Background: Despite significant advances in targeted therapies, difficult-to-treat rheumatoid arthritis (D2T-RA) remains a major clinical challenge. Chimeric antigen receptor (CAR) T-cell therapy can induce deep B-cell depletion and has shown potential to induce remission in refractory autoimmune diseases. Recently, we reported the safety and preliminary efficacy of CD19-targeted CAR T-cell therapy in D2T-RA patients.

Objectives: To evaluate the long-term efficacy of CD19 CAR T-cell therapy in patients with D2T RA and whether immune reset has been achieved in these patients.

Methods: This single-center, single-arm, open-label exploratory study (NCT06503237) enrolled three patients who meet the EULAR definition of D2T-RA. After lymphodepletion with cyclophosphamide (300 mg/m ² /day) plus fludarabine (25 mg/m ² /day), all patients received a single infusion of 1×10 ⁶ /kg CD19 CAR T-cells. Peripheral blood CAR transgene copies were quantified by qPCR. Disease activity was assessed using the Disease Activity Score in 28 joints (DAS28), the Simplified Disease Activity Index (SDAI), and the Clinical Disease Activity Index (CDAI). Longitudinal 5′ single-cell RNA sequencing with paired TCR/BCR profiling of PBMCs collected at baseline (D0), days 9 (D9), day 14 (D14), and month 3 (M3) after infusion was performed to delineate immune remodeling.

Results: CAR T-cells expanded rapidly in vivo, with CAR copy numbers peaking between D9 and D21. Circulating CD19 ⁺ B cells were fully depleted within days 3-7 and gradually reconstituted by months 2–3. Clinical disease activity improved promptly and sustained remission was achieved in patient 1 and patient 2 throughout 18-month follow-up. Serologically, rheumatoid factor (RF) and anti-CCP antibody became negative by M3 in patient 1 and patient 2 and remained negative at the last visit. Patient 3 relapsed at M15, coinciding with disruption and imbalance of the peripheral immune milieu. RNA-seq reveals a shared B-cell kinetic signature, with rapid depletion within 1 month followed by robust reconstitution dominated by naive B cells. T-cell analyses revealed expansion of a cytotoxic CD8 effector subset with high-frequency clonotypes and a CAR-T phenotypic shift from a proliferative program at D9 to an interferon/effector program at D14. Concordantly, we observed a systemic peak of type II interferon responses at D14 and a myeloid shift from classical to non-classical monocytes. Notably, patient 3 was accompanied by increased IGHV3-30–IGHJ6 rearrangement within circulating plasmablast/plasma cell compartments, which remained stable or disappeared in patient 1 and patient 2, implicating this clonotype as a potential relapse-associated biomarker.

Conclusions: CD19 CAR T-cell therapy induced rapid B-cell depletion and has potential to achieve immune reset and long-term remission in RA patients.

REFERENCES: [1] Li YJ, Li SJ, Zhao X, Sheng J, Xue L, Schett G, Shi C, Hu B, Wang X, Chen Z* . Fourth-generation chimeric antigen receptor T-cell therapy is tolerable and efficacious in treatment-resistant rheumatoid arthritis. Cell Research. 2025 Mar;35(3):220-223.

Acknowledgments: NIL.

Disclosure of Interests: None declared.