/112) in cell recipients versus 42.7% (47/110) in control patients (relative risk [RR], 0.88; 95% confidence interval, 0.64–1.21; P = 0.43). There were no significant differences in days alive off ventilation within 60 days (median rank, 117.3 [interquartile range, 60.0–169.5] in cell patients and 102.0 [interquartile range, 54.0–162.5] in control subjects; higher is better). Resolution or improvement of acute respiratory distress syndrome at 30 days was observed in 51/104 (49.0%) cell recipients and 46/106 (43.4%) control patients (odds ratio, 1.36; 95% confidence interval, 0.57–3.21). There were no infusion-related toxicities and overall serious adverse events over 30 days were similar. Conclusions Mesenchymal cells, while safe, did not improve 30-day survival or 60-day ventilator-free days in patients with moderate and/or severe COVID-19–related acute respiratory distress syndrome.

Background We previously reported a Phase 1/2 randomized placebo-controlled trial of systemic administration of bone marrow-derived allogeneic MSCs (remestemcel-L) in COPD. While safety profile was good, no functional efficacy was observed. However, in view of growing recognition of effects of inflammatory environments on MSC actions we conducted a post-hoc analysis with stratification by baseline levels of a circulating inflammatory marker, C-reactive protein (CRP) to determine the effects of MSC administration in COPD patients with varying circulating CRP levels. Methods Time course of lung function, exercise performance, patient reported responses, and exacerbation frequency following four monthly infusions of remestemcel-L vs. placebo were re-assessed in subgroups based on baseline circulating CRP levels. Results In COPD patients with baseline CRP ≥ 4 mg/L, compared to COPD patients receiving placebo (N = 17), those treated with remestemcel-L (N = 12), demonstrated significant improvements from baseline in forced expiratory volume in one second, forced vital capacity, and six minute walk distance at 120 days with treatment differences evident as early as 10 days after the first infusion. Significant although smaller benefits were also detected in those with CRP levels ≥ 2 or ≥ 3 mg/L. These improvements persisted variably over the 2-year observational period. No significant benefits were observed in patient reported responses or number of COPD exacerbations between treatment groups. Conclusion In an inflammatory environment, defined by elevated circulating CRP, remestemcel-L administration yielded at least transient meaningful pulmonary and functional improvements. These findings warrant further investigation of potential MSC-based therapies in COPD and other inflammatory pulmonary diseases. Trial registration: Clinicaltrials.gov NCT00683722.

Background: The combination of CNI (tacrolimus [Tac] or cyclosporine [CSP]) with MTX and MMF have been used for GVHD prophylaxis after RIC alloHCT, but there is limited comparative data on the efficacy of the two regimens. The Center for International Blood and Marrow Transplant Research (CIBMTR) database was used to answer the question if the outcomes were similar using MMF-CNI and MTX-CNI regimens for after RIC alloHCT. Methods: We evaluated 1584 adult patients who underwent RIC alloHCT for AML, ALL, CML and MDS from 2000-2013 using HLA-identical sibling or 7/8-or 8/8-matched unrelated donor and received CNI (CSP or Tac) with MTX or MMF for GVHD prophylaxis. Peripheral blood grafts and in vivo T-cell depletion were included. Primary outcomes of the study were acute (grades II-IV and III-IV) and chronic GVHD and overall survival (OS). To understand the impact of GVHD prophylaxis on outcomes, the patient population was divided into four cohorts depending on the GVHD prophylaxis: MMF-Tac, MMF-CSP, MTX-Tac and MTX-CSP. Two separate analyses were performed-one for patients with sibling donors (SD) and another for those with unrelated donors (URD). P-values<.01 were treated as statistically significant accounting for multiple comparisons across the endpoints. Results: The median follow-up of the survivors was 48 to 71 months in the 8 cohorts based on the donor and GVHD prophylaxis (SD-MMF-Tac, SD-MMF-CSP, SD-MTX-Tac, SD-MTX-CSP, URD-MMF-Tac, URD-MMF-CSP, URD-MTX-Tac, URD-MTX-CSP) (Table 1). Multivariate analysis (MVA) showed that, in the SD group, there was no significant difference in the risk of grade (G) II-IV and GIII-IV acute GVHD (aGVHD) among the four GVHD cohorts. In URD group, MMF-CSP increased the risk of GII-IV aGVHD (RR 1.78, P < .001) and GIII-IV aGVHD (RR 1.93, P = .006) compared to MTX-Tac. The risk of chronic GVHD (cGVHD) also did not differ with GVHD prophylaxis in the SD and URD groups, but the inclusion of ATG in conditioning lowered the incidence of cGVHD in both SD (RR .55, P = .001) and URD group (RR .74, P = .03). OS and diseasefree survival (DFS) also did not differ with GVHD regimen in both SD and URD groups. In the SD group, MVA failed to show any difference in risk of TRM or relapse regardless of GVHD prophylaxis. GVHD regimens MMF-CSP (RR .53, P < .001) and MMF-Tac (RR .72, P = .03) decreased the risk of relapse relative to MTX-Tac cohort in URD group. The study also showed consistently that Flu/Mel conditioning increased the risk of aGVHD, cGVHD and TRM, and lowered relapse risk in both SD and URD groups. Conclusion: In RIC alloHCT using SD, there was no difference in outcomes independent of GVHD prophylaxis. However, with URD alloHCT, MMF-CSP was an inferior regimen for acute GVHD prevention. In contrast, MMF-based regimens were associated with improved relapse rate compared to MTX-Tac.

compared to mice receiving wild type (WT) splenocytes 1. Here, we investigate the impact of miR-155 expression in T cell migration and elucidate the T cell population responsible for miR-155 mediated modulation of aGVHD. Materials and Methods: Lethally irradiated BALB/c or B6D2F1 recipients were infused with T cell depleted WT bone marrow (BM) cells and GFP expressing miR-155 KO or GFP-B6 WT T cells. Recipients were sacrificed, organs harvested and donor T cell infiltration evaluated via confocal microscopy. Transplants with only CD4+ donor T cells were also performed. Transwell migration assays towards CCR5 ligands macrophage inflammatory protein-1a (MIP-1a) (100ng/uL) and RANTES (100ng/uL) were performed utilizing allo-activated WT or miR-155-KO T cells. Results: There was a dramatic decrease in T cell infiltration of peripheral organs (Peyer's patches, liver, lung and skin) in recipients of miR-155-KO T cells as compared to WT T cells as evidenced by confocal microscopy of GFP labeled donor cells, on days 7, 14 and 21 post transplant. We reasoned that these effects could be due to the modulation of CCR5 and other chemokine receptors by miR-155. To demonstrate the functional significance of decreased CCR5 expression in miR-155 KO donor T cells, we performed in vitro transwell migration assays to CCR5 ligands RANTES and MIP-1a. To our knowledge, we are the first to show that allo-activated miR-155 KO T cells show significantly reduced migration (p<0.005) towards CCR5 ligands, as demonstrated by the average migration index of 1.08 when compared to the average migration index of WT T cells of 4.52. We performed a B6 into F1 transplant using only CD4+ donor T cells. Median survival of recipients of T cell depleted BM+ WT CD4+ T cells (n¼13) was 42 days as compared to 100% survival of all recipient mice of miR-155 KO CD4+ T cells (n¼12) on day 100, (p<0.0001). Recipients of miR-155 KO CD4+ T cells also exhibited significant lower aGVHD clinical (p<0.01) and pathological scores (p<0.01) than WT recipients. Conclusions: Our data suggest that miR-155 may exert its modulating effects in aGVHD by affecting T cell migration. Our results also indicate that the CD4+ T cell subset plays an important role in miR-155 regulation of aGVHD. Experiments are underway to determine the role of miR-155 in regulatory T cells and CD8+ T cell subsets in the modulation of aGVHD as well as evaluating the role of miR-155 in modulating T cell migration through other chemokine receptors CXCR4, S1P1 and ATP receptor P2X7R.

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