POS0464 SERUM PROTEOMIC ANALYSIS IDENTIFIES MARKERS ASSOCIATED WITH ANTI-CD19 CAR T THERAPEUTIC RESPONSE IN AUTOIMMUNE DISEASES
Authors: J. Chou, R. Grieshaber-Bouyer, D. Bohr, C. Bergmann, J. Taubmann, F. Müller, A. Bozec, T. Rothe, A. Mackensen, J. Chung, G. Schett
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Anti-CD19 CAR T-cell therapy has demonstrated promising therapeutic efficacy and tolerability in patients with systemic lupus erythematosus (SLE), dermatomyositis (DM), and systemic sclerosis (SSc) [1–4]. The broad, deep, and short duration of B-cell depletion possible with anti-CD19 CAR T-cell therapy may provide sustained treatment-free remission for patients with autoimmune disease; however, the immunological impact of CAR T-cell therapy remains unclear. <h3>Objectives:</h3> In this study, we evaluated immunologic mechanisms and explored novel biomarkers by analyzing serum proteomic profiles at baseline and remission. <h3>Methods:</h3> Serum samples were collected prior to conditioning chemotherapy (baseline) and 3 months post–CAR T-cell infusion for 3 SLE, 3 diffuse SSc, and 2 DM patients treated at the Friedrich-Alexander University Erlangen-Nürnberg. Additional serum samples from 10 normal, 7 SLE, and 7 SSc donors were obtained from ProteoGenex. More than 7000 proteins were profiled with SomaScan® technology, which uses probe-tagged protein-binding aptamers for high-throughput proteomic profiling with an NGS readout. Differentially expressed proteins were identified by Wilcoxon test and used for Reactome pathway analysis. <h3>Results:</h3> We first evaluated data quality by checking the proteins known to be modulated by CAR T-cell therapy. Levels of IgM, IgA, and IgE were significantly reduced at 3 months post–CD19-CAR T-cell infusion, while IgG showed no significant change. When comparing normal donors with patient-derived samples at baseline, we observed elevated IFN signaling molecules (CXCL10 and MX1) in SLE samples and endothelial dysfunction markers (VEGF and ANG2) in SSc samples. Our proteomic analysis showed that HSF-1–mediated heat shock response (HSPA1A, DNAJA4, etc.) and type I IFN signaling (IFIT3, ISG15, etc.) were the two major pathways downregulated after CD19-CAR T-cell therapy (Figure 1). Moreover, an autoantigen poly(U)-binding-splicing factor 60 kDa (PUF60) was also reduced at post-infusion. These markers are selectively expressed by innate immune cells and co-expressed with proteins related to neutrophil degranulation and IL12 signaling. <h3>Conclusion:</h3> Our analysis provides new insights into the potential mechanisms of CAR T-cell treatment in patients with autoimmune diseases. These findings may facilitate future identification of markers predictive of CAR T-cell therapy response. <h3>REFERENCES:</h3> [1] Feng J, et al. <i>Blood.</i> 2022;140 (suppl 1):10335-10336. [2] Bergmann C, et al. <i>Ann Rheum Dis</i>. 2023;82:1117-1120. [3] Mackensen A, et al. <i>Nat Med.</i> 2022;28:2124-2132. [4] Haghikia A, et al<i>. Lancet Neurol</i>. 2023;22:1104-1105. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> Justin Chou Kyverna, Kyverna, Ricardo Grieshaber-Bouyer: None declared, Daniela Bohr: None declared, Christina Bergmann Novartis Preceptorship, Lecture on "Treatment of Systemic Sclerosis" and "Case presentation on the first SSc patient treated with CD19 CAR-T cells.", Boehringer-Ingelheim, Jannsen, Boehringer-Ingelheim, Jule Taubmann: None declared, Fabian Müller: None declared, Aline Bozec: None declared, Tobias Rothe: None declared, Andreas Mackensen: None declared, James Chung Kyverna, Kyverna, Georg Schett Kyverna, Novartis and Janssen, Kyverna, BMS and Cabaletta.