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Background: For patients with steroid-refractory acute graft-versus-host disease (SR-aGVHD), effective second-line regimens are urgently needed. Mesenchymal stromal cells (MSCs) have been used as salvage regimens for SR-aGVHD in the past. However, clinical trials and an overall understanding of the molecular mechanisms of MSCs combined with basiliximab for SR-aGVHD are limited, especially in haploidentical haemopoietic stem cell transplantation (HID HSCT). Methods: The primary endpoint of this multicentre, randomized, controlled trial was the 4-week complete response (CR) rate of SR-aGVHD. A total of 130 patients with SR-aGVHD were assigned in a 1:1 randomization schedule to the MSC group (receiving basiliximab plus MSCs) or control group (receiving basiliximab alone) (NCT04738981). Results: Most enrolled patients (96.2%) received HID HSCT. The 4-week CR rate of SR-aGVHD in the MSC group was obviously better than that in the control group (83.1% vs. 55.4%, P = 0.001). However, for the overall response rates at week 4, the two groups were comparable. More patients in the control group used ≥ 6 doses of basiliximab (4.6% vs. 20%, P = 0.008). We collected blood samples from 19 consecutive patients and evaluated MSC-derived immunosuppressive cytokines, including HO1, GAL1, GAL9, TNFIA6, PGE2, PDL1, TGF-β and HGF. Compared to the levels before MSC infusion, the HO1 (P = 0.0072) and TGF-β (P = 0.0243) levels increased significantly 1 day after MSC infusion. At 7 days after MSC infusion, the levels of HO1, GAL1, TNFIA6 and TGF-β tended to increase; however, the differences were not statistically significant. Although the 52-week cumulative incidence of cGVHD in the MSC group was comparable to that in the control group, fewer patients in the MSC group developed cGVHD involving ≥3 organs (14.3% vs. 43.6%, P = 0.006). MSCs were well tolerated, no infusion-related adverse events (AEs) occurred and other AEs were also comparable between the two groups. However, patients with malignant haematological diseases in the MSC group had a higher 52-week disease-free survival rate than those in the control group (84.8% vs. 65.9%, P = 0.031). Conclusions: For SR-aGVHD after allo-HSCT, especially HID HSCT, the combination of MSCs and basiliximab as the second-line therapy led to significantly better 4-week CR rates than basiliximab alone. The addition of MSCs not only did not increase toxicity but also provided a survival benefit. [ABSTRACT FROM AUTHOR]

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal disorders and is rare in children. Allogeneic hematopoietic stem cell transplantation (HSCT) is commonly used in children with MDS with excess blasts and in patients with refractory cytopenia of childhood (RCC) associated with monosomy 7, complex karyotype, severe neutropenia, or transfusion dependence. We recruited 27 children with MDS who received haploidentical hematopoietic stem cell transplantation (haplo-HSCT). At transplantation, 10 patients had RCC, 12 patients had advanced MDS (RAEB and RAEB-T), and 5 patients had myelodysplasia-related acute myeloid leukemia (MDRAML). All patients received granulocyte colony-stimulating factor (G-CSF)-mobilized bone marrow cells and peripheral blood stem cells. At a median follow-up of 24.1 months (range: 2.0-74.5 months) after HSCT, the estimated probabilities of 3-year disease-free survival (DFS) and overall survival (OS) were both 81.9% (95% CI, 66.8-100.0%). The estimated 3-year incidences of relapse (CIR) and non-relapse mortality (NRM) were both 7.4% (95% CI, 1.2%-21.4%). The 100-day cumulative incidence of grade II-IV aGVHD was 52.6% (95% CI, 42.9-62.3%), while that of grade III-IV aGVHD was 11.1% (95% CI, 5.1-17.1%). The 3-year cumulative incidences of overall and extensive cGVHD were 42.3% (95% CI, 19.8%-57.5%) and 21.1% (95% CI, 2.5%-63.2%), respectively. Univariate analysis showed that chronic GVHD significantly affected OS and DFS. Haploidentical HSCT may be an effective treatment option with easier donor availability for pediatric patients with MDS. [ABSTRACT FROM AUTHOR]