Clinical Development Programme of the Innovative Mesenchymal Stromal Cell Product MSC-FFM/MC0518 for Steroid-Refractory Acute Graft-Versus-Host Disease: Design of 2 Randomised Controlled Trials in Adult and Paediatric Patients

Introduction: Acute graft-versus-host disease (aGvHD) is a potentially life-threatening complication that can occur following allogeneic haematopoietic stem cell transplantation. Although corticosteroids remain the standard first-line therapy, a considerable number of patients fail to respond adequately, leading to significant morbidity. Methods: Mesenchymal stromal cells (MSCs) are being investigated as a therapeutic option in this setting due to their immunomodulating and tissue-regenerative properties. Two ongoing clinical trials - IDUNN (NCT04629833) and BALDER (NCT06075706) - are assessing the role of the innovative product MSC-FFM/MC0518 in managing steroid-refractory aGvHD (SR-aGvHD). In parallel, a dedicated surveillance programme is collecting long-term efficacy and safety data to inform clinical use beyond the controlled trial environment. Conclusion: The IDUNN and BALDER trials will deliver definitive evidence on the efficacy and safety of MC0518 in SR-aGvHD and may shape future therapeutic strategies.