Background Several data suggest a role of B-cells in SSc-pathogenesis: disturbed B-cell homeostasis with expansion of naïve and decrease of memory B-cells (1), increased levels of B-cell stimulating factors [2] and anti-fibrotic effects of B-cell-depletion in murine fibrosis models [3]. Although first randomized controlled trials show promising effects of the CD20-targeting antibody rituximab (RTX) in SSc (4,5), the role of B-cell targeting treatments remains controversial. A possible explanation is the limited B-cell repertoire targeted by CD20-depleting antibodies that spare early B-cell precursors, which are particularly expanded in SSc, as well as plasmablasts responsible for autoantibody production. Hence, deeper and wider B-cell-depletion may be effective in SSc treatment. Recently, CD19-targeting CAR-T-cells, that are used to deeply deplete B-cells in refractory lymphoma and leukemia, showed remarkable effects in refractory systemic lupus erythematosus patients, suggesting the principle feasibility to intercept with autoimmune disease via CD19-targeting CAR-T-cells.

Objectives To test the feasibility of treating severe SSc with CD19-targeting CAR-T-cells. Outcomes: B-cell -, absolute and relative CAR-T-cell counts, ANA-titer, SSc-specific antibodies, ⁶⁸Ga-FAPI-04-uptake, carpal MRI, EUSTAR activity index, mRSS, TJC, forced vital capacity (FVC), diffusion coefficient (DLCO).

Methods This is a case study of compassionate use of CD19-targeting CAR-T-cells in a 60-year old male patient with severe, diffuse SSc (year of diagnosis 2020 (first non-Raynaud manifestation, mRSS 24 at baseline) with diffuse myocardial fibrosis, lung fibrosis, Raynaud´s phenomenon and carpal arthritis who previously failed several standard therapies including methotrexate and mycophenolate. CAR-T-cell-infusion was performed upon lymphodepletion with fludarabine (25 mg/m² on days -5, -4, -3) and cyclophosphamide (1g/m2 on day -3) in August 2020 as single infusion. Immunosuppressive treatment was stopped before. Main outcomes were assessed before baseline and three months after CAR-T-cell infusion.

Results CAR-T-cells expanded remarkably and fast in vivo from day 3 (0.3 cells/μl; 0.1% CARs of CD3+ T cells) until day 9 (0.30.19 (1275/μl; 66,35% CARs of CD3+ T cells) and were measurable until day 51 after infusion. B-cells were completely depleted by day 7 and were not detectable until day 77. Serum-IgG levels endured above 600mg/dl. CAR-T-cell therapy was well tolerated without signs of cytokine release syndrome or cell-associated neurotoxicity syndrome. ANA titers (before baseline: 1:320) and SSc-specific antibodies (anti-RNAP III antibodies, antigen RP11) were no longer detectable three months after CAR-T-cell-infusion. In parallel, myocardial tracer uptake was reduced by 30% in ⁶⁸Ga-FAPI-04-PET-CT imaging, a novel imaging technique that allows the molecular assessment of fibroblast activation in vivo. The extent of lung fibrosis on CT scan and pulmonary function test parameters was stable or slightly improved. As analyzed by contrast supported hand-MRI, carpal arthritis improved three months after CAR-T-cell therapy. Consistently, tender joint counts improved from n=22 at baseline to n=3 at 3 months follow up. In addition, tendon friction rubs were no longer present consistent with reduction of EUSTAR activity index. Skin fibrosis showed a tendency of improvement after 3 months as analyzed by two independent assessors.

Conclusion We show for the first time, that CAR-T-cell therapy can result in the fast loss of SSc-specific autoimmunity in a patient with severe, diffuse SSc and is paralleled by amelioration of clinical manifestations including skin- and heart-fibrosis and arthritis. Further studies with longer follow-up times and more patients will help to further characterize the role of CAR-T-cell therapy in SSc.

References [1]Sato S, et al. Arthritis Rheum. 2004

[2]Brown M, et al. Immunol. 2019

[3]Yoshizaki A. J Dermatol. 2016

[4]Ebata S, et al. The Lancet Rheumatology. 2021

[5]Maher TM, et al. Lancet Respir Med. 2022

Acknowledgements: NIL.

Disclosure of Interests Christina Bergmann Speakers bureau: Boehringer-Ingelheim, Pfizer, Grant/research support from: Boehringer-Ingelheim, Fabian Müller: None declared, Distler Jörg Consultant of: JHWD has consultancy relationships with Actelion, Active Biotech, Anamar, ARXX, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, Medac, Novartis, Pfizer, RuiYi and UCB, Grant/research support from: JHWD has received research funding from Anamar, Active Biotech, Array Biopharma, ARXX, aTyr, AstraZeneca, BMS, Bayer Pharma, Boehringer Ingelheim, Cantargia, Celgene, CSL Behring, Galapagos, GSK, Inventiva, Kiniksa, Sanofi-Aventis, RedX, UCB, Dr. med. Hermina Györfi: None declared, Simon Völkl: None declared, Michael Aigner: None declared, Thomas Harrer: None declared, Nadine Bayerl: None declared, Armin Atzinger: None declared, Jule Taubmann: None declared, Sebastian Boeltz: None declared, Jochen Wacker: None declared, Michael Uder: None declared, Torsten Kuwert: None declared, Mackensen Andreas: None declared, Georg Schett: None declared.