Background/Purpose: Our goal was to assess histological and transcriptomic effects of Abatacept (ABA) on RA synovium, and to compare them with previously published data obtained by our group using the same study design on other DMARDs: Tocilizumab (TCZ), Rituximab (RTX), Methotrexate (MTX) and Adalimumab (ADA).

Methods: Synovial tissue was obtained using ultrasound-guided biopsy from affected joints before (W0) and 16 weeks (W16) after treatment with subcutaneous Abatacept 125mg per week on a MTX background. Paraffin-sections were stained for CD3, CD20 and CD68 and scored by a pathologist for T cell, B cell and macrophage infiltration. Transcriptional profiling was performed using GeneChip Human Genome U133 Plus 2.0 arrays (Affymetrix), and analyzed on Genespring GX (Agilent). Pathway analyses were performed on Genespring GX, Metascape and EnrichR. Protein-Protein Interaction (PPI) networks were generated on STRING.

Results: 14 RA patients were included (female: 9, ACPA/RF positive: 8, erosive disease: 12, median disease duration in years (± SD): 11.7 (± 8.1), median DAS28CRP (± SD): 4.78 (± 1.11)). Median DAS28CRP significantly decreased between W0 and W16, as did US GS score. Evaluation of histological slides (n=11 pairs of samples) showed no significant effect of Abatacept on T cell, B cell or macrophage infiltration. Gene expression analysis (n=10 pairs of samples) identified 304 transcripts differentially expressed (129 downregulated, 175 upregulated) between W0 and W16 (FC≥1.5 and p< 0.05, paired Mann-Whitney). Downregulated genes were significantly enriched for immune processes and included several key T cell regulatory genes (IL2RA, CD28, IL7, IL7R), strongly overlapping with data from previous studies on TCZ (n= 12 pairs), RTX (n=12 pairs), MTX (n=8 pairs) and ADA (n=8 pairs). Thus, each treatment shares 31 to 48% of its downregulated genes with the others, with genes downregulated by at least three involved in key RA-associated pathways such as leukocyte activation, NF-kappa B signaling, TNF signaling and JAK-STAT signaling. Given their seemingly overlapping effects, data were pooled across these studies, markedly improving power thanks to their paired-design. This revealed that genes downregulated by DMARDs (n=573, Benjamini-Hochberg corrected p-value< 0.05, paired Mann-Whitney) were significantly enriched for both T cell and myeloid leukocyte activation pathways. Interestingly, DMARDs seem to have a coordinate effect on the two pathways (correlation of mean Log₂FC: r=0.8558, p< 0.0001), with a stronger impact (Log₂FC_W16-W0) in good responders to therapy (n=17) as compared to moderate (n=20) and to non-responders (n=13) (p< 0.0001, Mann-Whitney). Finally, Transcription Factor enrichment and PPI network analyses point to a central role for molecules including JAK/STATs as mediators of all studied therapies.

Conclusion: We provide evidence that the effects of five DMARDs on RA synovium culminate in the same pathways (namely, T cell and myeloid leukocyte activation). This confirms previous studies suggesting the existence of common mediators downstream of DMARDs, independent of their primary targets, and suggests attractive new therapeutic targets.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/abatacept-and-other-dmards-have-common-transcriptomic-effects-on-ra-synovial-tissue/