Graft versus host disease is a serious and often life-threatening complication in allogeneic haematopoietic stem cell transplantation. Although corticosteroids are the first-choice of treatment in these patients, but about 30-50% patients do not respond to it and develop steroid-refractory GVHD. Mesenchymal stem cells (MSC) have emerged as a promising treatment option in these patients. This phase-I/II clinical trial aims at establishing the safety and clinical efficacy of allogenic ex-vivo cultured MSCs to treat steroid-refractory GVHD in a Pakistani HSCT cohort.