CD19 CAR T therapy yields B cell depletion and clinical improvement in refractory seropositive RA (phase 1)

In a nonrandomized phase 1 COMPARE trial, six adults with treatment-refractory seropositive RA received a single infusion of autologous CD19 CAR T cells (mivocabtagene autoleucel) after lymphodepletion. Safety was acceptable: cytokine release syndrome was limited to grade 1–2 in all patients, with no ICANS and only one dose-limiting transaminase elevation that resolved. CD19+ B cell depletion occurred systemically, accompanied by seroconversion or reduction of autoantibodies (ACPAs and RF IgM) in most participants. Clinically, disease activity improved in all patients (median 34% DAS28-CRP reduction; remission and ACR70 responses observed in several participants). These early results support further phase 2 evaluation of CD19 CAR T cells for refractory RA.