CD19 CAR T cell therapy for treatment-refractory seropositive rheumatoid arthritis: a phase 1 trial

Chimeric antigen receptor (CAR) T cell-mediated B cell depletion has demonstrated efficacy in several autoimmune diseases. Here we report clinical and molecular data obtained during the nonrandomized phase 1 part of the phase 1/2 COMPARE trial, evaluating safety and efficacy of mivocabtagene autoleucel (miv-cel), an autologous fully human CD19 CAR T cell therapy, in rheumatoid arthritis (RA). The primary endpoint was met with acceptable safety findings, allowing advancement to phase 2. CAR T cell therapy resulted in depletion of CD19+ B cells across blood and tissue, coinciding with a continuous decline of autoantibodies with seroconversion in four of the six patients for ACPAs against mutated citrullinated vimentin and five of six for rheumatoid factor immunoglobulin M. Despite cessation of immunosuppressive treatments, disease activity improved in all patients (median 34% DAS28-CRP reduction at the latest follow-up with DAS28-CRP remission and American College of Rheumatology 70% response in 3 of 6 patients). CD19 CAR T cells showed acceptable short-term tolerability in patients with treatment-refractory RA, justifying further evaluation.