OP0203 Safety and efficacy of intravenous administration of bone-marrow derived mesenchymal stromal cells in therapy refractory juvenile idiopathic arthritis patients, a phase ib/iia pilot-study

Objectives To compare the total number of adverse events (AE’s) before and after mesenchymal stromal cell (MSC) infusion in refractory JIA and to evaluate its effectiveness. Methods Single-centre Phase Ib/IIa, open label intervention study in JIA patients previously failing all biologicals registered for their diagnosis. Six patients will receive 2 million/kg intravenous infusions of allogeneic bone-marrow derived MSC. In case of ACR-Ped30-response but subsequent loss of response one and maximal two repeated infusions are allowed. Results Six JIA patients with 9.2 years median disease duration, still active arthritis and damage were included. All had failed methotrexate, corticosteroids and median 5 different biologicals. MSC were administered twice in 3 patients. No acute infusion reactions were observed and a lower post-treatment than pre-treatment incidence in AE’s was found. The one sJIA patient had again an evolving macrophage activation syndrome, 9 weeks after tocilizumab discontinuation and 7 weeks post- MSC infusion. Eight weeks after one MSC infusion, 4 patients showed less active joints, 5 patients improved in many clinical parameters and inflammatory parameters decreased in 3/4. After 1 year, we found significantly lower active joint counts, improved well-being scores, normalised median ESR- and CRP-levels. Inactive disease was reached by 3 patients at 1 year. Conclusions MSC infusions in refractory JIA patients are safe, although in sJIA stopping the ‘failing’ biologic treatment carries a risk of a MAS flare since the drug might still suppress the systemic features. Furthermore, intravenous administration of MSC might be efficacious even in multiple biological-failing JIA patients with damage. Disclosure of Interest None declared