P1361: TREATMENT OF SEVERE STEROID-REFRACTORY ACUTE GVHD WITH MESENCHYMAL STROMAL CELLS: RESULTS OF THE PHASE III RANDOMIZED DOUBLE-BLIND MULTI-CENTER HOVON-113 TRIAL. (23rd June 2022) - Oosten, L.; van Pel, M.; van der Holt, B.; Bach, E.; Cross, M.; Roelofs, H.; Meij, P.; Wieles, B.; Zwaginga, J. J.; Lankester, A.; Veelken, H.; Platzbecker, U.; et al.