Background: Ruxolitinib, a JAK1 and 2, belumosudil a ROCK2 inhibitor, and ibrutinib, a BTK inhibitor, are efficacious and safe for the treatment of chronic graft vs. host disease (cGvHD) and were recently approved by the Food and Drug Administration for this indication (1). Since cGvHD, particularly in its sclerodermatous form, shares pathogenic similarities with SSc, we reasoned that these drugs might have therapeutic potential in SSc.

Objectives: To evaluate the therapeutic potential and the relative efficacy of ruxolitinib, ibrutinib and belumosudil for the treatment of systemic sclerosis.

Methods: The murine model of sclerodermatous cGvHD was generated, since it recapitulates early stages of SSc, with progressive fibrosis driven mainly by active inflammation and autoimmunity. Bone marrow and splenocytes from B10.D2 mice was transplanted in Balb/c mice (allogeneic bone marrow transplantation, alloBMT), and mice with syngeneic Balb/c →Balb/c transplant (synBMT) were used as controls. Mice were treated with ruxolitinib, ibrutinib or belumosudil, and skin and lung fibrosis were evaluated. Precision cut slices of SSc skin (SSc-PCSS) were generated from four donors, two of which had early, progressive SSc. SSc-PCSS were treated with ruxolitinib, ibrutinib or belumosudil for 48 hours. RNA was isolated from SSc-PCSS and RNA-sequencing was performed. Differential gene expression analysis, pathway overrepresentation analysis (ORA) and gene set enrichment analysis (GSEA) were subsequently performed.

Results: We demonstrate that ruxolitinib, belumosudil and ibrutinib are effective in ameliorating skin and lung fibrosis in alloBMT mice, with reduced skin thickness and Ashcroft scores, respectively, decreased myofibroblast counts and reduced hydroxyproline content. Of the three drugs, ruxolitinib showed the most potent effects, with almost complete prevention of fibrotic skin and lung remodeling. In SSc-PCSS, we identified 829 differentially expressed genes (DEGs) after treatment with ruxolitinib, 412 DEGs after treatment with belumosudil and 297 DEGs after treatment with ibrutinib. Pathway ORA and GSEA identified terms related to extracellular matrix production and profibrotic immune responses de-enriched upon treatment with ruxolitinib, belumosudil and ibrutinib. The DEGs after treatment with ruxolitinib showed the highest overlap with DEGs in SSc from the PRESS cohort, suggesting that ruxolitinib has the highest potential to revert an SSc signature.

Conclusion: By employing a model of sclerodermatous cGvHD and direct testing in SSc skin, we demonstrate that treatment with ruxolitinib, belumosudil and ibrutinib can prevent fibroblast activation and collagen production and can partially revert the aberrant gene expression profile in SSc. Of these drugs, ruxolitinib showed the most potent effects. We thus provide in vivo and ex vivo data that support the therapeutic potential of ruxolitinib, belumosudil and ibrutinib for the treatment of SSc, that might be of high translational potential, since these drugs are already approved for other indications.

REFERENCES: [1] Martini DJ, Chen YB, DeFilipp Z. Recent FDA Approvals in the Treatment of Graft-Versus-Host Disease. Oncologist. 2022;27(8):685-93.

Acknowledgements: NIL.

Disclosure of Interests: Xuezhi Hong: None declared, Yanhua Xiao: None declared, Andrea-Hermina Györfi: None declared, Liyan Xu: None declared, Lichong Shen: None declared, Ranjana Neelagar: None declared, Veda Devakumar: None declared, Tim Filla: None declared, Thuong Trinh-Minh: None declared, Minrui Liang: None declared, Aleix Rius Rigau: None declared, Jörg Distler stock owner of 4D Science and Scientific head of FibroCure, Actelion, Active Biotech, Anamar, ARXX, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, JB Therapeutics, Medac, Pfizer, RuiYi and UCB, Anamar, Active Biotech, Array Biopharma, aTyr, BMS, Bayer Pharma, Boehringer Ingelheim, Celgene, Galapagos, GSK, Inventiva, Novartis, Sanofi-Aventis, RedX, UCB, Alexandru-Emil Matei: None declared.