Mesenchymal Stromal Cell (MSC) Compassionate Use in France in Treatment of Steroid-Refractory Graft-Versus-Host-Disease (GVHD) after Approval By the Expert Committee of Société Française De Greffe De Moelle Et Thérapie Cellulaire (SFGM-TC)

Hematopoietic stem cell transplantation is a well-established efficient therapy for hematological diseases, but Graft-Versus-Host Disease (GVHD) is a major and frequent complication encumbering its outcome despite the administration of calcineurin inhibitor based GvHD-prophylaxis. Corticosteroids represent the worldwide first line treatment, however in case of steroid refractory acute GVHD there is no consensus about a subsequent treatment although Ruxolitinib is subject to a phase III trial. Multiple molecules have been tried, most of them immunosuppressive, increasing the risk of deadly infections and transplantation-related mortality (TRM). Recent studies reported that mesenchymal stromal cells (MSC) infusion which have immune modulatory abilities might be effective and harmless in steroid or treatment-refractory GVHD (R-GVHD). In France, MSCs are considered as an Advanced Therapy Medicinal Product. For 4 years, its administration as a compassionate use is subject to approval by an expert committee from SFGM-TC before its validation by the French regulatory agency (ANSM). We retrospectively analyzed the demands for MSC use in France since 2011 for patients suffering from R-GVHD. We evaluated the response at day 28 (range 23-28) and at the last follow-up and its safety. Eleven demands were validated by both expert committee and ANSM, 8 patients (pts) received ex-vivo expanded MSCs, 1 pt refused the therapy, 1 infusion was postponed due to COVID-19 related sanitary crisis and the last 1 didn't receive MSCs due to relapse. Among pts who received MSCs, median age was 6 years (2-69), sex ratio was 0,6. All pts underwent their first HSCT for either malignant disease (62,5%) or non-malignant disease (37,5%). Four pts were transplanted from sibling donor, 2 pts from mismatched unrelated donors and 2 pts from haplo-identical donors. Stem cells source was bone marrow for 4 pts, peripheral blood stem cells for 3 and cord blood for 1. Donors median age was 28,8 years (0-49,5), 1 male had a female donor. Six pts got a myeloablative conditioning regimen (TBI-based for 2). All pts received a ciclosporin-based (CSA) GVHD prophylaxis (CSA alone, n=1; CSA + Mycophenolate Mofetil (MMF) or Methotrexate, n=7). Five pts had ATG. Six pts were suffering from acute GVHD, while 2 from extensive chronic GVHD (cGVHD). All 6 pts with acute GVHD presented a grade III or IV, refractory to corticosteroids and at least 2 other lines of GVHD therapy. All but one had a multipolar GVHD wi