Safety, Feasibility, and Preliminary Efficacy of Allogeneic MSCs to Treat Advanced Femoral Head Osteonecrosis (ALOFEM): A Pilot Study in Young Onco‐Hematological Patients

Background Severe osteonecrosis of the femoral head (ONFH) secondary to corticosteroid therapy in symptomatic, hematological young patients currently has no therapeutic alternative, and early total hip replacement (THR) is a high‐risk intervention in those patients. Objectives To evaluate feasibility, safety, and early efficacy of allogeneic expanded mesenchymal stromal cells (MSCs) in a pilot clinical trial. Methods Pilot phase 1 open, noncontrolled, nonrandomized clinical trial evaluating the bone regeneration capacity in seven hips from four patients (young females 11–19 year old) with symptomatic, severe bilateral femoral head osteonecrosis (secondary to corticosteroid therapy), 1 year after being surgically treated with 140 × 10 6 allogenic MSC plus forage. Results The proposed therapy proved feasibility, safety at 1 and 4 years (no related serious adverse events [SAEs]), and early efficacy (nonsignificant) in the case analysis (5/7 hips avoiding THR at 4 years). Conclusions The implantation of expanded allogeneic MSC in young patients to prevent conversion to a THR or collapse of the femoral head due to severe osteonecrosis is feasible without safety concerns in the longer‐term follow‐up (FU) upto 4 years. Trial Registration: EudraCT number: 2018‐000886‐35