Early Intervention with Mesenchymal Stromal Cells for Refractory Grade III-IV Graft Versus Host Disease In Children Results In Excellent Long Term Outcome
Authors: Ball Lynne Margaret , Bernardo Maria E. , Zwaginga Jaap Jan , van Tol Maarten , Cometa Angela , Roelofs Helene , Giorgiani Giovanna , Jol-van der Zijde Cornelia M , Avanzini Maria Antonietta , Blanc Katarina Le , Bertaina Alice , Frassoni Francesco , Fibbe Willem E. , Ringden Olle , Egeler R. Maarten , Locatelli Franco , Lankester Arjan 
Published: October 2019

Abstract
Abstract 2336
Mesenchymal stromal cell (MSC) infusions have been reported to be effective in patients with severe, steroid-refractory, acute graft-versus-host disease (aGVHD). However, long term comprehensive follow up data on pediatric patients is limited. We analyzed the outcome of 37 children receiving MSC for steroid-refractory aGvHD in two centers between January 2005 and December 2009 (characteristics see Table 1). A median of 2 infusions (range 1–13) were administered, with a median cell dose of 2×106/kg (range 0.9–3.0). MSC were from 3rd party HLA-mismatched donors (n=31), haploidentical relative (n=3) or both (n=3). (see Table 2) Fifteen children had either no (n=6) or partial (n=9) response to MSC. In this group, transplantation-related mortality (TRM) was 60%. Complete response (CR) was observed in 22 children, TRM being 14%. (p=0.005). Among the 28 patients with hematological malignancies, 5 relapsed, three with CR and two with PR. With a median follow-up of 2.3 years (range 7 months–4.7 years), overall survival was 62% with 87% versus 27% in patients who did or did not achieve CR after MSC respectively (p value <0.001).
MSC after 2009 given at the time of steroid failure (median 8 days range 4 to 24) compared to pre 2009 (median 24 days range 5 to 85) (Maan-Whitney U = 65.5 two tailed p= 0.002) reduced fatal infections and was associated with a trend to better overall survival at 2 years post MSC infusion (p = 0.07). Although infections were evident at the time of immune suppression and mortality was high in NR/PR, response to MSC allows for reduction and eventual discontinuation of pharmacological immune suppression. Long term survival in responders is associated with eventual immune recovery, no late infections and persistent remission status.
Treatment of steroid refractory aGVHD should aim to induce rapid stable control and early reduction of steroids to reduce TRM from viral reactivations. We conclude that MSC are ideal candidates for this purpose. Our results show that children responding to MSC treatment for severe steroid refractory GvHD have an excellent long term survival.
Legend: ALL = acute lymphoblastic leukemia; AML = acute myeloid leukemia; MDS = myelodysplastic syndrome; jMML = juvenile myelomonocytic leukemia; HLH = hemophagocytic lymphohistiocytosis; MSD = matched sibling donor; (m) MUD (mis) Matched unrelated donor; PBSC = peripheral blood stem cells; TBI = total body irradiation; CSA = Cyclosporine A; MTX = short course methrotrexate; ATG = anti-thymocyte globulin; HSCT = hematopoietic stem cell transplantation; DLI = donor lymphocyte infusion; GvHD = graft versus host disease; M=Male; F=Female.

Disclosures:
No relevant conflicts of interest to declare.