Study design and participants.
difficult-to-treat
INS
We performed an open-label, nonrandomized phase I clinical study enrolling and treating pediatric patients at the IRCCS Bambino Gesù Children’s Hospital (Rome, Italy) and young adult patients at the Azienda Socio-Sanitaria Territoriale – Ospedale Papa Giovanni XXIII (Bergamo, Italy). The trial is registered with EudraCT (number 2016-004804-77). The investigational drug (autologous BM-MSCs), trial design, and procedures are described in Supplemental Material (Investigational Medicinal Product Description, Investigator Brochure, and Study Protocol). Patients were eligible for the study if they were between 5 and 40 years of age and had difficult-to-treat, frequently relapsing, or steroid-dependent INS. We included those with at least 2 relapses in the previous year in spite of prednisone and/or 1 or more other immunosuppressive steroid-sparing agent. Only patients reported to invariably relapse upon treatment tapering or withdrawal and on stable (from at least 1 month) complete (<0.3 g/24 hours for adults or <4 mg/h/m